Enable MPX

src/libos/src/lib.rs

@@ -21,7 +21,6 @@ extern crate lazy_static;
 use std::ffi::CStr; // a borrowed C string
 use std::backtrace::{self, PrintFormat};
 use std::panic;
-
 use sgx_types::*;
 use sgx_trts::libc;
 
@@ -32,27 +31,28 @@ mod fs;
 mod process;
 mod syscall;
 mod vm;
+mod util;
+
+use prelude::*;
 
 /// Export system calls
 pub use syscall::*;
 
+// TODO: return meaningful exit code
 #[no_mangle]
 pub extern "C" fn libos_boot(path_buf: *const i8) -> i32 {
     let path_str = unsafe {
         CStr::from_ptr(path_buf).to_string_lossy().into_owned()
     };
-    println!("LibOS boots: {}", path_str);
-
     let _ = backtrace::enable_backtrace("libocclum.signed.so", PrintFormat::Short);
     panic::catch_unwind(||{
         backtrace::__rust_begin_short_backtrace(||{
-            let argv = std::vec::Vec::new();
-            let envp = std::vec::Vec::new();
-            process::do_spawn(&path_str, &argv, &envp);
+            match do_boot(&path_str) {
+                Ok(()) => 0,
+                Err(err) => err.errno.as_retval() /* Normal error */,
+            }
         })
-    }).ok();
-
-    0
+    }).unwrap_or(-1 /* Fatal error */)
 }
 
 #[no_mangle]
@@ -60,10 +60,28 @@ pub extern "C" fn libos_run() -> i32 {
     let _ = backtrace::enable_backtrace("libocclum.signed.so", PrintFormat::Short);
     panic::catch_unwind(||{
         backtrace::__rust_begin_short_backtrace(||{
-            let _ = process::run_task();
+            match do_run() {
+                Ok(()) => 0,
+                Err(err) => err.errno.as_retval() /* Normal error */,
+            }
         })
-    }).ok();
-
-    0
+    }).unwrap_or(-1 /* Fatal error */)
 }
 
+
+// TODO: make sure do_boot can only be called once
+fn do_boot(path_str: &str) -> Result<(), Error> {
+    util::mpx_enable()?;
+
+    let argv = std::vec::Vec::new();
+    let envp = std::vec::Vec::new();
+    process::do_spawn(&path_str, &argv, &envp)?;
+
+    Ok(())
+}
+
+// TODO: make sure do_run() cannot be called before do_boot()
+fn do_run() -> Result<(), Error> {
+    process::run_task()?;
+    Ok(())
+}

src/libos/src/util/mod.rs

@@ -0,0 +1,5 @@
+use prelude::*;
+
+pub use self::mpx_util::{*};
+
+mod mpx_util;

