diff mbox series

[v6,06/10] powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext()

Message ID 20210221012401.22328-7-cmr@codefail.de (mailing list archive)
State Superseded
Headers show
Series Improve signal performance on PPC64 with KUAP | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/merge (626a6c3d2e20da80aaa710104f34ea6037b28b33)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/next (6895c5ba7bdcc55eacad03cf309ab23be63b9cac)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linus/master (92bf22614b21a2706f4993b278017e437f7785b3)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/fixes (24321ac668e452a4942598533d267805f291fdc9)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linux-next (1e0d27fce010b0a4a9e595506b6ede75934c31be)
snowpatch_ozlabs/apply_patch fail Failed to apply to any branch

Commit Message

Christopher M. Riedl Feb. 21, 2021, 1:23 a.m. UTC 
Previously setup_sigcontext() performed a costly KUAP switch on every
uaccess operation. These repeated uaccess switches cause a significant
drop in signal handling performance.

Rewrite setup_sigcontext() to assume that a userspace write access window
is open by replacing all uaccess functions with their 'unsafe' versions.
Modify the callers to first open, call unsafe_setup_sigcontext() and
then close the uaccess window.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
---
 arch/powerpc/kernel/signal_64.c | 71 ++++++++++++++++++++-------------
 1 file changed, 44 insertions(+), 27 deletions(-)

Comments

Christophe Leroy Feb. 23, 2021, 5:12 p.m. UTC | #1 
Le 21/02/2021 à 02:23, Christopher M. Riedl a écrit :
> Previously setup_sigcontext() performed a costly KUAP switch on every
> uaccess operation. These repeated uaccess switches cause a significant
> drop in signal handling performance.
> 
> Rewrite setup_sigcontext() to assume that a userspace write access window
> is open by replacing all uaccess functions with their 'unsafe' versions.
> Modify the callers to first open, call unsafe_setup_sigcontext() and
> then close the uaccess window.

Do you plan to also convert setup_tm_sigcontexts() ?
It would allow to then remove copy_fpr_to_user() and copy_ckfpr_to_user() and maybe other functions too.

