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:
commit
5e49856003
19
build.rs
19
build.rs
@ -21,9 +21,14 @@ fn main() {
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#[cfg(feature = "gen-tests")]
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#[cfg(feature = "gen-tests")]
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tests::generate();
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tests::generate();
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// Build missing intrinsics from compiler-rt C source code
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// Build missing intrinsics from compiler-rt C source code. If we're
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#[cfg(feature = "c")]
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// mangling names though we assume that we're also in test mode so we don't
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c::compile(&llvm_target);
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// build anything and we rely on the upstream implementation of compiler-rt
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// functions
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if !cfg!(feature = "mangled-names") {
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#[cfg(feature = "c")]
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c::compile(&llvm_target);
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}
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// To compile intrinsics.rs for thumb targets, where there is no libc
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// To compile intrinsics.rs for thumb targets, where there is no libc
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if llvm_target[0].starts_with("thumb") {
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if llvm_target[0].starts_with("thumb") {
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@ -4099,11 +4104,9 @@ mod c {
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// also needs to satisfy intrinsics that jemalloc or C in general may
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// also needs to satisfy intrinsics that jemalloc or C in general may
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// need, so include a few more that aren't typically needed by
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// need, so include a few more that aren't typically needed by
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// LLVM/Rust.
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// LLVM/Rust.
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if env::var_os("CARGO_FEATURE_RUSTBUILD").is_some() {
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sources.extend(&[
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sources.extend(&[
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"ffsdi2.c",
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"ffsdi2.c",
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]);
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]);
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}
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if target_os != "ios" {
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if target_os != "ios" {
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sources.extend(
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sources.extend(
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@ -93,6 +93,7 @@ for rlib in $(echo $path); do
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uniq -d | \
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uniq -d | \
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grep -v __x86.get_pc_thunk | \
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grep -v __x86.get_pc_thunk | \
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grep -v __builtin_cl | \
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grep -v __builtin_cl | \
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grep -v __builtin_ctz | \
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grep 'T __'
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grep 'T __'
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if test $? = 0; then
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if test $? = 0; then
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@ -13,6 +13,8 @@
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#![feature(lang_items)]
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#![feature(lang_items)]
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#![feature(start)]
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#![feature(start)]
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#![feature(i128_type)]
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#![feature(i128_type)]
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#![feature(global_allocator)]
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#![feature(allocator_api)]
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#![cfg_attr(windows, feature(panic_unwind))]
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#![cfg_attr(windows, feature(panic_unwind))]
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#![no_std]
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#![no_std]
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@ -22,6 +24,10 @@ extern crate compiler_builtins;
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#[cfg(windows)]
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#[cfg(windows)]
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extern crate panic_unwind;
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extern crate panic_unwind;
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#[cfg(not(thumb))]
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#[global_allocator]
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static A: alloc_system::System = alloc_system::System;
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// NOTE cfg(not(thumbv6m)) means that the operation is not supported on ARMv6-M at all. Not even
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// NOTE cfg(not(thumbv6m)) means that the operation is not supported on ARMv6-M at all. Not even
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// compiler-rt provides a C/assembly implementation.
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// compiler-rt provides a C/assembly implementation.
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@ -112,8 +112,9 @@ intrinsics! {
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int_to_float!(i, u32, f64)
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int_to_float!(i, u32, f64)
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}
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}
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#[use_c_shim_if(all(any(target_arch = "x86", target_arch = "x86_64"),
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#[use_c_shim_if(all(not(target_env = "msvc"),
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not(windows)))]
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any(target_arch = "x86",
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all(not(windows), target_arch = "x86_64"))))]
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#[arm_aeabi_alias = __aeabi_ul2d]
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#[arm_aeabi_alias = __aeabi_ul2d]
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pub extern "C" fn __floatundidf(i: u64) -> f64 {
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pub extern "C" fn __floatundidf(i: u64) -> f64 {
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int_to_float!(i, u64, f64)
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int_to_float!(i, u64, f64)
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@ -44,7 +44,7 @@
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#![cfg(not(windows))] // Windows already has builtins to do this
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#![cfg(not(windows))] // Windows already has builtins to do this
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#[naked]
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#[naked]
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#[no_mangle]
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#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
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#[cfg(target_arch = "x86_64")]
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#[cfg(target_arch = "x86_64")]
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pub unsafe extern fn __rust_probestack() {
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pub unsafe extern fn __rust_probestack() {
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// Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
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// Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
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@ -53,28 +53,33 @@ pub unsafe extern fn __rust_probestack() {
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// The ABI here is that the stack frame size is located in `%eax`. Upon
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// The ABI here is that the stack frame size is located in `%eax`. Upon
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// return we're not supposed to modify `%esp` or `%eax`.
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// return we're not supposed to modify `%esp` or `%eax`.
