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;
+}
+
+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);
+
+ /* 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();
+ }
+
+ 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();
+}
--
2.39.2On 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();
> +}
--
BR,
Muhammad Usama Anjum
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@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.
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.
>
>> +
>> + /* 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();
>> +}
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@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.
>
>
> 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();
>>> +}
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
© 2016 - 2026 Red Hat, Inc.