Commit c0ae966f authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

tools/testing/selftests/mm: add smaps visibility guard region test 

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.

Link: https://lkml.kernel.org/r/059e62b8c67e55e6d849878206a95ea1d7c1e885.1763460113.git.lorenzo.stoakes@oracle.com


Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 89330ec8

tools/testing/selftests/mm/guard-regions.c

+120 −0
Original line number Diff line number Diff line
@@ -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

tools/testing/selftests/mm/vm_util.c

+5 −0
Original line number Diff line number Diff line
@@ -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;

tools/testing/selftests/mm/vm_util.h

+1 −0
Original line number Diff line number Diff line
@@ -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);