[PATCH v12 0/2] Introduce XSAVE feature self-test

[PATCH v12 0/2] Introduce XSAVE feature self-test

[Pengfei Xu]

The XSAVE feature set supports the saving and restoring of xstate components.
XSAVE feature has been used for process context switching. XSAVE components
include x87 state for FP execution environment, SSE state, AVX state and so on.

In order to ensure that XSAVE works correctly, add XSAVE most basic test for
XSAVE architecture functionality.

This patch tests "FP, SSE(XMM), AVX2(YMM), AVX512_OPMASK/AVX512_ZMM_Hi256/
AVX512_Hi16_ZMM and PKRU parts" xstates with following cases:
1. The contents of these xstates in the process should not change after the
   signal handling.
2. The contents of these xstates in the child process should be the same as
   the contents of the xstate in the parent process after the fork syscall.
3. The contents of xstates in the parent process should not change after
   the context switch.

Because xstate like XMM will not be preserved across function calls, fork() and
raise() are implemented and inlined.
To prevent GCC from generating any FP/SSE(XMM)/AVX/PKRU code, add
"-mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku" compiler arguments. stdlib.h
can not be used because of the "-mno-sse" option.
Thanks Dave, Hansen for the above suggestion!
Thanks Chen Yu; Shuah Khan; Chatre Reinette and Tony Luck's comments!
Thanks to Bae, Chang Seok for a bunch of comments!

========
- Change from v11 to v12
  - Remove useless rbx register stuffing in assembly syscall functions.
    (Zhang, Li)

- Change from v10 to v11
  - Remove the small function like cpu_has_pkru(), get_xstate_size() and so
    on. (Shuah Khan)
  - Unify xfeature_num type to uint32_t.

- Change from v9 to v10
  - Remove the small function if the function will be called once and there
    is no good reason. (Shuah Khan)

- Change from v8 to v9
  - Use function pointers to make it more structured. (Hansen, Dave)
  - Improve the function name: xstate_tested -> xstate_in_test. (Chang S. Bae)
  - Break this test up into two pieces: keep the xstate key test steps with
    "-mno-sse" and no stdlib.h, keep others in xstate.c file. (Hansen, Dave)
  - Use kselftest infrastructure for xstate.c file. (Hansen, Dave)
  - Use instruction back to populate fp xstate buffer. (Hansen, Dave)
  - Will skip the test if cpu could not support xsave. (Chang S. Bae)
  - Use __cpuid_count() helper in kselftest.h. (Reinette, Chatre)

- Change from v7 to v8
  Many thanks to Bae, Chang Seok for a bunch of comments as follow:
  - Use the filling buffer way to prepare the xstate buffer, and use xrstor
    instruction way to load the tested xstates.
  - Remove useless dump_buffer, compare_buffer functions.
  - Improve the struct of xstate_info.
  - Added AVX512_ZMM_Hi256 and AVX512_Hi16_ZMM components in xstate test.
  - Remove redundant xstate_info.xstate_mask, xstate_flag[], and
    xfeature_test_mask, use xstate_info.mask instead.
  - Check if xfeature is supported outside of fill_xstate_buf() , this change
    is easier to read and understand.
  - Remove useless wrpkru, only use filling all tested xstate buffer in
    fill_xstates_buf().
  - Improve a bunch of function names and variable names.
  - Improve test steps flow for readability.

- Change from v6 to v7:
  - Added the error number and error description of the reason for the
    failure, thanks Shuah Khan's suggestion.
  - Added a description of what these tests are doing in the head comments.
  - Added changes update in the head comments.
  - Added description of the purpose of the function. thanks Shuah Khan.

- Change from v5 to v6:
  - 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. Thanks
    Dave Hansen's suggestion.
  - Removed the use of "kselftest.h", because kselftest.h included <stdlib.h>,
    and "stdlib.h" would use sse instructions in it's libc, and this *XSAVE*
    test needed to be compiled without libc sse instructions(-mno-sse).
  - Improved the description in commit header, thanks Chen Yu's suggestion.
  - Becasue test code could not use buildin xsave64 in libc without sse, added
    xsave function by instruction way.
  - Every key test action would not use libc(like printf) except syscall until
    it's failed or done. If it's failed, then it would print the failed reason.
  - Used __cpuid_count() instead of native_cpuid(), becasue __cpuid_count()
    was a macro definition function with one instruction in libc and did not
    change xstate. Thanks Chatre Reinette, Shuah Khan.
    https://lore.kernel.org/linux-sgx/8b7c98f4-f050-bc1c-5699-fa598ecc66a2@linuxfoundation.org/

- Change from v4 to v5:
  - Moved code files into tools/testing/selftests/x86.
  - Delete xsave instruction test, becaue it's not related to kernel.
  - Improved case description.
  - Added AVX512 opmask change and related XSAVE content verification.
  - Added PKRU part xstate test into instruction and signal handling test.
  - Added XSAVE process swich test for FPU, AVX2, AVX512 opmask and PKRU part.