Christophe

> 
> Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
> ---
>   arch/powerpc/kernel/signal_64.c | 71 ++++++++++++++++++++-------------
>   1 file changed, 44 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index bd8d210c9115..3faaa736ed62 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -101,9 +101,13 @@ static void prepare_setup_sigcontext(struct task_struct *tsk)
>    * Set up the sigcontext for the signal frame.
>    */
>   
> -static long setup_sigcontext(struct sigcontext __user *sc,
> -		struct task_struct *tsk, int signr, sigset_t *set,
> -		unsigned long handler, int ctx_has_vsx_region)
> +#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler,		\
> +				ctx_has_vsx_region, e)			\
> +	unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set,	\
> +			handler, ctx_has_vsx_region), e)
> +static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc,
> +					struct task_struct *tsk, int signr, sigset_t *set,
> +					unsigned long handler, int ctx_has_vsx_region)
>   {
>   	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
>   	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
> @@ -118,20 +122,19 @@ static long setup_sigcontext(struct sigcontext __user *sc,
>   #endif
>   	struct pt_regs *regs = tsk->thread.regs;
>   	unsigned long msr = regs->msr;
> -	long err = 0;
>   	/* Force usr to alway see softe as 1 (interrupts enabled) */
>   	unsigned long softe = 0x1;
>   
>   	BUG_ON(tsk != current);
>   
>   #ifdef CONFIG_ALTIVEC
> -	err |= __put_user(v_regs, &sc->v_regs);
> +	unsafe_put_user(v_regs, &sc->v_regs, efault_out);
>   
>   	/* save altivec registers */
>   	if (tsk->thread.used_vr) {
>   		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
> -		err |= __copy_to_user(v_regs, &tsk->thread.vr_state,
> -				      33 * sizeof(vector128));
> +		unsafe_copy_to_user(v_regs, &tsk->thread.vr_state,
> +				    33 * sizeof(vector128), efault_out);
>   		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
>   		 * contains valid data.
>   		 */
> @@ -140,12 +143,12 @@ static long setup_sigcontext(struct sigcontext __user *sc,
>   	/* We always copy to/from vrsave, it's 0 if we don't have or don't
>   	 * use altivec.
>   	 */
> -	err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]);
> +	unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out);
>   #else /* CONFIG_ALTIVEC */
> -	err |= __put_user(0, &sc->v_regs);
> +	unsafe_put_user(0, &sc->v_regs, efault_out);
>   #endif /* CONFIG_ALTIVEC */
>   	/* copy fpr regs and fpscr */
> -	err |= copy_fpr_to_user(&sc->fp_regs, tsk);
> +	unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out);
>   
>   	/*
>   	 * Clear the MSR VSX bit to indicate there is no valid state attached
> @@ -160,24 +163,27 @@ static long setup_sigcontext(struct sigcontext __user *sc,
>   	 */
>   	if (tsk->thread.used_vsr && ctx_has_vsx_region) {
>   		v_regs += ELF_NVRREG;
> -		err |= copy_vsx_to_user(v_regs, tsk);
> +		unsafe_copy_vsx_to_user(v_regs, tsk, efault_out);
>   		/* set MSR_VSX in the MSR value in the frame to
>   		 * indicate that sc->vs_reg) contains valid data.
>   		 */
>   		msr |= MSR_VSX;
>   	}
>   #endif /* CONFIG_VSX */
> -	err |= __put_user(&sc->gp_regs, &sc->regs);
> +	unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out);
>   	WARN_ON(!FULL_REGS(regs));
> -	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
> -	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
> -	err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]);
> -	err |= __put_user(signr, &sc->signal);
> -	err |= __put_user(handler, &sc->handler);
> +	unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out);
> +	unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out);
> +	unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out);
> +	unsafe_put_user(signr, &sc->signal, efault_out);
> +	unsafe_put_user(handler, &sc->handler, efault_out);
>   	if (set != NULL)
> -		err |=  __put_user(set->sig[0], &sc->oldmask);
> +		unsafe_put_user(set->sig[0], &sc->oldmask, efault_out);
>   
> -	return err;
> +	return 0;
> +
> +efault_out:
> +	return -EFAULT;
>   }
>   
>   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> @@ -670,12 +676,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
>   
>   	if (old_ctx != NULL) {
>   		prepare_setup_sigcontext(current);
> -		if (!access_ok(old_ctx, ctx_size)
> -		    || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0,
> -					ctx_has_vsx_region)
> -		    || __copy_to_user(&old_ctx->uc_sigmask,
> -				      &current->blocked, sizeof(sigset_t)))
> +		if (!user_write_access_begin(old_ctx, ctx_size))
>   			return -EFAULT;
> +
> +		unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL,
> +					0, ctx_has_vsx_region, efault_out);
> +		unsafe_copy_to_user(&old_ctx->uc_sigmask, &current->blocked,
> +				    sizeof(sigset_t), efault_out);
> +
> +		user_write_access_end();
>   	}
>   	if (new_ctx == NULL)
>   		return 0;
> @@ -704,6 +713,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
>   	/* This returns like rt_sigreturn */
>   	set_thread_flag(TIF_RESTOREALL);
>   	return 0;
> +
> +efault_out:
> +	user_write_access_end();
> +	return -EFAULT;
>   }
>   
>   
> @@ -854,9 +867,13 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>   	} else {
>   		err |= __put_user(0, &frame->uc.uc_link);
>   		prepare_setup_sigcontext(tsk);
> -		err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
> -					NULL, (unsigned long)ksig->ka.sa.sa_handler,
> -					1);
> +		if (!user_write_access_begin(&frame->uc.uc_mcontext,
> +					     sizeof(frame->uc.uc_mcontext)))
> +			return -EFAULT;
> +		err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk,
> +						ksig->sig, NULL,
> +						(unsigned long)ksig->ka.sa.sa_handler, 1);
> +		user_write_access_end();
>   	}
>   	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
>   	if (err)
>
Christopher M. Riedl Feb. 24, 2021, 10 p.m. UTC | #2 
On Tue Feb 23, 2021 at 11:12 AM CST, Christophe Leroy wrote:
>
>
> Le 21/02/2021 à 02:23, Christopher M. Riedl a écrit :
> > Previously setup_sigcontext() performed a costly KUAP switch on every
> > uaccess operation. These repeated uaccess switches cause a significant
> > drop in signal handling performance.
> > 
> > Rewrite setup_sigcontext() to assume that a userspace write access window
> > is open by replacing all uaccess functions with their 'unsafe' versions.
> > Modify the callers to first open, call unsafe_setup_sigcontext() and
> > then close the uaccess window.
>
> Do you plan to also convert setup_tm_sigcontexts() ?
> It would allow to then remove copy_fpr_to_user() and
> copy_ckfpr_to_user() and maybe other functions too.

