Assert that we observe guard regions appearing in /proc/$pid/smaps as expected, and when split/merge is performed too (with expected sticky behaviour).
Also add handling for file systems which don't sanely handle mmap() VMA merging so we don't incorrectly encounter a test failure in this situation. Signed-off-by: Lorenzo Stoakes <[email protected]> --- tools/testing/selftests/mm/guard-regions.c | 120 +++++++++++++++++++++ tools/testing/selftests/mm/vm_util.c | 5 + tools/testing/selftests/mm/vm_util.h | 1 + 3 files changed, 126 insertions(+) diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c index c549bcd6160b..795bf3f39f44 100644 --- a/tools/testing/selftests/mm/guard-regions.c +++ b/tools/testing/selftests/mm/guard-regions.c @@ -94,6 +94,7 @@ static void *mmap_(FIXTURE_DATA(guard_regions) * self, case ANON_BACKED: flags |= MAP_PRIVATE | MAP_ANON; fd = -1; + offset = 0; break; case SHMEM_BACKED: case LOCAL_FILE_BACKED: @@ -260,6 +261,54 @@ static bool is_buf_eq(char *buf, size_t size, char chr) return true; } +/* + * Some file systems have issues with merging due to changing merge-sensitive + * parameters in the .mmap callback, and prior to .mmap_prepare being + * implemented everywhere this will now result in an unexpected failure to + * merge (e.g. - overlayfs). + * + * Perform a simple test to see if the local file system suffers from this, if + * it does then we can skip test logic that assumes local file system merging is + * sane. + */ +static bool local_fs_has_sane_mmap(FIXTURE_DATA(guard_regions) * self, + const FIXTURE_VARIANT(guard_regions) * variant) +{ + const unsigned long page_size = self->page_size; + char *ptr, *ptr2; + struct procmap_fd procmap; + + if (variant->backing != LOCAL_FILE_BACKED) + return true; + + /* Map 10 pages. */ + ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0); + if (ptr == MAP_FAILED) + return false; + /* Unmap the middle. */ + munmap(&ptr[5 * page_size], page_size); + + /* Map again. */ + ptr2 = mmap_(self, variant, &ptr[5 * page_size], page_size, PROT_READ | PROT_WRITE, + MAP_FIXED, 5 * page_size); + + if (ptr2 == MAP_FAILED) + return false; + + /* Now make sure they all merged. */ + if (open_self_procmap(&procmap) != 0) + return false; + if (!find_vma_procmap(&procmap, ptr)) + return false; + if (procmap.query.vma_start != (unsigned long)ptr) + return false; + if (procmap.query.vma_end != (unsigned long)ptr + 10 * page_size) + return false; + close_procmap(&procmap); + + return true; +} + FIXTURE_SETUP(guard_regions) { self->page_size = (unsigned long)sysconf(_SC_PAGESIZE); @@ -2203,4 +2252,75 @@ TEST_F(guard_regions, collapse) } } +TEST_F(guard_regions, smaps) +{ + const unsigned long page_size = self->page_size; + struct procmap_fd procmap; + char *ptr, *ptr2; + int i; + + /* Map a region. */ + ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0); + ASSERT_NE(ptr, MAP_FAILED); + + /* We shouldn't yet see a guard flag. */ + ASSERT_FALSE(check_vmflag_guard(ptr)); + + /* Install a single guard region. */ + ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0); + + /* Now we should see a guard flag. */ + ASSERT_TRUE(check_vmflag_guard(ptr)); + + /* + * Removing the guard region should not change things because we simply + * cannot accurately track whether a given VMA has had all of its guard + * regions removed. + */ + ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_REMOVE), 0); + ASSERT_TRUE(check_vmflag_guard(ptr)); + + /* Install guard regions throughout. */ + for (i = 0; i < 10; i++) { + ASSERT_EQ(madvise(&ptr[i * page_size], page_size, MADV_GUARD_INSTALL), 0); + /* We should always see the guard region flag. */ + ASSERT_TRUE(check_vmflag_guard(ptr)); + } + + /* Split into two VMAs. */ + ASSERT_EQ(munmap(&ptr[4 * page_size], page_size), 0); + + /* Both VMAs should have the guard flag set. */ + ASSERT_TRUE(check_vmflag_guard(ptr)); + ASSERT_TRUE(check_vmflag_guard(&ptr[5 * page_size])); + + /* + * If the local file system is unable to merge VMAs due to having + * unusual characteristics, there is no point in asserting merge + * behaviour. + */ + if (!local_fs_has_sane_mmap(self, variant)) { + TH_LOG("local filesystem does not support sane merging skipping merge test"); + return; + } + + /* Map a fresh VMA between the two split VMAs. */ + ptr2 = mmap_(self, variant, &ptr[4 * page_size], page_size, + PROT_READ | PROT_WRITE, MAP_FIXED, 4 * page_size); + ASSERT_NE(ptr2, MAP_FAILED); + + /* + * Check the procmap to ensure that this VMA merged with the adjacent + * two. The guard region flag is 'sticky' so should not preclude + * merging. + */ + ASSERT_EQ(open_self_procmap(&procmap), 0); + ASSERT_TRUE(find_vma_procmap(&procmap, ptr)); + ASSERT_EQ(procmap.query.vma_start, (unsigned long)ptr); + ASSERT_EQ(procmap.query.vma_end, (unsigned long)ptr + 10 * page_size); + ASSERT_EQ(close_procmap(&procmap), 0); + /* And, of course, this VMA should have the guard flag set. */ + ASSERT_TRUE(check_vmflag_guard(ptr)); +} + TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index e33cda301dad..605cb58ea5c3 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -449,6 +449,11 @@ bool check_vmflag_pfnmap(void *addr) return check_vmflag(addr, "pf"); } +bool check_vmflag_guard(void *addr) +{ + return check_vmflag(addr, "gu"); +} + bool softdirty_supported(void) { char *addr; diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index 26c30fdc0241..a8abdf414d46 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -98,6 +98,7 @@ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len, unsigned long get_free_hugepages(void); bool check_vmflag_io(void *addr); bool check_vmflag_pfnmap(void *addr); +bool check_vmflag_guard(void *addr); int open_procmap(pid_t pid, struct procmap_fd *procmap_out); int query_procmap(struct procmap_fd *procmap); bool find_vma_procmap(struct procmap_fd *procmap, void *address); -- 2.51.2