- Change from v3 to v4:
  - Improve the comment in patch 1.

- Change from v2 to v3:
  - Improve the description of patch 2 git log.

- Change from v1 to v2:
  - Improve the cover-letter. Thanks Dave Hansen's suggestion.

Pengfei Xu (2):
  selftests/x86/xstate: Add xstate signal handling test for XSAVE
    feature
  selftests/x86/xstate: Add xstate fork test for XSAVE feature

 tools/testing/selftests/x86/.gitignore       |   1 +
 tools/testing/selftests/x86/Makefile         |  11 +-
 tools/testing/selftests/x86/xstate.c         | 215 +++++++++++++++++
 tools/testing/selftests/x86/xstate.h         | 228 +++++++++++++++++++
 tools/testing/selftests/x86/xstate_helpers.c | 209 +++++++++++++++++
 tools/testing/selftests/x86/xstate_helpers.h |   9 +
 6 files changed, 671 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/x86/xstate.c
 create mode 100644 tools/testing/selftests/x86/xstate.h
 create mode 100644 tools/testing/selftests/x86/xstate_helpers.c
 create mode 100644 tools/testing/selftests/x86/xstate_helpers.h

-- 
2.31.1

[PATCH v12 1/2] selftests/x86/xstate: Add xstate signal handling test for XSAVE feature

[Pengfei Xu]

The XSAVE feature set supports the saving and restoring of xstate components.

In order to ensure that XSAVE works correctly, add XSAVE most basic signal
handling test for XSAVE architecture functionality, this patch tests "FP,
SSE(XMM), AVX2(YMM), AVX512_OPMASK/AVX512_ZMM_Hi256/AVX512_Hi16_ZMM and PKRU"
xstates with the following:
The contents of these xstates in the process should not change after the
signal handling.

  [ Dave Hansen; Chang S. Bae; Shuah Khan: bunches of cleanups ]

Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
---
 tools/testing/selftests/x86/.gitignore       |   1 +
 tools/testing/selftests/x86/Makefile         |  11 +-
 tools/testing/selftests/x86/xstate.c         | 195 ++++++++++++++++
 tools/testing/selftests/x86/xstate.h         | 227 +++++++++++++++++++
 tools/testing/selftests/x86/xstate_helpers.c | 142 ++++++++++++
 tools/testing/selftests/x86/xstate_helpers.h |   7 +
 6 files changed, 581 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/x86/xstate.c
 create mode 100644 tools/testing/selftests/x86/xstate.h
 create mode 100644 tools/testing/selftests/x86/xstate_helpers.c
 create mode 100644 tools/testing/selftests/x86/xstate_helpers.h

diff --git a/tools/testing/selftests/x86/.gitignore b/tools/testing/selftests/x86/.gitignore
index 1aaef5bf119a..68951ceefe30 100644
--- a/tools/testing/selftests/x86/.gitignore
+++ b/tools/testing/selftests/x86/.gitignore
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 *_32
 *_64
+*.o
 single_step_syscall
 sysret_ss_attrs
 syscall_nt
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 0388c4d60af0..49a6d78e0831 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
+			corrupt_xstate_header amx xstate
 # Some selftests require 32bit support enabled also on 64bit systems
 TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
 
@@ -69,7 +69,7 @@ all_32: $(BINARIES_32)
 
 all_64: $(BINARIES_64)
 
