Improve userspace VM management

Occlum is a single-address-space library OS. Previously, userspace memory are divided for each process.
And all the memory are allocated when the process is created, which leads to a lot of wasted space and
complicated configuration.

In the current implementation, the whole userspace is managed as a memory pool that consists of chunks. There
are two kinds of chunks:
(1) Single VMA chunk: a chunk with only one VMA. Should be owned by exactly one process.
(2) Multi VMA chunk: a chunk with default chunk size and there could be a lot of VMAs in this chunk. Can be used
by different processes.

This design can help to achieve mainly two goals:
(1) Simplify the configuration: Users don't need to configure the process.default_mmap_size anymore. And multiple processes
running in the same Occlum instance can use dramatically different sizes of memory.
(2) Gain better performance: Two-level management(chunks & VMAs) reduces the time for finding, inserting, deleting, and iterating.

src/Enclave.edl

@@ -103,7 +103,6 @@ enclave {
          */
         public int occlum_ecall_kill(int pid, int sig);
 
-
         /*
          * Broadcast interrupts to LibOS threads.
          *

src/libos/Cargo.lock

@@ -8,11 +8,14 @@ dependencies = [
  "atomic",
  "bitflags",
  "bitvec",
+ "ctor",
  "derive_builder",
  "goblin",
+ "intrusive-collections",
+ "itertools",
  "lazy_static",
  "log",
- "memoffset",
+ "memoffset 0.6.1",
  "rcore-fs",
  "rcore-fs-devfs",
  "rcore-fs-mountfs",
@@ -110,6 +113,16 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "ctor"
+version = "0.1.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fbaabec2c953050352311293be5c6aba8e141ba19d6811862b232d6fd020484"
+dependencies = [
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "darling"
 version = "0.10.2"
@@ -227,6 +240,24 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
 
+[[package]]
+name = "intrusive-collections"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb4ed164b4cf1c6bd6e18c097490331a0e58fbb0f39e8f6b5ac7f168006511cd"
+dependencies = [
+ "memoffset 0.5.6",
+]
+
+[[package]]
+name = "itertools"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69ddb889f9d0d08a67338271fa9b62996bc788c7796a5c18cf057420aaed5eaf"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "0.4.5"
@@ -258,6 +289,15 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "memoffset"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "043175f069eda7b85febe4a74abbaeff828d9f8b448515d3151a14a3542811aa"
+dependencies = [
+ "autocfg 1.0.1",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.6.1"

src/libos/Cargo.toml

@@ -27,6 +27,8 @@ serde = { path = "../../deps/serde-sgx/serde", features = ["derive"] }
 serde_json = { path = "../../deps/serde-json-sgx" }
 memoffset = "0.6.1"
 scroll = { version = "0.10.2", default-features = false }
+itertools = { version = "0.10.0", default-features = false, features = ["use_alloc"]  }
+ctor = "0.1"
 
 [patch.'https://github.com/apache/teaclave-sgx-sdk.git']
 sgx_tstd = { path = "../../deps/rust-sgx-sdk/sgx_tstd" }
@@ -48,3 +50,4 @@ sgx_tse = { path = "../../deps/rust-sgx-sdk/sgx_tse" }
 sgx_tcrypto = { path = "../../deps/rust-sgx-sdk/sgx_tcrypto" }
 sgx_cov = { path = "../../deps/rust-sgx-sdk/sgx_cov", optional = true }
 goblin = { version = "0.3.4", default-features = false, features = ["elf64", "elf32", "endian_fd"] }
+intrusive-collections = "0.9"

src/libos/src/entry.rs

@@ -15,6 +15,7 @@ use crate::util::log::LevelFilter;
 use crate::util::mem_util::from_untrusted::*;
 use crate::util::resolv_conf_util::{parse_resolv_conf, write_resolv_conf};
 use crate::util::sgx::allow_debug as sgx_allow_debug;
+use crate::vm::USER_SPACE_VM_MANAGER;
 use sgx_tse::*;
 
 pub static mut INSTANCE_DIR: String = String::new();

src/libos/src/fs/procfs/meminfo.rs

@@ -14,7 +14,7 @@ impl MemInfoINode {
 impl ProcINode for MemInfoINode {
     fn generate_data_in_bytes(&self) -> vfs::Result<Vec<u8>> {
         let total_ram = USER_SPACE_VM_MANAGER.get_total_size();
-        let free_ram = USER_SPACE_VM_MANAGER.get_free_size();
+        let free_ram = current!().vm().get_free_size();
         Ok(format!(
             "MemTotal:       {} kB\n\
              MemFree:        {} kB\n\

src/libos/src/lib.rs

@@ -9,6 +9,7 @@
 #![feature(alloc_layout_extra)]
 #![feature(concat_idents)]
 #![feature(trace_macros)]
+#![feature(drain_filter)]
 // for !Send in rw_lock
 #![feature(negative_impls)]
 // for may_dangle in rw_lock
@@ -54,6 +55,8 @@ extern crate serde;
 extern crate serde_json;
 #[macro_use]
 extern crate memoffset;
+extern crate ctor;
+extern crate intrusive_collections;
 extern crate resolv_conf;
 
 use sgx_trts::libc;

src/libos/src/misc/sysinfo.rs

@@ -26,7 +26,7 @@ pub fn do_sysinfo() -> Result<sysinfo_t> {
     let info = sysinfo_t {
         uptime: time::up_time::get().unwrap().as_secs() as i64, // Duration can't be negative
         totalram: USER_SPACE_VM_MANAGER.get_total_size() as u64,
-        freeram: USER_SPACE_VM_MANAGER.get_free_size() as u64,
+        freeram: current!().vm().get_free_size() as u64,
         procs: table::get_all_processes().len() as u16,
         mem_unit: 1,
         ..Default::default()

src/libos/src/prelude.rs

@@ -2,6 +2,7 @@ pub use sgx_trts::libc;
 pub use sgx_trts::libc::off_t;
 pub use sgx_types::*;
 
+pub use core::intrinsics::unreachable;
 use std;
 pub use std::cell::{Cell, RefCell};
 pub use std::cmp::{max, min};

src/libos/src/process/do_exit.rs

@@ -9,6 +9,7 @@ use super::{table, ProcessRef, TermStatus, ThreadRef, ThreadStatus};
 use crate::prelude::*;
 use crate::signal::{KernelSignal, SigNum};
 use crate::syscall::CpuContext;
+use crate::vm::USER_SPACE_VM_MANAGER;
 
 pub fn do_exit_group(status: i32, curr_user_ctxt: &mut CpuContext) -> Result<isize> {
     if is_vforked_child_process() {
@@ -103,6 +104,8 @@ fn exit_process(thread: &ThreadRef, term_status: TermStatus) {
     };
     // Lock the current process
     let mut process_inner = process.inner();
+    // Clean used VM
+    USER_SPACE_VM_MANAGER.free_chunks_when_exit(thread);
 
     // The parent is the idle process
     if parent_inner.is_none() {
@@ -201,6 +204,9 @@ fn exit_process_for_execve(
 
     // Lock the current process
     let mut process_inner = process.inner();
+    // Clean used VM
+    USER_SPACE_VM_MANAGER.free_chunks_when_exit(thread);
+
     let mut new_parent_inner = new_parent_ref.inner();
     let pid = process.pid();
 

src/libos/src/syscall/mod.rs

@@ -710,7 +710,7 @@ fn do_syscall(user_context: &mut CpuContext) {
             retval
         }
     };
-    trace!("Retval = {:?}", retval);
+    trace!("Retval = 0x{:x}", retval);
 
     // Put the return value into user_context.rax, except for syscalls that may
     // modify user_context directly. Currently, there are three such syscalls:

