chore: support newer rust versions (probestack)

lib/vm/Cargo.toml

@@ -42,6 +42,7 @@ windows-sys = { version = "0.59", features = ["Win32_System_Diagnostics_Debug",
 
 [build-dependencies]
 cc = "1.0"
+rustversion = "1.0"
 
 [badges]
 maintenance = { status = "actively-developed" }

lib/vm/build.rs

@@ -0,0 +1,10 @@
+#[rustversion::since(1.89)]
+fn main() {
+    println!("cargo:rustc-cfg=missing_rust_probestack");
+    println!("cargo:rustc-check-cfg=cfg(missing_rust_probestack)");
+}
+
+#[rustversion::before(1.89)]
+fn main() {
+    println!("cargo:rustc-check-cfg=cfg(missing_rust_probestack)");
+}

lib/vm/src/compiler_builtins.rs

@@ -0,0 +1,339 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module defines the `__rust_probestack` intrinsic which is used in the
+//! implementation of "stack probes" on certain platforms.
+//!
+//! The purpose of a stack probe is to provide a static guarantee that if a
+//! thread has a guard page then a stack overflow is guaranteed to hit that
+//! guard page. If a function did not have a stack probe then there's a risk of
+//! having a stack frame *larger* than the guard page, so a function call could
+//! skip over the guard page entirely and then later hit maybe the heap or
+//! another thread, possibly leading to security vulnerabilities such as [The
+//! Stack Clash], for example.
+//!
+//! [The Stack Clash]: https://blog.qualys.com/securitylabs/2017/06/19/the-stack-clash
+//!
+//! The `__rust_probestack` is called in the prologue of functions whose stack
+//! size is larger than the guard page, for example larger than 4096 bytes on
+//! x86. This function is then responsible for "touching" all pages relevant to
+//! the stack to ensure that that if any of them are the guard page we'll hit
+//! them guaranteed.
+//!
+//! The precise ABI for how this function operates is defined by LLVM. There's
+//! no real documentation as to what this is, so you'd basically need to read
+//! the LLVM source code for reference. Often though the test cases can be
+//! illuminating as to the ABI that's generated, or just looking at the output
+//! of `llc`.
+//!
+//! Note that `#[naked]` is typically used here for the stack probe because the
+//! ABI corresponds to no actual ABI.
+//!
+//! Finally it's worth noting that at the time of this writing LLVM only has
+//! support for stack probes on x86 and x86_64. There's no support for stack
+//! probes on any other architecture like ARM or PowerPC64. LLVM I'm sure would
+//! be more than welcome to accept such a change!
+// Windows and Cygwin already has builtins to do this.
+#![cfg(not(any(windows, target_os = "cygwin")))]
+// We only define stack probing for these architectures today.
+#![cfg(any(target_arch = "x86_64", target_arch = "x86"))]
+
+// SAFETY: defined in this module.
+// FIXME(extern_custom): the ABI is not correct.
+unsafe extern "C" {
+    pub fn __rust_probestack();
+}
+
+// A wrapper for our implementation of __rust_probestack, which allows us to
+// keep the assembly inline while controlling all CFI directives in the assembly
+// emitted for the function.
+//
+// This is the ELF version.
+#[cfg(not(any(target_vendor = "apple", target_os = "uefi")))]
+macro_rules! define_rust_probestack {
+    ($body: expr) => {
+        concat!(
+            "
+            .pushsection .text.__rust_probestack
+            .globl __rust_probestack
+            .type  __rust_probestack, @function
+            .hidden __rust_probestack
+        __rust_probestack:
+            ",
+            $body,
+            "
+            .size __rust_probestack, . - __rust_probestack
+            .popsection
+            "
+        )
+    };
+}
+
+#[cfg(all(target_os = "uefi", target_arch = "x86_64"))]
+macro_rules! define_rust_probestack {
+    ($body: expr) => {
+        concat!(
+            "
+            .globl __rust_probestack
+        __rust_probestack:
+            ",
+            $body
+        )
+    };
+}
+
+// Same as above, but for Mach-O. Note that the triple underscore
+// is deliberate
+#[cfg(target_vendor = "apple")]
+macro_rules! define_rust_probestack {
+    ($body: expr) => {
+        concat!(
+            "
+            .globl ___rust_probestack
+        ___rust_probestack:
+            ",
+            $body
+        )
+    };
+}
+
+// In UEFI x86 arch, triple underscore is deliberate.
+#[cfg(all(target_os = "uefi", target_arch = "x86"))]
+macro_rules! define_rust_probestack {
+    ($body: expr) => {
+        concat!(
+            "
+            .globl ___rust_probestack
+        ___rust_probestack:
+            ",
+            $body
+        )
+    };
+}
+
+// Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
+// ensuring that if any pages are unmapped we'll make a page fault.
+//
+// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
+// it does not actually match `extern "C"`.
+//
+// The ABI here is that the stack frame size is located in `%rax`. Upon
+// return we're not supposed to modify `%rsp` or `%rax`.
+//
+// Any changes to this function should be replicated to the SGX version below.
+#[cfg(all(
+    target_arch = "x86_64",
+    not(all(target_env = "sgx", target_vendor = "fortanix"))
+))]
+core::arch::global_asm!(
+    define_rust_probestack!(
+        "
+    .cfi_startproc
+    pushq  %rbp
+    .cfi_adjust_cfa_offset 8
+    .cfi_offset %rbp, -16
+    movq   %rsp, %rbp
+    .cfi_def_cfa_register %rbp
+    mov    %rax,%r11        // duplicate %rax as we're clobbering %r11
+    // Main loop, taken in one page increments. We're decrementing rsp by
+    // a page each time until there's less than a page remaining. We're
+    // guaranteed that this function isn't called unless there's more than a
+    // page needed.
+    //
+    // Note that we're also testing against `8(%rsp)` to account for the 8
+    // bytes pushed on the stack orginally with our return address. Using
+    // `8(%rsp)` simulates us testing the stack pointer in the caller's
+    // context.
+    // It's usually called when %rax >= 0x1000, but that's not always true.
+    // Dynamic stack allocation, which is needed to implement unsized
+    // rvalues, triggers stackprobe even if %rax < 0x1000.
+    // Thus we have to check %r11 first to avoid segfault.
+    cmp    $0x1000,%r11
+    jna    3f
+2:
+    sub    $0x1000,%rsp
+    test   %rsp,8(%rsp)
+    sub    $0x1000,%r11
+    cmp    $0x1000,%r11
+    ja     2b
+3:
+    // Finish up the last remaining stack space requested, getting the last
+    // bits out of r11
+    sub    %r11,%rsp
+    test   %rsp,8(%rsp)
+    // Restore the stack pointer to what it previously was when entering
+    // this function. The caller will readjust the stack pointer after we
+    // return.
+    add    %rax,%rsp
+    leave
+    .cfi_def_cfa_register %rsp
+    .cfi_adjust_cfa_offset -8
+    ret
+    .cfi_endproc
+    "
+    ),
+    options(att_syntax)
+);
+
+// This function is the same as above, except that some instructions are
+// [manually patched for LVI].
+//
+// [manually patched for LVI]: https://software.intel.com/security-software-guidance/insights/deep-dive-load-value-injection#specialinstructions
+#[cfg(all(
+    target_arch = "x86_64",
+    all(target_env = "sgx", target_vendor = "fortanix")
+))]
+core::arch::global_asm!(
+    define_rust_probestack!(
+        "
+    .cfi_startproc
+    pushq  %rbp
+    .cfi_adjust_cfa_offset 8
+    .cfi_offset %rbp, -16
+    movq   %rsp, %rbp
+    .cfi_def_cfa_register %rbp
+    mov    %rax,%r11        // duplicate %rax as we're clobbering %r11
+    // Main loop, taken in one page increments. We're decrementing rsp by
+    // a page each time until there's less than a page remaining. We're
+    // guaranteed that this function isn't called unless there's more than a
+    // page needed.
+    //
+    // Note that we're also testing against `8(%rsp)` to account for the 8
+    // bytes pushed on the stack orginally with our return address. Using
+    // `8(%rsp)` simulates us testing the stack pointer in the caller's
+    // context.
+    // It's usually called when %rax >= 0x1000, but that's not always true.
+    // Dynamic stack allocation, which is needed to implement unsized
+    // rvalues, triggers stackprobe even if %rax < 0x1000.
+    // Thus we have to check %r11 first to avoid segfault.
+    cmp    $0x1000,%r11
+    jna    3f
+2:
+    sub    $0x1000,%rsp
+    test   %rsp,8(%rsp)
+    sub    $0x1000,%r11
+    cmp    $0x1000,%r11
+    ja     2b
+3:
+    // Finish up the last remaining stack space requested, getting the last
+    // bits out of r11
+    sub    %r11,%rsp
+    test   %rsp,8(%rsp)
+    // Restore the stack pointer to what it previously was when entering
+    // this function. The caller will readjust the stack pointer after we
+    // return.
+    add    %rax,%rsp
+    leave
+    .cfi_def_cfa_register %rsp
+    .cfi_adjust_cfa_offset -8
+    pop %r11
+    lfence
+    jmp *%r11
+    .cfi_endproc
+    "
+    ),
+    options(att_syntax)
+);
+
+#[cfg(all(target_arch = "x86", not(target_os = "uefi")))]
+// This is the same as x86_64 above, only translated for 32-bit sizes. Note
+// that on Unix we're expected to restore everything as it was, this
+// function basically can't tamper with anything.
+//
+// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
+// it does not actually match `extern "C"`.
+//
+// The ABI here is the same as x86_64, except everything is 32-bits large.
+core::arch::global_asm!(
+    define_rust_probestack!(
+        "
+    .cfi_startproc
+    push   %ebp
+    .cfi_adjust_cfa_offset 4
+    .cfi_offset %ebp, -8
+    mov    %esp, %ebp
+    .cfi_def_cfa_register %ebp
+    push   %ecx
+    mov    %eax,%ecx
+    cmp    $0x1000,%ecx
+    jna    3f
+2:
+    sub    $0x1000,%esp
+    test   %esp,8(%esp)
+    sub    $0x1000,%ecx
+    cmp    $0x1000,%ecx
+    ja     2b
+3:
+    sub    %ecx,%esp
+    test   %esp,8(%esp)
+    add    %eax,%esp
+    pop    %ecx
+    leave
+    .cfi_def_cfa_register %esp
+    .cfi_adjust_cfa_offset -4
+    ret
+    .cfi_endproc
+    "
+    ),
+    options(att_syntax)
+);
+
+#[cfg(all(target_arch = "x86", target_os = "uefi"))]
+// UEFI target is windows like target. LLVM will do _chkstk things like windows.
+// probestack function will also do things like _chkstk in MSVC.
+// So we need to sub %ax %sp in probestack when arch is x86.
+//
+// FIXME(abi_custom): This function is unsafe because it uses a custom ABI,
+// it does not actually match `extern "C"`.
+//
+// REF: Rust commit(74e80468347)
+// rust\src\llvm-project\llvm\lib\Target\X86\X86FrameLowering.cpp: 805
+// Comments in LLVM:
+//   MSVC x32's _chkstk and cygwin/mingw's _alloca adjust %esp themselves.
+//   MSVC x64's __chkstk and cygwin/mingw's ___chkstk_ms do not adjust %rsp
+//   themselves.
+core::arch::global_asm!(
+    define_rust_probestack!(
+        "
+    .cfi_startproc
+    push   %ebp
+    .cfi_adjust_cfa_offset 4
+    .cfi_offset %ebp, -8
+    mov    %esp, %ebp
+    .cfi_def_cfa_register %ebp
+    push   %ecx
+    push   %edx
+    mov    %eax,%ecx
+    cmp    $0x1000,%ecx
+    jna    3f
+2:
+    sub    $0x1000,%esp
+    test   %esp,8(%esp)
+    sub    $0x1000,%ecx
+    cmp    $0x1000,%ecx
+    ja     2b
+3:
+    sub    %ecx,%esp
+    test   %esp,8(%esp)
+    mov    4(%ebp),%edx
+    mov    %edx, 12(%esp)
+    add    %eax,%esp
+    pop    %edx
+    pop    %ecx
+    leave
+    sub   %eax, %esp
+    .cfi_def_cfa_register %esp
+    .cfi_adjust_cfa_offset -4
+    ret
+    .cfi_endproc
+    "
+    ),
+    options(att_syntax)
+);

lib/vm/src/lib.rs

@@ -15,6 +15,7 @@
 )]
 #![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
 
+mod compiler_builtins;
 mod export;
 mod extern_ref;
 mod function_env;

lib/vm/src/probestack.rs

@@ -55,10 +55,17 @@ cfg_if::cfg_if! {
         /// A default probestack for other architectures
         pub const PROBESTACK: unsafe extern "C" fn() = empty_probestack;
     } else {
-        extern "C" {
-            pub fn __rust_probestack();
+        cfg_if::cfg_if! {
+            if #[cfg(not(missing_rust_probestack))] {
+                extern "C" {
+                    pub fn __rust_probestack();
+                }
+                /// The probestack based on the Rust probestack
+                pub static PROBESTACK: unsafe extern "C" fn() = __rust_probestack;
+            } else if #[cfg(missing_rust_probestack)] {
+                /// The probestack based on the Rust probestack
+                pub static PROBESTACK: unsafe extern "C" fn() = crate::compiler_builtins::__rust_probestack;
+            }
         }
-        /// The probestack based on the Rust probestack
-        pub static PROBESTACK: unsafe extern "C" fn() = __rust_probestack;
     }
 }