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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2011-01-05 12:47:23 +0100
committerMartin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com>2011-01-05 12:47:24 +0100
commit0e917cc3297f3274993d25b5972c2b1c6f763819 (patch)
tree6638db354d17cee5a5fc0954b8b2b7a30aaa93d8 /arch/s390/kernel
parent92b8cbf17ae98a118d3e4a123246a05130114d06 (diff)
downloadlinux-linaro-stable-0e917cc3297f3274993d25b5972c2b1c6f763819.tar.gz
[S390] kprobes: restructure handler function
Restructure the kprobe breakpoint handler function. Add comments to make it more comprehensible and add a sanity check for re-entering kprobes. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel')
-rw-r--r--arch/s390/kernel/kprobes.c114
1 files changed, 71 insertions, 43 deletions
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 4efd5dbfd72d..2a19f4154f2d 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -238,25 +238,44 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
}
+static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
+ struct kprobe *p)
+{
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_SSDONE:
+ case KPROBE_HIT_ACTIVE:
+ kprobes_inc_nmissed_count(p);
+ break;
+ case KPROBE_HIT_SS:
+ case KPROBE_REENTER:
+ default:
+ /*
+ * A kprobe on the code path to single step an instruction
+ * is a BUG. The code path resides in the .kprobes.text
+ * section and is executed with interrupts disabled.
+ */
+ printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
+ dump_kprobe(p);
+ BUG();
+ }
+}
+
static int __kprobes kprobe_handler(struct pt_regs *regs)
{
- struct kprobe *p;
- int ret = 0;
- unsigned long *addr = (unsigned long *)
- ((regs->psw.addr & PSW_ADDR_INSN) - 2);
struct kprobe_ctlblk *kcb;
+ struct kprobe *p;
/*
- * We don't want to be preempted for the entire
- * duration of kprobe processing
+ * We want to disable preemption for the entire duration of kprobe
+ * processing. That includes the calls to the pre/post handlers
+ * and single stepping the kprobe instruction.
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
+ p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));
- /* Check we're not actually recursing */
- if (kprobe_running()) {
- p = get_kprobe(addr);
- if (p) {
+ if (p) {
+ if (kprobe_running()) {
/*
* We have hit a kprobe while another is still
* active. This can happen in the pre and post
@@ -266,45 +285,54 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
* push_kprobe and pop_kprobe saves and restores
* the currently active kprobe.
*/
+ kprobe_reenter_check(kcb, p);
push_kprobe(kcb, p);
- kprobes_inc_nmissed_count(p);
- enable_singlestep(kcb, regs,
- (unsigned long) p->ainsn.insn);
kcb->kprobe_status = KPROBE_REENTER;
- return 1;
} else {
- p = __get_cpu_var(current_kprobe);
- if (p->break_handler && p->break_handler(p, regs)) {
- goto ss_probe;
- }
+ /*
+ * If we have no pre-handler or it returned 0, we
+ * continue with single stepping. 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.
+ */
+ push_kprobe(kcb, p);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ if (p->pre_handler && p->pre_handler(p, regs))
+ return 1;
+ kcb->kprobe_status = KPROBE_HIT_SS;
}
- goto no_kprobe;
- }
-
- p = get_kprobe(addr);
- if (!p)
- /*
- * No kprobe at this address. The fault has not been
- * caused by a kprobe breakpoint. The race of breakpoint
- * vs. kprobe remove does not exist because on s390 we
- * use stop_machine to arm/disarm the breakpoints.
- */
- goto no_kprobe;
-
- kcb->kprobe_status = KPROBE_HIT_ACTIVE;
- push_kprobe(kcb, p);
- if (p->pre_handler && p->pre_handler(p, regs))
- /* handler has already set things up, so skip ss setup */
+ enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
return 1;
-
-ss_probe:
- enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
- kcb->kprobe_status = KPROBE_HIT_SS;
- return 1;
-
-no_kprobe:
+ } else if (kprobe_running()) {
+ p = __get_cpu_var(current_kprobe);
+ if (p->break_handler && p->break_handler(p, regs)) {
+ /*
+ * Continuation after the jprobe completed and
+ * caused the jprobe_return trap. The jprobe
+ * break_handler "returns" to the original
+ * function that still has the kprobe breakpoint
+ * installed. We continue with single stepping.
+ */
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ enable_singlestep(kcb, regs,
+ (unsigned long) p->ainsn.insn);
+ return 1;
+ } /* else:
+ * No kprobe at this address and the current kprobe
+ * has no break handler (no jprobe!). The kernel just
+ * exploded, let the standard trap handler pick up the
+ * pieces.
+ */
+ } /* else:
+ * No kprobe at this address and no active kprobe. The trap has
+ * not been caused by a kprobe breakpoint. The race of breakpoint
+ * vs. kprobe remove does not exist because on s390 as we use
+ * stop_machine to arm/disarm the breakpoints.
+ */
preempt_enable_no_resched();
- return ret;
+ return 0;
}
/*