src/libos/src/vm/chunk.rs

@@ -0,0 +1,239 @@
+use super::*;
+
+use super::vm_area::VMArea;
+use super::vm_chunk_manager::ChunkManager;
+use super::vm_perms::VMPerms;
+use super::vm_util::*;
+use crate::process::ProcessRef;
+use crate::process::ThreadRef;
+use std::cmp::Ordering;
+use std::collections::HashSet;
+use std::hash::{Hash, Hasher};
+
+// For single VMA chunk, the vma struct doesn't need to update the pid field. Because all the chunks are recorded by the process VM already.
+pub const DUMMY_CHUNK_PROCESS_ID: pid_t = 0;
+// Default chunk size: 32MB
+pub const CHUNK_DEFAULT_SIZE: usize = 32 * 1024 * 1024;
+
+pub type ChunkID = usize;
+pub type ChunkRef = Arc<Chunk>;
+
+pub struct Chunk {
+    range: VMRange,
+    internal: ChunkType,
+}
+
+impl Hash for Chunk {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.range.hash(state);
+    }
+}
+
+impl Ord for Chunk {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.range.start().cmp(&other.range.start())
+    }
+}
+
+impl PartialOrd for Chunk {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl PartialEq for Chunk {
+    fn eq(&self, other: &Self) -> bool {
+        self.range == other.range
+    }
+}
+
+impl Eq for Chunk {}
+
+impl Debug for Chunk {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.internal() {
+            ChunkType::SingleVMA(vma) => write!(f, "Single VMA chunk: {:?}", vma),
+            ChunkType::MultiVMA(internal_manager) => write!(f, "default chunk: {:?}", self.range()),
+        }
+    }
+}
+
+impl Chunk {
+    pub fn range(&self) -> &VMRange {
+        &self.range
+    }
+
+    pub fn internal(&self) -> &ChunkType {
+        &self.internal
+    }
+
+    pub fn free_size(&self) -> usize {
+        match self.internal() {
+            ChunkType::SingleVMA(vma) => 0, // for single VMA chunk, there is no free space
+            ChunkType::MultiVMA(internal_manager) => internal_manager.lock().unwrap().free_size(),
+        }
+    }
+
+    pub fn new_default_chunk(vm_range: VMRange) -> Result<Self> {
+        let internal_manager = ChunkInternal::new(vm_range)?;
+        Ok(Self {
+            range: vm_range,
+            internal: ChunkType::MultiVMA(SgxMutex::new(internal_manager)),
+        })
+    }
+
+    pub fn new_single_vma_chunk(vm_range: VMRange, options: &VMMapOptions) -> Self {
+        let writeback_file = options.writeback_file().clone();
+        let vm_area = VMArea::new(
+            vm_range.clone(),
+            *options.perms(),
+            writeback_file,
+            DUMMY_CHUNK_PROCESS_ID,
+        );
+        // Initialize the memory of the new range
+        unsafe {
+            let buf = vm_range.as_slice_mut();
+            options.initializer().init_slice(buf);
+        }
+        // Set memory permissions
+        if !options.perms().is_default() {
+            VMPerms::apply_perms(&vm_area, vm_area.perms());
+        }
+        Self::new_chunk_with_vma(vm_area)
+    }
+
+    pub fn new_chunk_with_vma(vma: VMArea) -> Self {
+        Self {
+            range: vma.range().clone(),
+            internal: ChunkType::SingleVMA(SgxMutex::new(vma)),
+        }
+    }
+
+    pub fn add_process(&self, current: &ThreadRef) {
+        match self.internal() {
+            ChunkType::SingleVMA(vma) => unreachable!(),
+            ChunkType::MultiVMA(internal_manager) => {
+                internal_manager
+                    .lock()
+                    .unwrap()
+                    .add_process(current.process().pid());
+            }
+        }
+    }
+
+    pub fn mmap(&self, options: &VMMapOptions) -> Result<usize> {
+        debug_assert!(!self.is_single_vma());
+        trace!("try allocate in chunk: {:?}", self);
+        let mut internal_manager = if let ChunkType::MultiVMA(internal_manager) = &self.internal {
+            internal_manager.lock().unwrap()
+        } else {
+            unreachable!();
+        };
+        if internal_manager.chunk_manager.free_size() < options.size() {
+            return_errno!(ENOMEM, "no enough size without trying. try other chunks");
+        }
+        return internal_manager.chunk_manager.mmap(options);
+    }
+
+    pub fn try_mmap(&self, options: &VMMapOptions) -> Result<usize> {
+        debug_assert!(!self.is_single_vma());
+        // Try lock ChunkManager. If it fails, just return and will try other chunks.
+        let mut internal_manager = if let ChunkType::MultiVMA(internal_manager) = &self.internal {
+            internal_manager
+                .try_lock()
+                .map_err(|_| errno!(EAGAIN, "try other chunks"))?
+        } else {
+            unreachable!();
+        };
+        trace!("get lock, try mmap in chunk: {:?}", self);
+        if internal_manager.chunk_manager().free_size() < options.size() {
+            return_errno!(ENOMEM, "no enough size without trying. try other chunks");
+        }
+        internal_manager.chunk_manager().mmap(options)
+    }
+
+    pub fn is_single_vma(&self) -> bool {
+        if let ChunkType::SingleVMA(_) = self.internal {
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn find_mmap_region(&self, addr: usize) -> Result<VMRange> {
+        let internal = &self.internal;
+        match self.internal() {
+            ChunkType::SingleVMA(vma) => {
+                let vma = vma.lock().unwrap();
+                if vma.contains(addr) {
+                    return Ok(vma.range().clone());
+                } else {
+                    return_errno!(ESRCH, "addr not found in this chunk")
+                }
+            }
+            ChunkType::MultiVMA(internal_manager) => {
+                return internal_manager
+                    .lock()
+                    .unwrap()
+                    .chunk_manager
+                    .find_mmap_region(addr);
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum ChunkType {
+    SingleVMA(SgxMutex<VMArea>),
+    MultiVMA(SgxMutex<ChunkInternal>),
+}
+
+#[derive(Debug)]
+pub struct ChunkInternal {
+    chunk_manager: ChunkManager,
+    process_set: HashSet<pid_t>,
+}
+
+const PROCESS_SET_INIT_SIZE: usize = 5;
+
+impl ChunkInternal {
+    pub fn new(vm_range: VMRange) -> Result<Self> {
+        let chunk_manager = ChunkManager::from(vm_range.start(), vm_range.size())?;
+
+        let mut process_set = HashSet::with_capacity(PROCESS_SET_INIT_SIZE);
+        process_set.insert(current!().process().pid());
+        Ok(Self {
+            chunk_manager,
+            process_set,
+        })
+    }
+
+    pub fn add_process(&mut self, pid: pid_t) {
+        self.process_set.insert(pid);
+    }
+
+    pub fn chunk_manager(&mut self) -> &mut ChunkManager {
+        &mut self.chunk_manager
+    }
+
+    pub fn is_owned_by_current_process(&self) -> bool {
+        let current_pid = current!().process().pid();
+        self.process_set.contains(&current_pid) && self.process_set.len() == 1
+    }
+
+    pub fn free_size(&self) -> usize {
+        *self.chunk_manager.free_size()
+    }
+
+    // Clean vmas when munmap a MultiVMA chunk, return whether this chunk is cleaned
+    pub fn clean_multi_vmas(&mut self) -> bool {
+        let current_pid = current!().process().pid();
+        self.chunk_manager.clean_vmas_with_pid(current_pid);
+        if self.chunk_manager.is_empty() {
+            self.process_set.remove(&current_pid);
+            return true;
+        } else {
+            return false;
+        }
+    }
+}

src/libos/src/vm/free_space_manager.rs

@@ -0,0 +1,149 @@
+// Implements free space management for memory.
+// Currently only use simple vector as the base structure.
+//
+// Basically use address-ordered first fit to find free ranges.
+
+use super::vm_util::VMMapAddr;
+use super::*;
+
+static INITIAL_SIZE: usize = 100;
+
+#[derive(Debug, Default)]
+pub struct VMFreeSpaceManager {
+    free_manager: Vec<VMRange>, // Address-ordered first fit
+}
+
+impl VMFreeSpaceManager {
+    pub fn new(initial_free_range: VMRange) -> Self {
+        let mut free_manager = Vec::with_capacity(INITIAL_SIZE);
+        free_manager.push(initial_free_range);
+
+        VMFreeSpaceManager {
+            free_manager: free_manager,
+        }
+    }
+
+    pub fn free_size(&self) -> usize {
+        self.free_manager
+            .iter()
+            .fold(0, |acc, free_range| acc + free_range.size())
+    }
+
+    // TODO: respect options.align when mmap
+    pub fn find_free_range_internal(
+        &mut self,
+        size: usize,
+        align: usize,
+        addr: VMMapAddr,
+    ) -> Result<VMRange> {
+        // Record the minimal free range that satisfies the contraints
+        let mut result_free_range: Option<VMRange> = None;
+        let mut result_idx: Option<usize> = None;
+        let mut free_list = &mut self.free_manager;
+
+        trace!("find free range, free list = {:?}", free_list);
+
+        for (idx, free_range) in free_list.iter().enumerate() {
+            let mut free_range = {
+                if free_range.size() < size {
+                    continue;
+                }
+                unsafe { VMRange::from_unchecked(free_range.start(), free_range.end()) }
+            };
+
+            match addr {
+                // Want a minimal free_range
+                VMMapAddr::Any => {}
+                // Prefer to have free_range.start == addr
+                VMMapAddr::Hint(addr) => {
+                    if addr % align == 0
+                        && free_range.contains(addr)
+                        && free_range.end() - addr >= size
+                    {
+                        free_range.start = addr;
+                        free_range.end = addr + size;
+                        self.free_list_update_range(idx, free_range);
+                        return Ok(free_range);
+                    } else {
+                        // Hint failure, record the result but keep iterating.
+                        if result_free_range == None
+                            || result_free_range.as_ref().unwrap().size() > free_range.size()
+                        {
+                            result_free_range = Some(free_range);
+                            result_idx = Some(idx);
+                        }
+                        continue;
+                    }
+                }
+                // Must have free_range.start == addr
+                VMMapAddr::Need(addr) | VMMapAddr::Force(addr) => {
+                    if free_range.start() > addr {
+                        return_errno!(ENOMEM, "not enough memory for fixed mmap");
+                    }
+                    if !free_range.contains(addr) {
+                        continue;
+                    }
+                    if free_range.end() - addr < size {
+                        return_errno!(ENOMEM, "not enough memory for fixed mmap");
+                    }
+                    free_range.start = addr;
+                    free_range.end = addr + size;
+                }
+            }
+
+            result_free_range = Some(free_range);
+            result_idx = Some(idx);
+            break;
+        }
+
+        if result_free_range.is_none() {
+            return_errno!(ENOMEM, "not enough memory");
+        }
+
+        let index = result_idx.unwrap();
+        let result_free_range = {
+            let free_range = result_free_range.unwrap();
+            let start = align_up(free_range.start(), align);
+            let end = start + size;
+            VMRange { start, end }
+        };
+
+        self.free_list_update_range(index, result_free_range);
+        trace!("after find free range, free list = {:?}", self.free_manager);
+        return Ok(result_free_range);
+    }
+
+    fn free_list_update_range(&mut self, index: usize, range: VMRange) {
+        let mut free_list = &mut self.free_manager;
+        let ranges_after_subtraction = free_list[index].subtract(&range);
+        debug_assert!(ranges_after_subtraction.len() <= 2);
+        if ranges_after_subtraction.len() == 0 {
+            free_list.remove(index);
+            return;
+        }
+        free_list[index] = ranges_after_subtraction[0];
+        if ranges_after_subtraction.len() == 2 {
+            free_list.insert(index + 1, ranges_after_subtraction[1]);
+        }
+    }
+
+    pub fn add_range_back_to_free_manager(&mut self, dirty_range: &VMRange) -> Result<()> {
+        let mut free_list = &mut self.free_manager;
+        free_list.push(*dirty_range);
+        // Sort and merge small ranges
+        free_list.sort_unstable_by(|range_a, range_b| range_a.start().cmp(&range_b.start()));
+        let mut idx = 0;
+        while (idx < free_list.len() - 1) {
+            let right_range = free_list[idx + 1];
+            let mut left_range = &mut free_list[idx];
+            if left_range.end() == right_range.start() {
+                left_range.set_end(right_range.end());
+                free_list.remove(idx + 1);
+                continue;
+            }
+            idx += 1;
+        }
+        trace!("after add range back free list = {:?}", free_list);
+        return Ok(());
+    }
+}

src/libos/src/vm/mod.rs

@@ -1,18 +1,79 @@
+/*
+Occlum is a single-address-space library OS. Previously, userspace memory are divided for each process.
+And all the memory are allocated when the process is created, which leads to a lot of wasted space and
+complicated configuration.
+
+In the current implementation, the whole userspace is managed as a memory pool that consists of chunks. There
+are two kinds of chunks:
+(1) Single VMA chunk: a chunk with only one VMA. Should be owned by exactly one process.
+(2) Multi VMA chunk: a chunk with default chunk size and there could be a lot of VMAs in this chunk. Can be used
+by different processes.
+
+This design can help to achieve mainly two goals:
+(1) Simplify the configuration: Users don't need to configure the process.default_mmap_size anymore. And multiple processes
+running in the same Occlum instance can use dramatically different sizes of memory.
+(2) Gain better performance: Two-level management(chunks & VMAs) reduces the time for finding, inserting, deleting, and iterating.
+
+***************** Chart for Occlum User Space Memory Management ***************
+ User Space VM Manager
+┌──────────────────────────────────────────────────────────────┐
+│                            VMManager                         │
+│                                                              │
+│  Chunks (in use): B-Tree Set                                 │
+│  ┌────────────────────────────────────────────────────────┐  │
+│  │                      Multi VMA Chunk                   │  │
+│  │                     ┌───────────────────────────────┐  │  │
+│  │  Single VMA Chunk   │          ChunkManager         │  │  │
+│  │  ┌──────────────┐   │                               │  │  │
+│  │  │              │   │  VMAs (in use): Red Black Tree│  │  │
+│  │  │    VMArea    │   │  ┌─────────────────────────┐  │  │  │
+│  │  │              │   │  │                         │  │  │  │
+│  │  └──────────────┘   │  │  ┌──────┐ ┌────┐ ┌────┐ │  │  │  │
+│  │                     │  │  │ VMA  │ │VMA │ │VMA │ │  │  │  │
+│  │  Single VMA Chunk   │  │  └──────┘ └────┘ └────┘ │  │  │  │
+│  │  ┌──────────────┐   │  │                         │  │  │  │
+│  │  │              │   │  └─────────────────────────┘  │  │  │
+│  │  │    VMArea    │   │                               │  │  │
+│  │  │              │   │                               │  │  │
+│  │  └──────────────┘   │   Free Manager (free)         │  │  │
+│  │                     │   ┌────────────────────────┐  │  │  │
+│  │  Single VMA Chunk   │   │                        │  │  │  │
+│  │  ┌──────────────┐   │   │   VMFreeSpaceManager   │  │  │  │
+│  │  │              │   │   │                        │  │  │  │
+│  │  │    VMArea    │   │   └────────────────────────┘  │  │  │
+│  │  │              │   │                               │  │  │
+│  │  └──────────────┘   └───────────────────────────────┘  │  │
+│  │                                                        │  │
+│  └────────────────────────────────────────────────────────┘  │
+│                                                              │
+│  Free Manager (free)                                         │
+│  ┌────────────────────────────────────────────────────────┐  │
+│  │                                                        │  │
+│  │                   VMFreeSpaceManager                   │  │
+│  │                                                        │  │
+│  └────────────────────────────────────────────────────────┘  │
+│                                                              │
+└──────────────────────────────────────────────────────────────┘
+*/
+
 use super::*;
 use fs::{File, FileDesc, FileRef};
 use process::{Process, ProcessRef};
 use std::fmt;
 
