On Wed, May 08, 2019 at 02:04:16PM +0200, Peter Zijlstra wrote: > On Wed, May 08, 2019 at 06:54:16AM -0500, Josh Poimboeuf wrote: > > We should put these macros in a header file somewhere (including > > stringified versions). > > Probably a good idea. I'll frob them into asm/frame.h. --- Subject: x86: Move ENCODE_FRAME_POINTER to asm/frame.h From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Wed May 8 14:30:48 CEST 2019 In preparation for wider use, move the ENCODE_FRAME_POINTER macros to a common header and provide inline asm versions. These macros are used to encode a pt_regs frame for the unwinder; see unwind_frame.c:decode_frame_pointer(). Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> --- arch/x86/entry/calling.h | 15 -------------- arch/x86/entry/entry_32.S | 16 -------------- arch/x86/include/asm/frame.h | 46 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 46 insertions(+), 31 deletions(-) --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -172,21 +172,6 @@ For 32-bit we have the following convent .endif .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* PUSH_AND_CLEAR_REGS because it corrupts - * the original rbp. - */ -.macro ENCODE_FRAME_POINTER ptregs_offset=0 -#ifdef CONFIG_FRAME_POINTER - leaq 1+\ptregs_offset(%rsp), %rbp -#endif -.endm - #ifdef CONFIG_PAGE_TABLE_ISOLATION /* --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -246,22 +246,6 @@ .Lend_\@: .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 clearing the MSB, 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_ALL because it corrupts the - * original rbp. - */ -.macro ENCODE_FRAME_POINTER -#ifdef CONFIG_FRAME_POINTER - mov %esp, %ebp - andl $0x7fffffff, %ebp -#endif -.endm - .macro RESTORE_INT_REGS popl %ebx popl %ecx --- a/arch/x86/include/asm/frame.h +++ b/arch/x86/include/asm/frame.h @@ -22,6 +22,39 @@ pop %_ASM_BP .endm +#ifdef CONFIG_X86_64 +/* + * 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* PUSH_AND_CLEAR_REGS because it corrupts + * the original rbp. + */ +.macro ENCODE_FRAME_POINTER ptregs_offset=0 +#ifdef CONFIG_FRAME_POINTER + leaq 1+\ptregs_offset(%rsp), %rbp +#endif +.endm +#else /* !CONFIG_X86_64 */ +/* + * 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 clearing the MSB, 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_ALL because it corrupts the + * original ebp. + */ +.macro ENCODE_FRAME_POINTER +#ifdef CONFIG_FRAME_POINTER + mov %esp, %ebp + andl $0x7fffffff, %ebp +#endif +.endm +#endif /* CONFIG_X86_64 */ + #else /* !__ASSEMBLY__ */ #define FRAME_BEGIN \ @@ -30,6 +63,19 @@ #define FRAME_END "pop %" _ASM_BP "\n" +#ifdef CONFIG_FRAME_POINTER +#ifdef CONFIG_X86_64 +#define ENCODE_FRAME_POINTER \ + "lea 1(%rsp), %rbp\n\t" +#else /* !CONFIG_X86_64 */ +#define ENCODE_FRAME_POINTER \ + "movl %esp, %ebp\n\t" \ + "andl $0x7fffffff, %ebp\n\t" +#endif /* CONFIG_X86_64 */ +#else /* CONFIG_FRAME_POINTER */ +#define ENCODE_FRAME_POINTER +#endif /* CONFIG_FRAME_POINTER */ + #endif /* __ASSEMBLY__ */ #define FRAME_OFFSET __ASM_SEL(4, 8)
