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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>
This commit is contained in:
Harvey Harrison 2008-01-30 13:32:19 +01:00 committed by Ingo Molnar
parent 33cb524383
commit b976015637
1 changed files with 29 additions and 33 deletions
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62
arch/x86/kernel/kprobes.c
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@ -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;
} 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;
{
ret = 1;
goto no_kprobe;
goto out;
}
goto preempt_out;
} else {
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 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;
}