+mod chunk;
+mod free_space_manager;
 mod process_vm;
 mod user_space_vm;
 mod vm_area;
+mod vm_chunk_manager;
 mod vm_layout;
 mod vm_manager;
 mod vm_perms;
 mod vm_range;
+mod vm_util;
 
 use self::vm_layout::VMLayout;
-use self::vm_manager::{VMManager, VMMapOptionsBuilder};
 
 pub use self::process_vm::{MMapFlags, MRemapFlags, MSyncFlags, ProcessVM, ProcessVMBuilder};
 pub use self::user_space_vm::USER_SPACE_VM_MANAGER;

src/libos/src/vm/process_vm.rs

@@ -1,12 +1,12 @@
 use super::*;
 
+use super::chunk::{Chunk, ChunkRef};
 use super::config;
 use super::process::elf_file::{ElfFile, ProgramHeaderExt};
-use super::user_space_vm::{UserSpaceVMManager, UserSpaceVMRange, USER_SPACE_VM_MANAGER};
-use super::vm_manager::{
-    VMInitializer, VMManager, VMMapAddr, VMMapOptions, VMMapOptionsBuilder, VMRemapOptions,
-};
+use super::user_space_vm::USER_SPACE_VM_MANAGER;
 use super::vm_perms::VMPerms;
+use super::vm_util::{VMInitializer, VMMapAddr, VMMapOptions, VMMapOptionsBuilder, VMRemapOptions};
+use std::collections::HashSet;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
 // Used for heap and stack start address randomization.
@@ -69,9 +69,6 @@ impl<'a, 'b> ProcessVMBuilder<'a, 'b> {
         let stack_size = self
             .stack_size
             .unwrap_or(config::LIBOS_CONFIG.process.default_stack_size);
-        let mmap_size = self
-            .mmap_size
-            .unwrap_or(config::LIBOS_CONFIG.process.default_mmap_size);
 
         // Before allocating memory, let's first calcualte how much memory
         // we need in total by iterating the memory layouts required by
@@ -92,11 +89,10 @@ impl<'a, 'b> ProcessVMBuilder<'a, 'b> {
             })
             .collect();
 
-        // TODO: Make heap and stack 16-byte aligned instead of page aligned.
+        // Make heap and stack 16-byte aligned
         let other_layouts = vec![
-            VMLayout::new(heap_size, PAGE_SIZE)?,
-            VMLayout::new(stack_size, PAGE_SIZE)?,
-            VMLayout::new(mmap_size, PAGE_SIZE)?,
+            VMLayout::new(heap_size, 16)?,
+            VMLayout::new(stack_size, 16)?,
         ];
         let process_layout = elf_layouts.iter().chain(other_layouts.iter()).fold(
             VMLayout::new_empty(),
@@ -108,85 +104,61 @@ impl<'a, 'b> ProcessVMBuilder<'a, 'b> {
 
         // Now that we end up with the memory layout required by the process,
         // let's allocate the memory for the process
-        let process_range = { USER_SPACE_VM_MANAGER.alloc(process_layout)? };
-        let process_base = process_range.range().start();
-        // Use the vm_manager to manage the whole process VM (including mmap region)
-        let mut vm_manager = VMManager::from(process_base, process_range.range().size())?;
-        // Note: we do not need to fill zeros of the mmap region.
-        // VMManager will fill zeros (if necessary) on mmap.
-
-        // Tracker to track the min_start for each part
-        let mut min_start =
-            process_base + Self::get_randomize_offset(process_range.range().size() >> 3);
+        let mut chunks = HashSet::new();
         // Init the memory for ELFs in the process
         let mut elf_ranges = Vec::with_capacity(2);
         elf_layouts
             .iter()
             .zip(self.elfs.iter())
             .map(|(elf_layout, elf_file)| {
-                let desired_range = VMRange::new_with_layout(elf_layout, min_start);
                 let vm_option = VMMapOptionsBuilder::default()
-                    .size(desired_range.size())
-                    .addr(VMMapAddr::Need(desired_range.start()))
+                    .size(elf_layout.size())
+                    .align(elf_layout.align())
                     .perms(VMPerms::ALL) // set it to read | write | exec for simplicity
                     .initializer(VMInitializer::DoNothing())
                     .build()?;
-                let elf_start = vm_manager.mmap(vm_option)?;
-                debug_assert!(desired_range.start == elf_start);
-                debug_assert!(elf_start % elf_layout.align() == 0);
-                debug_assert!(process_range.range().is_superset_of(&desired_range));
-                Self::init_elf_memory(&desired_range, elf_file)?;
-                min_start = desired_range.end();
-                elf_ranges.push(desired_range);
-                trace!("elf range = {:?}", desired_range);
+                let (elf_range, chunk_ref) = USER_SPACE_VM_MANAGER.alloc(&vm_option)?;
+                debug_assert!(elf_range.start() % elf_layout.align() == 0);
+                Self::init_elf_memory(&elf_range, elf_file)?;
+                trace!("elf range = {:?}", elf_range);
+                elf_ranges.push(elf_range);
+                chunks.insert(chunk_ref);
                 Ok(())
             })
             .collect::<Result<()>>()?;
 
         // Init the heap memory in the process
         let heap_layout = &other_layouts[0];
-        let heap_min_start = min_start + Self::get_randomize_offset(RANGE_FOR_RANDOMIZATION);
-        let heap_range = VMRange::new_with_layout(heap_layout, heap_min_start);
         let vm_option = VMMapOptionsBuilder::default()
-            .size(heap_range.size())
-            .addr(VMMapAddr::Need(heap_range.start()))
+            .size(heap_layout.size())
+            .align(heap_layout.align())
             .perms(VMPerms::READ | VMPerms::WRITE)
             .build()?;
-        let heap_start = vm_manager.mmap(vm_option)?;
-        debug_assert!(heap_range.start == heap_start);
+        let (heap_range, chunk_ref) = USER_SPACE_VM_MANAGER.alloc(&vm_option)?;
+        debug_assert!(heap_range.start() % heap_layout.align() == 0);
         trace!("heap range = {:?}", heap_range);
         let brk = AtomicUsize::new(heap_range.start());
-        min_start = heap_range.end();
+        chunks.insert(chunk_ref);
 
         // Init the stack memory in the process
         let stack_layout = &other_layouts[1];
-        let stack_min_start = min_start + Self::get_randomize_offset(RANGE_FOR_RANDOMIZATION);
-        let stack_range = VMRange::new_with_layout(stack_layout, stack_min_start);
         let vm_option = VMMapOptionsBuilder::default()
-            .size(stack_range.size())
-            .addr(VMMapAddr::Need(stack_range.start()))
+            .size(stack_layout.size())
+            .align(heap_layout.align())
             .perms(VMPerms::READ | VMPerms::WRITE)
             .build()?;
-        let stack_start = vm_manager.mmap(vm_option)?;
-        debug_assert!(stack_range.start == stack_start);
+        let (stack_range, chunk_ref) = USER_SPACE_VM_MANAGER.alloc(&vm_option)?;
+        debug_assert!(stack_range.start() % stack_layout.align() == 0);
+        chunks.insert(chunk_ref);
         trace!("stack range = {:?}", stack_range);
-        min_start = stack_range.end();
-        // Note: we do not need to fill zeros for stack
-
-        debug_assert!(process_range.range().is_superset_of(&heap_range));
-        debug_assert!(process_range.range().is_superset_of(&stack_range));
-
-        // Set mmap prefered start address
-        vm_manager.set_mmap_prefered_start_addr(min_start);
-        let vm_manager = SgxMutex::new(vm_manager);
 
+        let mem_chunks = Arc::new(RwLock::new(chunks));
         Ok(ProcessVM {
-            process_range,
             elf_ranges,
             heap_range,
             stack_range,
             brk,
-            vm_manager,
+            mem_chunks,
         })
     }
 
@@ -255,39 +227,83 @@ impl<'a, 'b> ProcessVMBuilder<'a, 'b> {
     }
 }
 
+// MemChunks is the structure to track all the chunks which are used by this process.
+type MemChunks = Arc<RwLock<HashSet<ChunkRef>>>;
+
 /// The per-process virtual memory
 #[derive(Debug)]
 pub struct ProcessVM {
-    vm_manager: SgxMutex<VMManager>, // manage the whole process VM
     elf_ranges: Vec<VMRange>,
     heap_range: VMRange,
     stack_range: VMRange,
     brk: AtomicUsize,
-    // Memory safety notes: the process_range field must be the last one.
+    // Memory safety notes: the mem_chunks field must be the last one.
     //
     // Rust drops fields in the same order as they are declared. So by making
-    // process_range the last field, we ensure that when all other fields are
+    // mem_chunks the last field, we ensure that when all other fields are
     // dropped, their drop methods (if provided) can still access the memory
-    // region represented by the process_range field.
-    process_range: UserSpaceVMRange,
+    // region represented by the mem_chunks field.
+    mem_chunks: MemChunks,
 }
 
 impl Default for ProcessVM {
     fn default() -> ProcessVM {
         ProcessVM {
-            process_range: USER_SPACE_VM_MANAGER.alloc_dummy(),
             elf_ranges: Default::default(),
             heap_range: Default::default(),
             stack_range: Default::default(),
             brk: Default::default(),
-            vm_manager: Default::default(),
+            mem_chunks: Arc::new(RwLock::new(HashSet::new())),
         }
     }
 }
 
