[PATCH 3.5 23/78] xtensa: don't use alternate signal stack on threads

[Luis Henriques]

3.5.7.26 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Baruch Siach <baruch at tkos.co.il>

commit cba9a90053e3b7973eff4f1946f33032e98eeed5 upstream.

According to create_thread(3): "The new thread does not inherit the creating
thread's alternate signal stack". Since commit f9a3879a (Fix sigaltstack
corruption among cloned threads), current->sas_ss_size is set to 0 for cloned
processes sharing VM with their parent. Don't use the (nonexistent) alternate
signal stack in this case. This has been broken since commit 29c4dfd9 ([XTENSA]
Remove non-rt signal handling).

Fixes the SA_ONSTACK part of the nptl/tst-cancel20 test from uClibc.

Signed-off-by: Baruch Siach <baruch at tkos.co.il>
Signed-off-by: Max Filippov <jcmvbkbc at gmail.com>
Signed-off-by: Chris Zankel <chris at zankel.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/xtensa/kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/xtensa/kernel/signal.c b/arch/xtensa/kernel/signal.c
index efe4e85..163cfc8 100644
--- a/arch/xtensa/kernel/signal.c
+++ b/arch/xtensa/kernel/signal.c
@@ -342,7 +342,7 @@ static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 
 	sp = regs->areg[1];
 
-	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
+	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
 		sp = current->sas_ss_sp + current->sas_ss_size;
 	}
 
-- 
1.8.3.2