kselftest/arm64: Check that SVCR is 0 in signal handlers

We don't currently validate that we exit streaming mode and clear ZA when
we enter a signal handler. Add simple checks for this in the SSVE and ZA
tests.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241106-arm64-fpmr-signal-test-v1-1-31fa34ce58fe@kernel.org
[catalin.marinas@arm.com: Use %lx in fprintf() as uint64_t seems to be unsigned long in glibc]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: broonie

tools/testing/selftests/arm64/signal/sve_helpers.h

@@ -18,4 +18,17 @@ extern unsigned int nvls;
 
 int sve_fill_vls(bool use_sme, int min_vls);
 
+static inline uint64_t get_svcr(void)
+{
+	uint64_t val;
+
+	asm volatile (
+		"mrs	%0, S3_3_C4_C2_2\n"
+		: "=r"(val)
+		:
+		: "cc");
+
+	return val;
+}
+
 #endif

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

@@ -85,6 +85,11 @@ static int do_one_sme_vl(struct tdescr *td, siginfo_t *si, ucontext_t *uc,
 	fprintf(stderr, "Got expected size %u and VL %d\n",
 		head->size, ssve->vl);
 
+	if (get_svcr() != 0) {
+		fprintf(stderr, "Unexpected SVCR %lx\n", get_svcr());
+		return 1;
+	}
+
 	return 0;
 }
 

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

@@ -91,6 +91,11 @@ static int do_one_sme_vl(struct tdescr *td, siginfo_t *si, ucontext_t *uc,
 		return 1;
 	}
 
+	if (get_svcr() != 0) {
+		fprintf(stderr, "Unexpected SVCR %lx\n", get_svcr());
+		return 1;
+	}
+
 	return 0;
 }