+impl Drop for ProcessVM {
+    fn drop(&mut self) {
+        let mut mem_chunks = self.mem_chunks.write().unwrap();
+        // There are two cases when this drop is called:
+        // (1) Process exits normally and in the end, drop process VM
+        // (2) During creating process stage, process VM is ready but there are some other errors when creating the process, e.g. spawn_attribute is set
+        // to a wrong value
+        //
+        // For the first case, the process VM is cleaned in the exit procedure and nothing is needed. For the second cases, mem_chunks is not empty and should
+        // be cleaned here.
+
+        // In the first case, the current is reset to idle thread
+        // In the second case, the current thread belongs to parent process
+        let current = current!();
+        if current.tid() != 0 {
+            mem_chunks
+                .drain_filter(|chunk| chunk.is_single_vma())
+                .for_each(|chunk| USER_SPACE_VM_MANAGER.free_chunk(&chunk))
+        }
+        assert!(mem_chunks.len() == 0);
+        info!("Process VM dropped");
+    }
+}
+
 impl ProcessVM {
+    pub fn mem_chunks(&self) -> &MemChunks {
+        &self.mem_chunks
+    }
+
+    pub fn add_mem_chunk(&self, chunk: ChunkRef) {
+        let mut mem_chunks = self.mem_chunks.write().unwrap();
+        mem_chunks.insert(chunk);
+    }
+
+    pub fn remove_mem_chunk(&self, chunk: &ChunkRef) {
+        let mut mem_chunks = self.mem_chunks.write().unwrap();
+        mem_chunks.remove(chunk);
+    }
+
+    pub fn replace_mem_chunk(&self, old_chunk: &ChunkRef, new_chunk: ChunkRef) {
+        self.remove_mem_chunk(old_chunk);
+        self.add_mem_chunk(new_chunk)
+    }
+
     pub fn get_process_range(&self) -> &VMRange {
-        self.process_range.range()
+        USER_SPACE_VM_MANAGER.range()
     }
 
     pub fn get_elf_ranges(&self) -> &[VMRange] {
@@ -335,6 +351,18 @@ impl ProcessVM {
         Ok(new_brk)
     }
 
+    // Get a NON-accurate free size for current process
+    pub fn get_free_size(&self) -> usize {
+        let chunk_free_size = {
+            let process_chunks = self.mem_chunks.read().unwrap();
+            process_chunks
+                .iter()
+                .fold(0, |acc, chunks| acc + chunks.free_size())
+        };
+        let free_size = chunk_free_size + USER_SPACE_VM_MANAGER.free_size();
+        free_size
+    }
+
     pub fn mmap(
         &self,
         addr: usize,
@@ -346,9 +374,6 @@ impl ProcessVM {
     ) -> Result<usize> {
         let addr_option = {
             if flags.contains(MMapFlags::MAP_FIXED) {
-                if !self.process_range.range().contains(addr) {
-                    return_errno!(EINVAL, "Beyond valid memory range");
-                }
                 VMMapAddr::Force(addr)
             } else {
                 if addr == 0 {
@@ -360,7 +385,8 @@ impl ProcessVM {
         };
         let initializer = {
             if flags.contains(MMapFlags::MAP_ANONYMOUS) {
-                VMInitializer::FillZeros()
+                // There is no need to fill zeros in mmap. Cleaning is done after munmap.
+                VMInitializer::DoNothing()
             } else {
                 let file_ref = current!().file(fd)?;
                 VMInitializer::LoadFromFile {
@@ -386,7 +412,7 @@ impl ProcessVM {
             .initializer(initializer)
             .writeback_file(writeback_file)
             .build()?;
-        let mmap_addr = self.vm_manager.lock().unwrap().mmap(mmap_options)?;
+        let mmap_addr = USER_SPACE_VM_MANAGER.mmap(&mmap_options)?;
         Ok(mmap_addr)
     }
 
@@ -397,18 +423,12 @@ impl ProcessVM {
         new_size: usize,
         flags: MRemapFlags,
     ) -> Result<usize> {
-        if let Some(new_addr) = flags.new_addr() {
-            if !self.process_range.range().contains(new_addr) {
-                return_errno!(EINVAL, "new_addr is beyond valid memory range");
-            }
-        }
-
         let mremap_option = VMRemapOptions::new(old_addr, old_size, new_size, flags)?;
-        self.vm_manager.lock().unwrap().mremap(&mremap_option)
+        USER_SPACE_VM_MANAGER.mremap(&mremap_option)
     }
 
     pub fn munmap(&self, addr: usize, size: usize) -> Result<()> {
-        self.vm_manager.lock().unwrap().munmap(addr, size)
+        USER_SPACE_VM_MANAGER.munmap(addr, size)
     }
 
     pub fn mprotect(&self, addr: usize, size: usize, perms: VMPerms) -> Result<()> {
@@ -419,38 +439,21 @@ impl ProcessVM {
             align_up(size, PAGE_SIZE)
         };
         let protect_range = VMRange::new_with_size(addr, size)?;
-        if !self.process_range.range().is_superset_of(&protect_range) {
-            return_errno!(ENOMEM, "invalid range");
-        }
-        let mut mmap_manager = self.vm_manager.lock().unwrap();
 
-        // TODO: support mprotect vm regions in addition to mmap
-        if !mmap_manager.range().is_superset_of(&protect_range) {
-            warn!("Do not support mprotect memory outside the mmap region yet");
-            return Ok(());
-        }
-
-        mmap_manager.mprotect(addr, size, perms)
+        return USER_SPACE_VM_MANAGER.mprotect(addr, size, perms);
     }
 
     pub fn msync(&self, addr: usize, size: usize) -> Result<()> {
-        let sync_range = VMRange::new_with_size(addr, size)?;
-        let mut mmap_manager = self.vm_manager.lock().unwrap();
-        mmap_manager.msync_by_range(&sync_range)
+        return USER_SPACE_VM_MANAGER.msync(addr, size);
     }
 
     pub fn msync_by_file(&self, sync_file: &FileRef) {
-        let mut mmap_manager = self.vm_manager.lock().unwrap();
-        mmap_manager.msync_by_file(sync_file);
+        return USER_SPACE_VM_MANAGER.msync_by_file(sync_file);
     }
 
     // Return: a copy of the found region
     pub fn find_mmap_region(&self, addr: usize) -> Result<VMRange> {
-        self.vm_manager
-            .lock()
-            .unwrap()
-            .find_mmap_region(addr)
-            .map(|range_ref| *range_ref)
+        USER_SPACE_VM_MANAGER.find_mmap_region(addr)
     }
 }
 

src/libos/src/vm/user_space_vm.rs

@@ -1,62 +1,69 @@
 use super::*;
+use crate::ctor::dtor;
 use config::LIBOS_CONFIG;
+use std::ops::{Deref, DerefMut};
+use vm_manager::VMManager;
 
 /// The virtual memory manager for the entire user space
-pub struct UserSpaceVMManager {
-    total_size: usize,
-    free_size: SgxMutex<usize>,
-}
+pub struct UserSpaceVMManager(VMManager);
 
 impl UserSpaceVMManager {
-    fn new() -> UserSpaceVMManager {
+    fn new() -> Result<UserSpaceVMManager> {
         let rsrv_mem_size = LIBOS_CONFIG.resource_limits.user_space_size;
-        UserSpaceVMManager {
-            total_size: rsrv_mem_size,
-            free_size: SgxMutex::new(rsrv_mem_size),
-        }
-    }
-
-    pub fn alloc(&self, vm_layout: VMLayout) -> Result<UserSpaceVMRange> {
-        let size = align_up(vm_layout.size(), vm_layout.align());
         let vm_range = unsafe {
-            let ptr = sgx_alloc_rsrv_mem(size);
+            // TODO: Current sgx_alloc_rsrv_mem implmentation will commit all the pages of the desired size, which will consume
+            // a lot of time. When EDMM is supported, there is no need to commit all the pages at the initialization stage. A function
+            // which reserves memory but not commit pages should be provided then.
+            let ptr = sgx_alloc_rsrv_mem(rsrv_mem_size);
             let perm = MemPerm::READ | MemPerm::WRITE;
             if ptr.is_null() {
                 return_errno!(ENOMEM, "run out of reserved memory");
             }
             // Change the page permission to RW (default)
-            assert!(sgx_tprotect_rsrv_mem(ptr, size, perm.bits()) == sgx_status_t::SGX_SUCCESS);
+            assert!(
+                sgx_tprotect_rsrv_mem(ptr, rsrv_mem_size, perm.bits()) == sgx_status_t::SGX_SUCCESS
+            );
 
             let addr = ptr as usize;
-            debug!("allocated rsrv addr is 0x{:x}, len is 0x{:x}", addr, size);
-            VMRange::from_unchecked(addr, addr + size)
+            debug!(
+                "allocated rsrv addr is 0x{:x}, len is 0x{:x}",
+                addr, rsrv_mem_size
+            );
+            VMRange::from_unchecked(addr, addr + rsrv_mem_size)
         };
 
-        *self.free_size.lock().unwrap() -= size;
-        Ok(UserSpaceVMRange::new(vm_range))
-    }
+        let vm_manager = VMManager::init(vm_range)?;
 
-    fn add_free_size(&self, user_space_vmrange: &UserSpaceVMRange) {
-        *self.free_size.lock().unwrap() += user_space_vmrange.range().size();
-    }
-
-    // The empty range is not added to sub_range
-    pub fn alloc_dummy(&self) -> UserSpaceVMRange {
-        let empty_user_vm_range = unsafe { VMRange::from_unchecked(0, 0) };
-        UserSpaceVMRange::new(empty_user_vm_range)
+        Ok(UserSpaceVMManager(vm_manager))
     }
 
     pub fn get_total_size(&self) -> usize {
-        self.total_size
+        self.range().size()
     }
+}
 
-    pub fn get_free_size(&self) -> usize {
-        *self.free_size.lock().unwrap()
+// This provides module teardown function attribute similar with `__attribute__((destructor))` in C/C++ and will
+// be called after the main function. Static variables are still safe to visit at this time.
+#[dtor]
+fn free_user_space() {
+    let range = USER_SPACE_VM_MANAGER.range();
+    assert!(USER_SPACE_VM_MANAGER.verified_clean_when_exit());
+    let addr = range.start() as *const c_void;
+    let size = range.size();
+    info!("free user space VM: {:?}", range);
+    assert!(unsafe { sgx_free_rsrv_mem(addr, size) == 0 });
+}
+
+impl Deref for UserSpaceVMManager {
+    type Target = VMManager;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
     }
 }
 
 lazy_static! {
-    pub static ref USER_SPACE_VM_MANAGER: UserSpaceVMManager = UserSpaceVMManager::new();
+    pub static ref USER_SPACE_VM_MANAGER: UserSpaceVMManager = UserSpaceVMManager::new().unwrap();
 }
 
 bitflags! {
@@ -96,32 +103,3 @@ extern "C" {
     //
     fn sgx_tprotect_rsrv_mem(addr: *const c_void, length: usize, prot: i32) -> sgx_status_t;
 }
-
-#[derive(Debug)]
-pub struct UserSpaceVMRange {
-    vm_range: VMRange,
-}
-
-impl UserSpaceVMRange {
-    fn new(vm_range: VMRange) -> UserSpaceVMRange {
-        UserSpaceVMRange { vm_range }
-    }
-
-    pub fn range(&self) -> &VMRange {
-        &self.vm_range
-    }
-}
-
-impl Drop for UserSpaceVMRange {
-    fn drop(&mut self) {
-        let addr = self.vm_range.start() as *const c_void;
-        let size = self.vm_range.size();
-        if size == 0 {
-            return;
-        }
-
-        USER_SPACE_VM_MANAGER.add_free_size(self);
-        info!("user space vm free: {:?}", self.vm_range);
-        assert!(unsafe { sgx_free_rsrv_mem(addr, size) == 0 });
-    }
-}

src/libos/src/vm/vm_area.rs

@@ -4,25 +4,40 @@ use super::vm_perms::VMPerms;
 use super::vm_range::VMRange;
 use super::*;
 