-EXTRA_CLEAN := $(BINARIES_32) $(BINARIES_64)
+EXTRA_CLEAN := $(BINARIES_32) $(BINARIES_64) *.o
 
 $(BINARIES_32): $(OUTPUT)/%_32: %.c helpers.h
 	$(CC) -m32 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl -lm
@@ -109,3 +109,10 @@ $(OUTPUT)/test_syscall_vdso_32: thunks_32.S
 # state.
 $(OUTPUT)/check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
 $(OUTPUT)/check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
+
+# xstate_64 is special: it needs xstate_helpers.o to prevent GCC from
+# generating any FP code by mistake and stdlib.h can't be used due to
+# "-mno-sse" parameter, so compile xstate_64 with the code file xstate.c
+# which can use stdlib.h and xstate_helpers.o which cannot use stdlib.h
+xstate_helpers.o: CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku
+$(OUTPUT)/xstate_64: xstate_helpers.o
diff --git a/tools/testing/selftests/x86/xstate.c b/tools/testing/selftests/x86/xstate.c
new file mode 100644
index 000000000000..0f8348aa1f15
--- /dev/null
+++ b/tools/testing/selftests/x86/xstate.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * xstate.c - tests XSAVE feature with fork and signal handling.
+ *
+ * The XSAVE feature set supports the saving and restoring of state components.
+ * It tests "FP, SSE(XMM), AVX2(YMM), AVX512_OPMASK/AVX512_ZMM_Hi256/
+ * AVX512_Hi16_ZMM and PKRU parts" xstates with following cases:
+ * 1. The contents of these xstates in the process should not change after the
+ *    signal handling.
+ * 2. The contents of these xstates in the child process should be the same as
+ *    the contents of the xstate in the parent process after the fork syscall.
+ * 3. The contents of xstates in the parent process should not change after
+ *    the context switch.
+ *
+ * The regions and reserved bytes of the components tested for XSAVE feature
+ * are as follows:
+ * x87(FP)/SSE    (0 - 159 bytes)
+ * SSE(XMM part)  (160-415 bytes)
+ * Reserved       (416-511 bytes)
+ * Header_used    (512-527 bytes; XSTATE BV(bitmap vector) mask:512-519 bytes)
+ * Header_reserved(528-575 bytes must be 00)
+ * YMM            (Offset:CPUID.(EAX=0D,ECX=2).EBX Size:CPUID(EAX=0D,ECX=2).EAX)
+ * AVX512_OPMASK  (Offset:CPUID.(EAX=0D,ECX=5).EBX Size:CPUID(EAX=0D,ECX=5).EAX)
+ * ZMM_Hi256      (Offset:CPUID.(EAX=0D,ECX=6).EBX Size:CPUID(EAX=0D,ECX=6).EAX)
+ * Hi16_ZMM       (Offset:CPUID.(EAX=0D,ECX=7).EBX Size:CPUID(EAX=0D,ECX=7).EAX)
+ * PKRU           (Offset:CPUID.(EAX=0D,ECX=9).EBX Size:CPUID(EAX=0D,ECX=9).EAX)
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <malloc.h>
+#include <stdlib.h>
+
+#include "xstate.h"
+#include "xstate_helpers.h"
+#include "../kselftest.h"
+
+#define NUM_TESTS	1
+#define xstate_test_array_init(idx, init_opt, fill_opt)		\
+	do {							\
+		xstate_tests[idx].init = init_opt;		\
+		xstate_tests[idx].fill_xbuf = fill_opt;		\
+	} while (0)
+
+static struct xsave_buffer *valid_xbuf, *compared_xbuf;
+static struct xstate_test xstate_tests[XFEATURE_MAX];
+static uint32_t xstate_size;
+
+static struct xsave_buffer *alloc_xbuf(uint32_t buf_size)
+{
+	struct xsave_buffer *xbuf;
+
+	/* XSAVE buffer should be 64B-aligned. */
+	xbuf = aligned_alloc(64, buf_size);
+	if (!xbuf)
+		ksft_exit_fail_msg("aligned_alloc() failed.\n");
+
+	return xbuf;
+}
+
+static void show_test_xfeatures(void)
+{
+	uint32_t xfeature_num;
+	const char *xfeature_name;
+
+	ksft_print_msg("[NOTE] Test following xstates with mask:%lx.\n",
+		       xstate_info.mask);
+	for (xfeature_num = 0; xfeature_num < XFEATURE_MAX; xfeature_num++) {
+		if (!(xstate_info.mask & (1 << xfeature_num)))
+			continue;
+		xfeature_name = xfeature_names[xfeature_num];
+		ksft_print_msg("[NOTE] XSAVE feature num %02d: '%s'.\n",
+			       xfeature_num, xfeature_name);
+	}
+}
+
+static void compare_buf_result(struct xsave_buffer *valid_buf,
+			       struct xsave_buffer *compare_buf,
+			       const char *case_name)
+{
+	if (memcmp(&valid_buf->bytes[0], &compare_buf->bytes[0], xstate_size))
+		ksft_test_result_fail("The case: %s.\n", case_name);
+	else
+		ksft_test_result_pass("The case: %s.\n", case_name);
+}
+
+static void test_xstate_sig_handle(void)
+{
+	const char *case_name1 = "xstate around process signal handling";
+
+	ksft_print_msg("[RUN] Check xstate around signal handling test.\n");
+
+	if (xstate_sig_handle(valid_xbuf, compared_xbuf, xstate_info.mask,
+	    xstate_size)) {
+		ksft_print_msg("[NOTE] SIGUSR1 handling is done.\n");
+	} else {
