This patch tests the 4GB VA restriction for 32-bit processes; it is
required to test the compat layer, whether the kernel knows that it is
running a 32-bit process or not. Chunks are allocated until the VA gets
exhausted; mmap must fail beyond 4GB. This is asserted against the VA
mappings found in /proc/self/maps.
Signed-off-by: Dev Jain <dev.j...@arm.com>
---
v2->v3:
- Split into multiple testcases
tools/testing/selftests/arm/mm/compat_va.c | 89 ++++++++++++++++++++++
1 file changed, 89 insertions(+)
create mode 100644 tools/testing/selftests/arm/mm/compat_va.c
diff --git a/tools/testing/selftests/arm/mm/compat_va.c
b/tools/testing/selftests/arm/mm/compat_va.c
new file mode 100644
index 000000000000..20aa419eff29
--- /dev/null
+++ b/tools/testing/selftests/arm/mm/compat_va.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 ARM Limited
+ *
+ * Author : Dev Jain <dev.j...@arm.com>
+ *
+ * Tests 4GB VA restriction for 32 bit process
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include <linux/sizes.h>
+#include <kselftest.h>
+
+#define MAP_CHUNK_SIZE SZ_1M
+#define NR_CHUNKS_4G ((SZ_1G / MAP_CHUNK_SIZE) * 4) /* prevent overflow */
+
+static int validate_address_hint(void)
+{
+ char *ptr;
+
+ ptr = mmap((void *) (1UL << 29), MAP_CHUNK_SIZE, PROT_READ |
+ PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+ if (ptr == MAP_FAILED)
+ return 0;
+
+ return -1;
+}
+
+int main(int argc, char *argv[])
+{
+ char *ptr[NR_CHUNKS_4G + 3];
+ char line[1000];
+ int chunks;
+ FILE *file;
+ int ret;
+ int i;
+
+ ksft_print_header();
+ ksft_set_plan(2);
+
+ /* try allocation beyond 4 GB */
+ for (i = 0; i < NR_CHUNKS_4G + 3; ++i) {
+ ptr[i] = mmap(NULL, MAP_CHUNK_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+ if (ptr[i] == MAP_FAILED) {
+ if (validate_address_hint())
+ ksft_exit_fail_msg("VA exhaustion failed\n");
+ break;
+ }
+ }
+
+ chunks = i;
+
+ ret = (chunks < NR_CHUNKS_4G);
+ ksft_test_result(ret, "mmapped chunks under 4GB\n");
+
+ /* parse /proc/self/maps, confirm 32 bit VA mappings */
+ file = fopen("/proc/self/maps", "r");
+ if (!file)
+ ksft_exit_fail_perror("/proc/self/maps");
+
+ ret = 0;
+ while (fgets(line, sizeof(line), file)) {
+ const char *whitespace_loc, *hyphen_loc;
+
+ hyphen_loc = strchr(line, '-');
+ whitespace_loc = strchr(line, ' ');
+
+ if (!(hyphen_loc && whitespace_loc))
+ ksft_exit_fail_msg("Unexpected format\n");
+
+ ret |= ((hyphen_loc - line > 8) ||
+ (whitespace_loc - hyphen_loc > 9));
+ }
+
+ ksft_test_result(!ret, "Memory map within 32 bits\n");
+
+ for (i = 0; i < chunks; ++i)
+ munmap(ptr[i], MAP_CHUNK_SIZE);
+
+ ksft_finished();
+}
--
2.39.2
