Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Mon, 05 Feb 2007 16:12:26 +0000, linux-mips@linux-mips.org wrote:
> Author: Chris Dearman <chris@mips.com> Thu Feb 1 19:54:13 2007 +0000
> Comitter: Ralf Baechle <ralf@linux-mips.org> Mon Feb 5 15:56:18 2007 +0000
> Commit: a9e080c2c615bc4e9d9987330c0be35ea5226eed
> Gitweb: http://www.linux-mips.org/g/linux/a9e080c2
> Branch: master
> 
> Signed-off-by: Chris Dearman <chris@mips.com>
> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
> 
> ---
> 
>  arch/mips/kernel/r4k_fpu.S |   16 ++++++++++++++++
>  1 files changed, 16 insertions(+), 0 deletions(-)

r2300_fpu.S and r6000_fpu.S should be fixed too?

Also, fpu_emulator_restore_context() should check FCSR too? (it should
not harm FPU-less CPU, but on MIPS_MT, FCSR value restored by fpu
emulator might be used for real FPU, right?)

---
Atsushi Nemoto

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Ralf Baechle]

On Wed, Feb 07, 2007 at 01:38:09PM +0900, Atsushi Nemoto wrote:

> >  arch/mips/kernel/r4k_fpu.S |   16 ++++++++++++++++
> >  1 files changed, 16 insertions(+), 0 deletions(-)
> 
> r2300_fpu.S and r6000_fpu.S should be fixed too?
> 
> Also, fpu_emulator_restore_context() should check FCSR too? (it should
> not harm FPU-less CPU, but on MIPS_MT, FCSR value restored by fpu
> emulator might be used for real FPU, right?)

Correct in all points.

  Ralf

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Wed, 7 Feb 2007 11:09:29 +0000, Ralf Baechle <ralf@linux-mips.org> wrote:
> > r2300_fpu.S and r6000_fpu.S should be fixed too?
> > 
> > Also, fpu_emulator_restore_context() should check FCSR too? (it should
> > not harm FPU-less CPU, but on MIPS_MT, FCSR value restored by fpu
> > emulator might be used for real FPU, right?)
> 
> Correct in all points.

If the format of FCSR was common to all CPU (I hope so), we can do
check it in caller of fp_restore_context(), in C language.

BTW, why R6000 does not use r4k_fpu.S?
---
Atsushi Nemoto

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Maciej W. Rozycki]

On Thu, 8 Feb 2007, Atsushi Nemoto wrote:

> If the format of FCSR was common to all CPU (I hope so), we can do
> check it in caller of fp_restore_context(), in C language.

 The R3010, etc. use bits 23 and 17:0 the same way as the R4000 and MIPS 
architecture processors do.  The other bits are unused and hardwired to 
zeroes.

  Maciej

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Wed, 7 Feb 2007 17:29:02 +0000 (GMT), "Maciej W. Rozycki" <macro@linux-mips.org> wrote:
> > If the format of FCSR was common to all CPU (I hope so), we can do
> > check it in caller of fp_restore_context(), in C language.
> 
>  The R3010, etc. use bits 23 and 17:0 the same way as the R4000 and MIPS 
> architecture processors do.  The other bits are unused and hardwired to 
> zeroes.

So we can do it in C, but it will conflicts with Franck's signal
cleanup patchset.  I hope his patchset applied first.

Also I wonder SIGSEGV is correct behavior on this case.  SIGFPE?

---
Atsushi Nemoto

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Thu, 08 Feb 2007 12:02:19 +0900 (JST), Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> So we can do it in C, but it will conflicts with Franck's signal
> cleanup patchset.  I hope his patchset applied first.
> 
> Also I wonder SIGSEGV is correct behavior on this case.  SIGFPE?

And I found that if signal handler set FPU_CSR_UNI_X, kernel complains
"FP exception in kernel code" ...

Here is a first cut.  Changes in r4k_fpu.S can be reverted, and after
Franck's patchset applied, this patch can be a bit smaller.  Please
review.

