[MIPS] Check FCSR for pending interrupts, alternative version

Commit 6d6671066a311703bca1b91645bb1e04cc983387 is incomplete and misses
non-r4k CPUs.  This patch reverts the commit and fixes in other way.

 o Do FCSR checking in caller of restore_fp_context.
 o Send SIGFPE if the signal handler set any FPU exception bits.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 43 insertions, 3 deletions

diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index f091786187a6..bf094fc4c7eb 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -124,6 +124,37 @@ int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
         return err;
 }
 
+int fpcsr_pending(unsigned int __user *fpcsr)
+{
+        int err, sig = 0;
+        unsigned int csr, enabled;
+
+        err = __get_user(csr, fpcsr);
+        enabled = FPU_CSR_UNI_X | ((csr & FPU_CSR_ALL_E) << 5);
+        /*
+         * If the signal handler set some FPU exceptions, clear it and
+         * send SIGFPE.
+         */
+        if (csr & enabled) {
+                csr &= ~enabled;
+                err |= __put_user(csr, fpcsr);
+                sig = SIGFPE;
+        }
+        return err ?: sig;
+}
+
+static int
+check_and_restore_fp_context(struct sigcontext __user *sc)
+{
+        int err, sig;
+
+        err = sig = fpcsr_pending(&sc->sc_fpc_csr);
+        if (err > 0)
+                err = 0;
+        err |= restore_fp_context(sc);
+        return err ?: sig;
+}
+
 int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 {
         unsigned int used_math;
@@ -162,7 +193,8 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
         if (used_math()) {
                 /* restore fpu context if we have used it before */
                 own_fpu();
-                err |= restore_fp_context(sc);
+                if (!err)
+                        err = check_and_restore_fp_context(sc);
         } else {
                 /* signal handler may have used FPU.  Give it up. */
                 lose_fpu();
@@ -332,6 +364,7 @@ asmlinkage void sys_sigreturn(nabi_no_regargs struct pt_regs regs)
 {
         struct sigframe __user *frame;
         sigset_t blocked;
+        int sig;
 
         frame = (struct sigframe __user *) regs.regs[29];
         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -345,8 +378,11 @@ asmlinkage void sys_sigreturn(nabi_no_regargs struct pt_regs regs)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        if (restore_sigcontext(&regs, &frame->sf_sc))
+        sig = restore_sigcontext(&regs, &frame->sf_sc);
+        if (sig < 0)
                 goto badframe;
+        else if (sig)
+                force_sig(sig, current);
 
         /*
          * Don't let your children do this ...
@@ -368,6 +404,7 @@ asmlinkage void sys_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
         struct rt_sigframe __user *frame;
         sigset_t set;
         stack_t st;
+        int sig;
 
         frame = (struct rt_sigframe __user *) regs.regs[29];
         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -381,8 +418,11 @@ asmlinkage void sys_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        if (restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext))
+        sig = restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext);
+        if (sig < 0)
                 goto badframe;
+        else if (sig)
+                force_sig(sig, current);
 
         if (__copy_from_user(&st, &frame->rs_uc.uc_stack, sizeof(st)))
                 goto badframe;