+use intrusive_collections::rbtree::{Link, RBTree};
+use intrusive_collections::{intrusive_adapter, KeyAdapter};
+
 #[derive(Clone, Debug, Default)]
 pub struct VMArea {
     range: VMRange,
     perms: VMPerms,
     writeback_file: Option<(FileRef, usize)>,
+    pid: pid_t,
 }
 
 impl VMArea {
-    pub fn new(range: VMRange, perms: VMPerms, writeback_file: Option<(FileRef, usize)>) -> Self {
+    pub fn new(
+        range: VMRange,
+        perms: VMPerms,
+        writeback_file: Option<(FileRef, usize)>,
+        pid: pid_t,
+    ) -> Self {
         Self {
             range,
             perms,
             writeback_file,
+            pid,
         }
     }
 
     /// Create a new VMArea object that inherits the write-back file (if any), but has
     /// a new range and permissions.
-    pub fn inherits_file_from(vma: &VMArea, new_range: VMRange, new_perms: VMPerms) -> Self {
+    pub fn inherits_file_from(
+        vma: &VMArea,
+        new_range: VMRange,
+        new_perms: VMPerms,
+        pid: pid_t,
+    ) -> Self {
         let new_writeback_file = vma.writeback_file.as_ref().map(|(file, file_offset)| {
             let new_file = file.clone();
 
@@ -36,7 +51,7 @@ impl VMArea {
             };
             (new_file, new_file_offset)
         });
-        Self::new(new_range, new_perms, new_writeback_file)
+        Self::new(new_range, new_perms, new_writeback_file, pid)
     }
 
     pub fn perms(&self) -> VMPerms {
@@ -47,6 +62,10 @@ impl VMArea {
         &self.range
     }
 
+    pub fn pid(&self) -> pid_t {
+        self.pid
+    }
+
     pub fn writeback_file(&self) -> &Option<(FileRef, usize)> {
         &self.writeback_file
     }
@@ -59,7 +78,7 @@ impl VMArea {
         self.deref()
             .subtract(other)
             .into_iter()
-            .map(|range| Self::inherits_file_from(self, range, self.perms()))
+            .map(|range| Self::inherits_file_from(self, range, self.perms(), self.pid()))
             .collect()
     }
 
@@ -72,7 +91,7 @@ impl VMArea {
             }
             new_range.unwrap()
         };
-        let new_vma = VMArea::inherits_file_from(self, new_range, self.perms());
+        let new_vma = VMArea::inherits_file_from(self, new_range, self.perms(), self.pid());
         Some(new_vma)
     }
 
@@ -109,3 +128,56 @@ impl Deref for VMArea {
         &self.range
     }
 }
+
+#[derive(Clone)]
+pub struct VMAObj {
+    link: Link,
+    vma: VMArea,
+}
+
+impl fmt::Debug for VMAObj {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self.vma)
+    }
+}
+
+// key adapter for RBTree which is sorted by the start of vma ranges
+intrusive_adapter!(pub VMAAdapter = Box<VMAObj>: VMAObj { link : Link });
+impl<'a> KeyAdapter<'a> for VMAAdapter {
+    type Key = usize;
+    fn get_key(&self, vma_obj: &'a VMAObj) -> usize {
+        vma_obj.vma.range().start()
+    }
+}
+
+impl VMAObj {
+    pub fn new_vma_obj(vma: VMArea) -> Box<Self> {
+        Box::new(Self {
+            link: Link::new(),
+            vma,
+        })
+    }
+
+    pub fn vma(&self) -> &VMArea {
+        &self.vma
+    }
+}
+
+impl VMArea {
+    pub fn new_obj(
+        range: VMRange,
+        perms: VMPerms,
+        writeback_file: Option<(FileRef, usize)>,
+        pid: pid_t,
+    ) -> Box<VMAObj> {
+        Box::new(VMAObj {
+            link: Link::new(),
+            vma: VMArea {
+                range,
+                perms,
+                writeback_file,
+                pid,
+            },
+        })
+    }
+}

