On 03/10/2023 07:41, Chaitanya S Prakash wrote:
Attempting to remap a range larger than what is owned by the capability triggers a -EINVAL error. Additionally, mappings that have to be moved in order to satisfy the new constraints, expect the MREMAP_MAYMOVE flag to be specified. Failure to do so triggers the -ERESERVATION error. Tests to verify this behaviour have been added.
Signed-off-by: Chaitanya S Prakash chaitanyas.prakash@arm.com
tools/testing/selftests/arm64/morello/mmap.c | 39 ++++++++++++++++++++ 1 file changed, 39 insertions(+)
diff --git a/tools/testing/selftests/arm64/morello/mmap.c b/tools/testing/selftests/arm64/morello/mmap.c index a2bf0c09dac1..645d6b977bdf 100644 --- a/tools/testing/selftests/arm64/morello/mmap.c +++ b/tools/testing/selftests/arm64/morello/mmap.c @@ -427,6 +427,44 @@ TEST(test_mmap_bounds_check) ASSERT_EQ(retval, 0); } +/* test to verify mremap() behaviour when capability bounds are modified */ +TEST(test_mremap_bounds_check) +{
- void *ptr, *new_ptr;
- int retval;
- int prot = PROT_READ | PROT_WRITE;
- int flags = MAP_PRIVATE | MAP_ANONYMOUS;
- /* moving a mapping with MREMAP_MAYMOVE flag specified */
- ptr = mmap(NULL, MMAP_SIZE_REDUCED, prot, flags, -1, 0);
- ASSERT_FALSE(IS_ERR_VALUE(ptr));
- new_ptr = mremap(ptr, MMAP_SIZE_REDUCED, MMAP_SIZE, MREMAP_MAYMOVE, 0);
Nit: using NULL instead of 0 is more readable for pointers.
- ASSERT_FALSE(IS_ERR_VALUE(new_ptr));
What we should also check here is that new_ptr != ptr (i.e. the mapping was moved). Aside from that the behaviour is the same regardless of the ABI.
- EXPECT_EQ(0, probe_mem_range(new_ptr, MMAP_SIZE,
PROBE_MODE_TOUCH | PROBE_MODE_VERIFY));- retval = munmap(new_ptr, MMAP_SIZE);
- ASSERT_EQ(retval, 0);
- /* moving a mapping without MREMAP_MAYMOVE flag triggers a reservation error */
- ptr = mmap(NULL, MMAP_SIZE_REDUCED, prot, flags, -1, 0);
- ASSERT_FALSE(IS_ERR_VALUE(ptr));
- new_ptr = mremap(ptr, MMAP_SIZE_REDUCED, MMAP_SIZE, 0, 0);
- VERIFY_ERRNO((unsigned long)new_ptr, (unsigned long)-ERESERVATION);
While mremap() indeed fails because of the insufficient size of the reservation, the expected error is not -ERESERVATION. Indeed, as per the spec:
The semantics of MREMAP_MAYMOVE is modified so that it is considered
that a mapping must be moved if the range (old_address.address, new_size) does not fit in the reservation to which the old mapping belongs, in addition to existing conditions (i.e. not clashing with existing mappings).
In other words, in this case, the mapping is required to be moved, but since MREMAP_MAYMOVE is not passed, the call fails. Regardless of why exactly the mapping should be moved, the expected error is -ENOMEM (as per mremap(2)).
Kevin
- retval = munmap(ptr, MMAP_SIZE_REDUCED);
- ASSERT_EQ(retval, 0);
- /* attempt to resize a mapping range greater than what the capability owns */
- ptr = mmap(NULL, MMAP_SIZE_REDUCED, prot, flags, -1, 0);
- ASSERT_FALSE(IS_ERR_VALUE(ptr));
- new_ptr = mremap(ptr, MMAP_SIZE, MMAP_SIZE, MREMAP_MAYMOVE, 0);
- VERIFY_ERRNO((unsigned long)new_ptr, (unsigned long)-EINVAL);
- retval = munmap(ptr, MMAP_SIZE_REDUCED);
- ASSERT_EQ(retval, 0);
+}
int main(int argc, char **argv, char **envp, struct morello_auxv *auxv) { reg_data.argc = argc; @@ -442,5 +480,6 @@ int main(int argc, char **argv, char **envp, struct morello_auxv *auxv) test_validity_tag_check(); test_range_check(); test_mmap_bounds_check();
- test_mremap_bounds_check(); return 0;
}