Message-Id: <a476bce6e7293858627f2301b5295be5b7111001.1640327326.git.pengfei.xu@intel.com>
Date:   Fri, 24 Dec 2021 16:53:23 +0800
From:   Pengfei Xu <pengfei.xu@...el.com>
To:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-kselftest <linux-kselftest@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Cc:     Pengfei Xu <pengfei.xu@...el.com>, Heng Su <heng.su@...el.com>,
        Hansen Dave <dave.hansen@...el.com>,
        Luck Tony <tony.luck@...el.com>,
        Mehta Sohil <sohil.mehta@...el.com>,
        Chen Yu C <yu.c.chen@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC PATCH v7 2/2] selftests/x86: add xsave test related to process switching

It will change FPU, SSE(XMM), AVX2(YMM), AVX512, PKRU xstates before process
switching test to ensure that these xstates have been tested.
In order to ensure that the content of xstates is not affected across process
switching, this case tests that:
1. The xstates content of the child process should be the same as that of the
   parent process.
2. The xstates content of the process should be the same across process
   switching.

Signed-off-by: Pengfei Xu <pengfei.xu@...el.com>
---
 tools/testing/selftests/x86/Makefile          |   3 +-
 tools/testing/selftests/x86/xsave_fork_test.c | 148 ++++++++++++++++++
 2 files changed, 150 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/x86/xsave_fork_test.c

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index a9e452b65ba2..049f8ffb2742 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -18,7 +18,7 @@ TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer
 TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering \
-			corrupt_xstate_header amx xsave_signal_handle
+			corrupt_xstate_header amx xsave_signal_handle xsave_fork_test
 # Some selftests require 32bit support enabled also on 64bit systems
 TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
 
