[IA64] signal(ia64): add a signal stack overflow check

The similar check has been added to x86_32(i386) in commit
id 83bd01024b1fdfc41d9b758e5669e80fca72df66.
So we add this check to ia64 and improve it a liitle bit in that
we need to check for stack overflow only when the signal is on stack.

Signed-off-by: Shi Weihua <shiwh@cn.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/kernel/signal.c b/arch/ia64/kernel/signal.c
index 309da3567bc851966e8a7ad27e01eccac2e26ff2..5740296c35afa3d597e8fd041db4385ff628f268 100644 (file)
--- a/arch/ia64/kernel/signal.c
+++ b/arch/ia64/kernel/signal.c
@@ -342,15 +342,33 @@ setup_frame (int sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *set,
 
        new_sp = scr->pt.r12;
        tramp_addr = (unsigned long) __kernel_sigtramp;
-       if ((ka->sa.sa_flags & SA_ONSTACK) && sas_ss_flags(new_sp) == 0) {
-               new_sp = current->sas_ss_sp + current->sas_ss_size;
-               /*
-                * We need to check for the register stack being on the signal stack
-                * separately, because it's switched separately (memory stack is switched
-                * in the kernel, register stack is switched in the signal trampoline).
-                */
-               if (!rbs_on_sig_stack(scr->pt.ar_bspstore))
-                       new_rbs = (current->sas_ss_sp + sizeof(long) - 1) & ~(sizeof(long) - 1);
+       if (ka->sa.sa_flags & SA_ONSTACK) {
+               int onstack = sas_ss_flags(new_sp);
+
+               if (onstack == 0) {
+                       new_sp = current->sas_ss_sp + current->sas_ss_size;
+                       /*
+                        * We need to check for the register stack being on the
+                        * signal stack separately, because it's switched
+                        * separately (memory stack is switched in the kernel,
+                        * register stack is switched in the signal trampoline).
+                        */
+                       if (!rbs_on_sig_stack(scr->pt.ar_bspstore))
+                               new_rbs = ALIGN(current->sas_ss_sp,
+                                               sizeof(long));
+               } else if (onstack == SS_ONSTACK) {
+                       unsigned long check_sp;
+
+                       /*
+                        * If we are on the alternate signal stack and would
+                        * overflow it, don't. Return an always-bogus address
+                        * instead so we will die with SIGSEGV.
+                        */
+                       check_sp = (new_sp - sizeof(*frame)) & -STACK_ALIGN;
+                       if (!likely(on_sig_stack(check_sp)))
+                               return force_sigsegv_info(sig, (void __user *)
+                                                         check_sp);
+               }
        }
        frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);