src/libos/src/util/mpx_util.c

@@ -0,0 +1,100 @@
+#include "mpx_util.h"
+#include <string.h>
+#include <stdint.h>
+
+/*
+ * Define data structures for the part of XSAVE area that are relevant
+ * to enabling MPX
+ */
+
+typedef struct {
+    uint64_t xstate_bv;
+    uint64_t __irrelevant[2];
+    uint64_t __reserved[5];
+} __attribute__ ((packed)) xsave_header_t;
+
+typedef struct {
+    uint64_t __irrelevant[8];
+} __attribute__ ((packed)) bndreg_t ;
+
+typedef struct {
+    uint64_t enable: 1;
+    uint64_t bndpreserve: 1;
+    uint64_t __reserved: 10;
+    uint64_t __irrelevant: 52;
+} __attribute__ ((packed)) bndcfgu_t;
+
+typedef struct {
+    bndcfgu_t bndcfgu;
+    uint64_t __irrelevant;
+} __attribute__((packed)) bndcsr_t;
+
+typedef struct {
+    uint8_t __irrelevant0[512];
+    xsave_header_t header;
+    uint8_t __irrelevant1[256];
+    uint8_t __irrelevant2[128];
+    bndreg_t bndreg;
+    bndcsr_t bndcsr;
+} __attribute__ ((packed, __aligned__(64))) xsave_area_t ;
+
+
+/*
+ * Restore the state components of CPU specified in rfbm from xsave_area.
+ *
+ * rfbm is the requested-feature bitmap, whose bits specifies which state
+ * components are to restored by this instruction.
+ */
+static void xrstor(xsave_area_t* xsave_area, uint64_t rfbm) {
+    uint32_t rfbm_l= rfbm;
+    uint32_t rfbm_h = rfbm >> 32;
+
+#define REX_PREFIX  "0x48, "
+#define XRSTOR64    REX_PREFIX "0x0f,0xae,0x2f "
+
+    __asm__ __volatile__ (
+        ".byte " XRSTOR64 "\n\t"
+            :
+            : "D" (xsave_area), "m" (*xsave_area), "a" (rfbm), "d" (rfbm)
+            : "memory");
+}
+
+/* The state component bitmaps for MPX
+ *
+ * The state component 3 (i.e., bit 3) is BNDREG state, which consists of the
+ * four MPX bound registers BND0-BND3.
+ *
+ * The state component 4 (i.e., bit 4) is BNDCSR state, which consists of the
+ * one MPX configuration register BNDCFGU and one MPX status register
+ * BNDSTATUS.
+ * */
+#define MPX_BNDREG_COMPONENT_MASK       (0x08UL)
+#define MPX_BNDCSR_COMPONENT_MASK       (0x10UL)
+#define MPX_ALL_COMPONENT_MASK          (MPX_BNDCSR_COMPONENT_MASK | \
+                                         MPX_BNDREG_COMPONENT_MASK)
+
+int __mpx_enable(void) {
+    xsave_area_t xsave_area;
+    memset(&xsave_area, 0, sizeof(xsave_area));
+
+    /* Initialize MPX states
+     *
+     * xrestor initializes state component i if rfbm[i] = 1 and
+     * xsave_area.header.xstate_bv[i] = 0 */
+    uint64_t rfbm = MPX_ALL_COMPONENT_MASK;
+    xrstor(&xsave_area, rfbm);
+
+    /* xrestor updates state component i if rfbm[i] = 1 and
+     * xsave_area.header.xstate_bv[i] = 1 */
+    xsave_area.header.xstate_bv = MPX_BNDCSR_COMPONENT_MASK;
+    /* Set enable bit to 1 to enable MPX */
+    xsave_area.bndcsr.bndcfgu.enable = 1;
+    /* Set bndpreserve bit to 1 so that BND0-BND3 remain unchanged upon
+     * control flow transfer instructions (e.g., call, jmp, etc.). */
+    xsave_area.bndcsr.bndcfgu.bndpreserve = 1;
+    /* Set BNDCSR state component so that MPX is enabled. */
+    rfbm = MPX_BNDCSR_COMPONENT_MASK;
+    xrstor(&xsave_area, rfbm);
+
+    return 0;
+}

src/libos/src/util/mpx_util.h

@@ -0,0 +1,34 @@
+#ifndef __MPX_UTIL__
+#define __MPX_UTIL__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Enable the use of MPX bound registers bnd0-bnd3 and bound instructions
+ * bndmk, bndcl and bndcu. */
+int __mpx_enable(void);
+
+/* Make a new bound in bnd<i>*/
+void __mpx_bndmk0(unsigned long base, unsigned long size);
+void __mpx_bndmk1(unsigned long base, unsigned long size);
+void __mpx_bndmk2(unsigned long base, unsigned long size);
+void __mpx_bndmk3(unsigned long base, unsigned long size);
+
+/* Check x against the lower bound of bnd<i>*/
+void __mpx_bndcl0(unsigned long x);
+void __mpx_bndcl1(unsigned long x);
+void __mpx_bndcl2(unsigned long x);
+void __mpx_bndcl3(unsigned long x);
+
+/* Check x against the upper bound of bnd<i> */
+void __mpx_bndcu0(unsigned long x);
+void __mpx_bndcu1(unsigned long x);
+void __mpx_bndcu2(unsigned long x);
+void __mpx_bndcu3(unsigned long x);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __MPX_UTIL__ */

