On 4/10/24 09:45, Dev Jain wrote:
On 4/7/24 02:53, Muhammad Usama Anjum wrote:
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.
My initial idea was to treat this as a single logical test, as I
am asserting the restriction on the number of chunks against
the VMAs. I guess your approach is cleaner; thanks.
Thinking again, using a lot of return statements is in fact making the
code easier
to follow. If I just set a variable ret = 0/1 and use it to pass or
fail, I'll have to
unnecessarily use a lot of if/else statements. Take a look at the
examples below.
+
+ /* 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;
I will have to set ret value here, forcing two statements inside the if
block.
+ }
+ }
+
+ 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");
+
I will have to set ret here, and enclose the below while statement inside
an else block. In short, saving the value of ret will require if/else blocks
if I were to use it in the end in ksft_test_result(). When I use ksft_exit
statements, it is clear that a problem was spotted here, and there is
no need to study the remaining code.
+ 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();
+}
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