[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>
diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c
index 61eb0c8..adcd069 100644
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -338,7 +338,11 @@
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.
diff --git a/arch/x86_64/ia32/ia32_signal.c b/arch/x86_64/ia32/ia32_signal.c
index 66e2821..0903cc1 100644
--- a/arch/x86_64/ia32/ia32_signal.c
+++ b/arch/x86_64/ia32/ia32_signal.c
@@ -425,7 +425,11 @@
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,