Note that calling __get_user(), __put_user() might lose FPU ownership.
But restore_fp_context() already has this breakage.  I already sent
two alternative patches to fix this longstanding issue ("[PATCH]
rewrite restore_fp_context/save_fp_context" and "[PATCH 2/3] Allow CpU
exception in kernel partially").


diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index b1f09d5..0811298 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -66,6 +66,38 @@ out:
 }
 
 static inline 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 inline 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;
+}
+
+static inline int
 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 {
 	unsigned int used_math;
@@ -112,7 +144,8 @@ restore_sigcontext(struct pt_regs *regs,
 	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();
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 9a44053..31d8ec0 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -190,6 +190,7 @@ _sys_sigreturn(nabi_no_regargs struct pt
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -203,8 +204,12 @@ _sys_sigreturn(nabi_no_regargs struct pt
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext(&regs, &frame->sf_sc))
+	sig = restore_sigcontext(&regs, &frame->sf_sc);
 		goto badframe;
+	if (sig < 0)
+		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...
@@ -228,6 +233,7 @@ _sys_rt_sigreturn(nabi_no_regargs struct
 	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)))
@@ -241,8 +247,11 @@ _sys_rt_sigreturn(nabi_no_regargs struct
 	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;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index c86a5dd..51eb21d 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -326,6 +326,38 @@ asmlinkage int sys32_sigaltstack(nabi_no
 	return ret;
 }
 
+static inline 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 inline int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+	int err, sig;
+
+	sig = fpcsr_pending(&sc->sc_fpc_csr);
+	if (sig < 0)
+		err = sig;
+	err |= restore_fp_context32(sc);
+	return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs, struct sigcontext32 __user *sc)
 {
 	u32 used_math;
@@ -372,7 +404,8 @@ static int restore_sigcontext32(struct p
 	if (used_math()) {
 		/* restore fpu context if we have used it before */
 		own_fpu();
-		err |= restore_fp_context32(sc);
+		if (!err)
+			err = check_and_restore_fp_context(sc);
 	} else {
 		/* signal handler may have used FPU.  Give it up. */
 		lose_fpu();
@@ -469,6 +502,7 @@ _sys32_sigreturn(nabi_no_regargs struct
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -482,8 +516,11 @@ _sys32_sigreturn(nabi_no_regargs struct
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->sf_sc))
+	sig = restore_sigcontext32(&regs, &frame->sf_sc);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Franck Bui-Huu]

On 2/8/07, Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> On Thu, 08 Feb 2007 12:02:19 +0900 (JST), Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> Here is a first cut.  Changes in r4k_fpu.S can be reverted, and after
> Franck's patchset applied, this patch can be a bit smaller.  Please
> review.
>

yes this's going to conflict a lot with the patchset I sent...

[snip]

> +static inline int
>  restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
>  {
>         unsigned int used_math;
> @@ -112,7 +144,8 @@ restore_sigcontext(struct pt_regs *regs,
>         if (used_math()) {

sorry for the stupid question but I don't know fpu code...Here
used_math() function is used as condition whereas used_math local is
already defined. Are we sure we want to use the function here ?

-- 
               Franck

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Thu, 8 Feb 2007 17:30:29 +0100, "Franck Bui-Huu" <vagabon.xyz@gmail.com> wrote:
> yes this's going to conflict a lot with the patchset I sent...

Here is a patch can be applied on top of your patchset.


Subject: Check FCSR for pending interrupts, alternative version

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

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

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/kernel/r4k_fpu.S       |   16 ------------
 arch/mips/kernel/signal-common.h |    3 ++
 arch/mips/kernel/signal.c        |   46 ++++++++++++++++++++++++++++++++++---
 arch/mips/kernel/signal32.c      |   27 +++++++++++++++++++--
 4 files changed, 70 insertions(+), 22 deletions(-)

diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 59c1577..dbd42ad 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -114,14 +114,6 @@ LEAF(_save_fp_context32)
  */
 LEAF(_restore_fp_context)
 	EX	lw t0, SC_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 #ifdef CONFIG_64BIT
 	EX	ldc1 $f1, SC_FPREGS+8(a0)
 	EX	ldc1 $f3, SC_FPREGS+24(a0)
@@ -165,14 +157,6 @@ LEAF(_restore_fp_context)
 LEAF(_restore_fp_context32)
 	/* Restore an o32 sigcontext.  */
 	EX	lw t0, SC32_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 	EX	ldc1 $f0, SC32_FPREGS+0(a0)
 	EX	ldc1 $f2, SC32_FPREGS+16(a0)
 	EX	ldc1 $f4, SC32_FPREGS+32(a0)
diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index 9a8abd6..1f24288 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -61,4 +61,7 @@ extern void __user *get_sigframe(struct
  */
 extern int install_sigtramp(unsigned int __user *tramp, unsigned int syscall);
 
