[PATCH 2/2] x86: setjmp: set base pointer to zero in initjmp

[Ahmad Fatoum]

Initializing the frame points to a known-bad value like zero makes it
easier for code unwinding the stack to know when to stop. Thus
initialize the stack pointer in initjmp-initialized jump buffers to
zero.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 arch/x86/lib/setjmp_32.S | 1 +
 arch/x86/lib/setjmp_64.S | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/lib/setjmp_32.S b/arch/x86/lib/setjmp_32.S
index 30db5f989af6..5814623f9478 100644
--- a/arch/x86/lib/setjmp_32.S
+++ b/arch/x86/lib/setjmp_32.S
@@ -54,6 +54,7 @@ ENDPROC(longjmp)
 ENTRY(initjmp)
 
 	movl %edx, 20(%eax)	/* Return address */
+	movl   $0, 8(%edx)	/* Base pointer */
 	sub $ASM_SZPTR, %ecx	/* ESP - 4 has to be 16-byte aligned on entry */
 	movl %ecx, 4(%eax)	/* Stack top */
 	xorl %eax, %eax		/* Return value */
diff --git a/arch/x86/lib/setjmp_64.S b/arch/x86/lib/setjmp_64.S
index d5cf99a1557f..bfa152149975 100644
--- a/arch/x86/lib/setjmp_64.S
+++ b/arch/x86/lib/setjmp_64.S
@@ -54,6 +54,7 @@ ENDPROC(longjmp)
 ENTRY(initjmp)
 
 	movq	%rsi, (%rdi)	/* Return address */
+	movq	$0,  16(%rdi)	/* Base pointer */
 	sub	$ASM_SZPTR, %rdx	/* RSP - 8 has to be 16-byte aligned on entry */
 	movq	%rdx, 8(%rdi)	/* Stack top */
 	xorq	%rax, %rax
-- 
2.39.2