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Subject[PATCH -tip v9 5/9] kprobes/x86: Boost probes when reentering
Date
Integrate prepare_singlestep() into setup_singlestep() to boost up reenter
probes, if possible.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
---
arch/x86/kernel/kprobes.c | 48 ++++++++++++++++++++++++---------------------
1 files changed, 26 insertions(+), 22 deletions(-)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 15177cd..c69bb65 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -406,18 +406,6 @@ static void __kprobes restore_btf(void)
update_debugctlmsr(current->thread.debugctlmsr);
}

-static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
-{
- clear_btf();
- regs->flags |= X86_EFLAGS_TF;
- regs->flags &= ~X86_EFLAGS_IF;
- /* single step inline if the instruction is an int3 */
- if (p->opcode == BREAKPOINT_INSTRUCTION)
- regs->ip = (unsigned long)p->addr;
- else
- regs->ip = (unsigned long)p->ainsn.insn;
-}
-
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
@@ -430,19 +418,38 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
}

static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
- struct kprobe_ctlblk *kcb)
+ struct kprobe_ctlblk *kcb, int reenter)
{
#if !defined(CONFIG_PREEMPT)
if (p->ainsn.boostable == 1 && !p->post_handler) {
/* Boost up -- we can execute copied instructions directly */
- reset_current_kprobe();
+ if (!reenter)
+ reset_current_kprobe();
+ /*
+ * Reentering boosted probe doesn't reset current_kprobe,
+ * nor set current_kprobe, because it doesn't use single
+ * stepping.
+ */
regs->ip = (unsigned long)p->ainsn.insn;
preempt_enable_no_resched();
return;
}
#endif
- prepare_singlestep(p, regs);
- kcb->kprobe_status = KPROBE_HIT_SS;
+ if (reenter) {
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p, regs, kcb);
+ kcb->kprobe_status = KPROBE_REENTER;
+ } else
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ /* Prepare real single stepping */
+ clear_btf();
+ regs->flags |= X86_EFLAGS_TF;
+ regs->flags &= ~X86_EFLAGS_IF;
+ /* single step inline if the instruction is an int3 */
+ if (p->opcode == BREAKPOINT_INSTRUCTION)
+ regs->ip = (unsigned long)p->addr;
+ else
+ regs->ip = (unsigned long)p->ainsn.insn;
}

/*
@@ -456,11 +463,8 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
switch (kcb->kprobe_status) {
case KPROBE_HIT_SSDONE:
case KPROBE_HIT_ACTIVE:
- save_previous_kprobe(kcb);
- set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
- prepare_singlestep(p, regs);
- kcb->kprobe_status = KPROBE_REENTER;
+ setup_singlestep(p, regs, kcb, 1);
break;
case KPROBE_HIT_SS:
/* A probe has been hit in the codepath leading up to, or just
@@ -535,13 +539,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
* more here.
*/
if (!p->pre_handler || !p->pre_handler(p, regs))
- setup_singlestep(p, regs, kcb);
+ setup_singlestep(p, regs, kcb, 0);
return 1;
}
} else if (kprobe_running()) {
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
- setup_singlestep(p, regs, kcb);
+ setup_singlestep(p, regs, kcb, 0);
return 1;
}
} /* else: not a kprobe fault; let the kernel handle it */

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


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