kselftest/arm64: signal: Support signal frames with SVE register data

A signal frame with SVE may validly either be a bare struct sve_context or
a struct sve_context followed by vector length dependent register data.
Support either in the generic helpers for the signal tests, and while we're
at it validate the SVE vector length reported.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210819134245.13935-3-broonie@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

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

@@ -50,12 +50,38 @@ bool validate_extra_context(struct extra_context *extra, char **err)
 	return true;
 }
 
+bool validate_sve_context(struct sve_context *sve, char **err)
+{
+	/* Size will be rounded up to a multiple of 16 bytes */
+	size_t regs_size
+		= ((SVE_SIG_CONTEXT_SIZE(sve_vq_from_vl(sve->vl)) + 15) / 16) * 16;
+
+	if (!sve || !err)
+		return false;
+
+	/* Either a bare sve_context or a sve_context followed by regs data */
+	if ((sve->head.size != sizeof(struct sve_context)) &&
+	    (sve->head.size != regs_size)) {
+		*err = "bad size for SVE context";
+		return false;
+	}
+
+	if (!sve_vl_valid(sve->vl)) {
+		*err = "SVE VL invalid";
+
+		return false;
+	}
+
+	return true;
+}
+
 bool validate_reserved(ucontext_t *uc, size_t resv_sz, char **err)
 {
 	bool terminated = false;
 	size_t offs = 0;
 	int flags = 0;
 	struct extra_context *extra = NULL;
+	struct sve_context *sve = NULL;
 	struct _aarch64_ctx *head =
 		(struct _aarch64_ctx *)uc->uc_mcontext.__reserved;
 
@@ -90,9 +116,8 @@ bool validate_reserved(ucontext_t *uc, size_t resv_sz, char **err)
 		case SVE_MAGIC:
 			if (flags & SVE_CTX)
 				*err = "Multiple SVE_MAGIC";
-			else if (head->size !=
-				 sizeof(struct sve_context))
-				*err = "Bad size for sve_context";
+			/* Size is validated in validate_sve_context() */
+			sve = (struct sve_context *)head;
 			flags |= SVE_CTX;
 			break;
 		case EXTRA_MAGIC:
@@ -137,6 +162,9 @@ bool validate_reserved(ucontext_t *uc, size_t resv_sz, char **err)
 		if (flags & EXTRA_CTX)
 			if (!validate_extra_context(extra, err))
 				return false;
+		if (flags & SVE_CTX)
+			if (!validate_sve_context(sve, err))
+				return false;
 
 		head = GET_RESV_NEXT_HEAD(head);
 	}