linux-kernel - [tip: x86/entry] x86/debug: Move cond_local_irq_enable() block into exc_debug

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Message-ID: <159922536850.20229.17354659676705985027.tip-bot2@tip-bot2>
Date:   Fri, 04 Sep 2020 13:16:08 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/entry] x86/debug: Move cond_local_irq_enable() block into
 exc_debug_user()

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     f0b67c39c190e19bc1604a13bcc985c4445a4b2f
Gitweb:        https://git.kernel.org/tip/f0b67c39c190e19bc1604a13bcc985c4445a4b2f
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 02 Sep 2020 15:25:57 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 04 Sep 2020 15:12:53 +02:00

x86/debug: Move cond_local_irq_enable() block into exc_debug_user()

The cond_local_irq_enable() block, dealing with vm86 and sending
signals is only relevant for #DB-from-user, move it there.

This then reduces handle_debug() to only the notifier call, so rename
it to notify_debug().

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Daniel Thompson <daniel.thompson@...aro.org>
Link: https://lore.kernel.org/r/20200902133201.094265982@infradead.org

---
 arch/x86/kernel/traps.c | 58 ++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 2605686..682af24 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -783,17 +783,10 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
  *
  * May run on IST stack.
  */
-static bool handle_debug(struct pt_regs *regs, unsigned long *dr6)
+
+static bool notify_debug(struct pt_regs *regs, unsigned long *dr6)
 {
 	struct task_struct *tsk = current;
-	bool icebp;
-
-	/*
-	 * If dr6 has no reason to give us about the origin of this trap,
-	 * then it's very likely the result of an icebp/int01 trap.
-	 * User wants a sigtrap for that.
-	 */
-	icebp = !*dr6;
 
 	/* Store the virtualized DR6 value */
 	tsk->thread.debugreg6 = *dr6;
@@ -801,26 +794,9 @@ static bool handle_debug(struct pt_regs *regs, unsigned long *dr6)
 	if (notify_die(DIE_DEBUG, "debug", regs, (long)dr6, 0, SIGTRAP) == NOTIFY_STOP)
 		return true;
 
-	/* It's safe to allow irq's after DR6 has been saved */
-	cond_local_irq_enable(regs);
-
-	if (v8086_mode(regs)) {
-		handle_vm86_trap((struct kernel_vm86_regs *) regs, 0,
-				 X86_TRAP_DB);
-		goto out;
-	}
-
-	/*
-	 * Reload dr6, the notifier might have changed it.
-	 */
+	/* Reload the DR6 value, the notifier might have changed it */
 	*dr6 = tsk->thread.debugreg6;
 
-	if (*dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
-		send_sigtrap(regs, 0, get_si_code(*dr6));
-
-out:
-	cond_local_irq_disable(regs);
-
 	return false;
 }
 
@@ -864,7 +840,7 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 	if (!dr6)
 		goto out;
 
-	if (handle_debug(regs, &dr6))
+	if (notify_debug(regs, &dr6))
 		goto out;
 
 	if (WARN_ON_ONCE(dr6 & DR_STEP)) {
@@ -889,6 +865,8 @@ out:
 static __always_inline void exc_debug_user(struct pt_regs *regs,
 					   unsigned long dr6)
 {
+	bool icebp;
+
 	/*
 	 * If something gets miswired and we end up here for a kernel mode
 	 * #DB, we will malfunction.
@@ -907,8 +885,30 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
 	irqentry_enter_from_user_mode(regs);
 	instrumentation_begin();
 
-	handle_debug(regs, &dr6);
+	/*
+	 * If dr6 has no reason to give us about the origin of this trap,
+	 * then it's very likely the result of an icebp/int01 trap.
+	 * User wants a sigtrap for that.
+	 */
+	icebp = !dr6;
+
+	if (notify_debug(regs, &dr6))
+		goto out;
 
+	/* It's safe to allow irq's after DR6 has been saved */
+	local_irq_enable();
+
+	if (v8086_mode(regs)) {
+		handle_vm86_trap((struct kernel_vm86_regs *)regs, 0, X86_TRAP_DB);
+		goto out_irq;
+	}
+
+	if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
+		send_sigtrap(regs, 0, get_si_code(dr6));
+
+out_irq:
+	local_irq_disable();
+out:
 	instrumentation_end();
 	irqentry_exit_to_user_mode(regs);
 }