From d347f372273c2b3d86a66e2e1c94c790c208e166 Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Sun, 9 Oct 2005 18:54:23 +0200
Subject: [PATCH] i386: fix stack alignment for signal handlers

This fixes the setup of the alignment of the signal frame, so that all
signal handlers are run with a properly aligned stack frame.

The current code "over-aligns" the stack pointer so that the stack frame
is effectively always mis-aligned by 4 bytes.  But what we really want
is that on function entry ((sp + 4) & 15) == 0, which matches what would
happen if the stack were aligned before a "call" instruction.

Signed-off-by: Markus F.X.J. Oberhumer <markus@oberhumer.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
 arch/x86_64/ia32/ia32_signal.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'arch/x86_64')

diff --git a/arch/x86_64/ia32/ia32_signal.c b/arch/x86_64/ia32/ia32_signal.c
index 66e2821533db..0903cc1faef2 100644
--- a/arch/x86_64/ia32/ia32_signal.c
+++ b/arch/x86_64/ia32/ia32_signal.c
@@ -425,7 +425,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 		rsp = (unsigned long) ka->sa.sa_restorer;
 	}
 
-	return (void __user *)((rsp - frame_size) & -8UL);
+	rsp -= frame_size;
+	/* Align the stack pointer according to the i386 ABI,
+	 * i.e. so that on function entry ((sp + 4) & 15) == 0. */
+	rsp = ((rsp + 4) & -16ul) - 4;
+	return (void __user *) rsp;
 }
 
 int ia32_setup_frame(int sig, struct k_sigaction *ka,
-- 
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