src/libos/src/vm/vm_chunk_manager.rs

@@ -0,0 +1,654 @@
+use super::*;
+
+use super::free_space_manager::VMFreeSpaceManager as FreeRangeManager;
+use super::vm_area::*;
+use super::vm_perms::VMPerms;
+use super::vm_util::*;
+use std::collections::BTreeSet;
+
+use intrusive_collections::rbtree::{Link, RBTree};
+use intrusive_collections::Bound;
+use intrusive_collections::RBTreeLink;
+use intrusive_collections::{intrusive_adapter, KeyAdapter};
+
+/// Memory chunk manager.
+///
+/// Chunk is the memory unit for Occlum. For chunks with `default` size, every chunk is managed by a ChunkManager which provides
+/// usedful memory management APIs such as mmap, munmap, mremap, mprotect, etc.
+/// ChunkManager is implemented basically with two data structures: a red-black tree to track vmas in use and a FreeRangeManager to track
+/// ranges which are free.
+/// For vmas-in-use, there are two sentry vmas with zero length at the front and end of the red-black tree.
+#[derive(Debug, Default)]
+pub struct ChunkManager {
+    range: VMRange,
+    free_size: usize,
+    vmas: RBTree<VMAAdapter>,
+    free_manager: FreeRangeManager,
+}
+
+impl ChunkManager {
+    pub fn from(addr: usize, size: usize) -> Result<Self> {
+        let range = VMRange::new(addr, addr + size)?;
+        let vmas = {
+            let start = range.start();
+            let end = range.end();
+            let start_sentry = {
+                let range = VMRange::new_empty(start)?;
+                let perms = VMPerms::empty();
+                // sentry vma shouldn't belong to any process
+                VMAObj::new_vma_obj(VMArea::new(range, perms, None, 0))
+            };
+            let end_sentry = {
+                let range = VMRange::new_empty(end)?;
+                let perms = VMPerms::empty();
+                VMAObj::new_vma_obj(VMArea::new(range, perms, None, 0))
+            };
+            let mut new_tree = RBTree::new(VMAAdapter::new());
+            new_tree.insert(start_sentry);
+            new_tree.insert(end_sentry);
+            new_tree
+        };
+        Ok(ChunkManager {
+            range,
+            free_size: range.size(),
+            vmas,
+            free_manager: FreeRangeManager::new(range.clone()),
+        })
+    }
+
+    pub fn range(&self) -> &VMRange {
+        &self.range
+    }
+
+    pub fn vmas(&self) -> &RBTree<VMAAdapter> {
+        &self.vmas
+    }
+
+    pub fn free_size(&self) -> &usize {
+        &self.free_size
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.vmas.iter().count() == 2 // only sentry vmas
+    }
+
+    pub fn clean_vmas_with_pid(&mut self, pid: pid_t) {
+        let mut vmas_cursor = self.vmas.cursor_mut();
+        vmas_cursor.move_next(); // move to the first element of the tree
+        while !vmas_cursor.is_null() {
+            let vma = vmas_cursor.get().unwrap().vma();
+            if vma.pid() != pid || vma.size() == 0 {
+                // Skip vmas which doesn't belong to this process
+                vmas_cursor.move_next();
+                continue;
+            }
+
+            Self::flush_file_vma(vma);
+
+            if !vma.perms().is_default() {
+                VMPerms::apply_perms(vma, VMPerms::default());
+            }
+
+            unsafe {
+                let buf = vma.as_slice_mut();
+                buf.iter_mut().for_each(|b| *b = 0)
+            }
+
+            self.free_manager.add_range_back_to_free_manager(vma);
+            self.free_size += vma.size();
+
+            // Remove this vma from vmas list
+            vmas_cursor.remove();
+        }
+    }
+
+    pub fn mmap(&mut self, options: &VMMapOptions) -> Result<usize> {
+        let addr = *options.addr();
+        let size = *options.size();
+        let align = *options.align();
+
+        if let VMMapAddr::Force(addr) = addr {
+            self.munmap(addr, size)?;
+        }
+
+        // Find and allocate a new range for this mmap request
+        let new_range = self
+            .free_manager
+            .find_free_range_internal(size, align, addr)?;
+        let new_addr = new_range.start();
+        let writeback_file = options.writeback_file().clone();
+        let current_pid = current!().process().pid();
+        let new_vma = VMArea::new(new_range, *options.perms(), writeback_file, current_pid);
+
+        // Initialize the memory of the new range
+        unsafe {
+            let buf = new_vma.as_slice_mut();
+            options.initializer().init_slice(buf)?;
+        }
+        // Set memory permissions
+        if !options.perms().is_default() {
+            VMPerms::apply_perms(&new_vma, new_vma.perms());
+        }
+        self.free_size -= new_vma.size();
+        // After initializing, we can safely insert the new VMA
+        self.vmas.insert(VMAObj::new_vma_obj(new_vma));
+        Ok(new_addr)
+    }
+
+    pub fn munmap_range(&mut self, range: VMRange) -> Result<()> {
+        let bound = range.start();
+        let current_pid = current!().process().pid();
+
+        // The cursor to iterate vmas that might intersect with munmap_range.
+        // Upper bound returns the vma whose start address is below and nearest to the munmap range. Start from this range.
+        let mut vmas_cursor = self.vmas.upper_bound_mut(Bound::Included(&bound));
+        while !vmas_cursor.is_null() && vmas_cursor.get().unwrap().vma().start() <= range.end() {
+            let vma = &vmas_cursor.get().unwrap().vma();
+            warn!("munmap related vma = {:?}", vma);
+            if vma.size() == 0 || current_pid != vma.pid() {
+                vmas_cursor.move_next();
+                continue;
+            }
+            let intersection_vma = match vma.intersect(&range) {
+                None => {
+                    vmas_cursor.move_next();
+                    continue;
+                }
+                Some(intersection_vma) => intersection_vma,
+            };
+
+            // File-backed VMA needs to be flushed upon munmap
+            Self::flush_file_vma(&intersection_vma);
+            if !&intersection_vma.perms().is_default() {
+                VMPerms::apply_perms(&intersection_vma, VMPerms::default());
+            }
+
+            if vma.range() == intersection_vma.range() {
+                // Exact match. Just remove.
+                vmas_cursor.remove();
+            } else {
+                // The intersection_vma is a subset of current vma
+                let mut remain_vmas = vma.subtract(&intersection_vma);
+                if remain_vmas.len() == 1 {
+                    let new_obj = VMAObj::new_vma_obj(remain_vmas.pop().unwrap());
+                    vmas_cursor.replace_with(new_obj);
+                    vmas_cursor.move_next();
+                } else {
+                    debug_assert!(remain_vmas.len() == 2);
+                    let vma_left_part = VMAObj::new_vma_obj(remain_vmas.swap_remove(0));
+                    vmas_cursor.replace_with(vma_left_part);
+                    let vma_right_part = VMAObj::new_vma_obj(remain_vmas.pop().unwrap());
+                    // The new element will be inserted at the correct position in the tree based on its key automatically.
+                    vmas_cursor.insert(vma_right_part);
+                }
+            }
+
+            // Reset zero
+            unsafe {
+                warn!("intersection vma = {:?}", intersection_vma);
+                let buf = intersection_vma.as_slice_mut();
+                buf.iter_mut().for_each(|b| *b = 0)
+            }
+
+            self.free_manager
+                .add_range_back_to_free_manager(intersection_vma.range());
+            self.free_size += intersection_vma.size();
+        }
+        Ok(())
+    }
+
+    pub fn munmap(&mut self, addr: usize, size: usize) -> Result<()> {
+        let size = {
+            if size == 0 {
+                return_errno!(EINVAL, "size of munmap must not be zero");
+            }
+            align_up(size, PAGE_SIZE)
+        };
+        let munmap_range = {
+            let munmap_range = VMRange::new(addr, addr + size)?;
+
+            let effective_munmap_range_opt = munmap_range.intersect(&self.range);
+            if effective_munmap_range_opt.is_none() {
+                return Ok(());
+            }
+
+            let effective_munmap_range = effective_munmap_range_opt.unwrap();
+            if effective_munmap_range.empty() {
+                return Ok(());
+            }
+            effective_munmap_range
+        };
+
+        self.munmap_range(munmap_range)
+    }
+
+    pub fn mremap(&mut self, options: &VMRemapOptions) -> Result<usize> {
+        let old_addr = options.old_addr();
+        let old_size = options.old_size();
+        let old_range = VMRange::new_with_size(old_addr, old_size)?;
+        let new_size = options.new_size();
+        let flags = options.flags();
+        let size_type = SizeType::new(&old_size, &new_size);
+
+        return_errno!(ENOSYS, "Under development");
+
+        // Old dead code. Could be used for future development.
+        #[cfg(dev)]
+        {
+            // The old range must be contained in one VMA
+            let idx = self
+                .find_containing_vma_idx(&old_range)
+                .ok_or_else(|| errno!(EFAULT, "invalid range"))?;
+            let containing_vma = &self.vmas[idx];
+            // Get the memory permissions of the old range
+            let perms = containing_vma.perms();
+            // Get the write back file of the old range if there is one.
+            let writeback_file = containing_vma.writeback_file();
+
+            // FIXME: Current implementation for file-backed memory mremap has limitation that if a SUBRANGE of the previous
+            // file-backed mmap with MAP_SHARED is then mremap-ed with MREMAP_MAYMOVE, there will be two vmas that have the same backed file.
+            // For Linux, writing to either memory vma or the file will update the other two equally. But we won't be able to support this before
+            // we really have paging. Thus, if the old_range is not equal to a recorded vma, we will just return with error.
+            if writeback_file.is_some() && &old_range != containing_vma.range() {
+                return_errno!(EINVAL, "Known limition")
+            }
+
+            // Implement mremap as one optional mmap followed by one optional munmap.
+            //
+            // The exact arguments for the mmap and munmap are determined by the values of MRemapFlags,
+            // SizeType and writeback_file. There is a total of 18 combinations among MRemapFlags and
+            // SizeType and writeback_file. As some combinations result in the same mmap and munmap operations,
+            // the following code only needs to match below patterns of (MRemapFlags, SizeType, writeback_file)
+            // and treat each case accordingly.
+
+            // Determine whether need to do mmap. And when possible, determine the returned address
+            let (need_mmap, mut ret_addr) = match (flags, size_type, writeback_file) {
+                (MRemapFlags::None, SizeType::Growing, None) => {
+                    let vm_initializer_for_new_range = VMInitializer::FillZeros();
+                    let mmap_opts = VMMapOptionsBuilder::default()
+                        .size(new_size - old_size)
+                        .addr(VMMapAddr::Need(old_range.end()))
+                        .perms(perms)
+                        .initializer(vm_initializer_for_new_range)
+                        .build()?;
+                    let ret_addr = Some(old_addr);
+                    (Some(mmap_opts), ret_addr)
+                }
+                (MRemapFlags::None, SizeType::Growing, Some((backed_file, offset))) => {
+                    // Update writeback file offset
+                    let new_writeback_file =
+                        Some((backed_file.clone(), offset + containing_vma.size()));
+                    let vm_initializer_for_new_range = VMInitializer::LoadFromFile {
+                        file: backed_file.clone(),
+                        offset: offset + containing_vma.size(), // file-backed mremap should start from the end of previous mmap/mremap file
+                    };
+                    let mmap_opts = VMMapOptionsBuilder::default()
+                        .size(new_size - old_size)
+                        .addr(VMMapAddr::Need(old_range.end()))
+                        .perms(perms)
+                        .initializer(vm_initializer_for_new_range)
+                        .writeback_file(new_writeback_file)
+                        .build()?;
+                    let ret_addr = Some(old_addr);
+                    (Some(mmap_opts), ret_addr)
+                }
+                (MRemapFlags::MayMove, SizeType::Growing, None) => {
+                    let prefered_new_range =
+                        VMRange::new_with_size(old_addr + old_size, new_size - old_size)?;
+                    if self.is_free_range(&prefered_new_range) {
+                        // Don't need to move the old range
+                        let vm_initializer_for_new_range = VMInitializer::FillZeros();
+                        let mmap_ops = VMMapOptionsBuilder::default()
+                            .size(prefered_new_range.size())
+                            .addr(VMMapAddr::Need(prefered_new_range.start()))
+                            .perms(perms)
+                            .initializer(vm_initializer_for_new_range)
+                            .build()?;
+                        (Some(mmap_ops), Some(old_addr))
+                    } else {
+                        // Need to move old range to a new range and init the new range
+                        let vm_initializer_for_new_range =
+                            VMInitializer::CopyFrom { range: old_range };
+                        let mmap_ops = VMMapOptionsBuilder::default()
+                            .size(new_size)
+                            .addr(VMMapAddr::Any)
+                            .perms(perms)
+                            .initializer(vm_initializer_for_new_range)
+                            .build()?;
+                        // Cannot determine the returned address for now, which can only be obtained after calling mmap
+                        let ret_addr = None;
+                        (Some(mmap_ops), ret_addr)
+                    }
+                }
+                (MRemapFlags::MayMove, SizeType::Growing, Some((backed_file, offset))) => {
+                    let prefered_new_range =
+                        VMRange::new_with_size(old_addr + old_size, new_size - old_size)?;
+                    if self.is_free_range(&prefered_new_range) {
+                        // Don't need to move the old range
+                        let vm_initializer_for_new_range = VMInitializer::LoadFromFile {
+                            file: backed_file.clone(),
+                            offset: offset + containing_vma.size(), // file-backed mremap should start from the end of previous mmap/mremap file
+                        };
+                        // Write back file should start from new offset
+                        let new_writeback_file =
+                            Some((backed_file.clone(), offset + containing_vma.size()));
+                        let mmap_ops = VMMapOptionsBuilder::default()
+                            .size(prefered_new_range.size())
+                            .addr(VMMapAddr::Need(prefered_new_range.start()))
+                            .perms(perms)
+                            .initializer(vm_initializer_for_new_range)
+                            .writeback_file(new_writeback_file)
+                            .build()?;
+                        (Some(mmap_ops), Some(old_addr))
+                    } else {
+                        // Need to move old range to a new range and init the new range
+                        let vm_initializer_for_new_range = {
+                            let copy_end = containing_vma.end();
+                            let copy_range = VMRange::new(old_range.start(), copy_end)?;
+                            let reread_file_start_offset = copy_end - containing_vma.start();
+                            VMInitializer::CopyOldAndReadNew {
+                                old_range: copy_range,
+                                file: backed_file.clone(),
+                                offset: reread_file_start_offset,
+                            }
+                        };
+                        let new_writeback_file = Some((backed_file.clone(), *offset));
+                        let mmap_ops = VMMapOptionsBuilder::default()
+                            .size(new_size)
+                            .addr(VMMapAddr::Any)
+                            .perms(perms)
+                            .initializer(vm_initializer_for_new_range)
+                            .writeback_file(new_writeback_file)
+                            .build()?;
+                        // Cannot determine the returned address for now, which can only be obtained after calling mmap
+                        let ret_addr = None;
+                        (Some(mmap_ops), ret_addr)
+                    }
+                }
+                (MRemapFlags::FixedAddr(new_addr), _, None) => {
+                    let vm_initializer_for_new_range =
+                        { VMInitializer::CopyFrom { range: old_range } };
+                    let mmap_opts = VMMapOptionsBuilder::default()
+                        .size(new_size)
+                        .addr(VMMapAddr::Force(new_addr))
+                        .perms(perms)
+                        .initializer(vm_initializer_for_new_range)
+                        .build()?;
+                    let ret_addr = Some(new_addr);
+                    (Some(mmap_opts), ret_addr)
+                }
+                (MRemapFlags::FixedAddr(new_addr), _, Some((backed_file, offset))) => {
+                    let vm_initializer_for_new_range = {
+                        let copy_end = containing_vma.end();
+                        let copy_range = VMRange::new(old_range.start(), copy_end)?;
+                        let reread_file_start_offset = copy_end - containing_vma.start();
+                        VMInitializer::CopyOldAndReadNew {
+                            old_range: copy_range,
+                            file: backed_file.clone(),
+                            offset: reread_file_start_offset,
+                        }
+                    };
+                    let new_writeback_file = Some((backed_file.clone(), *offset));
+                    let mmap_opts = VMMapOptionsBuilder::default()
+                        .size(new_size)
+                        .addr(VMMapAddr::Force(new_addr))
+                        .perms(perms)
+                        .initializer(vm_initializer_for_new_range)
+                        .writeback_file(new_writeback_file)
+                        .build()?;
+                    let ret_addr = Some(new_addr);
+                    (Some(mmap_opts), ret_addr)
+                }
+                _ => (None, Some(old_addr)),
+            };
+
+            let need_munmap = match (flags, size_type) {
+                (MRemapFlags::None, SizeType::Shrinking)
+                | (MRemapFlags::MayMove, SizeType::Shrinking) => {
+                    let unmap_addr = old_addr + new_size;
+                    let unmap_size = old_size - new_size;
+                    Some((unmap_addr, unmap_size))
+                }
+                (MRemapFlags::MayMove, SizeType::Growing) => {
+                    if ret_addr.is_none() {
+                        // We must need to do mmap. Thus unmap the old range
+                        Some((old_addr, old_size))
+                    } else {
+                        // We must choose to reuse the old range. Thus, no need to unmap
+                        None
+                    }
+                }
+                (MRemapFlags::FixedAddr(new_addr), _) => {
+                    let new_range = VMRange::new_with_size(new_addr, new_size)?;
+                    if new_range.overlap_with(&old_range) {
+                        return_errno!(EINVAL, "new range cannot overlap with the old one");
+                    }
+                    Some((old_addr, old_size))
+                }
+                _ => None,
+            };
+
+            // Perform mmap and munmap if needed
+            if let Some(mmap_options) = need_mmap {
+                let mmap_addr = self.mmap(&mmap_options)?;
+
+                if ret_addr.is_none() {
+                    ret_addr = Some(mmap_addr);
+                }
+            }
+            if let Some((addr, size)) = need_munmap {
+                self.munmap(addr, size).expect("never fail");
+            }
+
+            debug_assert!(ret_addr.is_some());
+            Ok(ret_addr.unwrap())
+        }
+    }
+
+    pub fn mprotect(&mut self, addr: usize, size: usize, new_perms: VMPerms) -> Result<()> {
+        let protect_range = VMRange::new_with_size(addr, size)?;
+        let bound = protect_range.start();
+        let mut containing_vmas = self.vmas.upper_bound_mut(Bound::Included(&bound));
+        if containing_vmas.is_null() {
+            return_errno!(ENOMEM, "invalid range");
+        }
+        let current_pid = current!().process().pid();
+
+        // If a mprotect range is not a subrange of one vma, it must be subrange of multiple connecting vmas.
+        while !containing_vmas.is_null()
+            && containing_vmas.get().unwrap().vma().start() <= protect_range.end()
+        {
+            let mut containing_vma = containing_vmas.get().unwrap().vma().clone();
+            if containing_vma.pid() != current_pid {
+                containing_vmas.move_next();
+                continue;
+            }
+
+            let old_perms = containing_vma.perms();
+            if new_perms == old_perms {
+                containing_vmas.move_next();
+                continue;
+            }
+
+            let intersection_vma = match containing_vma.intersect(&protect_range) {
+                None => {
+                    containing_vmas.move_next();
+                    continue;
+                }
+                Some(intersection_vma) => intersection_vma,
+            };
+
+            if intersection_vma.range() == containing_vma.range() {
+                // The whole containing_vma is mprotected
+                containing_vma.set_perms(new_perms);
+                VMPerms::apply_perms(&containing_vma, containing_vma.perms());
+                warn!("containing_vma = {:?}", containing_vma);
+                containing_vmas.replace_with(VMAObj::new_vma_obj(containing_vma));
+                containing_vmas.move_next();
+                continue;
+            } else {
+                // A subrange of containing_vma is mprotected
+                debug_assert!(containing_vma.is_superset_of(&intersection_vma));
+                let mut remain_vmas = containing_vma.subtract(&intersection_vma);
+                match remain_vmas.len() {
+                    2 => {
+                        // The containing VMA is divided into three VMAs:
+                        // Shrinked old VMA:    [containing_vma.start,     protect_range.start)
+                        // New VMA:             [protect_range.start,      protect_range.end)
+                        // Another new vma:     [protect_range.end,        containing_vma.end)
+                        let old_end = containing_vma.end();
+                        let protect_end = protect_range.end();
+
+                        // Shrinked old VMA
+                        containing_vma.set_end(protect_range.start());
+
+                        // New VMA
+                        let new_vma = VMArea::inherits_file_from(
+                            &containing_vma,
+                            protect_range,
+                            new_perms,
+                            current_pid,
+                        );
+                        VMPerms::apply_perms(&new_vma, new_vma.perms());
+                        let new_vma = VMAObj::new_vma_obj(new_vma);
+
+                        // Another new VMA
+                        let new_vma2 = {
+                            let range = VMRange::new(protect_end, old_end).unwrap();
+                            let new_vma = VMArea::inherits_file_from(
+                                &containing_vma,
+                                range,
+                                old_perms,
+                                current_pid,
+                            );
+                            VMAObj::new_vma_obj(new_vma)
+                        };
+
+                        containing_vmas.replace_with(VMAObj::new_vma_obj(containing_vma));
+                        containing_vmas.insert(new_vma);
+                        containing_vmas.insert(new_vma2);
+                        // In this case, there is no need to check other vmas.
+                        break;
+                    }
+                    1 => {
+                        let remain_vma = remain_vmas.pop().unwrap();
+                        if remain_vma.start() == containing_vma.start() {
+                            // mprotect right side of the vma
+                            containing_vma.set_end(remain_vma.end());
+                        } else {
+                            // mprotect left side of the vma
+                            debug_assert!(remain_vma.end() == containing_vma.end());
+                            containing_vma.set_start(remain_vma.start());
+                        }
+                        let new_vma = VMArea::inherits_file_from(
+                            &containing_vma,
+                            intersection_vma.range().clone(),
+                            new_perms,
+                            current_pid,
+                        );
+                        VMPerms::apply_perms(&new_vma, new_vma.perms());
+
+                        containing_vmas.replace_with(VMAObj::new_vma_obj(containing_vma));
+                        containing_vmas.insert(VMAObj::new_vma_obj(new_vma));
+                        containing_vmas.move_next();
+                        continue;
+                    }
+                    _ => unreachable!(),
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Sync all shared, file-backed memory mappings in the given range by flushing the
+    /// memory content to its underlying file.
+    pub fn msync_by_range(&mut self, sync_range: &VMRange) -> Result<()> {
+        if !self.range().is_superset_of(sync_range) {
+            return_errno!(ENOMEM, "invalid range");
+        }
+
+        // ?FIXME: check if sync_range covers unmapped memory
+        for vma_obj in &self.vmas {
+            let vma = match vma_obj.vma().intersect(sync_range) {
+                None => continue,
+                Some(vma) => vma,
+            };
+            Self::flush_file_vma(&vma);
+        }
+        Ok(())
+    }
+
+    /// Sync all shared, file-backed memory mappings of the given file by flushing
+    /// the memory content to the file.
+    pub fn msync_by_file(&mut self, sync_file: &FileRef) {
+        for vma_obj in &self.vmas {
+            let is_same_file = |file: &FileRef| -> bool { Arc::ptr_eq(&file, &sync_file) };
+            Self::flush_file_vma_with_cond(&vma_obj.vma(), is_same_file);
+        }
+    }
+
+    /// Flush a file-backed VMA to its file. This has no effect on anonymous VMA.
+    pub fn flush_file_vma(vma: &VMArea) {
+        Self::flush_file_vma_with_cond(vma, |_| true)
+    }
+
+    /// Same as flush_vma, except that an extra condition on the file needs to satisfy.
+    pub fn flush_file_vma_with_cond<F: Fn(&FileRef) -> bool>(vma: &VMArea, cond_fn: F) {
+        let (file, file_offset) = match vma.writeback_file().as_ref() {
+            None => return,
+            Some((file_and_offset)) => file_and_offset,
+        };
+        let file_writable = file
+            .access_mode()
+            .map(|ac| ac.writable())
+            .unwrap_or_default();
+        if !file_writable {
+            return;
+        }
+        if !cond_fn(file) {
+            return;
+        }
+        file.write_at(*file_offset, unsafe { vma.as_slice() });
+    }
+
+    pub fn find_mmap_region(&self, addr: usize) -> Result<VMRange> {
+        let vma = self.vmas.upper_bound(Bound::Included(&addr));
+        if vma.is_null() {
+            return_errno!(ESRCH, "no mmap regions that contains the address");
+        }
+        let vma = vma.get().unwrap().vma();
+        if vma.pid() != current!().process().pid() || !vma.contains(addr) {
+            return_errno!(ESRCH, "no mmap regions that contains the address");
+        }
+
+        return Ok(vma.range().clone());
+    }
+
+    pub fn usage_percentage(&self) -> f32 {
+        let totol_size = self.range.size();
+        let mut used_size = 0;
+        self.vmas
+            .iter()
+            .for_each(|vma_obj| used_size += vma_obj.vma().size());
+
+        return used_size as f32 / totol_size as f32;
+    }
+
+    // Returns whether the requested range is free
+    fn is_free_range(&self, request_range: &VMRange) -> bool {
+        self.range.is_superset_of(request_range)
+            && self
+                .vmas
+                .iter()
+                .any(|vma_obj| vma_obj.vma().range().is_superset_of(request_range) == true)
+    }
+}
+
+impl Drop for ChunkManager {
+    fn drop(&mut self) {
+        assert!(self.is_empty());
+        assert!(self.free_size == self.range.size());
+        assert!(self.free_manager.free_size() == self.range.size());
+    }
+}

