kselftest/arm64: signal: Check SVE signal frame shows expected vector length

As a basic check that the SVE signal frame is being set up correctly
verify that the vector length in the signal frame is the vector length
that the process has.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210819134245.13935-4-broonie@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

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

 # SPDX-License-Identifier: GPL-2.0-only
 mangle_*
 fake_sigreturn_*
+sve_*
 !*.[ch]

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

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 ARM Limited
+ *
+ * Check that the SVE vector length reported in signal contexts is the
+ * expected one.
+ */
+
+#include <signal.h>
+#include <ucontext.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+struct fake_sigframe sf;
+unsigned int vl;
+
+static bool get_sve_vl(struct tdescr *td)
+{
+	int ret = prctl(PR_SVE_GET_VL);
+	if (ret == -1)
+		return false;
+
+	vl = ret;
+
+	return true;
+}
+
+static int sve_vl(struct tdescr *td, siginfo_t *si, ucontext_t *uc)
+{
+	size_t resv_sz, offset;
+	struct _aarch64_ctx *head = GET_SF_RESV_HEAD(sf);
+	struct sve_context *sve;
+
+	/* Get a signal context which should have a SVE frame in it */
+	if (!get_current_context(td, &sf.uc))
+		return 1;
+
+	resv_sz = GET_SF_RESV_SIZE(sf);
+	head = get_header(head, SVE_MAGIC, resv_sz, &offset);
+	if (!head) {
+		fprintf(stderr, "No SVE context\n");
+		return 1;
+	}
+	sve = (struct sve_context *)head;
+
+	if (sve->vl != vl) {
+		fprintf(stderr, "sigframe VL %u, expected %u\n",
+			sve->vl, vl);
+		return 1;
+	} else {
+		fprintf(stderr, "got expected VL %u\n", vl);
+	}
+
+	td->pass = 1;
+
+	return 0;
+}
+
+struct tdescr tde = {
+	.name = "SVE VL",
+	.descr = "Check that we get the right SVE VL reported",
+	.feats_required = FEAT_SVE,
+	.timeout = 3,
+	.init = get_sve_vl,
+	.run = sve_vl,
+};