src/libos/src/util/mpx_util.rs

@@ -0,0 +1,66 @@
+use super::*;
+
+pub fn mpx_enable() -> Result<(), Error> {
+    match unsafe { __mpx_enable () } {
+        0 => { Ok(()) }
+        _ => { errno!(EPERM, "MPX cannot be enabled") }
+    }
+}
+
+pub enum MpxReg {
+    BND0,
+    BND1,
+    BND2,
+    BND3,
+}
+
+pub fn mpx_bndmk(bndreg: MpxReg, base: usize, size: usize) -> Result<(), Error> {
+    /* Check whether the upper bound overflows the max of 64-bit */
+    if base.checked_add(size).is_none() {
+        return errno!(ERANGE, "Upper bound overflows");
+    }
+
+    match bndreg {
+        MpxReg::BND0 => unsafe { __mpx_bndmk0(base, size) },
+        MpxReg::BND1 => unsafe { __mpx_bndmk1(base, size) },
+        MpxReg::BND2 => unsafe { __mpx_bndmk2(base, size) },
+        MpxReg::BND3 => unsafe { __mpx_bndmk3(base, size) },
+    }
+    Ok(())
+}
+
+pub fn mpx_bndcl(bndreg: MpxReg, addr: usize) {
+    match bndreg {
+        MpxReg::BND0 => unsafe { __mpx_bndcl0(addr) },
+        MpxReg::BND1 => unsafe { __mpx_bndcl1(addr) },
+        MpxReg::BND2 => unsafe { __mpx_bndcl2(addr) },
+        MpxReg::BND3 => unsafe { __mpx_bndcl3(addr) },
+    }
+}
+
+pub fn mpx_bndcu(bndreg: MpxReg, addr: usize) {
+    match bndreg {
+        MpxReg::BND0 => unsafe { __mpx_bndcu0(addr) },
+        MpxReg::BND1 => unsafe { __mpx_bndcu1(addr) },
+        MpxReg::BND2 => unsafe { __mpx_bndcu2(addr) },
+        MpxReg::BND3 => unsafe { __mpx_bndcu3(addr) },
+    }
+}
+
+
+extern {
+    // See mpx_util.h
+    fn __mpx_enable() -> i32;
+    fn __mpx_bndmk0(base: usize, size: usize);
+    fn __mpx_bndmk1(base: usize, size: usize);
+    fn __mpx_bndmk2(base: usize, size: usize);
+    fn __mpx_bndmk3(base: usize, size: usize);
+    fn __mpx_bndcl0(x: usize);
+    fn __mpx_bndcl1(x: usize);
+    fn __mpx_bndcl2(x: usize);
+    fn __mpx_bndcl3(x: usize);
+    fn __mpx_bndcu0(x: usize);
+    fn __mpx_bndcu1(x: usize);
+    fn __mpx_bndcu2(x: usize);
+    fn __mpx_bndcu3(x: usize);
+}

src/libos/src/util/mpx_util_x86-64.S

@@ -0,0 +1,81 @@
+    .file "mpx_util_x86-64.S"
+
+/* For bnd0 */
+
+    .global __mpx_bndmk0
+    .type __mpx_bndmk0, @function
+__mpx_bndmk0:
+    bndmk (%rdi, %rsi, 1), %bnd0
+    ret
+
+    .global __mpx_bndcl0
+    .type __mpx_bndcl0, @function
+__mpx_bndcl0:
+    bndcl %rdi, %bnd0
+    ret
+
+    .global __mpx_bndcu0
+    .type __mpx_bndcu0, @function
+__mpx_bndcu0:
+    bndcu %rdi, %bnd0
+    ret
+
+/* For bnd1 */
+
+    .global __mpx_bndmk1
+    .type __mpx_bndmk1, @function
+__mpx_bndmk1:
+    bndmk (%rdi, %rsi, 1), %bnd1
+    ret
+
+    .global __mpx_bndcl1
+    .type __mpx_bndcl1, @function
+__mpx_bndcl1:
+    bndcl %rdi, %bnd1
+    ret
+
+    .global __mpx_bndcu1
+    .type __mpx_bndcu1, @function
+__mpx_bndcu1:
+    bndcu %rdi, %bnd1
+    ret
+
+/* For bnd2 */
+
+    .global __mpx_bndmk2
+    .type __mpx_bndmk2, @function
+__mpx_bndmk2:
+    bndmk (%rdi, %rsi, 1), %bnd2
+    ret
+
+    .global __mpx_bndcl2
+    .type __mpx_bndcl2, @function
+__mpx_bndcl2:
+    bndcl %rdi, %bnd2
+    ret
+
+    .global __mpx_bndcu2
+    .type __mpx_bndcu2, @function
+__mpx_bndcu2:
+    bndcu %rdi, %bnd2
+    ret
+
+/* For bnd3 */
+
+    .global __mpx_bndmk3
+    .type __mpx_bndmk3, @function
+__mpx_bndmk3:
+    bndmk (%rdi, %rsi, 1), %bnd3
+    ret
+
+    .global __mpx_bndcl3
+    .type __mpx_bndcl3, @function
+__mpx_bndcl3:
+    bndcl %rdi, %bnd3
+    ret
+
+    .global __mpx_bndcu3
+    .type __mpx_bndcu3, @function
+__mpx_bndcu3:
+    bndcu %rdi, %bnd3
+    ret