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SubjectRe: [PATCH v11 08/12] signal, x86: add SIGSYS info and make it synchronous.
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On Mon, Feb 27, 2012 at 11:22 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 02/24, Will Drewry wrote:
>>
>> To ensure that SIGSYS delivery occurs on return from the triggering
>> system call, SIGSYS is added to the SYNCHRONOUS_MASK macro.
>
> Hmm. Can't understand... please help.
>
>>  #define SYNCHRONOUS_MASK \
>>       (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
>> -      sigmask(SIGTRAP) | sigmask(SIGFPE))
>> +      sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
>
> Why?
>
> SYNCHRONOUS_MASK just tells dequeue_signal() "pick them first".
> This is needed to make sure that the handler for, say SIGSEGV,
> can use ucontext->ip as a faulting addr.

I think that Roland covered this. (Since the syscall_rollback was
called it's nice to let our handler get first go.)

> But seccomp adds info->si_call_addr, this looks unneeded.

True enough. I can drop it. It'd only be useful if the SIGSYS wasn't
being forced and the signal was being handled without ucontext_t
access.

thanks!
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