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Commit d347f372 authored by Markus F.X.J. Oberhumer's avatar Markus F.X.J. Oberhumer Committed by Linus Torvalds
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[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: default avatarMarkus F.X.J. Oberhumer <markus@oberhumer.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 867f8b4e

arch/i386/kernel/signal.c

+5 −1
Original line number Diff line number Diff line
@@ -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.

arch/x86_64/ia32/ia32_signal.c

+5 −1
Original line number Diff line number Diff line
@@ -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,