Messages in this thread Patch in this message | | | Subject | [PATCH] x86: kprobes change kprobe_handler flow | From | Harvey Harrison <> | Date | Thu, 27 Dec 2007 17:44:25 -0800 |
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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.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> --- Masami, please have a look at this, I think it's much more obvious written this way. The way the old code fell through or not was rather non-obvious. Some further work eliminating the nested returns and creating a out: and preempt_out: target at the end of the function would make it easier to notice preempt imbalances in later changes.
arch/x86/kernel/kprobes.c | 48 ++++++++++++++++---------------------------- 1 files changed, 18 insertions(+), 30 deletions(-)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 4e33329..d656215 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -480,32 +480,22 @@ 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; + goto no_kprobe; } 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; - } - p = __get_cpu_var(current_kprobe); - if (p->break_handler && p->break_handler(p, regs)) - goto ss_probe; + 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 */ + return 1; } - goto no_kprobe; - } - - p = get_kprobe(addr); - if (!p) { + } else { if (*addr != BREAKPOINT_INSTRUCTION) { /* * The breakpoint instruction was removed right @@ -518,18 +508,16 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) */ regs->ip = (unsigned long)addr; ret = 1; + goto no_kprobe; + } + if (kprobe_running()) { + p = __get_cpu_var(current_kprobe); + if (p->break_handler && p->break_handler(p, regs)) + goto ss_probe; + goto no_kprobe; } - /* Not one of ours: let kernel handle it */ - goto no_kprobe; } - 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: #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM) if (p->ainsn.boostable == 1 && !p->post_handler) { -- 1.5.4.rc2.1097.gb6e0d
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