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Date: Wed, 02 Jan 2008 01:10:10 +0530
From: Abhishek Sagar <sagar.abhishek@...il.com>
To: Ingo Molnar <mingo@...e.hu>
CC: Harvey Harrison <harvey.harrison@...il.com>,
Masami Hiramatsu <mhiramat@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>, qbarnes@...il.com,
ananth@...ibm.com, jkenisto@...ibm.com
Subject: Re: [PATCH] x86: kprobes change kprobe_handler flow
Ingo Molnar wrote:
> hm, this patch does not apply to x86.git#mm, due to the fixes,
> unifications and cleanups done there. Could you send a patch against -mm
> or against x86.git? (see the tree-fetching instructions below) Thanks,
>
> Ingo
>
> --------------{ x86.git instructions }---------->
>
> git-clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git linux-2.6.git
> cd linux-2.6.git
> git-branch x86
> git-checkout x86
> git-pull git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86.git mm
>
> (do subsequent pulls via "git-pull --force", as we frequently rebase the
> git tree. NOTE: this might override your own local changes, so do this
> only if you dont mind about losing thse changes in that tree.)
>
Thanks for pointing me to the right tree. I have made some code re-arrangements in this one.
Signed-off-by: Abhishek Sagar <sagar.abhishek@...il.com>
Signed-off-by: Quentin Barnes <qbarnes@...il.com>
---
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index a72e02b..45adc8e 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -441,6 +441,26 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
}
+
+#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
+static __always_inline int setup_boost(struct kprobe *p, struct pt_regs *regs)
+{
+ 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 0;
+ }
+ return 1;
+}
+#else
+static __always_inline int setup_boost(struct kprobe *p, struct pt_regs *regs)
+{
+ return 1;
+}
+#endif
+
/*
* We have reentered the kprobe_handler(), since another probe was hit while
* within the handler. We save the original kprobes variables and just single
@@ -449,29 +469,47 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
- if (kcb->kprobe_status == KPROBE_HIT_SS &&
- *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
- regs->flags &= ~X86_EFLAGS_TF;
- regs->flags |= kcb->kprobe_saved_flags;
- return 0;
+ int ret = 0;
+
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_SSDONE:
#ifdef CONFIG_X86_64
- } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
- /* TODO: Provide re-entrancy from post_kprobes_handler() and
- * avoid exception stack corruption while single-stepping on
+ /* TODO: Provide re-entrancy from
+ * post_kprobes_handler() and avoid exception
+ * stack corruption while single-stepping on
* the instruction of the new probe.
*/
arch_disarm_kprobe(p);
regs->ip = (unsigned long)p->addr;
reset_current_kprobe();
- return 1;
+ preempt_enable_no_resched();
+ ret = 1;
+ break;
#endif
+ case KPROBE_HIT_ACTIVE:
+ /* a probe has been hit inside a
+ * user handler */
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p, regs, kcb);
+ kprobes_inc_nmissed_count(p);
+ prepare_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_REENTER;
+ ret = 1;
+ break;
+ case KPROBE_HIT_SS:
+ if (*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
+ regs->flags &= ~TF_MASK;
+ regs->flags |= kcb->kprobe_saved_flags;
+ } else {
+ /* BUG? */
+ }
+ break;
+ default:
+ /* impossible cases */
+ BUG();
}
- save_previous_kprobe(kcb);
- set_current_kprobe(p, regs, kcb);
- kprobes_inc_nmissed_count(p);
- prepare_singlestep(p, regs);
- kcb->kprobe_status = KPROBE_REENTER;
- return 1;
+
+ return ret;
}
/*
@@ -480,82 +518,67 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
*/
static int __kprobes kprobe_handler(struct pt_regs *regs)
{
- struct kprobe *p;
int ret = 0;
kprobe_opcode_t *addr;
+ struct kprobe *p, *cur;
struct kprobe_ctlblk *kcb;
addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /*
+ * The breakpoint instruction was removed right
+ * after we hit it. Another cpu has removed
+ * either a probepoint or a debugger breakpoint
+ * at this address. In either case, no further
+ * handling of this interrupt is appropriate.
+ * Back up over the (now missing) int3 and run
+ * the original instruction.
+ */
+ regs->ip = (unsigned long)addr;
+ return 1;
+ }
- /*
- * We don't want to be preempted for the entire
- * duration of kprobe processing
- */
preempt_disable();
kcb = get_kprobe_ctlblk();
-
+ cur = kprobe_running();
p = get_kprobe(addr);
+
if (p) {
- /* Check we're not actually recursing */
- if (kprobe_running()) {
+ if (cur) {
ret = reenter_kprobe(p, regs, kcb);
- if (kcb->kprobe_status == KPROBE_REENTER)
- {
- ret = 1;
- 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;
- }
- }
- } else {
- if (*addr != BREAKPOINT_INSTRUCTION) {
+
/*
- * The breakpoint instruction was removed right
- * after we hit it. Another cpu has removed
- * either a probepoint or a debugger breakpoint
- * at this address. In either case, no further
- * handling of this interrupt is appropriate.
- * Back up over the (now missing) int3 and run
- * the original instruction.
+ * If we have no pre-handler or it returned 0, we
+ * continue with normal processing. If we have a
+ * pre-handler and it returned non-zero, it prepped
+ * for calling the break_handler below on re-entry
+ * for jprobe processing, so get out doing nothing
+ * more here.
*/
- regs->ip = (unsigned long)addr;
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
+ if (setup_boost(p, regs)) {
+ prepare_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ }
+ }
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;
+ } else if (cur) {
+ p = __get_cpu_var(current_kprobe);
+ if (p->break_handler && p->break_handler(p, regs)) {
+ if (setup_boost(p, regs)) {
+ prepare_singlestep(p, regs);
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ }
+ ret = 1;
}
- /* Not one of ours: let kernel handle it */
- goto preempt_out;
- }
+ } /* else: not a kprobe fault; let the kernel handle it */
-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;
- goto preempt_out;
- }
-#endif
- prepare_singlestep(p, regs);
- kcb->kprobe_status = KPROBE_HIT_SS;
- goto out;
-
-preempt_out:
- preempt_enable_no_resched();
-out:
+ if (!ret)
+ preempt_enable_no_resched();
return ret;
}
--
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