epoll_pwait can have a NULL sigmask.

epoll_pwait can have a NULL sigmask.

According to the epoll_pwait(2) man page:

       The  sigmask  argument  may  be  specified  as  NULL,  in  which  case
       epoll_pwait() is equivalent to epoll_wait().

But doing that under valgrind gives:

==13887== Syscall param epoll_pwait(sigmask) points to unaddressable byte(s)
==13887==    at 0x4F2B940: epoll_pwait (epoll_pwait.c:43)
==13887==    by 0x400ADE: main (syscalls-2007.c:89)
==13887==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

This is because the sys_epoll_pwait wrapper has:

   if (ARG4)
      PRE_MEM_READ( "epoll_pwait(sigmask)", ARG5, sizeof(vki_sigset_t) );

Which looks like a typo (ARG4 is timeout and ARG5 is sigmask).

This shows up with newer glibc which translates an epoll_wait call into
an epoll_pwait call with NULL sigmask.

Fix typo and add a testcase.

https://bugs.kde.org/show_bug.cgi?id=381289

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@16451