I don't intend to convert the TM functions as part of this series.
Partially because I've been "threatened" with TM ownership for touching
the code :) and also because TM enhancements are a pretty low priority I
think.

>
> Christophe
>
> > 
> > Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
> > ---
> >   arch/powerpc/kernel/signal_64.c | 71 ++++++++++++++++++++-------------
> >   1 file changed, 44 insertions(+), 27 deletions(-)
> > 
> > diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> > index bd8d210c9115..3faaa736ed62 100644
> > --- a/arch/powerpc/kernel/signal_64.c
> > +++ b/arch/powerpc/kernel/signal_64.c
> > @@ -101,9 +101,13 @@ static void prepare_setup_sigcontext(struct task_struct *tsk)
> >    * Set up the sigcontext for the signal frame.
> >    */
> >   
> > -static long setup_sigcontext(struct sigcontext __user *sc,
> > -		struct task_struct *tsk, int signr, sigset_t *set,
> > -		unsigned long handler, int ctx_has_vsx_region)
> > +#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler,		\
> > +				ctx_has_vsx_region, e)			\
> > +	unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set,	\
> > +			handler, ctx_has_vsx_region), e)
> > +static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc,
> > +					struct task_struct *tsk, int signr, sigset_t *set,
> > +					unsigned long handler, int ctx_has_vsx_region)
> >   {
> >   	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
> >   	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
> > @@ -118,20 +122,19 @@ static long setup_sigcontext(struct sigcontext __user *sc,
> >   #endif
> >   	struct pt_regs *regs = tsk->thread.regs;
> >   	unsigned long msr = regs->msr;
> > -	long err = 0;
> >   	/* Force usr to alway see softe as 1 (interrupts enabled) */
> >   	unsigned long softe = 0x1;
> >   
> >   	BUG_ON(tsk != current);
> >   
> >   #ifdef CONFIG_ALTIVEC
> > -	err |= __put_user(v_regs, &sc->v_regs);
> > +	unsafe_put_user(v_regs, &sc->v_regs, efault_out);
> >   
> >   	/* save altivec registers */
> >   	if (tsk->thread.used_vr) {
> >   		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
> > -		err |= __copy_to_user(v_regs, &tsk->thread.vr_state,
> > -				      33 * sizeof(vector128));
> > +		unsafe_copy_to_user(v_regs, &tsk->thread.vr_state,
> > +				    33 * sizeof(vector128), efault_out);
> >   		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
> >   		 * contains valid data.
> >   		 */
> > @@ -140,12 +143,12 @@ static long setup_sigcontext(struct sigcontext __user *sc,
> >   	/* We always copy to/from vrsave, it's 0 if we don't have or don't
> >   	 * use altivec.
> >   	 */
> > -	err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]);
> > +	unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out);
> >   #else /* CONFIG_ALTIVEC */
> > -	err |= __put_user(0, &sc->v_regs);
> > +	unsafe_put_user(0, &sc->v_regs, efault_out);
> >   #endif /* CONFIG_ALTIVEC */
> >   	/* copy fpr regs and fpscr */
> > -	err |= copy_fpr_to_user(&sc->fp_regs, tsk);
> > +	unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out);
> >   
> >   	/*
> >   	 * Clear the MSR VSX bit to indicate there is no valid state attached
> > @@ -160,24 +163,27 @@ static long setup_sigcontext(struct sigcontext __user *sc,
> >   	 */
> >   	if (tsk->thread.used_vsr && ctx_has_vsx_region) {
> >   		v_regs += ELF_NVRREG;
> > -		err |= copy_vsx_to_user(v_regs, tsk);
