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authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>2014-10-09 13:01:06 (GMT)
committerSteven Rostedt <rostedt@goodmis.org>2014-11-20 16:42:48 (GMT)
commita017784f1b236cbc42ce83b4345a667c21113481 (patch)
tree3ea28f325757811c85ebf655ca953e6eea49cc37 /arch/x86/kernel/kprobes
parent0af26492d5f5c00a08d52e9f3f3831faead90246 (diff)
downloadlinux-a017784f1b236cbc42ce83b4345a667c21113481.tar.xz
kprobes/ftrace: Recover original IP if pre_handler doesn't change it
Recover original IP register if the pre_handler doesn't change it. Since current kprobes doesn't expect that another ftrace handler may change regs->ip, it sets kprobe.addr + MCOUNT_INSN_SIZE to regs->ip and returns to ftrace. This seems wrong behavior since kprobes can recover regs->ip and safely pass it to another handler. This adds code which recovers original regs->ip passed from ftrace right before returning to ftrace, so that another ftrace user can change regs->ip. Link: http://lkml.kernel.org/r/20141009130106.4698.26362.stgit@kbuild-f20.novalocal Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/kprobes')
-rw-r--r--arch/x86/kernel/kprobes/ftrace.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 717b02a..5f8f0b3 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -27,7 +27,7 @@
static nokprobe_inline
int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
- struct kprobe_ctlblk *kcb)
+ struct kprobe_ctlblk *kcb, unsigned long orig_ip)
{
/*
* Emulate singlestep (and also recover regs->ip)
@@ -39,6 +39,8 @@ int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
p->post_handler(p, regs, 0);
}
__this_cpu_write(current_kprobe, NULL);
+ if (orig_ip)
+ regs->ip = orig_ip;
return 1;
}
@@ -46,7 +48,7 @@ int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
if (kprobe_ftrace(p))
- return __skip_singlestep(p, regs, kcb);
+ return __skip_singlestep(p, regs, kcb, 0);
else
return 0;
}
@@ -71,13 +73,14 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
if (kprobe_running()) {
kprobes_inc_nmissed_count(p);
} else {
+ unsigned long orig_ip = regs->ip;
/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
regs->ip = ip + sizeof(kprobe_opcode_t);
__this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (!p->pre_handler || !p->pre_handler(p, regs))
- __skip_singlestep(p, regs, kcb);
+ __skip_singlestep(p, regs, kcb, orig_ip);
/*
* If pre_handler returns !0, it sets regs->ip and
* resets current kprobe.