@@ -106,3 +106,4 @@ $(OUTPUT)/test_syscall_vdso_32: thunks_32.S
 $(OUTPUT)/check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
 $(OUTPUT)/check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
 $(OUTPUT)/xsave_signal_handle_64: CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku
+$(OUTPUT)/xsave_fork_test_64: CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku
diff --git a/tools/testing/selftests/x86/xsave_fork_test.c b/tools/testing/selftests/x86/xsave_fork_test.c
new file mode 100644
index 000000000000..b470020ed368
--- /dev/null
+++ b/tools/testing/selftests/x86/xsave_fork_test.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * xsave_fork_test.c - XSAVE test with process switching.
+ *
+ * XSAVE feature will save/restore xstate, each process on x86 CPUs has it's
+ * own xstates. The xstates content of process should be same through the
+ * process switching.
+ * It tests that:
+ * 1. The xstates content of the child process should be the same as that of the
+ *    parent process.
+ * 2. The xstates content of the process should be the same across process
+ *    switching.
+ *
+ * Updates:
+ * - Because it tests FP SSE xstate, in order to prevent GCC from generating any
+ *   FP code by mistake, "-mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku"
+ *   compiler parameter was added, it's referred to the parameters for compiling
+ *   the x86 kernel.
+ * - Remove the use of "kselftest.h", because kselftest.h includes <stdlib.h>,
+ *   and "stdlib.h" uses sse instructions in it's libc, and this *XSAVE*
+ *   test needs to be compiled without libc sse instructions(-mno-sse).
+ * - Test code could not use buildin xsave64 in libc without sse, added
+ *   xsave function by instruction way.
+ * - Every key test action does not use libc(like printf) except syscall until
+ *   it's failed or done. If it's failed, then it will print the failed reason.
+ * - Use __cpuid_count() instead of native_cpuid(), becasue __cpuid_count()
+ *   was a macro definition function with one instruction in libc and did not
+ *   change xstate.
+ * - It tests FP, SSE(XMM), YMM, AVX512_opmask, PKRU xstates through process
+ *   switching.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <sched.h>
+#include <sys/syscall.h>
+
+#include "xsave_common.h"
+
+void *aligned_alloc(size_t alignment, size_t size);
+static unsigned char *xsave_buf0, *xsave_buf1, *xsave_buf2;
+static int xsave_size;
+
+void prepare_environment(void)
+{
+	xsave_size = get_xsave_size();
+	printf("XSAVE_TEST_MASK:0x%x, xsave size:0x%x\n",
+		XSAVE_TEST_MASK, xsave_size);
+	check_cpu_capability();
+
+	/* SDM XSAVE: misalignment to a 64-byte boundary will result in #GP */
+	xsave_buf0 = aligned_alloc(64, xsave_size);
+	if (!xsave_buf0)
+		execution_failed("aligned_alloc xsave_buf0 failed\n");
+	xsave_buf1 = aligned_alloc(64, xsave_size);
+	if (!xsave_buf1)
+		execution_failed("aligned_alloc xsave_buf1 failed\n");
+	xsave_buf2 = aligned_alloc(64, xsave_size);
+	if (!xsave_buf2)
+		execution_failed("aligned_alloc xsave_buf2 failed\n");
+}
+
+/* Use fork to create pid and trigger process switch test */
+int test_xsave_fork(void)
+{
+	pid_t child, grandchild;
+	int status, result[2];
+	const char *test_xsave_child = "Child xstate was same as parent";
+	const char *test_process_switch = "Xstate after the process switch didn't change";
+	uint32_t ui32_change = 0xffff0000;
+
+	populate_xstate_regs();
+	xsave(xsave_buf0, XSAVE_TEST_MASK);
+	child = syscall(SYS_fork);
+	if (child < 0)
+		execution_failed("fork failed\n");
+	if (child == 0) {
+		xsave(xsave_buf1, XSAVE_TEST_MASK);
+		result[0] = compare_xsave_buf(xsave_buf0, xsave_buf1, xsave_size,
+			test_xsave_child, NO_CHANGE);
+
+		/*
+		 * If the above case fails, print reason for failure, and then xstate
+		 * like xmm, ymm would be cleared by vzeroupper in printf(-mnosse), so
+		 * populate xstates for next test case, otherwise, xmm and ymm xstate
+		 * is all 0, there is no guarantee that xmm, ymm will be restored as
+		 * expected.
+		 */
+		populate_xstate_regs();
+		xsave(xsave_buf1, XSAVE_TEST_MASK);
+
+		/* fork grandchild will trigger process switching in child process */
+		grandchild = syscall(SYS_fork);
+		if (grandchild == 0) {
+			printf("Grandchild pid:%d changed it's own xstates\n", getpid());
+			change_xstate(ui32_change);
+			return 0;
+		}
+		if (grandchild) {
+			if (waitpid(grandchild, &status, 0) != grandchild || !WIFEXITED(status)) {
+				printf("[FAIL]:Grandchild exit with error, status:0x%x\n",
+					status);
+				err_num++;
+			}
+		}
+		/* After switch back to child process and check xstate */
+		xsave(xsave_buf2, XSAVE_TEST_MASK);
+		result[1] = compare_xsave_buf(xsave_buf1, xsave_buf2, xsave_size,
+			test_process_switch, NO_CHANGE);
+		printf("Child pid:%d check xstate after swtich back\n", getpid());
+
+		check_result(result[0], test_xsave_child);
+		check_result(result[1], test_process_switch);
+		printf("Xstate in process switch test pass[%d/%d], err_num:%d\n",
+			pass_num, case_num, err_num);
+
+		return 0;
+	}
+
+	if (child) {
+		if (waitpid(child, &status, 0) != child || !WIFEXITED(status)) {
+			printf("[FAIL]:Child exit with error, status:0x%x\n", status);
+			err_num++;
+		}
+	}
+
+	return 0;
+}
+
+int main(void)
+{
+	cpu_set_t set;
+
+	case_num = 2;
+	CPU_ZERO(&set);
+	CPU_SET(0, &set);
+	sched_setaffinity(getpid(), sizeof(set), &set);
+
+	prepare_environment();
+	test_xsave_fork();
+
+	return 0;
+}
-- 
2.31.1

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