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asm!("
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asm!("
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lea 8(%rsp),%r11 // rsp before calling this routine -> r11
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mov %rax,%r11 // duplicate %rax as we're clobbering %r11
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// Main loop, taken in one page increments. We're decrementing r11 by
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// Main loop, taken in one page increments. We're decrementing rsp by
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// a page each time until there's less than a page remaining. We're
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// a page each time until there's less than a page remaining. We're
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// guaranteed that this function isn't called unless there's more than a
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// guaranteed that this function isn't called unless there's more than a
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// page needed
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// page needed.
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//
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// Note that we're also testing against `8(%rsp)` to account for the 8
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// bytes pushed on the stack orginally with our return address. Using
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// `8(%rsp)` simulates us testing the stack pointer in the caller's
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// context.
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2:
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2:
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sub $$0x1000,%rsp
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test %rsp,8(%rsp)
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sub $$0x1000,%r11
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sub $$0x1000,%r11
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test %r11,(%r11)
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cmp $$0x1000,%r11
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sub $$0x1000,%rax
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cmp $$0x1000,%rax
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ja 2b
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ja 2b
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// Finish up the last remaining stack space requested, getting the last
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// Finish up the last remaining stack space requested, getting the last
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// bits out of rax
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// bits out of r11
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sub %rax,%r11
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sub %r11,%rsp
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test %r11,(%r11)
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test %rsp,8(%rsp)
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// We now know that %r11 is (%rsp + 8 - %rax) so to recover rax
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// Restore the stack pointer to what it previously was when entering
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// we calculate (%rsp + 8) - %r11 which will give us %rax
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// this function. The caller will readjust the stack pointer after we
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lea 8(%rsp),%rax
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// return.
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sub %r11,%rax
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add %rax,%rsp
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ret
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ret
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");
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");
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@ -82,7 +87,7 @@ pub unsafe extern fn __rust_probestack() {
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}
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}
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#[naked]
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#[naked]
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#[no_mangle]
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#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
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#[cfg(target_arch = "x86")]
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#[cfg(target_arch = "x86")]
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pub unsafe extern fn __rust_probestack() {
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pub unsafe extern fn __rust_probestack() {
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// This is the same as x86_64 above, only translated for 32-bit sizes. Note
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// This is the same as x86_64 above, only translated for 32-bit sizes. Note
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@ -92,19 +97,18 @@ pub unsafe extern fn __rust_probestack() {
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// The ABI here is the same as x86_64, except everything is 32-bits large.
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// The ABI here is the same as x86_64, except everything is 32-bits large.
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asm!("
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asm!("
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push %ecx
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push %ecx
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lea 8(%esp),%ecx
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mov %eax,%ecx
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2:
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2:
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sub $$0x1000,%esp
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test %esp,8(%esp)
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sub $$0x1000,%ecx
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sub $$0x1000,%ecx
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test %ecx,(%ecx)
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cmp $$0x1000,%ecx
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sub $$0x1000,%eax
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cmp $$0x1000,%eax
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ja 2b
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ja 2b
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sub %eax,%ecx
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sub %ecx,%esp
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test %ecx,(%ecx)
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test %esp,8(%esp)
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lea 8(%esp),%eax
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add %eax,%esp
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sub %ecx,%eax
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pop %ecx
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pop %ecx
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ret
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ret
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");
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");
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@ -10,7 +10,7 @@ use core::intrinsics;
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#[cfg(windows)]
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#[cfg(windows)]
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#[naked]
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#[naked]
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#[no_mangle]
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#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
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pub unsafe fn ___chkstk_ms() {
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pub unsafe fn ___chkstk_ms() {
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asm!("push %rcx
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asm!("push %rcx
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push %rax
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push %rax
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@ -34,7 +34,7 @@ pub unsafe fn ___chkstk_ms() {
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#[cfg(windows)]
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#[cfg(windows)]
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#[naked]
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#[naked]
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#[no_mangle]
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#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
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pub unsafe fn __alloca() {
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pub unsafe fn __alloca() {
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asm!("mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx
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asm!("mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx
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jmp ___chkstk // Jump to ___chkstk since fallthrough may be unreliable");
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jmp ___chkstk // Jump to ___chkstk since fallthrough may be unreliable");
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@ -43,7 +43,7 @@ pub unsafe fn __alloca() {
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#[cfg(windows)]
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#[cfg(windows)]
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#[naked]
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#[naked]
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#[no_mangle]
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#[cfg_attr(not(feature = "mangled-names"), no_mangle)]
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pub unsafe fn ___chkstk() {
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pub unsafe fn ___chkstk() {
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asm!("push %rcx
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asm!("push %rcx
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cmp $$0x1000,%rax
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cmp $$0x1000,%rax
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