selftests/x86/mov_ss_trap: Fix the SYSENTER test
authorAndy Lutomirski <luto@kernel.org>
Wed, 20 Nov 2019 20:59:13 +0000 (12:59 -0800)
committerPeter Zijlstra <peterz@infradead.org>
Thu, 21 Nov 2019 20:55:51 +0000 (21:55 +0100)
commit8caa016bfc129f2c925d52da43022171d1d1de91
tree6d07aa64ec511f3175cbeb31ad170fcb96e478bc
parent895429076512e9d1cf5428181076299c90713159
selftests/x86/mov_ss_trap: Fix the SYSENTER test

For reasons that I haven't quite fully diagnosed, running
mov_ss_trap_32 on a 32-bit kernel results in an infinite loop in
userspace.  This appears to be because the hacky SYSENTER test
doesn't segfault as desired; instead it corrupts the program state
such that it infinite loops.

Fix it by explicitly clearing EBP before doing SYSENTER.  This will
give a more reliable segfault.

Fixes: 59c2a7226fc5 ("x86/selftests: Add mov_to_ss test")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
tools/testing/selftests/x86/mov_ss_trap.c