[PATCH v2 01/10] selftests/x86: In syscall_nt, test NT|TF as well

[Andy Lutomirski]

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 <l...@kernel.org>
---
 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 60c06af4646a..43fcab367fb0 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;
+}
-- 
2.5.0