> > +		unsafe_copy_vsx_to_user(v_regs, tsk, efault_out);
> >   		/* set MSR_VSX in the MSR value in the frame to
> >   		 * indicate that sc->vs_reg) contains valid data.
> >   		 */
> >   		msr |= MSR_VSX;
> >   	}
> >   #endif /* CONFIG_VSX */
> > -	err |= __put_user(&sc->gp_regs, &sc->regs);
> > +	unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out);
> >   	WARN_ON(!FULL_REGS(regs));
> > -	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
> > -	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
> > -	err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]);
> > -	err |= __put_user(signr, &sc->signal);
> > -	err |= __put_user(handler, &sc->handler);
> > +	unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out);
> > +	unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out);
> > +	unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out);
> > +	unsafe_put_user(signr, &sc->signal, efault_out);
> > +	unsafe_put_user(handler, &sc->handler, efault_out);
> >   	if (set != NULL)
> > -		err |=  __put_user(set->sig[0], &sc->oldmask);
> > +		unsafe_put_user(set->sig[0], &sc->oldmask, efault_out);
> >   
> > -	return err;
> > +	return 0;
> > +
> > +efault_out:
> > +	return -EFAULT;
> >   }
> >   
> >   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> > @@ -670,12 +676,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
> >   
> >   	if (old_ctx != NULL) {
> >   		prepare_setup_sigcontext(current);
> > -		if (!access_ok(old_ctx, ctx_size)
> > -		    || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0,
> > -					ctx_has_vsx_region)
> > -		    || __copy_to_user(&old_ctx->uc_sigmask,
> > -				      &current->blocked, sizeof(sigset_t)))
> > +		if (!user_write_access_begin(old_ctx, ctx_size))
> >   			return -EFAULT;
> > +
> > +		unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL,
> > +					0, ctx_has_vsx_region, efault_out);
> > +		unsafe_copy_to_user(&old_ctx->uc_sigmask, &current->blocked,
> > +				    sizeof(sigset_t), efault_out);
> > +
> > +		user_write_access_end();
> >   	}
> >   	if (new_ctx == NULL)
> >   		return 0;
> > @@ -704,6 +713,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
> >   	/* This returns like rt_sigreturn */
> >   	set_thread_flag(TIF_RESTOREALL);
> >   	return 0;
> > +
> > +efault_out:
> > +	user_write_access_end();
> > +	return -EFAULT;
> >   }
> >   
> >   
> > @@ -854,9 +867,13 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
> >   	} else {
> >   		err |= __put_user(0, &frame->uc.uc_link);
> >   		prepare_setup_sigcontext(tsk);
> > -		err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
> > -					NULL, (unsigned long)ksig->ka.sa.sa_handler,
> > -					1);
> > +		if (!user_write_access_begin(&frame->uc.uc_mcontext,
> > +					     sizeof(frame->uc.uc_mcontext)))
> > +			return -EFAULT;
> > +		err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk,
> > +						ksig->sig, NULL,
> > +						(unsigned long)ksig->ka.sa.sa_handler, 1);
> > +		user_write_access_end();
> >   	}
> >   	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
> >   	if (err)
> >
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index bd8d210c9115..3faaa736ed62 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -101,9 +101,13 @@  static void prepare_setup_sigcontext(struct task_struct *tsk)
  * Set up the sigcontext for the signal frame.
  */
 
