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.jain@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.jain@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(); +}