[PATCH] selftests/powerpc: Add a test of bad (out-of-range) accesses

[PATCH] selftests/powerpc: Add a test of bad (out-of-range) accesses

[Michael Ellerman]

Userspace isn't allowed to access certain address ranges, make sure we
actually test that to at least some degree.

This would have caught the recent bug where the SLB fault handler was
incorrectly called on an out-of-range access when using the Radix MMU.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 tools/testing/selftests/powerpc/mm/.gitignore |  3 +-
 tools/testing/selftests/powerpc/mm/Makefile   |  3 +-
 .../selftests/powerpc/mm/bad_accesses.c       | 68 +++++++++++++++++++
 3 files changed, 72 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/powerpc/mm/bad_accesses.c

diff --git a/tools/testing/selftests/powerpc/mm/.gitignore b/tools/testing/selftests/powerpc/mm/.gitignore
index ba919308fe30..c189170ba041 100644
--- a/tools/testing/selftests/powerpc/mm/.gitignore
+++ b/tools/testing/selftests/powerpc/mm/.gitignore
@@ -3,4 +3,5 @@ subpage_prot
 tempfile
 prot_sao
 segv_errors
-wild_bctr
\ No newline at end of file
+wild_bctr
+bad_accesses
\ No newline at end of file
diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile
index 43d68420e363..683047d66b72 100644
--- a/tools/testing/selftests/powerpc/mm/Makefile
+++ b/tools/testing/selftests/powerpc/mm/Makefile
@@ -2,7 +2,8 @@
 noarg:
 	$(MAKE) -C ../
 
-TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr
+TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors \
+		  wild_bctr bad_accesses
 TEST_GEN_FILES := tempfile
 
 top_srcdir = ../../../../..
diff --git a/tools/testing/selftests/powerpc/mm/bad_accesses.c b/tools/testing/selftests/powerpc/mm/bad_accesses.c
new file mode 100644
index 000000000000..86717c39e696
--- /dev/null
+++ b/tools/testing/selftests/powerpc/mm/bad_accesses.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2019, Michael Ellerman, IBM Corp.
+ *
+ * Test that out-of-bounds reads/writes behave as expected.
+ */
+
+#include <setjmp.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+
+static jmp_buf setjmp_env;
+
+static void segv_handler(int signum)
+{
+	siglongjmp(setjmp_env, 1);
+}
+
+int bad_access(char *p, bool write)
+{
+	char x;
+
+	if (sigsetjmp(setjmp_env, 1) == 0) {
+		if (write)
+			*p = 1;
+		else
+			x = *p;
+
+		printf("Bad - no SEGV! (%c)\n", x);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int test(void)
+{
+	unsigned long addr, i, j;
+
+	FAIL_IF(signal(SIGSEGV, segv_handler));
+
+	for (i = 1; i < 0x10; i++) {
+		for (j = 11; j < 60; j++) {
+			addr = (i << 60) | (1ul << j);
+
+			printf("Attempting bad access of 0x%16lx\n", addr);
+			FAIL_IF(bad_access((char *)addr, false));
+			FAIL_IF(bad_access((char *)addr, true));
+		}
+	}
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(test, "test_bad_accesses");
+}
-- 
2.20.1