[PATCH] kprobes: Temporary disarming of reentrant probe for x86_64
This patch includes x86_64 architecture specific changes to support temporary
disarming on reentrancy of probes.
Signed-of-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 324bf57..4e680f8 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -45,12 +45,10 @@
static DECLARE_MUTEX(kprobe_mutex);
-/* kprobe_status settings */
-#define KPROBE_HIT_ACTIVE 0x00000001
-#define KPROBE_HIT_SS 0x00000002
-
static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_old_rflags, kprobe_saved_rflags;
+static struct kprobe *kprobe_prev;
+static unsigned long kprobe_status_prev, kprobe_old_rflags_prev, kprobe_saved_rflags_prev;
static struct pt_regs jprobe_saved_regs;
static long *jprobe_saved_rsp;
static kprobe_opcode_t *get_insn_slot(void);
@@ -240,6 +238,31 @@
down(&kprobe_mutex);
}
+static inline void save_previous_kprobe(void)
+{
+ kprobe_prev = current_kprobe;
+ kprobe_status_prev = kprobe_status;
+ kprobe_old_rflags_prev = kprobe_old_rflags;
+ kprobe_saved_rflags_prev = kprobe_saved_rflags;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+ current_kprobe = kprobe_prev;
+ kprobe_status = kprobe_status_prev;
+ kprobe_old_rflags = kprobe_old_rflags_prev;
+ kprobe_saved_rflags = kprobe_saved_rflags_prev;
+}
+
+static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+ current_kprobe = p;
+ kprobe_saved_rflags = kprobe_old_rflags
+ = (regs->eflags & (TF_MASK | IF_MASK));
+ if (is_IF_modifier(p->ainsn.insn))
+ kprobe_saved_rflags &= ~IF_MASK;
+}
+
static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
regs->eflags |= TF_MASK;
@@ -319,10 +342,30 @@
regs->eflags |= kprobe_saved_rflags;
unlock_kprobes();
goto no_kprobe;
+ } else if (kprobe_status == KPROBE_HIT_SSDONE) {
+ /* 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->rip = (unsigned long)p->addr;
+ ret = 1;
+ } else {
+ /* We have reentered the kprobe_handler(), since
+ * another probe was hit while within the
+ * handler. We here save the original kprobe
+ * variables and just single step on instruction
+ * of the new probe without calling any user
+ * handlers.
+ */
+ save_previous_kprobe();
+ set_current_kprobe(p, regs);
+ p->nmissed++;
+ prepare_singlestep(p, regs);
+ kprobe_status = KPROBE_REENTER;
+ return 1;
}
- arch_disarm_kprobe(p);
- regs->rip = (unsigned long)p->addr;
- ret = 1;
} else {
p = current_kprobe;
if (p->break_handler && p->break_handler(p, regs)) {
@@ -352,11 +395,7 @@
}
kprobe_status = KPROBE_HIT_ACTIVE;
- current_kprobe = p;
- kprobe_saved_rflags = kprobe_old_rflags
- = (regs->eflags & (TF_MASK | IF_MASK));
- if (is_IF_modifier(p->ainsn.insn))
- kprobe_saved_rflags &= ~IF_MASK;
+ set_current_kprobe(p, regs);
if (p->pre_handler && p->pre_handler(p, regs))
/* handler has already set things up, so skip ss setup */
@@ -506,14 +545,23 @@
if (!kprobe_running())
return 0;
- if (current_kprobe->post_handler)
+ if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
+ kprobe_status = KPROBE_HIT_SSDONE;
current_kprobe->post_handler(current_kprobe, regs, 0);
+ }
if (current_kprobe->post_handler != trampoline_post_handler)
resume_execution(current_kprobe, regs);
regs->eflags |= kprobe_saved_rflags;
- unlock_kprobes();
+ /* Restore the original saved kprobes variables and continue. */
+ if (kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe();
+ goto out;
+ } else {
+ unlock_kprobes();
+ }
+out:
preempt_enable_no_resched();
/*