+/* Check and clear pending FPU exceptions in saved CSR */
+extern int fpcsr_pending(unsigned int __user *fpcsr);
+
 #endif	/* __SIGNAL_COMMON_H */
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 8dfb7b1..d7531d5 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -103,6 +103,37 @@ int setup_sigcontext(struct pt_regs *reg
 	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;
@@ -137,7 +168,8 @@ int restore_sigcontext(struct pt_regs *r
 	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();
@@ -307,6 +339,7 @@ asmlinkage void sys_sigreturn(nabi_no_re
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -320,8 +353,11 @@ asmlinkage void sys_sigreturn(nabi_no_re
 	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 ...
@@ -343,6 +379,7 @@ asmlinkage void sys_rt_sigreturn(nabi_no
 	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)))
@@ -356,8 +393,11 @@ asmlinkage void sys_rt_sigreturn(nabi_no
 	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;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 183fc7e..c37ff65 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -207,6 +207,18 @@ static int setup_sigcontext32(struct pt_
 	return err;
 }
 
+static int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+	int err, sig;
+
+	sig = fpcsr_pending(&sc->sc_fpc_csr);
+	if (sig < 0)
+		err = sig;
+	err |= restore_fp_context32(sc);
+	return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs,
 				struct sigcontext32 __user *sc)
 {
@@ -242,7 +254,8 @@ static int restore_sigcontext32(struct p
 	if (used_math()) {
 		/* restore fpu context if we have used it before */
 		own_fpu();
-		err |= restore_fp_context32(sc);
+		if (!err)
+			err = check_and_restore_fp_context32(sc);
 	} else {
 		/* signal handler may have used FPU.  Give it up. */
 		lose_fpu();
@@ -495,6 +508,7 @@ asmlinkage void sys32_sigreturn(nabi_no_
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -508,8 +522,11 @@ asmlinkage void sys32_sigreturn(nabi_no_
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->sf_sc))
+	sig = restore_sigcontext32(&regs, &frame->sf_sc);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...
@@ -532,6 +549,7 @@ asmlinkage void sys32_rt_sigreturn(nabi_
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -545,8 +563,11 @@ asmlinkage void sys32_rt_sigreturn(nabi_
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext))
+	sig = restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Thu, 8 Feb 2007 17:30:29 +0100, "Franck Bui-Huu" <vagabon.xyz@gmail.com> wrote:
> >         unsigned int used_math;
> > @@ -112,7 +144,8 @@ restore_sigcontext(struct pt_regs *regs,
> >         if (used_math()) {
> 
> sorry for the stupid question but I don't know fpu code...Here
> used_math() function is used as condition whereas used_math local is
> already defined. Are we sure we want to use the function here ?

Well, used_math() returns condition which are set by preceeding
conditional_used_math().  In this case the condition is used_math :)
Maybe we can use the used_math variable here to optimize a bit.

---
Atsushi Nemoto

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Fri, 09 Feb 2007 01:54:05 +0900 (JST), Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> Here is a patch can be applied on top of your patchset.

I missed n32 part.  Revised.


Subject: Check FCSR for pending interrupts, alternative version

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

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

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/kernel/r4k_fpu.S       |   16 ------------
 arch/mips/kernel/signal-common.h |    3 ++
 arch/mips/kernel/signal.c        |   46 ++++++++++++++++++++++++++++++++++---
 arch/mips/kernel/signal32.c      |   27 +++++++++++++++++++--
 arch/mips/kernel/signal_n32.c    |    6 ++++
 5 files changed, 75 insertions(+), 23 deletions(-)

diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 59c1577..dbd42ad 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -114,14 +114,6 @@ LEAF(_save_fp_context32)
  */
 LEAF(_restore_fp_context)
 	EX	lw t0, SC_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 #ifdef CONFIG_64BIT
 	EX	ldc1 $f1, SC_FPREGS+8(a0)
 	EX	ldc1 $f3, SC_FPREGS+24(a0)
@@ -165,14 +157,6 @@ LEAF(_restore_fp_context)
 LEAF(_restore_fp_context32)
 	/* Restore an o32 sigcontext.  */
 	EX	lw t0, SC32_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 	EX	ldc1 $f0, SC32_FPREGS+0(a0)
 	EX	ldc1 $f2, SC32_FPREGS+16(a0)
 	EX	ldc1 $f4, SC32_FPREGS+32(a0)
diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index 9a8abd6..1f24288 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -61,4 +61,7 @@ extern void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
  */
 extern int install_sigtramp(unsigned int __user *tramp, unsigned int syscall);
 
