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gh-128605: Add branch protections for x86_64 in asm_trampoline.S #128606

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Merged
merged 1 commit into from
Jun 3, 2025
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gh-128605: Add branch protections for x86_64 in asm_trampoline.S #128606

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22 changes: 22 additions & 0 deletions Python/asm_trampoline.S
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@
# }
_Py_trampoline_func_start:
#ifdef __x86_64__
#if defined(__CET__) && (__CET__ & 1)
endbr64
#endif
sub $8, %rsp
call *%rcx
add $8, %rsp
Expand All @@ -34,3 +37,22 @@ _Py_trampoline_func_start:
.globl _Py_trampoline_func_end
_Py_trampoline_func_end:
.section .note.GNU-stack,"",@progbits
# Note for indicating the assembly code supports CET
#if defined(__x86_64__) && defined(__CET__) && (__CET__ & 1)
.section .note.gnu.property,"a"
.align 8
.long 1f - 0f
.long 4f - 1f
.long 5
0:
.string "GNU"
1:
.align 8
.long 0xc0000002
.long 3f - 2f
2:
.long 0x3
3:
.align 8
4:
#endif // __x86_64__
4 changes: 4 additions & 0 deletions Python/perf_jit_trampoline.c
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Expand Up @@ -869,7 +869,11 @@ static void elf_init_ehframe(ELFObjectContext* ctx) {
*/
#ifdef __x86_64__
/* x86_64 calling convention unwinding rules */
# if defined(__CET__) && (__CET__ & 1)
DWRF_U8(DWRF_CFA_advance_loc | 8); // Advance location by 8 bytes when CET protection is enabled
# else
DWRF_U8(DWRF_CFA_advance_loc | 4); // Advance location by 4 bytes
# endif
DWRF_U8(DWRF_CFA_def_cfa_offset); // Redefine CFA offset
DWRF_UV(16); // New offset: SP + 16
DWRF_U8(DWRF_CFA_advance_loc | 6); // Advance location by 6 bytes
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