powerpc: Fix clearing of the FPSCR when invoking a signal handler

As pointed out by Gary Byers, we were clearing the image of the FPSCR
(floating point status and control register) in the thread_struct before
copying it to the user stack when invoking a signal.  Thus the task
would see its FPSCR getting cleared when it took a signal.

While fixing it I noticed that our swapcontext system call was also
clearing FPSCR.  It shouldn't, so I fixed that too.

Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 8 insertions, 5 deletions

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 8bdf95b7e420..5a2eba60dd39 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -403,8 +403,6 @@ static int save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
                     ELF_NFPREG * sizeof(double)))
                 return 1;
 
-        current->thread.fpscr.val = 0;  /* turn off all fp exceptions */
-
 #ifdef CONFIG_ALTIVEC
         /* save altivec registers */
         if (current->thread.used_vr) {
@@ -818,6 +816,9 @@ static int handle_rt_signal(unsigned long sig, struct k_sigaction *ka,
                         goto badframe;
                 regs->link = (unsigned long) frame->tramp;
         }
+
+        current->thread.fpscr.val = 0;  /* turn off all fp exceptions */
+
         if (put_user(regs->gpr[1], (u32 __user *)newsp))
                 goto badframe;
         regs->gpr[1] = newsp;
@@ -1097,6 +1098,8 @@ static int handle_signal(unsigned long sig, struct k_sigaction *ka,
                 regs->link = (unsigned long) frame->mctx.tramp;
         }
 
+        current->thread.fpscr.val = 0;  /* turn off all fp exceptions */
+
         if (put_user(regs->gpr[1], (u32 __user *)newsp))
                 goto badframe;
         regs->gpr[1] = newsp;
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 58194e150711..1decf2785530 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -131,9 +131,6 @@ static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
 
         flush_fp_to_thread(current);
 
-        /* Make sure signal doesn't get spurrious FP exceptions */
-        current->thread.fpscr.val = 0;
-
 #ifdef CONFIG_ALTIVEC
         err |= __put_user(v_regs, &sc->v_regs);
 
@@ -423,6 +420,9 @@ static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
         if (err)
                 goto badframe;
 
+        /* Make sure signal handler doesn't get spurious FP exceptions */
+        current->thread.fpscr.val = 0;
+
         /* Set up to return from userspace. */
         if (vdso64_rt_sigtramp && current->thread.vdso_base) {
                 regs->link = current->thread.vdso_base + vdso64_rt_sigtramp;