src/libos/src/vm/vm_layout.rs

@@ -8,7 +8,7 @@ pub struct VMLayout {
 
 impl VMLayout {
     pub fn new(size: usize, align: usize) -> Result<VMLayout> {
-        if !align.is_power_of_two() || align % PAGE_SIZE != 0 {
+        if !align.is_power_of_two() {
             return_errno!(EINVAL, "invalid layout");
         }
         Ok(VMLayout { size, align })

src/libos/src/vm/vm_perms.rs

@@ -31,6 +31,26 @@ impl VMPerms {
     pub fn is_default(&self) -> bool {
         self.bits == Self::DEFAULT.bits
     }
+
+    pub fn apply_perms(protect_range: &VMRange, perms: VMPerms) {
+        extern "C" {
+            pub fn occlum_ocall_mprotect(
+                retval: *mut i32,
+                addr: *const c_void,
+                len: usize,
+                prot: i32,
+            ) -> sgx_status_t;
+        };
+
+        unsafe {
+            let mut retval = 0;
+            let addr = protect_range.start() as *const c_void;
+            let len = protect_range.size();
+            let prot = perms.bits() as i32;
+            let sgx_status = occlum_ocall_mprotect(&mut retval, addr, len, prot);
+            assert!(sgx_status == sgx_status_t::SGX_SUCCESS && retval == 0);
+        }
+    }
 }
 
 impl Default for VMPerms {

src/libos/src/vm/vm_range.rs

@@ -1,6 +1,6 @@
 use super::*;
 