+		ksft_test_result_error("%s: Didn't access SIGUSR1 handling.\n",
+				       case_name1);
+		return;
+	}
+
+	compare_buf_result(valid_xbuf, compared_xbuf, case_name1);
+}
+
+static void prepare_xstate_test(void)
+{
+	xstate_test_array_init(XFEATURE_FP, init_legacy_info,
+			       fill_fp_mxcsr_xstate_buf);
+	xstate_test_array_init(XFEATURE_SSE, init_legacy_info,
+			       fill_xmm_xstate_buf);
+	xstate_test_array_init(XFEATURE_YMM, init_ymm_info,
+			       fill_common_xstate_buf);
+	xstate_test_array_init(XFEATURE_OPMASK, init_avx512_info,
+			       fill_common_xstate_buf);
+	xstate_test_array_init(XFEATURE_ZMM_Hi256, init_avx512_info,
+			       fill_common_xstate_buf);
+	xstate_test_array_init(XFEATURE_Hi16_ZMM, init_avx512_info,
+			       fill_common_xstate_buf);
+	xstate_test_array_init(XFEATURE_PKRU, init_pkru_info,
+			       fill_pkru_xstate_buf);
+
+	xstate_tests[XSTATE_CASE_SIG].xstate_case = test_xstate_sig_handle;
+}
+
+static void test_xstate(void)
+{
+	uint32_t xfeature_num, case_num, eax, ebx, ecx, edx;
+
+	/*
+	 * CPUID.0xd.0:EBX[bit 5] enumerates the size(in bytes) required by
+	 * the XSAVE instruction for an XSAVE area containing all the user
+	 * state components corresponding to bits currently set in XCR0.
+	 */
+	__cpuid_count(CPUID_LEAF_XSTATE, CPUID_SUBLEAF_XSTATE_USER, eax, ebx,
+		      ecx, edx);
+	xstate_size = ebx;
+	valid_xbuf = alloc_xbuf(xstate_size);
+	compared_xbuf = alloc_xbuf(xstate_size);
+
+	for (xfeature_num = XFEATURE_FP; xfeature_num < XFEATURE_MAX;
+	     xfeature_num++) {
+		/* If there is no the xfeature init function, will continue. */
+		if (xstate_tests[xfeature_num].init) {
+			/* If CPU doesn't support the xfeature, will continue */
+			if (!xstate_tests[xfeature_num].init(xfeature_num))
+				continue;
+		} else {
+			continue;
+		}
+
+		/* Fill xstate buffer. */
+		if (xfeature_num != XFEATURE_PKRU) {
+			xstate_tests[xfeature_num].fill_xbuf(valid_xbuf,
+				xfeature_num, XSTATE_TESTBYTE);
+		} else {
+			/*
+			 * Bits 0-1 in first byte of PKRU must be 0 for
+			 * RW access to linear address.
+			 */
+			xstate_tests[xfeature_num].fill_xbuf(valid_xbuf,
+				xfeature_num, PKRU_TESTBYTE);
+		}
+	}
+
+	/*
+	 * Fill xstate-component bitmap(512-519 bytes) into the beginning of
+	 * xstate header. xstate header range is 512-575 bytes.
+	 */
+	*(uint64_t *)(&valid_xbuf->header) = xstate_info.mask;
+
+	show_test_xfeatures();
+
+	for (case_num = XSTATE_CASE_SIG; case_num < XSTATE_CASE_MAX; case_num++)
+		xstate_tests[case_num].xstate_case();
+
+	free(valid_xbuf);
+	free(compared_xbuf);
+}
+
+int main(void)
+{
+	ksft_print_header();
+	ksft_set_plan(NUM_TESTS);
+
+	/* Check hardware availability for xsave at first. */
+	check_cpuid_xsave_availability();
+	prepare_xstate_test();
+	test_xstate();
+
+	ksft_exit(ksft_cnt.ksft_pass == ksft_plan);
+}
diff --git a/tools/testing/selftests/x86/xstate.h b/tools/testing/selftests/x86/xstate.h
new file mode 100644
index 000000000000..f0eb7a430905
--- /dev/null
+++ b/tools/testing/selftests/x86/xstate.h
@@ -0,0 +1,227 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include "../kselftest.h"
+
+#define XSTATE_TESTBYTE		0x8f
+/* Bits 0-1 in first byte of PKRU must be 0 for RW access to linear address. */
+#define PKRU_TESTBYTE		0xfc
+/* FP xstate(0-159 bytes) offset(0) and size(160 bytes) are fixed. */
+#define FP_SIZE			160
+/* XMM xstate(160-415 bytes) offset(160 byte) and size(256 bytes) are fixed. */
+#define XMM_OFFSET		160
+#define XMM_SIZE		256
+/*
+ * xstate 416-511 bytes are reserved, XSAVE header offset 512 bytes
+ * and header size 64 bytes are fixed.
+ */
+#define XSAVE_HDR_OFFSET	512
+#define XSAVE_HDR_SIZE		64
+
+#define CPUID_LEAF1_ECX_XSAVE_MASK	(1 << 26) /* XSAVE instructions */
+#define CPUID_LEAF1_ECX_OSXSAVE_MASK	(1 << 27) /* OSXSAVE flag */
+
+#define CPUID_LEAF7_EBX_AVX2_MASK	(1U << 5) /* AVX2 instructions */
+#define CPUID_LEAF7_EBX_AVX512F_MASK	(1U << 16) /* AVX-512 Foundation */
+
+#define CPUID_LEAF7_ECX_OSPKE_MASK	(1U << 4) /* OS Protection Keys Enable */
+
+#define CPUID_LEAF_XSTATE		0xd
+#define CPUID_SUBLEAF_XSTATE_USER	0x0
+
+/* It's from arch/x86/kernel/fpu/xstate.c. */
+static const char * const xfeature_names[] = {
+	"x87 floating point registers",
+	"SSE registers",
+	"AVX registers",
+	"MPX bounds registers",
+	"MPX CSR",
+	"AVX-512 opmask",
+	"AVX-512 Hi256",
+	"AVX-512 ZMM_Hi256",
+	"Processor Trace (unused)",
+	"Protection Keys User registers",
