diff mbox series

[v2,5/8] powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext()

Message ID 20201105051701.25053-6-cmr@codefail.de
State Superseded
Headers show
Series Improve signal performance on PPC64 with KUAP | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch fail Failed to apply to any branch
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linux-next (cf7cd542d1b538f6e9e83490bc090dd773f4266d)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/fixes (1344a232016dbb0492be81f8517c4bf8fc1c6610)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linus/master (4ef8451b332662d004df269d4cdeb7d9f31419b5)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/next (3cea11cd5e3b00d91caf0b4730194039b45c5891)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/merge (58b9041431fcf9f3f87c8def87ca82dd54cf80dd)

Commit Message

Christopher M. Riedl Nov. 5, 2020, 5:16 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. Replace all uaccess functions with their 'unsafe' versions
which avoid the repeated uaccess switches.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
---
 arch/powerpc/kernel/signal_64.c | 70 ++++++++++++++++++++-------------
 1 file changed, 43 insertions(+), 27 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index d3e9519b2e62..3f25309826b6 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, int ctx_has_vsx_re
  * 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
@@ -664,12 +670,15 @@  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
 
 	if (old_ctx != NULL) {
 		prepare_setup_sigcontext(current, ctx_has_vsx_region);
-		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;
@@ -698,6 +707,10 @@  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;
 }
 
 
@@ -849,9 +862,12 @@  int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	} else {
 		err |= __put_user(0, &frame->uc.uc_link);
 		prepare_setup_sigcontext(tsk, 1);
-		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, sizeof(struct rt_sigframe)))
+			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)