linux-kernel - [patch V4 part 4 21/24] x86/traps: Address objtool noinstr complaints in #DB

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Date:   Tue, 05 May 2020 15:49:47 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        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>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: [patch V4 part 4 21/24] x86/traps: Address objtool noinstr complaints in #DB

The functions invoked from handle_debug() can be instrumented. Tell objtool
about it.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/traps.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -762,14 +762,19 @@ static void noinstr handle_debug(struct
 	/* Store the virtualized DR6 value */
 	tsk->thread.debugreg6 = dr6;
 
+	instr_begin();
 #ifdef CONFIG_KPROBES
-	if (kprobe_debug_handler(regs))
+	if (kprobe_debug_handler(regs)) {
+		instr_end();
 		return;
+	}
 #endif
 
 	if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
-		       SIGTRAP) == NOTIFY_STOP)
+		       SIGTRAP) == NOTIFY_STOP) {
+		instr_end();
 		return;
+	}
 
 	/*
 	 * Let others (NMI) know that the debug stack is in use
@@ -805,6 +810,7 @@ static void noinstr handle_debug(struct
 out:
 	cond_local_irq_disable(regs);
 	debug_stack_usage_dec();
+	instr_end();
 }
 
 static __always_inline void exc_debug_kernel(struct pt_regs *regs,
@@ -816,7 +822,7 @@ static __always_inline void exc_debug_ke
 	 * generates a debug exception."  Clear TIF_BLOCKSTEP to keep
 	 * TIF_BLOCKSTEP in sync with the hardware BTF flag.
 	 */
-	clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);
+	clear_thread_flag(TIF_BLOCKSTEP);
 
 	/*
 	 * Catch SYSENTER with TF set and clear DR_STEP. If this hit a
@@ -839,7 +845,7 @@ static __always_inline void exc_debug_us
 					   unsigned long dr6)
 {
 	idtentry_enter(regs);
-	clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);
+	clear_thread_flag(TIF_BLOCKSTEP);
 
 	/*
 	 * If dr6 has no reason to give us about the origin of this trap,