+/* Check and clear pending FPU exceptions in saved CSR */
+extern int fpcsr_pending(unsigned int __user *fpcsr);
+
 #endif	/* __SIGNAL_COMMON_H */
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 8dfb7b1..d7531d5 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -103,6 +103,37 @@ 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;
@@ -137,7 +168,8 @@ 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();
@@ -307,6 +339,7 @@ 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)))
@@ -320,8 +353,11 @@ 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 ...
@@ -343,6 +379,7 @@ 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)))
@@ -356,8 +393,11 @@ 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;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 183fc7e..c37ff65 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -207,6 +207,18 @@ static int setup_sigcontext32(struct pt_regs *regs,
 	return err;
 }
 
+static int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+	int err, sig;
+
+	sig = fpcsr_pending(&sc->sc_fpc_csr);
+	if (sig < 0)
+		err = sig;
+	err |= restore_fp_context32(sc);
+	return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs,
 				struct sigcontext32 __user *sc)
 {
@@ -242,7 +254,8 @@ static int restore_sigcontext32(struct pt_regs *regs,
 	if (used_math()) {
 		/* restore fpu context if we have used it before */
 		own_fpu();
-		err |= restore_fp_context32(sc);
+		if (!err)
+			err = check_and_restore_fp_context32(sc);
 	} else {
 		/* signal handler may have used FPU.  Give it up. */
 		lose_fpu();
@@ -495,6 +508,7 @@ asmlinkage void sys32_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)))
@@ -508,8 +522,11 @@ asmlinkage void sys32_sigreturn(nabi_no_regargs struct pt_regs regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->sf_sc))
+	sig = restore_sigcontext32(&regs, &frame->sf_sc);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...
@@ -532,6 +549,7 @@ asmlinkage void sys32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -545,8 +563,11 @@ asmlinkage void sys32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext))
+	sig = restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))
diff --git a/arch/mips/kernel/signal_n32.c b/arch/mips/kernel/signal_n32.c
index 57456e6..01c6627 100644
--- a/arch/mips/kernel/signal_n32.c
+++ b/arch/mips/kernel/signal_n32.c
@@ -123,6 +123,7 @@ asmlinkage void sysn32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe_n32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -136,8 +137,11 @@ asmlinkage void sysn32_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);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

Revised again.  Fix check_and_restore_fp_context32 and rediff against
current git.


Subject: Check FCSR for pending interrupts, alternative version

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

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

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/kernel/r4k_fpu.S       |   16 ------------
 arch/mips/kernel/signal-common.h |    3 ++
 arch/mips/kernel/signal.c        |   46 ++++++++++++++++++++++++++++++++++---
 arch/mips/kernel/signal32.c      |   27 +++++++++++++++++++--
 arch/mips/kernel/signal_n32.c    |    6 ++++
 5 files changed, 75 insertions(+), 23 deletions(-)

diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 59c1577..dbd42ad 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -114,14 +114,6 @@ LEAF(_save_fp_context32)
  */
 LEAF(_restore_fp_context)
 	EX	lw t0, SC_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 #ifdef CONFIG_64BIT
 	EX	ldc1 $f1, SC_FPREGS+8(a0)
 	EX	ldc1 $f3, SC_FPREGS+24(a0)
@@ -165,14 +157,6 @@ LEAF(_restore_fp_context)
 LEAF(_restore_fp_context32)
 	/* Restore an o32 sigcontext.  */
 	EX	lw t0, SC32_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 	EX	ldc1 $f0, SC32_FPREGS+0(a0)
 	EX	ldc1 $f2, SC32_FPREGS+16(a0)
 	EX	ldc1 $f4, SC32_FPREGS+32(a0)
diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index fdbdbdc..297dfcb 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -31,4 +31,7 @@ extern void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
  */
 extern int install_sigtramp(unsigned int __user *tramp, unsigned int syscall);
 
