x86: kprobes change kprobe_handler flow

Make the control flow of kprobe_handler more obvious.

Collapse the separate if blocks/gotos with if/else blocks
this unifies the duplication of the check for a breakpoint
instruction race with another cpu.

Create two jump targets:
	preempt_out: re-enables preemption before returning ret
	out: only returns ret

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 80bcb7635465c2b6936951bf3176f72c77456593..a72e02bf11353293a3bec6ea9cf891d8f47389ca 100644 (file)
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -494,32 +494,28 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
        preempt_disable();
        kcb = get_kprobe_ctlblk();
 
-       /* Check we're not actually recursing */
-       if (kprobe_running()) {
-               p = get_kprobe(addr);
-               if (p) {
+       p = get_kprobe(addr);
+       if (p) {
+               /* Check we're not actually recursing */
+               if (kprobe_running()) {
                        ret = reenter_kprobe(p, regs, kcb);
                        if (kcb->kprobe_status == KPROBE_REENTER)
-                               return 1;
+                       {
+                               ret = 1;
+                               goto out;
+                       }
+                       goto preempt_out;
                } else {
-                       if (*addr != BREAKPOINT_INSTRUCTION) {
-                       /* The breakpoint instruction was removed by
-                        * another cpu right after we hit, no further
-                        * handling of this interrupt is appropriate
-                        */
-                               regs->ip = (unsigned long)addr;
+                       set_current_kprobe(p, regs, kcb);
+                       kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+                       if (p->pre_handler && p->pre_handler(p, regs))
+                       {
+                               /* handler set things up, skip ss setup */
                                ret = 1;
-                               goto no_kprobe;
+                               goto out;
                        }
-                       p = __get_cpu_var(current_kprobe);
-                       if (p->break_handler && p->break_handler(p, regs))
-                               goto ss_probe;
                }
-               goto no_kprobe;
-       }
-
-       p = get_kprobe(addr);
-       if (!p) {
+       } else {
                if (*addr != BREAKPOINT_INSTRUCTION) {
                        /*
                         * The breakpoint instruction was removed right
@@ -532,34 +528,34 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
                         */
                        regs->ip = (unsigned long)addr;
                        ret = 1;
+                       goto preempt_out;
+               }
+               if (kprobe_running()) {
+                       p = __get_cpu_var(current_kprobe);
+                       if (p->break_handler && p->break_handler(p, regs))
+                               goto ss_probe;
                }
                /* Not one of ours: let kernel handle it */
-               goto no_kprobe;
+               goto preempt_out;
        }
 
-       set_current_kprobe(p, regs, kcb);
-       kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-
-       if (p->pre_handler && p->pre_handler(p, regs))
-               /* handler has already set things up, so skip ss setup */
-               return 1;
-
 ss_probe:
+       ret = 1;
 #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
        if (p->ainsn.boostable == 1 && !p->post_handler) {
                /* Boost up -- we can execute copied instructions directly */
                reset_current_kprobe();
                regs->ip = (unsigned long)p->ainsn.insn;
-               preempt_enable_no_resched();
-               return 1;
+               goto preempt_out;
        }
 #endif
        prepare_singlestep(p, regs);
        kcb->kprobe_status = KPROBE_HIT_SS;
-       return 1;
+       goto out;
 
-no_kprobe:
+preempt_out:
        preempt_enable_no_resched();
+out:
        return ret;
 }