[PATCH] x86: fix initjmp storing base pointer at wrong address

[PATCH] x86: fix initjmp storing base pointer at wrong address

[Ahmad Fatoum]

initjmp was writing zero to 8(%edx), which is func + 8 (corrupting
memory at the function pointer address), instead of 8(%eax), which is
the __ebp (base pointer) slot in the jmp_buf. When longjmp later
restored the buffer, it would load uninitialized data into %ebp.

With regparm(3), the arguments are passed as:
  %eax = jmp_buf, %edx = func, %ecx = stack_top

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 arch/x86/lib/setjmp_32.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/setjmp_32.S b/arch/x86/lib/setjmp_32.S
index cf340d35d8fd..ff080179ef9d 100644
--- a/arch/x86/lib/setjmp_32.S
+++ b/arch/x86/lib/setjmp_32.S
@@ -56,7 +56,7 @@ ENDPROC(longjmp)
 ENTRY(initjmp)
 
 	movl %edx, 20(%eax)	/* Return address */
-	movl   $0, 8(%edx)	/* Base pointer */
+	movl   $0, 8(%eax)	/* 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 */
-- 
2.47.3