+	"PASID state",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"unknown xstate feature",
+	"AMX Tile config",
+	"AMX Tile data",
+	"unknown xstate feature",
+};
+
+/* List of XSAVE features Linux knows about. */
+enum xfeature {
+	XFEATURE_FP,
+	XFEATURE_SSE,
+	/*
+	 * Values above here are "legacy states".
+	 * Those below are "extended states".
+	 */
+	XFEATURE_YMM,
+	XFEATURE_BNDREGS,
+	XFEATURE_BNDCSR,
+	XFEATURE_OPMASK,
+	XFEATURE_ZMM_Hi256,
+	XFEATURE_Hi16_ZMM,
+	XFEATURE_PT_UNIMPLEMENTED_SO_FAR,
+	XFEATURE_PKRU,
+	XFEATURE_PASID,
+	XFEATURE_RSRVD_COMP_11,
+	XFEATURE_RSRVD_COMP_12,
+	XFEATURE_RSRVD_COMP_13,
+	XFEATURE_RSRVD_COMP_14,
+	XFEATURE_LBR,
+	XFEATURE_RSRVD_COMP_16,
+	XFEATURE_XTILE_CFG,
+	XFEATURE_XTILE_DATA,
+	XFEATURE_MAX,
+};
+
+enum xstate_case {
+	XSTATE_CASE_SIG,
+	XSTATE_CASE_MAX,
+};
+
+struct xsave_buffer {
+	union {
+		struct {
+			char legacy[XSAVE_HDR_OFFSET];
+			char header[XSAVE_HDR_SIZE];
+			char extended[0];
+		};
+		char bytes[0];
+	};
+};
+
+struct {
+	uint64_t mask;
+	uint32_t size[XFEATURE_MAX];
+	uint32_t offset[XFEATURE_MAX];
+} xstate_info;
+
+struct xstate_test {
+	bool (*init)(uint32_t xfeature_num);
+	void (*fill_xbuf)(void *buf, uint32_t xfeature_num, uint8_t test_byte);
+	void (*xstate_case)(void);
+};
+
+static void check_cpuid_xsave_availability(void)
+{
+	uint32_t eax, ebx, ecx, edx;
+
+	/*
+	 * CPUID.1:ECX.XSAVE[bit 26] enumerates general
+	 * support for the XSAVE feature set, including
+	 * XGETBV.
+	 */
+	__cpuid_count(1, 0, eax, ebx, ecx, edx);
+	if (!(ecx & CPUID_LEAF1_ECX_XSAVE_MASK))
+		ksft_exit_skip("cpuid: CPU doesn't support xsave.\n");
+
+	if (!(ecx & CPUID_LEAF1_ECX_OSXSAVE_MASK))
+		ksft_exit_skip("cpuid: CPU doesn't support OS xsave.\n");
+}
+
+/* Retrieve the mask, offset and size of a specific xstate. */
+static void retrieve_xstate_mask_size_offset(uint32_t xfeature_num)
+{
+	uint32_t eax, ebx, ecx, edx;
+
+	xstate_info.mask |= 1 << xfeature_num;
+	/*
+	 * The offset and size of xstate FP and SSE are not recorded by CPUID,
+	 * the contents of FP (x87 state) and MXCSR register are mixed in
+	 * bytes 0-511.
+	 */
+	if (xfeature_num == XFEATURE_FP || xfeature_num == XFEATURE_SSE)
+		return;
+
+	__cpuid_count(CPUID_LEAF_XSTATE, xfeature_num, eax, ebx, ecx, edx);
+	/*
+	 * CPUID.(EAX=0xd, ECX=xfeature_num), and output is as follow:
+	 * eax: xfeature num state component size
+	 * ebx: xfeature num state component offset in user buffer
+	 */
+	if (!eax || !ebx)
+		ksft_exit_fail_msg("xfeature num:%d size/offset:%d/%d is 0.\n",
+				   xfeature_num, eax, ebx);
+
+	xstate_info.size[xfeature_num] = eax;
+	xstate_info.offset[xfeature_num] = ebx;
+}
+
+/* Retrieve legacy FP and SSE xstate info. */
+static bool init_legacy_info(uint32_t xfeature_num)
+{
+	retrieve_xstate_mask_size_offset(xfeature_num);
+	return true;
+}
+
+static bool init_ymm_info(uint32_t xfeature_num)
+{
+	uint32_t eax, ebx, ecx, edx;
+
+	/* CPUID.7.0:EBX.AVX2[bit 5]: the support for AVX2 instructions. */
+	__cpuid_count(7, 0, eax, ebx, ecx, edx);
+	if (ebx & CPUID_LEAF7_EBX_AVX2_MASK) {
+		retrieve_xstate_mask_size_offset(xfeature_num);
+		return true;
+	}
+	return false;
+}
+
+static bool init_avx512_info(uint32_t xfeature_num)
+{
+	uint32_t eax, ebx, ecx, edx;
+
+	/* CPUID.7.0:EBX.AVX512F[bit 16]: support for AVX512F instructions. */
+	__cpuid_count(7, 0, eax, ebx, ecx, edx);
+	if (ebx & CPUID_LEAF7_EBX_AVX512F_MASK) {
+		retrieve_xstate_mask_size_offset(xfeature_num);
+		return true;
+	}
+	return false;
+}
+
+static bool init_pkru_info(uint32_t xfeature_num)
+{
+	uint32_t eax, ebx, ecx, edx;
+
+	/* CPUID.7.0:ECX.OSPKE[bit 4]: the support for OS set CR4.PKE. */
+	__cpuid_count(7, 0, eax, ebx, ecx, edx);
+	if (ecx & CPUID_LEAF7_ECX_OSPKE_MASK) {
+		retrieve_xstate_mask_size_offset(xfeature_num);
+		return true;
+	}
+	return false;
+}
+
+static void fill_xmm_xstate_buf(void *buf, uint32_t xfeature_num,
+				uint8_t test_byte)
+{
+	/*
+	 * Fill test byte value into SSE XMM part xstate buffer(160-415 bytes).
+	 * xstate 416-511 bytes are reserved as all 0.
+	 */
+	memset((unsigned char *)buf + XMM_OFFSET, test_byte, XMM_SIZE);
+}
+
+static void fill_common_xstate_buf(void *buf, uint32_t xfeature_num,
+				   uint8_t test_byte)
+{
+	memset((unsigned char *)buf + xstate_info.offset[xfeature_num],
+	       test_byte, xstate_info.size[xfeature_num]);
+}
+
+static void fill_pkru_xstate_buf(void *buf, uint32_t xfeature_num,
+				 uint8_t test_byte)
+{
+	/*
+	 * Only 0-3 bytes of PKRU xstate are allowed to be written. 4-7
