[S390] kprobes: activation and deactivation
Replace set_current_kprobe/reset_current_kprobe/save_previous_kprobe/
restore_previous_kprobe with a simpler scheme push_kprobe/pop_kprobe.
The mini kprobes stack can store up to two active kprobes.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index fcbc258..f68eaaa 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -214,25 +214,29 @@
regs->psw.addr = ip | PSW_ADDR_AMODE;
}
-
-static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+/*
+ * Activate a kprobe by storing its pointer to current_kprobe. The
+ * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
+ * two kprobes can be active, see KPROBE_REENTER.
+ */
+static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
{
- kcb->prev_kprobe.kp = kprobe_running();
+ kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
kcb->prev_kprobe.status = kcb->kprobe_status;
+ __get_cpu_var(current_kprobe) = p;
}
-static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+/*
+ * Deactivate a kprobe by backing up to the previous state. If the
+ * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
+ * for any other state prev_kprobe.kp will be NULL.
+ */
+static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
{
__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
kcb->kprobe_status = kcb->prev_kprobe.status;
}
-static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
- struct kprobe_ctlblk *kcb)
-{
- __get_cpu_var(current_kprobe) = p;
-}
-
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
@@ -261,14 +265,16 @@
if (kprobe_running()) {
p = get_kprobe(addr);
if (p) {
- /* We have reentered the kprobe_handler(), since
- * another probe was hit while within the handler.
- * We here save the original kprobes variables and
- * just single step on the instruction of the new probe
- * without calling any user handlers.
+ /*
+ * We have hit a kprobe while another is still
+ * active. This can happen in the pre and post
+ * handler. Single step the instruction of the
+ * new probe but do not call any handler function
+ * of this secondary kprobe.
+ * push_kprobe and pop_kprobe saves and restores
+ * the currently active kprobe.
*/
- save_previous_kprobe(kcb);
- set_current_kprobe(p, regs, kcb);
+ push_kprobe(kcb, p);
kprobes_inc_nmissed_count(p);
enable_singlestep(kcb, regs,
(unsigned long) p->ainsn.insn);
@@ -294,7 +300,7 @@
goto no_kprobe;
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
- set_current_kprobe(p, regs, kcb);
+ push_kprobe(kcb, p);
if (p->pre_handler && p->pre_handler(p, regs))
/* handler has already set things up, so skip ss setup */
return 1;
@@ -395,7 +401,7 @@
regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
- reset_current_kprobe();
+ pop_kprobe(get_kprobe_ctlblk());
kretprobe_hash_unlock(current, &flags);
preempt_enable_no_resched();
@@ -457,14 +463,7 @@
}
resume_execution(cur, regs);
-
- /*Restore back the original saved kprobes variables and continue. */
- if (kcb->kprobe_status == KPROBE_REENTER) {
- restore_previous_kprobe(kcb);
- goto out;
- }
- reset_current_kprobe();
-out:
+ pop_kprobe(kcb);
preempt_enable_no_resched();
/*
@@ -499,11 +498,7 @@
* normal page fault.
*/
disable_singlestep(kcb, regs, (unsigned long) cur->addr);
- if (kcb->kprobe_status == KPROBE_REENTER)
- restore_previous_kprobe(kcb);
- else {
- reset_current_kprobe();
- }
+ pop_kprobe(kcb);
preempt_enable_no_resched();
break;
case KPROBE_HIT_ACTIVE: