Python/asm_trampoline_aarch64.S

/*
 * References:
 *  - https://developer.arm.com/documentation/101028/0012/5--Feature-test-macros
 *  - https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst
 */

#if defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
  #define BTI_J hint 36 /* bti j: for jumps, IE br instructions */
  #define BTI_C hint 34  /* bti c: for calls, IE bl instructions */
  #define GNU_PROPERTY_AARCH64_BTI 1 /* bit 0 GNU Notes is for BTI support */
#else
  #define BTI_J
  #define BTI_C
  #define GNU_PROPERTY_AARCH64_BTI 0
#endif

#if defined(__ARM_FEATURE_PAC_DEFAULT)
  #if __ARM_FEATURE_PAC_DEFAULT & 1
    #define SIGN_LR hint 25 /* paciasp: sign with the A key */
    #define VERIFY_LR hint 29 /* autiasp: verify with the A key */
  #elif __ARM_FEATURE_PAC_DEFAULT & 2
    #define SIGN_LR hint 27 /* pacibsp: sign with the b key */
    #define VERIFY_LR hint 31 /* autibsp: verify with the b key */
  #endif
  #define GNU_PROPERTY_AARCH64_POINTER_AUTH 2 /* bit 1 GNU Notes is for PAC support */
#else
  #define SIGN_LR BTI_C
  #define VERIFY_LR
  #define GNU_PROPERTY_AARCH64_POINTER_AUTH 0
#endif

#if defined(__ARM_FEATURE_GCS_DEFAULT) && __ARM_FEATURE_GCS_DEFAULT == 1
  #define GNU_PROPERTY_AARCH64_GCS 4 /* bit 2 GNU Notes is for GCS support */
#else
  #define GNU_PROPERTY_AARCH64_GCS 0
#endif

    .text
#if defined(__aarch64__) && defined(__AARCH64EL__) && !defined(__ILP32__)
#if defined(__APPLE__)
    .globl	__Py_trampoline_func_start
__Py_trampoline_func_start:
#else
    .globl	_Py_trampoline_func_start
_Py_trampoline_func_start:
#endif
    SIGN_LR
    stp     x29, x30, [sp, -16]!
    mov     x29, sp
    blr     x3
    ldp     x29, x30, [sp], 16
    VERIFY_LR
    ret
#if defined(__APPLE__)
    .globl	__Py_trampoline_func_end
__Py_trampoline_func_end:
#else
    .globl	_Py_trampoline_func_end
_Py_trampoline_func_end:
    .section        .note.GNU-stack,"",@progbits
#endif

/* Add the BTI, PAC and GCS support to GNU Notes section */
#if GNU_PROPERTY_AARCH64_BTI != 0 || GNU_PROPERTY_AARCH64_POINTER_AUTH != 0 || GNU_PROPERTY_AARCH64_GCS != 0
    .pushsection .note.gnu.property, "a"; /* Start a new allocatable section */
    .balign 8; /* align it on a byte boundry */
    .long 4; /* size of "GNU\0" */
    .long 0x10; /* size of descriptor */
    .long 0x5; /* NT_GNU_PROPERTY_TYPE_0 */
    .asciz "GNU";
    .long 0xc0000000; /* GNU_PROPERTY_AARCH64_FEATURE_1_AND */
    .long 4; /* Four bytes of data */
    .long (GNU_PROPERTY_AARCH64_BTI|GNU_PROPERTY_AARCH64_POINTER_AUTH|GNU_PROPERTY_AARCH64_GCS); /* BTI, PAC or GCS is enabled */
    .long 0; /* padding for 8 byte alignment */
    .popsection; /* end the section */
#endif
#endif // __aarch64__ && __AARCH64EL__ && !__ILP32__