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x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h 

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@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-05-08 14:30:48 +02:00 committed by Ingo Molnar
parent 5e1246ff2d
commit a9b3c6998d
3 changed files with 49 additions and 31 deletions
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15
arch/x86/entry/calling.h
View File

@ -172,21 +172,6 @@ For 32-bit we have the following conventions - kernel is built with
.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
/*

16
arch/x86/entry/entry_32.S
View File

@ -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

49
arch/x86/include/asm/frame.h
View File

@ -22,6 +22,35 @@
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
leaq 1+\ptregs_offset(%rsp), %rbp
.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
mov %esp, %ebp
andl $0x7fffffff, %ebp
.endm
#endif /* CONFIG_X86_64 */
#else /* !__ASSEMBLY__ */
#define FRAME_BEGIN \
@ -30,12 +59,32 @@
#define FRAME_END "pop %" _ASM_BP "\n"
#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 */
#endif /* __ASSEMBLY__ */
#define FRAME_OFFSET __ASM_SEL(4, 8)
#else /* !CONFIG_FRAME_POINTER */
#ifdef __ASSEMBLY__
.macro ENCODE_FRAME_POINTER ptregs_offset=0
.endm
#else /* !__ASSEMBLY */
#define ENCODE_FRAME_POINTER
#endif
#define FRAME_BEGIN
#define FRAME_END
#define FRAME_OFFSET 0