kselftest/arm64: Add test coverage for ZT register signal frames

We should have a ZT register frame with an expected size when ZA is enabled
and have no ZT frame when ZA is disabled. Since we don't load any data into
ZT we expect the data to all be zeros since the architecture guarantees it
will be set to 0 as ZA is enabled.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-arm64-sme2-v4-18-f2fa0aef982f@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

tools/testing/selftests/arm64/signal/.gitignore

@@ -5,4 +5,5 @@ sme_*
 ssve_*
 sve_*
 za_*
+zt_*
 !*.[ch]

tools/testing/selftests/arm64/signal/testcases/zt_no_regs.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 ARM Limited
+ *
+ * Verify that using an instruction not supported in streaming mode
+ * traps when in streaming mode.
+ */
+
+#include <signal.h>
+#include <ucontext.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+static union {
+	ucontext_t uc;
+	char buf[1024 * 128];
+} context;
+
+int zt_no_regs_run(struct tdescr *td, siginfo_t *si, ucontext_t *uc)
+{
+	size_t offset;
+	struct _aarch64_ctx *head = GET_BUF_RESV_HEAD(context);
+
+	/*
+	 * Get a signal context which should not have a ZT frame and
+	 * registers in it.
+	 */
+	if (!get_current_context(td, &context.uc, sizeof(context)))
+		return 1;
+
+	head = get_header(head, ZT_MAGIC, GET_BUF_RESV_SIZE(context), &offset);
+	if (head) {
+		fprintf(stderr, "Got unexpected ZT context\n");
+		return 1;
+	}
+
+	td->pass = 1;
+
+	return 0;
+}
+
+struct tdescr tde = {
+	.name = "ZT register data not present",
+	.descr = "Validate that ZT is not present when ZA is disabled",
+	.feats_required = FEAT_SME2,
+	.timeout = 3,
+	.sanity_disabled = true,
+	.run = zt_no_regs_run,
+};

tools/testing/selftests/arm64/signal/testcases/zt_regs.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 ARM Limited
+ *
+ * Verify that using an instruction not supported in streaming mode
+ * traps when in streaming mode.
+ */
+
+#include <signal.h>
+#include <ucontext.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+static union {
+	ucontext_t uc;
+	char buf[1024 * 128];
+} context;
+
+static void enable_za(void)
+{
+	/* smstart za; real data is TODO */
+	asm volatile(".inst 0xd503457f" : : : );
+}
+
+int zt_regs_run(struct tdescr *td, siginfo_t *si, ucontext_t *uc)
+{
+	size_t offset;
+	struct _aarch64_ctx *head = GET_BUF_RESV_HEAD(context);
+	struct zt_context *zt;
+	char *zeros;
+
+	/*
+	 * Get a signal context which should have a ZT frame and registers
+	 * in it.
+	 */
+	enable_za();
+	if (!get_current_context(td, &context.uc, sizeof(context)))
+		return 1;
+
+	head = get_header(head, ZT_MAGIC, GET_BUF_RESV_SIZE(context), &offset);
+	if (!head) {
+		fprintf(stderr, "No ZT context\n");
+		return 1;
+	}
+
+	zt = (struct zt_context *)head;
+	if (zt->nregs == 0) {
+		fprintf(stderr, "Got context with no registers\n");
+		return 1;
+	}
+
+	fprintf(stderr, "Got expected size %u for %d registers\n",
+		head->size, zt->nregs);
+
+	/* We didn't load any data into ZT so it should be all zeros */
+	zeros = malloc(ZT_SIG_REGS_SIZE(zt->nregs));
+	if (!zeros) {
+		fprintf(stderr, "Out of memory, nregs=%u\n", zt->nregs);
+		return 1;
+	}
+	memset(zeros, 0, ZT_SIG_REGS_SIZE(zt->nregs));
+
+	if (memcmp(zeros, (char *)zt + ZT_SIG_REGS_OFFSET,
+		   ZT_SIG_REGS_SIZE(zt->nregs)) != 0) {
+		fprintf(stderr, "ZT data invalid\n");
+		return 1;
+	}
+
+	free(zeros);
+
+	td->pass = 1;
+
+	return 0;
+}
+
+struct tdescr tde = {
+	.name = "ZT register data",
+	.descr = "Validate that ZT is present and has data when ZA is enabled",
+	.feats_required = FEAT_SME2,
+	.timeout = 3,
+	.sanity_disabled = true,
+	.run = zt_regs_run,
+};