+/* Check and clear pending FPU exceptions in saved CSR */
+extern int fpcsr_pending(unsigned int __user *fpcsr);
+
 #endif	/* __SIGNAL_COMMON_H */
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index b2e9ab1..2420ed6 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -121,6 +121,37 @@ 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;
@@ -155,7 +186,8 @@ 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();
@@ -325,6 +357,7 @@ 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)))
@@ -338,8 +371,11 @@ 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 ...
@@ -361,6 +397,7 @@ 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)))
@@ -374,8 +411,11 @@ 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;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index dd4e518..813279d 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -220,6 +220,18 @@ static int setup_sigcontext32(struct pt_regs *regs,
 	return err;
 }
 
+static int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+	int err, sig;
+
+	err = sig = fpcsr_pending(&sc->sc_fpc_csr);
+	if (err > 0)
+		err = 0;
+	err |= restore_fp_context32(sc);
+	return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs,
 				struct sigcontext32 __user *sc)
 {
@@ -255,7 +267,8 @@ static int restore_sigcontext32(struct pt_regs *regs,
 	if (used_math()) {
 		/* restore fpu context if we have used it before */
 		own_fpu();
-		err |= restore_fp_context32(sc);
+		if (!err)
+			err = check_and_restore_fp_context32(sc);
 	} else {
 		/* signal handler may have used FPU.  Give it up. */
 		lose_fpu();
@@ -508,6 +521,7 @@ asmlinkage void sys32_sigreturn(nabi_no_regargs struct pt_regs regs)
 {
 	struct sigframe32 __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -521,8 +535,11 @@ asmlinkage void sys32_sigreturn(nabi_no_regargs struct pt_regs regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->sf_sc))
+	sig = restore_sigcontext32(&regs, &frame->sf_sc);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...
@@ -545,6 +562,7 @@ asmlinkage void sys32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -558,8 +576,11 @@ asmlinkage void sys32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext))
+	sig = restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))
diff --git a/arch/mips/kernel/signal_n32.c b/arch/mips/kernel/signal_n32.c
index 7ca2a07..26ca944 100644
--- a/arch/mips/kernel/signal_n32.c
+++ b/arch/mips/kernel/signal_n32.c
@@ -126,6 +126,7 @@ asmlinkage void sysn32_rt_sigreturn(nabi_no_regargs struct pt_regs regs)
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe_n32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -139,8 +140,11 @@ asmlinkage void sysn32_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);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Franck Bui-Huu]

Hi Atsushi,

On 2/14/07, Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> Revised again.  Fix check_and_restore_fp_context32 and rediff against
> current git.
>
>
> Subject: Check FCSR for pending interrupts, alternative version
>

[snip]

> diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
> index fdbdbdc..297dfcb 100644
> --- a/arch/mips/kernel/signal-common.h
> +++ b/arch/mips/kernel/signal-common.h
> @@ -31,4 +31,7 @@ extern void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
>   */
>  extern int install_sigtramp(unsigned int __user *tramp, unsigned int syscall);
>
> +/* Check and clear pending FPU exceptions in saved CSR */
> +extern int fpcsr_pending(unsigned int __user *fpcsr);
> +

Just my 2 cents: This looks like the wrong place for this fpu
prototype. I mean shouldn't it belong to a fpu header file or
something else ?
-- 
               Franck

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Wed, 14 Feb 2007 09:34:53 +0100, "Franck Bui-Huu" <vagabon.xyz@gmail.com> wrote:
> > +/* Check and clear pending FPU exceptions in saved CSR */
> > +extern int fpcsr_pending(unsigned int __user *fpcsr);
> > +
> 
> Just my 2 cents: This looks like the wrong place for this fpu
> prototype. I mean shouldn't it belong to a fpu header file or
> something else ?

Well, this is a helper function for signal so signal-common.h is not
so bad, I think.  And adding to kernel/signal-common.h looks less
intrusive than adding to include/asm-mips/fpu.h, in my impression.

---
Atsushi Nemoto

Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.

[Atsushi Nemoto]

On Wed, 14 Feb 2007 17:04:20 +0900 (JST), Atsushi Nemoto <anemo@mba.ocn.ne.jp> wrote:
> Subject: Check FCSR for pending interrupts, alternative version
> 
> The commit 6d6671066a311703bca1b91645bb1e04cc983387 is incomplete and
> misses non-r4k CPUs.  This patch reverts the commit and fixes in other
> way.
> 
> * Do FCSR checking in caller of restore_fp_context.
> * Send SIGFPE if the signal handler set any FPU exception bits.