-static long setup_sigcontext(struct sigcontext __user *sc,
-		struct task_struct *tsk, int signr, sigset_t *set,
-		unsigned long handler, int ctx_has_vsx_region)
+#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler,		\
+				ctx_has_vsx_region, e)			\
+	unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set,	\
+			handler, ctx_has_vsx_region), e)
+static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc,
+					struct task_struct *tsk, int signr, sigset_t *set,
+					unsigned long handler, int ctx_has_vsx_region)
 {
 	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
 	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
@@ -118,20 +122,19 @@  static long setup_sigcontext(struct sigcontext __user *sc,
 #endif
 	struct pt_regs *regs = tsk->thread.regs;
 	unsigned long msr = regs->msr;
-	long err = 0;
 	/* Force usr to alway see softe as 1 (interrupts enabled) */
 	unsigned long softe = 0x1;
 
 	BUG_ON(tsk != current);
 
 #ifdef CONFIG_ALTIVEC
-	err |= __put_user(v_regs, &sc->v_regs);
+	unsafe_put_user(v_regs, &sc->v_regs, efault_out);
 
 	/* save altivec registers */
 	if (tsk->thread.used_vr) {
 		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
-		err |= __copy_to_user(v_regs, &tsk->thread.vr_state,
-				      33 * sizeof(vector128));
+		unsafe_copy_to_user(v_regs, &tsk->thread.vr_state,
+				    33 * sizeof(vector128), efault_out);
 		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 		 * contains valid data.
 		 */
@@ -140,12 +143,12 @@  static long setup_sigcontext(struct sigcontext __user *sc,
 	/* We always copy to/from vrsave, it's 0 if we don't have or don't
 	 * use altivec.
 	 */
-	err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]);
+	unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out);
 #else /* CONFIG_ALTIVEC */
-	err |= __put_user(0, &sc->v_regs);
+	unsafe_put_user(0, &sc->v_regs, efault_out);
 #endif /* CONFIG_ALTIVEC */
 	/* copy fpr regs and fpscr */
-	err |= copy_fpr_to_user(&sc->fp_regs, tsk);
+	unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out);
 
 	/*
 	 * Clear the MSR VSX bit to indicate there is no valid state attached
@@ -160,24 +163,27 @@  static long setup_sigcontext(struct sigcontext __user *sc,
 	 */
 	if (tsk->thread.used_vsr && ctx_has_vsx_region) {
 		v_regs += ELF_NVRREG;
-		err |= copy_vsx_to_user(v_regs, tsk);
+		unsafe_copy_vsx_to_user(v_regs, tsk, efault_out);
 		/* set MSR_VSX in the MSR value in the frame to
 		 * indicate that sc->vs_reg) contains valid data.
 		 */
 		msr |= MSR_VSX;
 	}
 #endif /* CONFIG_VSX */
-	err |= __put_user(&sc->gp_regs, &sc->regs);
+	unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out);
 	WARN_ON(!FULL_REGS(regs));
-	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
-	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
-	err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]);
-	err |= __put_user(signr, &sc->signal);
-	err |= __put_user(handler, &sc->handler);
+	unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out);
+	unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out);
+	unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out);
+	unsafe_put_user(signr, &sc->signal, efault_out);
+	unsafe_put_user(handler, &sc->handler, efault_out);
 	if (set != NULL)
-		err |=  __put_user(set->sig[0], &sc->oldmask);
+		unsafe_put_user(set->sig[0], &sc->oldmask, efault_out);
 
-	return err;
+	return 0;
+
+efault_out:
+	return -EFAULT;
 }
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
@@ -670,12 +676,15 @@  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
 
 	if (old_ctx != NULL) {
 		prepare_setup_sigcontext(current);
-		if (!access_ok(old_ctx, ctx_size)
-		    || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0,
-					ctx_has_vsx_region)
-		    || __copy_to_user(&old_ctx->uc_sigmask,
-				      &current->blocked, sizeof(sigset_t)))
+		if (!user_write_access_begin(old_ctx, ctx_size))
 			return -EFAULT;
+
+		unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL,
+					0, ctx_has_vsx_region, efault_out);
+		unsafe_copy_to_user(&old_ctx->uc_sigmask, &current->blocked,
+				    sizeof(sigset_t), efault_out);
+
+		user_write_access_end();
 	}
 	if (new_ctx == NULL)
 		return 0;
@@ -704,6 +713,10 @@  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
 	/* This returns like rt_sigreturn */
 	set_thread_flag(TIF_RESTOREALL);
 	return 0;
+
+efault_out:
+	user_write_access_end();
+	return -EFAULT;
 }
 
 
@@ -854,9 +867,13 @@  int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	} else {
 		err |= __put_user(0, &frame->uc.uc_link);
 		prepare_setup_sigcontext(tsk);
-		err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
-					NULL, (unsigned long)ksig->ka.sa.sa_handler,
-					1);
+		if (!user_write_access_begin(&frame->uc.uc_mcontext,
+					     sizeof(frame->uc.uc_mcontext)))
+			return -EFAULT;
+		err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk,
+						ksig->sig, NULL,
+						(unsigned long)ksig->ka.sa.sa_handler, 1);
+		user_write_access_end();
 	}
 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 	if (err)