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@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200902133200.907020598@infradead.org

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9cb39d3..58bc434 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -783,25 +783,18 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
  *
  * 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_kernel(struct pt_regs *regs,
        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_user(struct pt_regs *regs,
        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);