Re: [PATCH 1/4] selftests/arm: Add mm test

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@arm.com

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@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;

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();

+}