+	 * bytes are reserved as all 0.
+	 */
+	memset((unsigned char *)buf + xstate_info.offset[XFEATURE_PKRU],
+	       test_byte, sizeof(uint32_t));
+}
diff --git a/tools/testing/selftests/x86/xstate_helpers.c b/tools/testing/selftests/x86/xstate_helpers.c
new file mode 100644
index 000000000000..461f5e9d16cb
--- /dev/null
+++ b/tools/testing/selftests/x86/xstate_helpers.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * xstate_helpers.c - xstate helpers to prevent GCC from generating any FP code.
+ *
+ * Because xstate like XMM will not be preserved across function calls, it uses
+ * assembly instruction to call a system call of fork or raise signal, and uses
+ * the "inline" keyword in test functions in this file.
+ * To prevent GCC from generating any FP/SSE(XMM)/AVX/PKRU code, add
+ * "-mno-sse -mno-mmx -mno-sse2 -mno-avx -mno-pku" compiler arguments. stdlib.h
+ * can not be used in this test file due to GCC bug.
+ * The test functions that prepare the xstate buffers are placed in a separate
+ * xstate.c because they do not require the above requirements.
+ */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+
+#include "xstate_helpers.h"
+
+/* err() exits and will not return. */
+#define fatal_error(msg, ...)	err(1, "[FAIL]\t" msg, ##__VA_ARGS__)
+/* FP and SSE are legacy xstates with fixed masks in regions 0-511 bytes. */
+#define MASK_FP_SSE	3
+
+static bool sigusr1_done;
+
+static inline void __xsave(void *xbuf, uint64_t rfbm)
+{
+	uint32_t rfbm_lo = rfbm;
+	uint32_t rfbm_hi = rfbm >> 32;
+
+	asm volatile("xsave (%%rdi)"
+		     : : "D" (xbuf), "a" (rfbm_lo), "d" (rfbm_hi)
+		     : "memory");
+}
+
+static inline void __xrstor(void *xbuf, uint64_t rfbm)
+{
+	uint32_t rfbm_lo = rfbm;
+	uint32_t rfbm_hi = rfbm >> 32;
+
+	asm volatile("xrstor (%%rdi)"
+		     : : "D" (xbuf), "a" (rfbm_lo), "d" (rfbm_hi));
+}
+
+inline void fill_fp_mxcsr_xstate_buf(void *buf, uint32_t xfeature_num,
+				     uint8_t ui8_fp)
+{
+	/*
+	 * Sets the FPU control, status, tag, instruction pointer, and
+	 * data pointer registers to their default states.
+	 */
+	asm volatile("finit");
+	/* Populate tested bytes onto FP registers stack ST0-7. */
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	asm volatile("fldl %0" : : "m" (ui8_fp));
+	/* Xsave the x87 FPU and SSE MXCSR(bytes 24-27) xstate into the buf. */
+	__xsave(buf, MASK_FP_SSE);
+}
+
+/*
+ * Because xstate like XMM, YMM registers are not preserved across function
+ * calls, so use inline function with assembly code only to raise signal.
+ */
+static inline long __raise(long pid_num, long sig_num)
+{
+	long ret, nr = SYS_kill;
+
+	asm volatile("movq %0, %%rdi" : : "r"(pid_num) : "%rdi");
+	asm volatile("movq %0, %%rsi" : : "r"(sig_num) : "%rsi");
+	asm volatile("syscall"
+		     : "=a" (ret)
+		     : "a" (nr)
+		     : "rcx", "r11", "memory", "cc");
+
+	return ret;
+}
+
+static void sigusr1_handler(int signum, siginfo_t *info, void *__ctxp)
+{
+	sigusr1_done = true;
+}
+
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+		       int flags)
+{
+	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))
+		fatal_error("sigaction");
+}
+
+static void clearhandler(int sig)
+{
+	struct sigaction sa;
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = SIG_DFL;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, 0))
+		fatal_error("sigaction");
+}
+
+bool xstate_sig_handle(void *valid_xbuf, void *compared_xbuf, uint64_t mask,
+		       uint32_t xstate_size)
+{
+	pid_t process_pid;
+
+	sigusr1_done = false;
+	memset(compared_xbuf, 0, xstate_size);
+	sethandler(SIGUSR1, sigusr1_handler, 0);
+	process_pid = getpid();
+	/*
+	 * Xrstor the valid buf and call syscall assembly instruction, then
+	 * save the xstate to compared buf after signal handling for comparison.
+	 */
+	__xrstor(valid_xbuf, mask);
+	__raise(process_pid, SIGUSR1);
+	__xsave(compared_xbuf, mask);
+	clearhandler(SIGUSR1);
+
+	return sigusr1_done;
+}
diff --git a/tools/testing/selftests/x86/xstate_helpers.h b/tools/testing/selftests/x86/xstate_helpers.h
new file mode 100644
index 000000000000..f50a4c1d907f
--- /dev/null
+++ b/tools/testing/selftests/x86/xstate_helpers.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <stdint.h>
+
+extern void fill_fp_mxcsr_xstate_buf(void *buf, uint32_t xfeature_num,
+				     uint8_t ui8_fp);
+extern bool xstate_sig_handle(void *valid_xbuf, void *compared_xbuf,
+			      uint64_t mask, uint32_t xstate_size);
-- 
2.31.1

