diff mbox series

[v2,6/8] powerpc/signal64: Replace restore_sigcontext() w/ unsafe_restore_sigcontext()

Message ID 20201105051701.25053-7-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State Superseded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 restore_sigcontext() performed a costly KUAP switch on every
uaccess operation. These repeated uaccess switches cause a significant
drop in signal handling performance.

Rewrite restore_sigcontext() to assume that a userspace read 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 | 68 ++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 27 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 3f25309826b6..d72153825719 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -326,14 +326,14 @@  static long setup_tm_sigcontexts(struct sigcontext __user *sc,
 /*
  * Restore the sigcontext from the signal frame.
  */
-
-static long restore_sigcontext(struct task_struct *tsk, sigset_t *set, int sig,
-			      struct sigcontext __user *sc)
+#define unsafe_restore_sigcontext(tsk, set, sig, sc, e) \
+	unsafe_op_wrap(__unsafe_restore_sigcontext(tsk, set, sig, sc), e)
+static long notrace __unsafe_restore_sigcontext(struct task_struct *tsk, sigset_t *set,
+						int sig, struct sigcontext __user *sc)
 {
 #ifdef CONFIG_ALTIVEC
 	elf_vrreg_t __user *v_regs;
 #endif
-	unsigned long err = 0;
 	unsigned long save_r13 = 0;
 	unsigned long msr;
 	struct pt_regs *regs = tsk->thread.regs;
@@ -348,27 +348,28 @@  static long restore_sigcontext(struct task_struct *tsk, sigset_t *set, int sig,
 		save_r13 = regs->gpr[13];
 
 	/* copy the GPRs */
-	err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
-	err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
+	unsafe_copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr),
+			      efault_out);
+	unsafe_get_user(regs->nip, &sc->gp_regs[PT_NIP], efault_out);
 	/* get MSR separately, transfer the LE bit if doing signal return */
-	err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
+	unsafe_get_user(msr, &sc->gp_regs[PT_MSR], efault_out);
 	if (sig)
 		regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
-	err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
-	err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
-	err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
-	err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
-	err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
+	unsafe_get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3], efault_out);
+	unsafe_get_user(regs->ctr, &sc->gp_regs[PT_CTR], efault_out);
+	unsafe_get_user(regs->link, &sc->gp_regs[PT_LNK], efault_out);
+	unsafe_get_user(regs->xer, &sc->gp_regs[PT_XER], efault_out);
+	unsafe_get_user(regs->ccr, &sc->gp_regs[PT_CCR], efault_out);
 	/* Don't allow userspace to set SOFTE */
 	set_trap_norestart(regs);
-	err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
-	err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
-	err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);
+	unsafe_get_user(regs->dar, &sc->gp_regs[PT_DAR], efault_out);
+	unsafe_get_user(regs->dsisr, &sc->gp_regs[PT_DSISR], efault_out);
+	unsafe_get_user(regs->result, &sc->gp_regs[PT_RESULT], efault_out);
 
 	if (!sig)
 		regs->gpr[13] = save_r13;
 	if (set != NULL)
-		err |=  __get_user(set->sig[0], &sc->oldmask);
+		unsafe_get_user(set->sig[0], &sc->oldmask, efault_out);
 
 	/*
 	 * Force reload of FP/VEC.
@@ -378,29 +379,28 @@  static long restore_sigcontext(struct task_struct *tsk, sigset_t *set, int sig,
 	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
 
 #ifdef CONFIG_ALTIVEC
-	err |= __get_user(v_regs, &sc->v_regs);
-	if (err)
-		return err;
+	unsafe_get_user(v_regs, &sc->v_regs, efault_out);
 	if (v_regs && !access_ok(v_regs, 34 * sizeof(vector128)))
 		return -EFAULT;
 	/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 	if (v_regs != NULL && (msr & MSR_VEC) != 0) {
-		err |= __copy_from_user(&tsk->thread.vr_state, v_regs,
-					33 * sizeof(vector128));
+		unsafe_copy_from_user(&tsk->thread.vr_state, v_regs,
+				      33 * sizeof(vector128), efault_out);
 		tsk->thread.used_vr = true;
 	} else if (tsk->thread.used_vr) {
 		memset(&tsk->thread.vr_state, 0, 33 * sizeof(vector128));
 	}
 	/* Always get VRSAVE back */
 	if (v_regs != NULL)
-		err |= __get_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]);
+		unsafe_get_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33],
+				efault_out);
 	else
 		tsk->thread.vrsave = 0;
 	if (cpu_has_feature(CPU_FTR_ALTIVEC))
 		mtspr(SPRN_VRSAVE, tsk->thread.vrsave);
 #endif /* CONFIG_ALTIVEC */
 	/* restore floating point */
-	err |= copy_fpr_from_user(tsk, &sc->fp_regs);
+	unsafe_copy_fpr_from_user(tsk, &sc->fp_regs, efault_out);
 #ifdef CONFIG_VSX
 	/*
 	 * Get additional VSX data. Update v_regs to point after the
@@ -409,14 +409,17 @@  static long restore_sigcontext(struct task_struct *tsk, sigset_t *set, int sig,
 	 */
 	v_regs += ELF_NVRREG;
 	if ((msr & MSR_VSX) != 0) {
-		err |= copy_vsx_from_user(tsk, v_regs);
+		unsafe_copy_vsx_from_user(tsk, v_regs, efault_out);
 		tsk->thread.used_vsr = true;
 	} else {
 		for (i = 0; i < 32 ; i++)
 			tsk->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = 0;
 	}
 #endif
-	return err;
+	return 0;
+
+efault_out:
+	return -EFAULT;
 }
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
@@ -701,8 +704,14 @@  SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
 	if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 		do_exit(SIGSEGV);
 	set_current_blocked(&set);
-	if (restore_sigcontext(current, NULL, 0, &new_ctx->uc_mcontext))
+
+	if (!user_read_access_begin(new_ctx, ctx_size))
+		return -EFAULT;
+	if (__unsafe_restore_sigcontext(current, NULL, 0, &new_ctx->uc_mcontext)) {
+		user_read_access_end();
 		do_exit(SIGSEGV);
+	}
+	user_read_access_end();
 
 	/* This returns like rt_sigreturn */
 	set_thread_flag(TIF_RESTOREALL);
@@ -806,8 +815,13 @@  SYSCALL_DEFINE0(rt_sigreturn)
 		 * causing a TM bad thing.
 		 */
 		current->thread.regs->msr &= ~MSR_TS_MASK;
-		if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
+		if (!user_read_access_begin(uc, sizeof(*uc)))
+			return -EFAULT;
+		if (__unsafe_restore_sigcontext(current, NULL, 1, &uc->uc_mcontext)) {
+			user_read_access_end();
 			goto badframe;
+		}
+		user_read_access_end();
 	}
 
 	if (restore_altstack(&uc->uc_stack))