x86 trap fix-single_step_syscall_32

---
 arch/x86/kernel/traps.c | 49 +++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index f58679e487f6..bb511836b929 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -809,8 +809,17 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
     * If DR6 is zero, no point in trying to handle it. The kernel is
     * not using INT1.
     */
-   if (!user && !dr6)
-       return;
+   if (!user) {
+       /*
+        * Catch SYSENTER with TF set and clear DR_STEP. If this hit a
+        * watchpoint at the same time then that will still be handled.
+        */
+       if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs))
+           dr6 &= ~DR_STEP;
+
+       if (!dr6)
+           return;
+   }

    /*
     * If dr6 has no reason to give us about the origin of this trap,
@@ -862,6 +871,7 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
    cond_local_irq_disable(regs);
 }

+#ifdef CONFIG_X86_64
 static __always_inline void exc_debug_kernel(struct pt_regs *regs,
                         unsigned long dr6)
 {
@@ -869,13 +879,6 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
    instrumentation_begin();
    trace_hardirqs_off_finish();

-   /*
-    * Catch SYSENTER with TF set and clear DR_STEP. If this hit a
-    * watchpoint at the same time then that will still be handled.
-    */
-   if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs))
-       dr6 &= ~DR_STEP;
-
    handle_debug(regs, dr6, false);

    if (regs->flags & X86_EFLAGS_IF)
@@ -884,6 +887,16 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
    nmi_exit();
 }

+/* IST stack entry */
+DEFINE_IDTENTRY_DEBUG(exc_debug)
+{
+   unsigned long dr6, dr7;
+
+   debug_enter(&dr6, &dr7);
+   exc_debug_kernel(regs, dr6);
+   debug_exit(dr7);
+}
+
 static __always_inline void exc_debug_user(struct pt_regs *regs,
                       unsigned long dr6)
 {
@@ -895,17 +908,6 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
    idtentry_exit_user(regs);
 }

-#ifdef CONFIG_X86_64
-/* IST stack entry */
-DEFINE_IDTENTRY_DEBUG(exc_debug)
-{
-   unsigned long dr6, dr7;
-
-   debug_enter(&dr6, &dr7);
-   exc_debug_kernel(regs, dr6);
-   debug_exit(dr7);
-}
-
 /* User entry, runs on regular task stack */
 DEFINE_IDTENTRY_DEBUG_USER(exc_debug)
 {
@@ -922,12 +924,7 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
    unsigned long dr6, dr7;

    debug_enter(&dr6, &dr7);
-
-   if (user_mode(regs))
-       exc_debug_user(regs, dr6);
-   else
-       exc_debug_kernel(regs, dr6);
-
+   handle_debug(regs, dr6, user_mode(regs));
    debug_exit(dr7);
 }
 #endif
--
2.27.0