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kprobes/x86: Fix to support jprobes on ftrace-based kprobe

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Fix kprobes/x86 to support jprobes on ftrace-based kprobes.
Because of -mfentry support of ftrace, ftrace is now put
on the beginning of function where jprobes are put.

Originally ftrace-based kprobes doesn't support jprobe
because it will change regs->ip and ftrace doesn't support
changing IP and ftrace itself doesn't conflict jprobe.
However, ftrace -mfentry support moves mcount call on the
top of functions where jprobes are put. This means that
jprobe always conflicts with ftrace-based kprobe and fails.

This patch allows ftrace-based kprobes to support jprobes
by allowing to modify regs->ip and kprobes breakpoint
handler also allows to skip singlestepping because there
is a ftrace call (not an original instruction).

Link: http://lkml.kernel.org/r/20120905143125.10329.90836.stgit@localhost.localdomain

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2012-09-05 23:31:25 +09:00 • committed by Steven Rostedt
parent 47d5a5f88b
commit c6aaf4d0bb
2 changed files with 29 additions and 16 deletions
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42
arch/x86/kernel/kprobes.c
View file

@ -541,6 +541,8 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb
return 1;
}
static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb);
/*
* Interrupts are disabled on entry as trap3 is an interrupt gate and they
* remain disabled throughout this function.
@ -599,6 +601,12 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
} else if (kprobe_running()) {
p = __this_cpu_read(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
#ifdef KPROBES_CAN_USE_FTRACE
if (kprobe_ftrace(p)) {
skip_singlestep(p, regs, kcb);
return 1;
}
#endif
setup_singlestep(p, regs, kcb, 0);
return 1;
}
@ -1053,6 +1061,21 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
}
#ifdef KPROBES_CAN_USE_FTRACE
static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
/*
* Emulate singlestep (and also recover regs->ip)
* as if there is a 5byte nop
*/
regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
if (unlikely(p->post_handler)) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
__this_cpu_write(current_kprobe, NULL);
}
/* Ftrace callback handler for kprobes */
void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct pt_regs *regs)
@ -1077,19 +1100,12 @@ void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
__this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (p->pre_handler)
p->pre_handler(p, regs);
if (unlikely(p->post_handler)) {
/*
* Emulate singlestep (and also recover regs->ip)
* as if there is a 5byte nop
*/
regs->ip = ip + MCOUNT_INSN_SIZE;
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
__this_cpu_write(current_kprobe, NULL);
if (!p->pre_handler || !p->pre_handler(p, regs))
skip_singlestep(p, regs, kcb);
/*
* If pre_handler returns !0, it sets regs->ip and
* resets current kprobe.
*/
}
end:
local_irq_restore(flags);

3
kernel/kprobes.c
View file

@ -1418,9 +1418,6 @@ static __kprobes int check_kprobe_address_safe(struct kprobe *p,
/* Given address is not on the instruction boundary */
if ((unsigned long)p->addr != ftrace_addr)
return -EILSEQ;
/* break_handler (jprobe) can not work with ftrace */
if (p->break_handler)
return -EINVAL;
p->flags |= KPROBE_FLAG_FTRACE;
#else /* !KPROBES_CAN_USE_FTRACE */
return -EINVAL;