x86/debug: Simplify #DB signal code

There's no point in calculating si_code if it's not going to be used.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200902133200.967434217@infradead.org

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 58bc434..24e09f8 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -786,15 +786,14 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
 static void handle_debug(struct pt_regs *regs, unsigned long dr6)
 {
        struct task_struct *tsk = current;
-       bool user_icebp;
-       int si_code;
+       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.
         */
-       user_icebp = !dr6;
+       icebp = !dr6;
 
        /* Store the virtualized DR6 value */
        tsk->thread.debugreg6 = dr6;
@@ -813,6 +812,11 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
                goto out;
        }
 
+       /*
+        * Reload dr6, the notifier might have changed it.
+        */
+       dr6 = tsk->thread.debugreg6;
+
        if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
                /*
                 * Historical junk that used to handle SYSENTER single-stepping.
@@ -825,9 +829,8 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
                regs->flags &= ~X86_EFLAGS_TF;
        }
 
-       si_code = get_si_code(tsk->thread.debugreg6);
-       if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
-               send_sigtrap(regs, 0, si_code);
+       if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
+               send_sigtrap(regs, 0, get_si_code(dr6));
 
 out:
        cond_local_irq_disable(regs);