[POWERPC] Merge creation of signal frame

The code for creating signal frames was still duplicated and split
in strange ways between 32 and 64 bits, including the SA_ONSTACK
handling being in do_signal on 32 bits but inside handle_rt_signal
on 64 bits etc...

This moves the 64 bits get_sigframe() to the generic signal.c,
cleans it a bit, moves the access_ok() call done by all callers to
it as well, and adapts/cleanups the 3 different signal handling cases
to use that common function.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 29 insertions, 10 deletions

diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index a9c148a09361..dee275014e00 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -11,6 +11,7 @@
 
 #include <linux/ptrace.h>
 #include <linux/signal.h>
+#include <asm/uaccess.h>
 #include <asm/unistd.h>
 
 #include "signal.h"
@@ -28,6 +29,32 @@ static inline int is_32bit_task(void)
 }
 #endif
 
+/*
+ * Allocate space for the signal frame
+ */
+void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
+                           size_t frame_size)
+{
+        unsigned long oldsp, newsp;
+
+        /* Default to using normal stack */
+        oldsp = regs->gpr[1];
+
+        /* Check for alt stack */
+        if ((ka->sa.sa_flags & SA_ONSTACK) &&
+            current->sas_ss_size && !on_sig_stack(oldsp))
+                oldsp = (current->sas_ss_sp + current->sas_ss_size);
+
+        /* Get aligned frame */
+        newsp = (oldsp - frame_size) & ~0xFUL;
+
+        /* Check access */
+        if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
+                return NULL;
+
+        return (void __user *)newsp;
+}
+
 
 /*
  * Restore the user process's signal mask
@@ -130,20 +157,12 @@ int do_signal(sigset_t *oldset, struct pt_regs *regs)
 #endif
 
         if (is32) {
-                unsigned int newsp;
-
-                if ((ka.sa.sa_flags & SA_ONSTACK) &&
-                    current->sas_ss_size && !on_sig_stack(regs->gpr[1]))
-                        newsp = current->sas_ss_sp + current->sas_ss_size;
-                else
-                        newsp = regs->gpr[1];
-
                 if (ka.sa.sa_flags & SA_SIGINFO)
                         ret = handle_rt_signal32(signr, &ka, &info, oldset,
-                                        regs, newsp);
+                                        regs);
                 else
                         ret = handle_signal32(signr, &ka, &info, oldset,
-                                        regs, newsp);
+                                        regs);
 #ifdef CONFIG_PPC64
         } else {
                 ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);