[PATCH v5 26/28] selftest/x86/amx: Test case for AMX state copy optimization in signal delivery

Chang S. Bae
2021-05-23T19:39:29Z

Add a test case to verify that unused states are excluded, by leaving a
known pattern on the signal stack and verifying that it is still intact
after taking a subsequent signal.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
---
Changes from v4:
* Separated out as a new patch.
* Improved the test routine by explicitly checking sigframe write.
---
tools/testing/selftests/x86/amx.c | 137 ++++++++++++++++++++++++++++++
1 file changed, 137 insertions(+)

diff --git a/tools/testing/selftests/x86/amx.c b/tools/testing/selftests/x86/amx.c
index 7d177c03cdcf..c5a5582e2b6f 100644
--- a/tools/testing/selftests/x86/amx.c
+++ b/tools/testing/selftests/x86/amx.c
@@ -562,6 +562,142 @@ static void test_ptrace(void)
test_tile_write();
}

+/* Signal handling test */
+
+static bool init_tiledata_state_before_signal;
+static bool load_tiledata_at_first;
+static bool sigalarmed, sigused;
+
+#define SIGFRAME_TILEDATA_SIGNATURE 0xFF
+
+static void handle_sigusr1(int sig, siginfo_t *info, void *ctx_void)
+{
+ void *xsave = ((ucontext_t *)ctx_void)->uc_mcontext.fpregs;
+
+ memset(xsave + xsave_xtiledata_offset, SIGFRAME_TILEDATA_SIGNATURE, xsave_xtiledata_size);
+
+ sigused = true;
+}
+
+static void handle_sigalrm(int sig, siginfo_t *info, void *ctx_void)
+{
+ void *xsave = ((ucontext_t *)ctx_void)->uc_mcontext.fpregs;
+ char d = SIGFRAME_TILEDATA_SIGNATURE;
+ bool written = false;
+ int i;
+
+ for (i = 0; i < xsave_xtiledata_size; i++) {
+ written = memcmp(xsave + xsave_xtiledata_offset + i, &d, 1);
+ if (written)
+ break;
+ }
+
+ if (__xgetbv(1) & XFEATURE_MASK_XTILEDATA)
+ err(1, "tile data state at signal delivery");
+
+ if (init_tiledata_state_before_signal && written) {
+ errs++;
+ printf("[FAIL]\tTile data was %swritten on sigframe.\n", !written ? "not " : "");
+ }
+
+ set_xstatebv(xsave_buffer, XFEATURE_MASK_XTILEDATA);
+ set_tiledata(xsave_buffer + xsave_xtiledata_offset);
+ xrstor(xsave_buffer, -1, -1);
+ sigalarmed = true;
+}
+
+static void test_signal_handling(void)
+{
+ pid_t child;
+
+ sigalarmed = false;
+ sigused = false;
+
+ child = fork();
+ if (child < 0) {
+ err(1, "fork");
+ } else if (child > 0) {
+ do {
+ int status;
+
+ wait(&status);
+ if (WIFSTOPPED(status))
+ kill(child, SIGCONT);
+ else if (WIFEXITED(status) && !WEXITSTATUS(status))
+ break;
+ else
+ err(1, "signal test child");
+ } while (1);
+ return;
+ }
+
+ printf("\tBefore signal, load tile data -- %s, re-initialized -- %s:\n",
+ load_tiledata_at_first ? "yes" : "no",
+ init_tiledata_state_before_signal ? "yes" : "no");
+
+ syscall(SYS_arch_prctl, ARCH_GET_XSTATE, XFEATURE_MASK_XTILE);
+
+ raise(SIGUSR1);
+ if (!sigused)
+ err(1, "SIGUSR1");
+
+ if (load_tiledata_at_first) {
+ set_xstatebv(xsave_buffer, XFEATURE_MASK_XTILEDATA);
+ set_tiledata(xsave_buffer + xsave_xtiledata_offset);
+ xrstor(xsave_buffer, -1, -1);
+ memcpy(tiledata, xsave_buffer + xsave_xtiledata_offset, xsave_xtiledata_size);
+ }
+
+ if (init_tiledata_state_before_signal) {
+ set_xstatebv(xsave_buffer, 0);
+ xrstor(xsave_buffer, -1, -1);
+ memset(tiledata, 0, xsave_xtiledata_size);
+ }
+
+ raise(SIGALRM);
+ if (!sigalarmed)
+ err(1, "SIGALRM");
+
+ __xsave(xsave_buffer, XFEATURE_MASK_XTILEDATA, 0);
+ if (memcmp(tiledata, xsave_buffer + xsave_xtiledata_offset, xsave_xtiledata_size)) {
+ errs++;
+ printf("[FAIL]\tTile data was not restored at sigreturn\n");
+ }
+
+ if (errs)
+ nerrs++;
+ else
+ printf("[OK]\tTile data was %swritten on sigframe and restored at sigreturn\n",
+ init_tiledata_state_before_signal ? "not " : "");
+ _exit(0);
+}
+
+static void test_signal(void)
+{
+ printf("[RUN]\tCheck tile data state in signal path:\n");
+
+ sethandler(SIGALRM, handle_sigalrm, 0);
+ sethandler(SIGUSR1, handle_sigusr1, 0);
+
+ load_tiledata_at_first = false;
+ init_tiledata_state_before_signal = true;
+ errs = 0;
+ test_signal_handling();
+
+ load_tiledata_at_first = true;
+ init_tiledata_state_before_signal = false;
+ errs = 0;
+ test_signal_handling();
+
+ load_tiledata_at_first = true;
+ init_tiledata_state_before_signal = true;
+ errs = 0;
+ test_signal_handling();
+
+ clearhandler(SIGALRM);
+ clearhandler(SIGUSR1);
+}
+
int main(void)
{
/* Check hardware availability at first */
@@ -592,6 +728,7 @@ int main(void)
test_fork();
test_context_switch();
test_ptrace();
+ test_signal();

clearhandler(SIGSEGV);

--
2.17.1