The ia64 handling of failure to setup a signal frame has been trying
to set overlapping fields in struct siginfo since 2.3.43.  The si_pid
and si_uid fields are stomped when the si_addr field is set.  The
si_code of SI_KERNEL indicates that si_pid and si_uid should be valid,
and that si_addr does not exist.

Being at odds with the definition of SI_KERNEL and with nothing to
indicate that this was a signal frame setup failure there is no way
for userspace to know that si_addr was filled out instead.

In practice failure to setup a signal frame is rare, and si_pid and
si_uid are always set to 0 when si_code is SI_KERNEL so I expect no
one has looked closely enough before to see this weirdness.  Further
the only difference between force_sigsegv_info and the generic
force_sigsegv other than the return code is that force_sigsegv_info
stomps the si_uid and si_pid fields.

Remove the bug and simplify the code by using force_sigsegv in this
case just like other architectures.

Fixes: 2.3.43
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>