#![cfg(not(windows))]
#[naked]
#[no_mangle]
#[cfg(all(target_arch = "x86_64", not(feature = "mangled-names")))]
pub unsafe extern fn __rust_probestack() {
asm!("
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
ret
" ::: "memory" : "volatile");
::core::intrinsics::unreachable();
}
#[naked]
#[no_mangle]
#[cfg(all(target_arch = "x86", not(feature = "mangled-names")))]
pub unsafe extern fn __rust_probestack() {
asm!("
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
ret
" ::: "memory" : "volatile");
::core::intrinsics::unreachable();
}