[tip:x86/asm] selftests/x86: In syscall_nt, test NT|TF as well

From: tip-bot for Andy Lutomirski
Date: Thu Mar 10 2016 - 06:02:28 EST


Commit-ID: a318beea224d255c38652f88a7ae0d30ac4c23c3
Gitweb: http://git.kernel.org/tip/a318beea224d255c38652f88a7ae0d30ac4c23c3
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Wed, 9 Mar 2016 19:00:24 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 10 Mar 2016 09:48:12 +0100

selftests/x86: In syscall_nt, test NT|TF as well

Setting TF prevents fastpath returns in most cases, which causes the
test to fail on 32-bit kernels because 32-bit kernels do not, in
fact, handle NT correctly on SYSENTER entries.

The next patch will fix 32-bit kernels.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/bd4bb48af6b10c0dc84aec6dbcf487ed25683495.1457578375.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
tools/testing/selftests/x86/syscall_nt.c | 57 +++++++++++++++++++++++++++-----
1 file changed, 49 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/x86/syscall_nt.c b/tools/testing/selftests/x86/syscall_nt.c
index 60c06af4..43fcab36 100644
--- a/tools/testing/selftests/x86/syscall_nt.c
+++ b/tools/testing/selftests/x86/syscall_nt.c
@@ -17,6 +17,9 @@

#include <stdio.h>
#include <unistd.h>
+#include <string.h>
+#include <signal.h>
+#include <err.h>
#include <sys/syscall.h>
#include <asm/processor-flags.h>

@@ -26,6 +29,8 @@
# define WIDTH "l"
#endif

+static unsigned int nerrs;
+
static unsigned long get_eflags(void)
{
unsigned long eflags;
@@ -39,16 +44,52 @@ static void set_eflags(unsigned long eflags)
: : "rm" (eflags) : "flags");
}

-int main()
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+ int flags)
{
- printf("[RUN]\tSet NT and issue a syscall\n");
- set_eflags(get_eflags() | X86_EFLAGS_NT);
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_sigaction = handler;
+ sa.sa_flags = SA_SIGINFO | flags;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+}
+
+static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
+{
+}
+
+static void do_it(unsigned long extraflags)
+{
+ unsigned long flags;
+
+ set_eflags(get_eflags() | extraflags);
syscall(SYS_getpid);
- if (get_eflags() & X86_EFLAGS_NT) {
- printf("[OK]\tThe syscall worked and NT is still set\n");
- return 0;
+ flags = get_eflags();
+ if ((flags & extraflags) == extraflags) {
+ printf("[OK]\tThe syscall worked and flags are still set\n");
} else {
- printf("[FAIL]\tThe syscall worked but NT was cleared\n");
- return 1;
+ printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
+ flags, extraflags);
+ nerrs++;
}
}
+
+int main(void)
+{
+ printf("[RUN]\tSet NT and issue a syscall\n");
+ do_it(X86_EFLAGS_NT);
+
+ /*
+ * Now try it again with TF set -- TF forces returns via IRET in all
+ * cases except non-ptregs-using 64-bit full fast path syscalls.
+ */
+
+ sethandler(SIGTRAP, sigtrap, 0);
+
+ printf("[RUN]\tSet NT|TF and issue a syscall\n");
+ do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
+
+ return nerrs == 0 ? 0 : 1;
+}