On Thu, Nov 13, 2014 at 10:08 PM, Srikar Dronamraju
<[email protected]> wrote:
> * Andy Lutomirski <[email protected]> [2014-11-13 14:31:21]:
>
>> x86 call do_notify_resume on paranoid returns if TIF_UPROBE is set
>> but not on non-paranoid returns. I suspect that this is a mistake
>> and that the code only works because int3 is paranoid.
>>
>> Setting _TIF_NOTIFY_RESUME in the uprobe code was probably a
>> workaround for the x86 bug. With that bug fixed, we can remove
>
>> _TIF_NOTIFY_RESUME from the uprobes code.
>>
>> Cc: Srikar Dronamraju <[email protected]>
>> Reported-by: Oleg Nesterov <[email protected]>
>> Signed-off-by: Andy Lutomirski <[email protected]>
>> ---
>> arch/x86/include/asm/thread_info.h | 2 +-
>> kernel/events/uprobes.c | 1 -
>> 2 files changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/thread_info.h
>> b/arch/x86/include/asm/thread_info.h
>> index 854053889d4d..547e344a6dc6 100644
>> --- a/arch/x86/include/asm/thread_info.h
>> +++ b/arch/x86/include/asm/thread_info.h
>> @@ -141,7 +141,7 @@ struct thread_info {
>> /* Only used for 64 bit */
>> #define _TIF_DO_NOTIFY_MASK \
>> (_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME | \
>> - _TIF_USER_RETURN_NOTIFY)
>> + _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE)
>
>
> The comment above says only for 64 bit. So would this still work for
> i386?
>
i386 seems to look at _TIF_WORK_MASK (which includes _TIF_UPROBE) for
everything except syscalls and at _TIF_WORK_SYSCALL_EXIT for syscall
return (which does not include _TIF_UPROBE). Is that okay?
--Andy
>>
>> /* flags to check in __switch_to() */
>> #define _TIF_WORK_CTXSW
>> \
>> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
>> index 1d0af8a2c646..ed8f2cde34c5 100644
>> --- a/kernel/events/uprobes.c
>> +++ b/kernel/events/uprobes.c
>> @@ -1640,7 +1640,6 @@ bool uprobe_deny_signal(void)
>> if (__fatal_signal_pending(t) ||
>> arch_uprobe_xol_was_trapped(t)) {
>> utask->state = UTASK_SSTEP_TRAPPED;
>> set_tsk_thread_flag(t, TIF_UPROBE);
>> - set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
>> }
>> }
>>
>> --
>> 1.9.3
>>
>
> --
> Thanks and Regards
> Srikar Dronamraju
>
--
Andy Lutomirski
AMA Capital Management, LLC
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