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[PATCH] i386: fix stack alignment for signal handlers

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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>
This commit is contained in:
Markus F.X.J. Oberhumer
2005-10-09 18:54:23 +02:00
committed by Linus Torvalds
parent 867f8b4e47
commit d347f37227
2 changed files with 10 additions and 2 deletions
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6
arch/i386/kernel/signal.c
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@@ -338,7 +338,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
esp = (unsigned long) ka->sa.sa_restorer;
}
return (void __user *)((esp - frame_size) & -8ul);
esp -= frame_size;
/* Align the stack pointer according to the i386 ABI,
* i.e. so that on function entry ((sp + 4) & 15) == 0. */
esp = ((esp + 4) & -16ul) - 4;
return (void __user *) esp;
}
/* These symbols are defined with the addresses in the vsyscall page.