[PATCH v12 2/2] selftests/x86/xstate: Add xstate fork test for XSAVE feature

[Pengfei Xu]

In order to ensure that XSAVE works correctly, add XSAVE most basic fork
test:
1. The contents of these xstates in the child process should be the same as
   the contents of the xstate in the parent process after the fork syscall.
2. The contents of xstates in the parent process should not change after
   the context switch.

  [ Dave Hansen; Chang S. Bae; Shuah Khan: bunches of cleanups ]

Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
---
 tools/testing/selftests/x86/xstate.c         | 22 ++++++-
 tools/testing/selftests/x86/xstate.h         |  1 +
 tools/testing/selftests/x86/xstate_helpers.c | 67 ++++++++++++++++++++
 tools/testing/selftests/x86/xstate_helpers.h |  2 +
 4 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/xstate.c b/tools/testing/selftests/x86/xstate.c
index 0f8348aa1f15..e3707f0ea597 100644
--- a/tools/testing/selftests/x86/xstate.c
+++ b/tools/testing/selftests/x86/xstate.c
@@ -39,7 +39,7 @@
 #include "xstate_helpers.h"
 #include "../kselftest.h"
 
-#define NUM_TESTS	1
+#define NUM_TESTS	3
 #define xstate_test_array_init(idx, init_opt, fill_opt)		\
 	do {							\
 		xstate_tests[idx].init = init_opt;		\
@@ -106,6 +106,25 @@ static void test_xstate_sig_handle(void)
 	compare_buf_result(valid_xbuf, compared_xbuf, case_name1);
 }
 
