linux-kernel - [PATCH v2 4/8] x86/debug: Remove handle

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Message-ID: <20200821102052.969925934@infradead.org>
Date:   Fri, 21 Aug 2020 11:39:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Kyle Huey <me@...ehuey.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Robert O'Callahan <rocallahan@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v2 4/8] x86/debug: Remove handle_debug(.user) argument

The handle_debug(.user) argument is used to terminate the #DB handler
early for the INT1-from-kernel case, since the kernel doesn't use
INT1.

Remove the argument and handle this explicitly in #DB-from-kernel.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kernel/traps.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -783,25 +783,18 @@ static __always_inline unsigned long deb
  *
  * May run on IST stack.
  */
-static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
+static void handle_debug(struct pt_regs *regs, unsigned long dr6)
 {
 	struct task_struct *tsk = current;
 	bool user_icebp;
 	int si_code;
 
 	/*
-	 * If DR6 is zero, no point in trying to handle it. The kernel is
-	 * not using INT1.
-	 */
-	if (!user && !dr6)
-		return;
-
-	/*
 	 * 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.
 	 */
-	user_icebp = user && !dr6;
+	user_icebp = !dr6;
 
 	/* Store the virtualized DR6 value */
 	tsk->thread.debugreg6 = dr6;
@@ -874,7 +867,13 @@ static __always_inline void exc_debug_ke
 	if (kprobe_debug_handler(regs))
 		goto out;
 
-	handle_debug(regs, dr6, false);
+	/*
+	 * The kernel doesn't use INT1
+	 */
+	if (!dr6)
+		goto out;
+
+	handle_debug(regs, dr6);
 
 out:
 	instrumentation_end();
@@ -904,7 +903,7 @@ static __always_inline void exc_debug_us
 	irqentry_enter_from_user_mode(regs);
 	instrumentation_begin();
 
-	handle_debug(regs, dr6, true);
+	handle_debug(regs, dr6);
 
 	instrumentation_end();
 	irqentry_exit_to_user_mode(regs);