70 lines
2.0 KiB
Rust
70 lines
2.0 KiB
Rust
#![allow(unused_imports)]
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use core::intrinsics;
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// NOTE These functions are implemented using assembly because they using a custom
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// calling convention which can't be implemented using a normal Rust function
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// NOTE These functions are never mangled as they are not tested against compiler-rt
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// and mangling ___chkstk would break the `jmp ___chkstk` instruction in __alloca
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#[cfg(windows)]
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#[naked]
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#[no_mangle]
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pub unsafe fn ___chkstk_ms() {
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asm!("push %rcx
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push %rax
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cmp $$0x1000,%rax
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lea 24(%rsp),%rcx
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jb 1f
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2:
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sub $$0x1000,%rcx
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test %rcx,(%rcx)
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sub $$0x1000,%rax
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cmp $$0x1000,%rax
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ja 2b
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1:
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sub %rax,%rcx
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test %rcx,(%rcx)
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pop %rax
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pop %rcx
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ret");
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intrinsics::unreachable();
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}
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#[cfg(windows)]
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#[naked]
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#[no_mangle]
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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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jmp ___chkstk // Jump to ___chkstk since fallthrough may be unreliable");
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intrinsics::unreachable();
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}
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#[cfg(windows)]
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#[naked]
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#[no_mangle]
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pub unsafe fn ___chkstk() {
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asm!("push %rcx
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cmp $$0x1000,%rax
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lea 16(%rsp),%rcx // rsp before calling this routine -> rcx
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jb 1f
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2:
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sub $$0x1000,%rcx
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test %rcx,(%rcx)
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sub $$0x1000,%rax
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cmp $$0x1000,%rax
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ja 2b
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1:
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sub %rax,%rcx
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test %rcx,(%rcx)
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lea 8(%rsp),%rax // load pointer to the return address into rax
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mov %rcx,%rsp // install the new top of stack pointer into rsp
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mov -8(%rax),%rcx // restore rcx
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push (%rax) // push return address onto the stack
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sub %rsp,%rax // restore the original value in rax
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ret");
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intrinsics::unreachable();
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}
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