+static void test_xstate_fork(void)
+{
+	const char *case_name2 = "xstate of child process should be same as xstate of parent";
+	const char *case_name3 = "parent xstate should be same after context switch";
+
+	ksft_print_msg("[RUN]\tParent pid:%d check xstate around fork test.\n",
+		       getpid());
+	/* Child process xstate should be same as the parent process xstate. */
+	if (xstate_fork(valid_xbuf, compared_xbuf, xstate_info.mask,
+	    xstate_size)) {
+		ksft_test_result_pass("The case: %s.\n", case_name2);
+	} else {
+		ksft_test_result_fail("The case: %s.\n", case_name2);
+	}
+
+	/* The parent process xstate should not change after context switch. */
+	compare_buf_result(valid_xbuf, compared_xbuf, case_name3);
+}
+
 static void prepare_xstate_test(void)
 {
 	xstate_test_array_init(XFEATURE_FP, init_legacy_info,
@@ -124,6 +143,7 @@ static void prepare_xstate_test(void)
 			       fill_pkru_xstate_buf);
 
 	xstate_tests[XSTATE_CASE_SIG].xstate_case = test_xstate_sig_handle;
+	xstate_tests[XSTATE_CASE_FORK].xstate_case = test_xstate_fork;
 }
 
 static void test_xstate(void)
diff --git a/tools/testing/selftests/x86/xstate.h b/tools/testing/selftests/x86/xstate.h
index f0eb7a430905..872404e246a6 100644
--- a/tools/testing/selftests/x86/xstate.h
+++ b/tools/testing/selftests/x86/xstate.h
@@ -81,6 +81,7 @@ enum xfeature {
 
 enum xstate_case {
 	XSTATE_CASE_SIG,
+	XSTATE_CASE_FORK,
 	XSTATE_CASE_MAX,
 };
 
diff --git a/tools/testing/selftests/x86/xstate_helpers.c b/tools/testing/selftests/x86/xstate_helpers.c
index 461f5e9d16cb..64bd014de6d5 100644
--- a/tools/testing/selftests/x86/xstate_helpers.c
+++ b/tools/testing/selftests/x86/xstate_helpers.c
@@ -73,6 +73,22 @@ inline void fill_fp_mxcsr_xstate_buf(void *buf, uint32_t xfeature_num,
 	__xsave(buf, MASK_FP_SSE);
 }
 
+/*
+ * Because xstate like XMM, YMM registers are not preserved across function
+ * calls, so use inline function with assembly code only for fork syscall.
+ */
+static inline long __fork(void)
+{
+	long ret, nr = SYS_fork;
+
+	asm volatile("syscall"
+		     : "=a" (ret)
+		     : "a" (nr)
+		     : "rcx", "r11", "memory", "cc");
+
+	return ret;
+}
+
 /*
  * Because xstate like XMM, YMM registers are not preserved across function
  * calls, so use inline function with assembly code only to raise signal.
@@ -140,3 +156,54 @@ bool xstate_sig_handle(void *valid_xbuf, void *compared_xbuf, uint64_t mask,
 
 	return sigusr1_done;
 }
+
+bool xstate_fork(void *valid_xbuf, void *compared_xbuf, uint64_t mask,
+		 uint32_t xstate_size)
+{
+	pid_t child;
+	int status, fd[2];
+	bool child_result;
+
+	memset(compared_xbuf, 0, xstate_size);
+	/* Use pipe to transfer test result to parent process. */
+	if (pipe(fd) < 0)
+		fatal_error("create pipe failed");
+	/*
+	 * Xrstor the valid_xbuf and call syscall assembly instruction, then
+	 * save the xstate to compared_xbuf in child process for comparison.
+	 */
+	__xrstor(valid_xbuf, mask);
+	child = __fork();
+	if (child < 0) {
+		/* Fork syscall failed. */
+		fatal_error("fork failed");
+	} else if (child == 0) {
+		/* Fork syscall succeeded, now in the child. */
+		__xsave(compared_xbuf, mask);
+
+		if (memcmp(valid_xbuf, compared_xbuf, xstate_size))
+			child_result = false;
+		else
+			child_result = true;
+
+		/*
+		 * Transfer the child process test result to
+		 * the parent process for aggregation.
+		 */
+		close(fd[0]);
+		if (!write(fd[1], &child_result, sizeof(child_result)))
+			fatal_error("write fd failed");
+		_exit(0);
+	} else {
+		/* Fork syscall succeeded, now in the parent. */
+		__xsave(compared_xbuf, mask);
+		if (waitpid(child, &status, 0) != child || !WIFEXITED(status)) {
+			fatal_error("Child exit with error status");
+		} else {
+			close(fd[1]);
+			if (!read(fd[0], &child_result, sizeof(child_result)))
+				fatal_error("read fd failed");
+			return child_result;
+		}
+	}
+}
diff --git a/tools/testing/selftests/x86/xstate_helpers.h b/tools/testing/selftests/x86/xstate_helpers.h
index f50a4c1d907f..c46d26ec6750 100644
--- a/tools/testing/selftests/x86/xstate_helpers.h
+++ b/tools/testing/selftests/x86/xstate_helpers.h
@@ -5,3 +5,5 @@ extern void fill_fp_mxcsr_xstate_buf(void *buf, uint32_t xfeature_num,
 				     uint8_t ui8_fp);
 extern bool xstate_sig_handle(void *valid_xbuf, void *compared_xbuf,
 			      uint64_t mask, uint32_t xstate_size);
+extern bool xstate_fork(void *valid_xbuf, void *compared_xbuf,
+			uint64_t mask, uint32_t xstate_size);
-- 
2.31.1