On Tue 2015-03-03 13:09:05, Wang Nan wrote:
> Before ftrace convertin instruction to nop, if an early kprobe is
> registered then unregistered, without this patch its first bytes will
> be replaced by head of NOP, which may confuse ftrace.
>
> Actually, since we have a patch which convert ftrace entry to nop
> when probing, this problem should never be triggered. Provide it for
> safety.
>
> Signed-off-by: Wang Nan <wangn...@huawei.com>
> ---
> arch/x86/kernel/kprobes/core.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 87beb64..c7d304d 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -225,6 +225,9 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long
> addr)
> struct kprobe *kp;
> unsigned long faddr;
>
> + if (!kprobes_on_ftrace_initialized)
> + return addr;
This is not correct. The function has to return a buffer with the original
code also when it is modified by normal kprobes. If it is a normal
Kprobe, it reads the current code and replaces the first byte (INT3
instruction) with the saved kp->opcode.
> +
> kp = get_kprobe((void *)addr);
> faddr = ftrace_location(addr);
IMHO, the proper fix might be to replace the above line with
if (kprobes_on_ftrace_initialized)
faddr = ftrace_location(addr);
else
faddr = 0UL;
By other words, it might pretend that it is not a ftrace location
when the ftrace is not ready yet.
Or is the code modified another special way when it is a ftrace location but
ftrace has not been initialized yet?
Best Regards,
Petr
> /*
> --
> 1.8.4
>
> --
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