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@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200902133201.094265982@infradead.org

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 2605686..682af24 100644 (file)
--- 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);
 }