Auto merge of #176 - alexcrichton:probestack2, r=alexcrichton

Tweak definition of probestack functions

It looks like the old `__rust_probestack` routine is incompatible with newer
linux kernels. My best guess for this is that the kernel's auto-growth logic is
failing to trigger, causing what looks like a legitimate segfault to get
delivered. My best guess for why *that's* happening is that the faulting address
is below `%rsp`, whereas previously all faulting stack addresses were above
`%rsp`. The probestack routine does not modify `%rsp` as it's probing the stack,
and presumably newer kernels are interpreting this as a legitimate violation.

This commit tweaks the probestack routine to instead update `%rsp` incrementally
as probing happens. The ABI of the function, however, requires that `%rsp`
isn't changed as part of the function so it's restored at the end to the
previous value.
This commit is contained in:
bors 2017-07-08 03:36:04 +00:00
commit 5e49856003
6 changed files with 51 additions and 36 deletions

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@ -21,9 +21,14 @@ fn main() {
#[cfg(feature = "gen-tests")]
tests::generate();
// Build missing intrinsics from compiler-rt C source code
#[cfg(feature = "c")]
c::compile(&llvm_target);
// Build missing intrinsics from compiler-rt C source code. If we're
// mangling names though we assume that we're also in test mode so we don't
// build anything and we rely on the upstream implementation of compiler-rt
// functions
if !cfg!(feature = "mangled-names") {
#[cfg(feature = "c")]
c::compile(&llvm_target);
}
// To compile intrinsics.rs for thumb targets, where there is no libc
if llvm_target[0].starts_with("thumb") {
@ -4099,11 +4104,9 @@ mod c {
// also needs to satisfy intrinsics that jemalloc or C in general may
// need, so include a few more that aren't typically needed by
// LLVM/Rust.
if env::var_os("CARGO_FEATURE_RUSTBUILD").is_some() {
sources.extend(&[
"ffsdi2.c",
]);
}
sources.extend(&[
"ffsdi2.c",
]);
if target_os != "ios" {
sources.extend(

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@ -93,6 +93,7 @@ for rlib in $(echo $path); do
uniq -d | \
grep -v __x86.get_pc_thunk | \
grep -v __builtin_cl | \
grep -v __builtin_ctz | \
grep 'T __'
if test $? = 0; then

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@ -13,6 +13,8 @@
#![feature(lang_items)]
#![feature(start)]
#![feature(i128_type)]
#![feature(global_allocator)]
#![feature(allocator_api)]
#![cfg_attr(windows, feature(panic_unwind))]
#![no_std]
@ -22,6 +24,10 @@ extern crate compiler_builtins;
#[cfg(windows)]
extern crate panic_unwind;
#[cfg(not(thumb))]
#[global_allocator]
static A: alloc_system::System = alloc_system::System;
// NOTE cfg(not(thumbv6m)) means that the operation is not supported on ARMv6-M at all. Not even
// compiler-rt provides a C/assembly implementation.

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@ -112,8 +112,9 @@ intrinsics! {
int_to_float!(i, u32, f64)
}
#[use_c_shim_if(all(any(target_arch = "x86", target_arch = "x86_64"),
not(windows)))]
#[use_c_shim_if(all(not(target_env = "msvc"),
any(target_arch = "x86",
all(not(windows), target_arch = "x86_64"))))]
#[arm_aeabi_alias = __aeabi_ul2d]
pub extern "C" fn __floatundidf(i: u64) -> f64 {
int_to_float!(i, u64, f64)

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@ -44,7 +44,7 @@
#![cfg(not(windows))] // Windows already has builtins to do this
#[naked]
#[no_mangle]
#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
#[cfg(target_arch = "x86_64")]
pub unsafe extern fn __rust_probestack() {
// Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
@ -53,28 +53,33 @@ pub unsafe extern fn __rust_probestack() {
// The ABI here is that the stack frame size is located in `%eax`. Upon
// return we're not supposed to modify `%esp` or `%eax`.
asm!("
lea 8(%rsp),%r11 // rsp before calling this routine -> r11
mov %rax,%r11 // duplicate %rax as we're clobbering %r11
// Main loop, taken in one page increments. We're decrementing r11 by
// 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
// 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.
2:
sub $$0x1000,%rsp
test %rsp,8(%rsp)
sub $$0x1000,%r11
test %r11,(%r11)
sub $$0x1000,%rax
cmp $$0x1000,%rax
cmp $$0x1000,%r11
ja 2b
// Finish up the last remaining stack space requested, getting the last
// bits out of rax
sub %rax,%r11
test %r11,(%r11)
// bits out of r11
sub %r11,%rsp
test %rsp,8(%rsp)
// We now know that %r11 is (%rsp + 8 - %rax) so to recover rax
// we calculate (%rsp + 8) - %r11 which will give us %rax
lea 8(%rsp),%rax
sub %r11,%rax
// Restore the stack pointer to what it previously was when entering
// this function. The caller will readjust the stack pointer after we
// return.
add %rax,%rsp
ret
");
@ -82,7 +87,7 @@ pub unsafe extern fn __rust_probestack() {
}
#[naked]
#[no_mangle]
#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
#[cfg(target_arch = "x86")]
pub unsafe extern fn __rust_probestack() {
// This is the same as x86_64 above, only translated for 32-bit sizes. Note
@ -92,19 +97,18 @@ pub unsafe extern fn __rust_probestack() {
// The ABI here is the same as x86_64, except everything is 32-bits large.
asm!("
push %ecx
lea 8(%esp),%ecx
mov %eax,%ecx
2:
sub $$0x1000,%esp
test %esp,8(%esp)
sub $$0x1000,%ecx
test %ecx,(%ecx)
sub $$0x1000,%eax
cmp $$0x1000,%eax
cmp $$0x1000,%ecx
ja 2b
sub %eax,%ecx
test %ecx,(%ecx)
sub %ecx,%esp
test %esp,8(%esp)
lea 8(%esp),%eax
sub %ecx,%eax
add %eax,%esp
pop %ecx
ret
");

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@ -10,7 +10,7 @@ use core::intrinsics;
#[cfg(windows)]
#[naked]
#[no_mangle]
#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
pub unsafe fn ___chkstk_ms() {
asm!("push %rcx
push %rax
@ -34,7 +34,7 @@ pub unsafe fn ___chkstk_ms() {
#[cfg(windows)]
#[naked]
#[no_mangle]
#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
pub unsafe fn __alloca() {
asm!("mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx
jmp ___chkstk // Jump to ___chkstk since fallthrough may be unreliable");
@ -43,7 +43,7 @@ pub unsafe fn __alloca() {
#[cfg(windows)]
#[naked]
#[no_mangle]
#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
pub unsafe fn ___chkstk() {
asm!("push %rcx
cmp $$0x1000,%rax