[Bug tapsets/15219] syscall.exp failures on RHEL5, RHEL6, and rawhide

["dsmith at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15219

--- Comment #8 from David Smith <dsmith at redhat dot com> ---
(In reply to David Smith from comment #7)
> - Whether we need that line or not can change with kernels. For example, the
> syscall.rt_sigprocmask probe should be skipped on RHEL[56] kernels, but not
> on rawhide.

I couldn't figure out why this change didn't work for rawhide, so I dug in a
bit more. Here's what I found. Over in
arch/x86/include/generated/asm/syscalls_32.h (which gets generated during the
kernel build), you'll see this:

====
__SYSCALL_I386(173, sys_rt_sigreturn, stub32_rt_sigreturn)
__SYSCALL_I386(174, sys_rt_sigaction, compat_sys_rt_sigaction)
__SYSCALL_I386(175, sys_rt_sigprocmask, sys_rt_sigprocmask)
__SYSCALL_I386(176, sys_rt_sigpending, compat_sys_rt_sigpending)
__SYSCALL_I386(177, sys_rt_sigtimedwait, compat_sys_rt_sigtimedwait)
__SYSCALL_I386(178, sys_rt_sigqueueinfo, compat_sys_rt_sigqueueinfo)
__SYSCALL_I386(179, sys_rt_sigsuspend, sys_rt_sigsuspend)
====

Notice that for syscall 175, rt_sigprocmask doesn't call
'compat_sys_rt_sigprocmask', it just calls the real 64-bit 'sys_rt_sigprocmask'
(see the 3rd argument and compare to rt_sigaction or rt_sigpending).

On RHEL[56], the compat function for rt_sigprocmask does get called.

(Also note that 'rt_sigreturn' calls 'stub32_rt_sigreturn', which the syscall
tapset isn't expecting. So, we probably don't handle a 32-bit rt_sigreturn
properly.)

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