diff options
Diffstat (limited to 'arch/x86/entry/calling.h')
| -rw-r--r-- | arch/x86/entry/calling.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 38dcdfa2be55..05ed3d393da7 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -192,6 +192,26 @@ For 32-bit we have the following conventions - kernel is built with .byte 0xf1 .endm +/* + * This is a sneaky trick to help the unwinder find pt_regs on the stack. The + * frame pointer is replaced with an encoded pointer to pt_regs. The encoding + * is just setting the LSB, which makes it an invalid stack address and is also + * a signal to the unwinder that it's a pt_regs pointer in disguise. + * + * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts + * the original rbp. + */ +.macro ENCODE_FRAME_POINTER ptregs_offset=0 +#ifdef CONFIG_FRAME_POINTER + .if \ptregs_offset + leaq \ptregs_offset(%rsp), %rbp + .else + mov %rsp, %rbp + .endif + orq $0x1, %rbp +#endif +.endm + #endif /* CONFIG_X86_64 */ /* |