[PATCH v2 2/3] kselftst/arm64: Test NT_ARM_SVE FPSIMD format writes on non-SVE systems

Mark Brown
2025-10-15T18:34:06Z

In order to allow exiting streaming mode on systems with SME but not SVE
we allow writes of FPSIMD format data via NT_ARM_SVE even when SVE is not
supported, add a test case that covers this to sve-ptrace.

We do not support reads.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
tools/testing/selftests/arm64/fp/sve-ptrace.c | 61 +++++++++++++++++++++++++++
1 file changed, 61 insertions(+)

diff --git a/tools/testing/selftests/arm64/fp/sve-ptrace.c b/tools/testing/selftests/arm64/fp/sve-ptrace.c
index e0fc3a001e28..f44d44618575 100644
--- a/tools/testing/selftests/arm64/fp/sve-ptrace.c
+++ b/tools/testing/selftests/arm64/fp/sve-ptrace.c
@@ -394,6 +394,58 @@ static void ptrace_sve_fpsimd(pid_t child, const struct vec_type *type)
free(svebuf);
}

+/* Write the FPSIMD registers via the SVE regset when SVE is not supported */
+static void ptrace_sve_fpsimd_no_sve(pid_t child)
+{
+ void *svebuf;
+ struct user_sve_header *sve;
+ struct user_fpsimd_state *fpsimd, new_fpsimd;
+ unsigned int i, j;
+ unsigned char *p;
+ int ret;
+
+ svebuf = malloc(SVE_PT_SIZE(0, SVE_PT_REGS_FPSIMD));
+ if (!svebuf) {
+ ksft_test_result_fail("Failed to allocate FPSIMD buffer\n");
+ return;
+ }
+
+ /* On a system without SVE the VL should be set to 0 */
+ memset(svebuf, 0, SVE_PT_SIZE(0, SVE_PT_REGS_FPSIMD));
+ sve = svebuf;
+ sve->flags = SVE_PT_REGS_FPSIMD;
+ sve->size = SVE_PT_SIZE(0, SVE_PT_REGS_FPSIMD);
+ sve->vl = 0;
+
+ /* Try to set a known FPSIMD state via PT_REGS_SVE */
+ fpsimd = (struct user_fpsimd_state *)((char *)sve +
+ SVE_PT_FPSIMD_OFFSET);
+ for (i = 0; i < 32; ++i) {
+ p = (unsigned char *)&fpsimd->vregs[i];
+
+ for (j = 0; j < sizeof(fpsimd->vregs[i]); ++j)
+ p[j] = j;
+ }
+
+ ret = set_sve(child, &vec_types[0], sve);
+ ksft_test_result(ret == 0, "FPSIMD write via SVE\n");
+ if (ret) {
+ ksft_test_result_skip("Verify FPSIMD write via SVE\n");
+ goto out;
+ }
+
+ /* Verify via the FPSIMD regset */
+ if (get_fpsimd(child, &new_fpsimd)) {
+ ksft_test_result_skip("Verify FPSIMD write via SVE\n");
+ goto out;
+ }
+ ksft_test_result(memcmp(fpsimd, &new_fpsimd, sizeof(*fpsimd)) == 0,
+ "Verify FPSIMD write via SVE\n");
+
+out:
+ free(svebuf);
+}
+
/* Validate attempting to set SVE data and read SVE data */
static void ptrace_set_sve_get_sve_data(pid_t child,
const struct vec_type *type,
@@ -826,6 +878,15 @@ static int do_parent(pid_t child)
}
}

+ /* We support SVE writes of FPSMID format on SME only systems */
+ if (!(getauxval(AT_HWCAP) & HWCAP_SVE) &&
+ (getauxval(AT_HWCAP2) & HWCAP2_SME)) {
+ ptrace_sve_fpsimd_no_sve(child);
+ } else {
+ ksft_test_result_skip("FPSIMD write via SVE\n");
+ ksft_test_result_skip("Verify FPSIMD write via SVE\n");
+ }
+
ret = EXIT_SUCCESS;

error:

--
2.47.2