Hi Masami,
On 03/12/2018 11:27 AM, Masami Hiramatsu wrote:
> On Mon, 12 Mar 2018 19:00:49 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
>> Since the kprobe which was optimized by jump can not change
>> the execution path, the kprobe for error-injection must not
>> be optimized. To prohibit it, set a dummy post-handler as
>> officially stated in Documentation/kprobes.txt.
>
> Note that trace-probe based BPF is not affected, because it
> ensures the trace-probe is based on ftrace, which is not
> jump optimized.
Thanks for the fix! I presume this should go via bpf instead of bpf-next
tree since 4b1a29a7f542 ("error-injection: Support fault injection framework")
is in Linus' tree as well. Unless there are objection I would rather route
it that way so it would be for 4.16.
Thanks,
Daniel
> Thanks,
>
>>
>> Fixes: 4b1a29a7f542 ("error-injection: Support fault injection framework")
>> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
>> ---
>> kernel/fail_function.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/kernel/fail_function.c b/kernel/fail_function.c
>> index 21b0122cb39c..1d5632d8bbcc 100644
>> --- a/kernel/fail_function.c
>> +++ b/kernel/fail_function.c
>> @@ -14,6 +14,15 @@
>>
>> static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
>>
>> +static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
>> + unsigned long flags)
>> +{
>> + /*
>> + * A dummy post handler is required to prohibit optimizing, because
>> + * jump optimization does not support execution path overriding.
>> + */
>> +}
>> +
>> struct fei_attr {
>> struct list_head list;
>> struct kprobe kp;
>> @@ -56,6 +65,7 @@ static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
>> return NULL;
>> }
>> attr->kp.pre_handler = fei_kprobe_handler;
>> + attr->kp.post_handler = fei_post_handler;
>> attr->retval = adjust_error_retval(addr, 0);
>> INIT_LIST_HEAD(&attr->list);
>> }
>>
>
>
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