path: root/tools/testing/selftests/x86
diff options
authorAndy Lutomirski <luto@kernel.org>2019-11-20 12:59:13 -0800
committerPeter Zijlstra <peterz@infradead.org>2019-11-21 21:55:51 +0100
commit8caa016bfc129f2c925d52da43022171d1d1de91 (patch)
tree6d07aa64ec511f3175cbeb31ad170fcb96e478bc /tools/testing/selftests/x86
parentx86/entry/32: Fix NMI vs ESPFIX (diff)
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
Diffstat (limited to 'tools/testing/selftests/x86')
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/testing/selftests/x86/mov_ss_trap.c b/tools/testing/selftests/x86/mov_ss_trap.c
index 3c3a022654f3..6da0ac3f0135 100644
--- a/tools/testing/selftests/x86/mov_ss_trap.c
+++ b/tools/testing/selftests/x86/mov_ss_trap.c
@@ -257,7 +257,8 @@ int main()
err(1, "sigaltstack");
sethandler(SIGSEGV, handle_and_longjmp, SA_RESETHAND | SA_ONSTACK);
nr = SYS_getpid;
- asm volatile ("mov %[ss], %%ss; SYSENTER" : "+a" (nr)
+ /* Clear EBP first to make sure we segfault cleanly. */
+ asm volatile ("xorl %%ebp, %%ebp; mov %[ss], %%ss; SYSENTER" : "+a" (nr)
: [ss] "m" (ss) : "flags", "rcx"
#ifdef __x86_64__
, "r11"