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#![allow(unused_imports)]
use core::intrinsics;
// NOTE These functions are implemented using assembly because they using a custom
// calling convention which can't be implemented using a normal Rust function
// NOTE These functions are never mangled as they are not tested against compiler-rt
// and mangling ___chkstk would break the `jmp ___chkstk` instruction in __alloca
intrinsics! {
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn ___chkstk_ms() {
core::arch::asm!(
"push %ecx",
"push %eax",
"cmp $0x1000,%eax",
"lea 12(%esp),%ecx",
"jb 1f",
"2:",
"sub $0x1000,%ecx",
"test %ecx,(%ecx)",
"sub $0x1000,%eax",
"cmp $0x1000,%eax",
"ja 2b",
"1:",
"sub %eax,%ecx",
"test %ecx,(%ecx)",
"pop %eax",
"pop %ecx",
"ret",
options(noreturn, att_syntax)
);
}
// FIXME: __alloca should be an alias to __chkstk
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn __alloca() {
core::arch::asm!(
"jmp ___chkstk", // Jump to ___chkstk since fallthrough may be unreliable"
options(noreturn, att_syntax)
);
}
#[naked]
#[cfg(all(
windows,
target_env = "gnu",
not(feature = "no-asm")
))]
pub unsafe extern "C" fn ___chkstk() {
core::arch::asm!(
"push %ecx",
"cmp $0x1000,%eax",
"lea 8(%esp),%ecx", // esp before calling this routine -> ecx
"jb 1f",
"2:",
"sub $0x1000,%ecx",
"test %ecx,(%ecx)",
"sub $0x1000,%eax",
"cmp $0x1000,%eax",
"ja 2b",
"1:",
"sub %eax,%ecx",
"test %ecx,(%ecx)",
"lea 4(%esp),%eax", // load pointer to the return address into eax
"mov %ecx,%esp", // install the new top of stack pointer into esp
"mov -4(%eax),%ecx", // restore ecx
"push (%eax)", // push return address onto the stack
"sub %esp,%eax", // restore the original value in eax
"ret",
options(noreturn, att_syntax)
);
}
}
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