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Date: Thu, 27 Dec 2007 18:08:22 -0800
From: Harvey Harrison <harvey.harrison@...il.com>
To: Masami Hiramatsu <mhiramat@...hat.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] 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@...il.com>
---
Masami, noticed a small bug in the previous version in the !p
case when the breakpoint was the kernel's. Please review this
version.
arch/x86/kernel/kprobes.c | 60 +++++++++++++++++++++------------------------
1 files changed, 28 insertions(+), 32 deletions(-)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 4e33329..f8c7ac1 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -480,32 +480,28 @@ 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
@@ -518,34 +514,34 @@ 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;
}
--
1.5.4.rc2.1097.gb6e0d
--
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