-#[derive(Clone, Copy, Default, PartialEq)]
+#[derive(Clone, Copy, Default, Eq, PartialEq, Hash)]
 pub struct VMRange {
     pub(super) start: usize,
     pub(super) end: usize,
@@ -130,7 +130,7 @@ impl VMRange {
     pub fn intersect(&self, other: &VMRange) -> Option<VMRange> {
         let intersection_start = self.start().max(other.start());
         let intersection_end = self.end().min(other.end());
-        if intersection_start > intersection_end {
+        if intersection_start >= intersection_end {
             return None;
         }
         unsafe {

src/libos/src/vm/vm_util.rs

@@ -0,0 +1,276 @@
+use super::*;
+
+// use super::vm_area::VMArea;
+// use super::free_space_manager::VMFreeSpaceManager;
+use super::vm_area::*;
+use super::vm_perms::VMPerms;
+use std::collections::BTreeSet;
+
+use intrusive_collections::rbtree::{Link, RBTree};
+use intrusive_collections::Bound;
+use intrusive_collections::RBTreeLink;
+use intrusive_collections::{intrusive_adapter, KeyAdapter};
+
+#[derive(Clone, Debug)]
+pub enum VMInitializer {
+    DoNothing(),
+    FillZeros(),
+    CopyFrom {
+        range: VMRange,
+    },
+    LoadFromFile {
+        file: FileRef,
+        offset: usize,
+    },
+    // For file-backed mremap which may move from old range to new range and read extra bytes from file
+    CopyOldAndReadNew {
+        old_range: VMRange,
+        file: FileRef,
+        offset: usize, // read file from this offset
+    },
+}
+
+impl Default for VMInitializer {
+    fn default() -> VMInitializer {
+        VMInitializer::DoNothing()
+    }
+}
+
+impl VMInitializer {
+    pub fn init_slice(&self, buf: &mut [u8]) -> Result<()> {
+        match self {
+            VMInitializer::DoNothing() => {
+                // Do nothing
+            }
+            VMInitializer::FillZeros() => {
+                for b in buf {
+                    *b = 0;
+                }
+            }
+            VMInitializer::CopyFrom { range } => {
+                let src_slice = unsafe { range.as_slice() };
+                let copy_len = min(buf.len(), src_slice.len());
+                buf[..copy_len].copy_from_slice(&src_slice[..copy_len]);
+                for b in &mut buf[copy_len..] {
+                    *b = 0;
+                }
+            }
+            VMInitializer::LoadFromFile { file, offset } => {
+                // TODO: make sure that read_at does not move file cursor
+                let len = file
+                    .read_at(*offset, buf)
+                    .cause_err(|_| errno!(EIO, "failed to init memory from file"))?;
+                for b in &mut buf[len..] {
+                    *b = 0;
+                }
+            }
+            VMInitializer::CopyOldAndReadNew {
+                old_range,
+                file,
+                offset,
+            } => {
+                // TODO: Handle old_range with non-readable subrange
+                let src_slice = unsafe { old_range.as_slice() };
+                let copy_len = src_slice.len();
+                debug_assert!(copy_len <= buf.len());
+                let read_len = buf.len() - copy_len;
+                buf[..copy_len].copy_from_slice(&src_slice[..copy_len]);
+                let len = file
+                    .read_at(*offset, &mut buf[copy_len..])
+                    .cause_err(|_| errno!(EIO, "failed to init memory from file"))?;
+                for b in &mut buf[(copy_len + len)..] {
+                    *b = 0;
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum VMMapAddr {
+    Any,          // Free to choose any address
+    Hint(usize),  // Prefer the address, but can use other address
+    Need(usize),  // Need to use the address, otherwise report error
+    Force(usize), // Force using the address by munmap first
+}
+
+impl Default for VMMapAddr {
+    fn default() -> VMMapAddr {
+        VMMapAddr::Any
+    }
+}
+
+#[derive(Builder, Debug)]
+#[builder(pattern = "owned", build_fn(skip), no_std)]
+pub struct VMMapOptions {
+    size: usize,
+    align: usize,
+    perms: VMPerms,
+    addr: VMMapAddr,
+    initializer: VMInitializer,
+    // The content of the VMA can be written back to a given file at a given offset
+    writeback_file: Option<(FileRef, usize)>,
+}
+
+// VMMapOptionsBuilder is generated automatically, except the build function
+impl VMMapOptionsBuilder {
+    pub fn build(mut self) -> Result<VMMapOptions> {
+        let size = {
+            let size = self
+                .size
+                .ok_or_else(|| errno!(EINVAL, "invalid size for mmap"))?;
+            if size == 0 {
+                return_errno!(EINVAL, "invalid size for mmap");
+            }
+            align_up(size, PAGE_SIZE)
+        };
+        let align = {
+            let align = self.align.unwrap_or(PAGE_SIZE);
+            if align == 0 || !align.is_power_of_two() {
+                return_errno!(EINVAL, "invalid size for mmap");
+            }
+            align
+        };
+        let perms = self
+            .perms
+            .ok_or_else(|| errno!(EINVAL, "perms must be given"))?;
+        let addr = {
+            let addr = self.addr.unwrap_or_default();
+            match addr {
+                // TODO: check addr + size overflow
+                VMMapAddr::Any => VMMapAddr::Any,
+                VMMapAddr::Hint(addr) => {
+                    let addr = align_down(addr, PAGE_SIZE);
+                    VMMapAddr::Hint(addr)
+                }
+                VMMapAddr::Need(addr_) | VMMapAddr::Force(addr_) => {
+                    if addr_ % align != 0 {
+                        return_errno!(EINVAL, "unaligned addr for fixed mmap");
+                    }
+                    addr
+                }
+            }
+        };
+        let initializer = match self.initializer.as_ref() {
+            Some(initializer) => initializer.clone(),
+            None => VMInitializer::default(),
+        };
+        let writeback_file = self.writeback_file.take().unwrap_or_default();
+        Ok(VMMapOptions {
+            size,
+            align,
+            perms,
+            addr,
+            initializer,
+            writeback_file,
+        })
+    }
+}
+
+impl VMMapOptions {
+    pub fn size(&self) -> &usize {
+        &self.size
+    }
+
+    pub fn addr(&self) -> &VMMapAddr {
+        &self.addr
+    }
+
+    pub fn perms(&self) -> &VMPerms {
+        &self.perms
+    }
+
+    pub fn align(&self) -> &usize {
+        &self.align
+    }
+
+    pub fn initializer(&self) -> &VMInitializer {
+        &self.initializer
+    }
+
+    pub fn writeback_file(&self) -> &Option<(FileRef, usize)> {
+        &self.writeback_file
+    }
+}
+
+#[derive(Clone, Copy, PartialEq)]
+pub enum SizeType {
+    Same,
+    Shrinking,
+    Growing,
+}
+
+impl SizeType {
+    pub fn new(old_size: &usize, new_size: &usize) -> Self {
+        if new_size == old_size {
+            SizeType::Same
+        } else if new_size < old_size {
+            SizeType::Shrinking
+        } else {
+            SizeType::Growing
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct VMRemapOptions {
+    old_addr: usize,
+    old_size: usize,
+    new_size: usize,
+    flags: MRemapFlags,
+}
+
+impl VMRemapOptions {
+    pub fn new(
+        old_addr: usize,
+        old_size: usize,
+        new_size: usize,
+        flags: MRemapFlags,
+    ) -> Result<Self> {
+        let old_addr = if old_addr % PAGE_SIZE != 0 {
+            return_errno!(EINVAL, "unaligned old address");
+        } else {
+            old_addr
+        };
+        let old_size = if old_size == 0 {
+            // TODO: support old_size is zero for shareable mapping
+            warn!("do not support old_size is zero");
+            return_errno!(EINVAL, "invalid old size");
+        } else {
+            align_up(old_size, PAGE_SIZE)
+        };
+        if let Some(new_addr) = flags.new_addr() {
+            if new_addr % PAGE_SIZE != 0 {
+                return_errno!(EINVAL, "unaligned new address");
+            }
+        }
+        let new_size = if new_size == 0 {
+            return_errno!(EINVAL, "invalid new size");
+        } else {
+            align_up(new_size, PAGE_SIZE)
+        };
+        Ok(Self {
+            old_addr,
+            old_size,
+            new_size,
+            flags,
+        })
+    }
+
+    pub fn old_addr(&self) -> usize {
+        self.old_addr
+    }
+
+    pub fn old_size(&self) -> usize {
+        self.old_size
+    }
+
+    pub fn new_size(&self) -> usize {
+        self.new_size
+    }
+
+    pub fn flags(&self) -> MRemapFlags {
+        self.flags
+    }
+}

src/pal/src/pal_api.c

@@ -239,7 +239,6 @@ int occlum_pal_destroy(void) {
     }
 
     int ret = 0;
-
     if (pal_interrupt_thread_stop() < 0) {
         ret = -1;
         PAL_WARN("Cannot stop the interrupt thread: %s", errno2str(errno));

test/mmap/main.c

@@ -47,6 +47,10 @@ static int get_a_valid_range_of_hints(size_t *hint_begin, size_t *hint_end) {
     if (big_buf == MAP_FAILED) {
         THROW_ERROR("mmap failed");
     }
+
+    // Check if munmap will clean the range
+    memset(big_buf, 0xff, big_buf_len);
+
     int ret = munmap(big_buf, big_buf_len);
     if (ret < 0) {
         THROW_ERROR("munmap failed");
@@ -1038,6 +1042,47 @@ int test_mprotect_with_non_page_aligned_size() {
     *(char *)buf = 1;
     *(char *)(buf  + PAGE_SIZE) = 1;
 
+    ret = munmap(buf, PAGE_SIZE * 2);
+    if (ret < 0) {
+        THROW_ERROR("munmap failed");
+    }
+    return 0;
+}
+
+int test_mprotect_multiple_vmas() {
+    // Create multiple VMA with PROT_NONE
+    int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+    void *buf_a = mmap((void *)HINT_BEGIN, PAGE_SIZE * 2, PROT_NONE, flags, -1, 0);
+    if (buf_a == MAP_FAILED || buf_a != (void *)HINT_BEGIN) {
+        THROW_ERROR("mmap failed");
+    }
+    void *buf_b = mmap((void *)(HINT_BEGIN + 2 * PAGE_SIZE), PAGE_SIZE, PROT_NONE, flags, -1,
+                       0);
+    if (buf_b == MAP_FAILED || buf_b != (void *)(HINT_BEGIN + 2 * PAGE_SIZE)) {
+        THROW_ERROR("mmap failed");
+    }
+    void *buf_c = mmap((void *)(HINT_BEGIN + 3 * PAGE_SIZE), PAGE_SIZE * 2, PROT_NONE, flags,
+                       -1, 0);
+    if (buf_c == MAP_FAILED || buf_c != (void *)(HINT_BEGIN + 3 * PAGE_SIZE)) {
+        THROW_ERROR("mmap failed");
+    }
+
+    // Set a part of the ranges to read-write
+    int ret = mprotect(buf_a + PAGE_SIZE, 3 * PAGE_SIZE, PROT_READ | PROT_WRITE);
+    if (ret < 0) {
+        THROW_ERROR("mprotect multiple vmas failed");
+    }
+
+    // Check if these ranges are writable
+    *(char *)(buf_a + PAGE_SIZE) = 1;
+    *(char *)(buf_b) = 1;
+    *(char *)(buf_c) = 1;
+
+    ret = munmap(buf_a, PAGE_SIZE * 5);
+    if (ret < 0) {
+        THROW_ERROR("munmap multiple vmas failed");
+    }
+
     return 0;
 }
 
@@ -1231,11 +1276,13 @@ static test_case_t test_cases[] = {
     TEST_CASE(test_munmap_with_null_addr),
     TEST_CASE(test_munmap_with_zero_len),
     TEST_CASE(test_munmap_with_non_page_aligned_len),
+#ifdef MREMAP_SUPPORTED
     TEST_CASE(test_mremap),
     TEST_CASE(test_mremap_subrange),
     TEST_CASE(test_mremap_with_fixed_addr),
     TEST_CASE(test_file_backed_mremap),
     TEST_CASE(test_file_backed_mremap_mem_may_move),
+#endif
     TEST_CASE(test_mprotect_once),
     TEST_CASE(test_mprotect_twice),
     TEST_CASE(test_mprotect_triple),
@@ -1243,6 +1290,7 @@ static test_case_t test_cases[] = {
     TEST_CASE(test_mprotect_with_invalid_addr),
     TEST_CASE(test_mprotect_with_invalid_prot),
     TEST_CASE(test_mprotect_with_non_page_aligned_size),
+    TEST_CASE(test_mprotect_multiple_vmas),
 };
 
 int main() {