And this is for 2.6.20-stable tree.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/kernel/r4k_fpu.S       |   16 --------------
 arch/mips/kernel/signal-common.h |   35 ++++++++++++++++++++++++++++++-
 arch/mips/kernel/signal.c        |   12 +++++++++-
 arch/mips/kernel/signal32.c      |   41 +++++++++++++++++++++++++++++++++++--
 arch/mips/kernel/signal_n32.c    |    6 ++++-
 5 files changed, 88 insertions(+), 22 deletions(-)

diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 59c1577..dbd42ad 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -114,14 +114,6 @@ LEAF(_save_fp_context32)
  */
 LEAF(_restore_fp_context)
 	EX	lw t0, SC_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 #ifdef CONFIG_64BIT
 	EX	ldc1 $f1, SC_FPREGS+8(a0)
 	EX	ldc1 $f3, SC_FPREGS+24(a0)
@@ -165,14 +157,6 @@ LEAF(_restore_fp_context)
 LEAF(_restore_fp_context32)
 	/* Restore an o32 sigcontext.  */
 	EX	lw t0, SC32_FPC_CSR(a0)
-
-	/* Fail if the CSR has exceptions pending */
-	srl	t1, t0, 5
-	and	t1, t0
-	andi	t1, 0x1f << 7
-	bnez	t1, fault
-	 nop
-
 	EX	ldc1 $f0, SC32_FPREGS+0(a0)
 	EX	ldc1 $f2, SC32_FPREGS+16(a0)
 	EX	ldc1 $f4, SC32_FPREGS+32(a0)
diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index b1f09d5..0811298 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -66,6 +66,38 @@ out:
 }
 
 static inline 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 inline 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;
+}
+
+static inline int
 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 {
 	unsigned int used_math;
@@ -112,7 +144,8 @@ restore_sigcontext(struct pt_regs *regs,
 	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();
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index b9d358e..c19408e 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -190,6 +190,7 @@ _sys_sigreturn(nabi_no_regargs struct pt
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -203,8 +204,11 @@ _sys_sigreturn(nabi_no_regargs struct pt
 	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 ...
@@ -228,6 +232,7 @@ _sys_rt_sigreturn(nabi_no_regargs struct
 	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)))
@@ -241,8 +246,11 @@ _sys_rt_sigreturn(nabi_no_regargs struct
 	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;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 7464df4..80ac070 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -321,6 +321,38 @@ asmlinkage int sys32_sigaltstack(nabi_no
 	return ret;
 }
 
+static inline 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 inline int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+	int err, sig;
+
+	err = sig = fpcsr_pending(&sc->sc_fpc_csr);
+	if (err > 0)
+		err = 0;
+	err |= restore_fp_context32(sc);
+	return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs, struct sigcontext32 __user *sc)
 {
 	u32 used_math;
@@ -367,7 +399,8 @@ static int restore_sigcontext32(struct p
 	if (used_math()) {
 		/* restore fpu context if we have used it before */
 		own_fpu();
-		err |= restore_fp_context32(sc);
+		if (!err)
+			err = check_and_restore_fp_context32(sc);
 	} else {
 		/* signal handler may have used FPU.  Give it up. */
 		lose_fpu();
@@ -464,6 +497,7 @@ _sys32_sigreturn(nabi_no_regargs struct
 {
 	struct sigframe __user *frame;
 	sigset_t blocked;
+	int sig;
 
 	frame = (struct sigframe __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -477,8 +511,11 @@ _sys32_sigreturn(nabi_no_regargs struct
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext32(&regs, &frame->sf_sc))
+	sig = restore_sigcontext32(&regs, &frame->sf_sc);
+	if (sig < 0)
 		goto badframe;
+	else if (sig)
+		force_sig(sig, current);
 
 	/*
 	 * Don't let your children do this ...
diff --git a/arch/mips/kernel/signal_n32.c b/arch/mips/kernel/signal_n32.c
index d6160c9..617edd9 100644
--- a/arch/mips/kernel/signal_n32.c
+++ b/arch/mips/kernel/signal_n32.c
@@ -123,6 +123,7 @@ _sysn32_rt_sigreturn(nabi_no_regargs str
 	sigset_t set;
 	stack_t st;
 	s32 sp;
+	int sig;
 
 	frame = (struct rt_sigframe_n32 __user *) regs.regs[29];
 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -136,8 +137,11 @@ _sysn32_rt_sigreturn(nabi_no_regargs str
 	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);
 
 	/* The ucontext contains a stack32_t, so we must convert!  */
 	if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))