On 4/5/24 1:44 PM, Dev Jain wrote:
> 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@xxxxxxx>
> ---
> tools/testing/selftests/arm/mm/compat_va.c | 94 ++++++++++++++++++++++
> 1 file changed, 94 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..3a78f240bc87
> --- /dev/null
> +++ b/tools/testing/selftests/arm/mm/compat_va.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2024 ARM Limited
> + *
> + * Author : Dev Jain <dev.jain@xxxxxxx>
> + *
> + * 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;
Usually we return negative value instead of positive one which indicates
error situation.
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + char *ptr[NR_CHUNKS_4G + 3];
> + char line[1000];
> + const char *file_name;
> + int chunks;
> + FILE *file;
> + int i;
> +
> + ksft_print_header();
> + ksft_set_plan(1);
There are multiple test cases. Instead of saying there is only 1 test.
There should be multiple ksft_test_result{_pass,_fail} statements for each
sub-tests.
> +
> + /* 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;
> + if (chunks >= NR_CHUNKS_4G) {
> + ksft_test_result_fail("mmapped chunks beyond 4GB\n");
> + ksft_finished();
> + }
> +
> + /* parse /proc/self/maps, confirm 32 bit VA mappings */
> + file_name = "/proc/self/maps";
> + file = fopen(file_name, "r");
> + if (file == NULL)
> + ksft_exit_fail_msg("/proc/self/maps cannot be opened\n");
> +
> + 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_test_result_skip("Unexpected format");
> + ksft_finished();
I'm unable to follow as there are too many return statements. If you divide
the test into multiple sub-tests, you can skip/pass/fail each sub-test easily.
> + }
> +
> + if ((hyphen_loc - line > 8) ||
> + (whitespace_loc - hyphen_loc) > 9) {
> + ksft_test_result_fail("Memory map more than 32 bits\n");
> + ksft_finished();
> + }
> + }
> +
> + for (int i = 0; i < chunks; ++i)
> + munmap(ptr[i], MAP_CHUNK_SIZE);
> +
> + ksft_test_result_pass("Test\n");
> + ksft_finished();
> +}
--
BR,
Muhammad Usama Anjum
