From 5963b70b97a9ba9d80863180f0f635ddd52e871f Mon Sep 17 00:00:00 2001
From: "Hui, Chunyang" <sanqian.hcy@antfin.com>
Date: Wed, 21 Jul 2021 07:18:03 +0000
Subject: [PATCH] Don't allocate extra memory if already aligned

---
 src/libos/src/vm/process_vm.rs    | 6 +-----
 src/libos/src/vm/user_space_vm.rs | 3 ++-
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/src/libos/src/vm/process_vm.rs b/src/libos/src/vm/process_vm.rs
index 3887ef78..adde03a2 100644
--- a/src/libos/src/vm/process_vm.rs
+++ b/src/libos/src/vm/process_vm.rs
@@ -108,11 +108,7 @@ 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 = {
-            // TODO: ensure alignment through USER_SPACE_VM_MANAGER, not by
-            // preserving extra space for alignment
-            USER_SPACE_VM_MANAGER.alloc(process_layout.align() + process_layout.size())?
-        };
+        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())?;
diff --git a/src/libos/src/vm/user_space_vm.rs b/src/libos/src/vm/user_space_vm.rs
index 7e01a1c5..c2466ff0 100644
--- a/src/libos/src/vm/user_space_vm.rs
+++ b/src/libos/src/vm/user_space_vm.rs
@@ -16,7 +16,8 @@ impl UserSpaceVMManager {
         }
     }
 
-    pub fn alloc(&self, size: usize) -> Result<UserSpaceVMRange> {
+    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);
             let perm = MemPerm::READ | MemPerm::WRITE;