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authorPaul Mackerras <paulus@samba.org>2014-02-26 17:07:38 +1100
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2014-02-28 18:06:26 +1100
commit573ebfa6601fa58b439e7f15828762839ccd306a (patch)
tree8355a83a1388b1917b4944170809aed74b1f3b10 /arch/powerpc/kernel/signal_64.c
parenta95fc58549e8f462e560868a16b1fa97b12d5db6 (diff)
powerpc: Increase stack redzone for 64-bit userspace to 512 bytes
The new ELFv2 little-endian ABI increases the stack redzone -- the area below the stack pointer that can be used for storing data -- from 288 bytes to 512 bytes. This means that we need to allow more space on the user stack when delivering a signal to a 64-bit process. To make the code a bit clearer, we define new USER_REDZONE_SIZE and KERNEL_REDZONE_SIZE symbols in ptrace.h. For now, we leave the kernel redzone size at 288 bytes, since increasing it to 512 bytes would increase the size of interrupt stack frames correspondingly. Gcc currently only makes use of 288 bytes of redzone even when compiling for the new little-endian ABI, and the kernel cannot currently be compiled with the new ABI anyway. In the future, hopefully gcc will provide an option to control the amount of redzone used, and then we could reduce it even more. This also changes the code in arch_compat_alloc_user_space() to preserve the expanded redzone. It is not clear why this function would ever be used on a 64-bit process, though. Signed-off-by: Paul Mackerras <paulus@samba.org> CC: <stable@vger.kernel.org> [v3.13] Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
-rw-r--r--arch/powerpc/kernel/signal_64.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index e35bf773df7a..8d253c29649b 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -65,8 +65,8 @@ struct rt_sigframe {
struct siginfo __user *pinfo;
void __user *puc;
struct siginfo info;
- /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
- char abigap[288];
+ /* New 64 bit little-endian ABI allows redzone of 512 bytes below sp */
+ char abigap[USER_REDZONE_SIZE];
} __attribute__ ((aligned (16)));
static const char fmt32[] = KERN_INFO \

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