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-rw-r--r--tools/testing/selftests/mm/guard-regions.c2074
1 files changed, 2074 insertions, 0 deletions
diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
new file mode 100644
index 000000000000..b3d0e2771096
--- /dev/null
+++ b/tools/testing/selftests/mm/guard-regions.c
@@ -0,0 +1,2074 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define _GNU_SOURCE
+#include "../kselftest_harness.h"
+#include <asm-generic/mman.h> /* Force the import of the tools version. */
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/limits.h>
+#include <linux/userfaultfd.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include "vm_util.h"
+
+#include "../pidfd/pidfd.h"
+
+/*
+ * Ignore the checkpatch warning, as per the C99 standard, section 7.14.1.1:
+ *
+ * "If the signal occurs other than as the result of calling the abort or raise
+ * function, the behavior is undefined if the signal handler refers to any
+ * object with static storage duration other than by assigning a value to an
+ * object declared as volatile sig_atomic_t"
+ */
+static volatile sig_atomic_t signal_jump_set;
+static sigjmp_buf signal_jmp_buf;
+
+/*
+ * Ignore the checkpatch warning, we must read from x but don't want to do
+ * anything with it in order to trigger a read page fault. We therefore must use
+ * volatile to stop the compiler from optimising this away.
+ */
+#define FORCE_READ(x) (*(volatile typeof(x) *)x)
+
+/*
+ * How is the test backing the mapping being tested?
+ */
+enum backing_type {
+ ANON_BACKED,
+ SHMEM_BACKED,
+ LOCAL_FILE_BACKED,
+};
+
+FIXTURE(guard_regions)
+{
+ unsigned long page_size;
+ char path[PATH_MAX];
+ int fd;
+};
+
+FIXTURE_VARIANT(guard_regions)
+{
+ enum backing_type backing;
+};
+
+FIXTURE_VARIANT_ADD(guard_regions, anon)
+{
+ .backing = ANON_BACKED,
+};
+
+FIXTURE_VARIANT_ADD(guard_regions, shmem)
+{
+ .backing = SHMEM_BACKED,
+};
+
+FIXTURE_VARIANT_ADD(guard_regions, file)
+{
+ .backing = LOCAL_FILE_BACKED,
+};
+
+static bool is_anon_backed(const FIXTURE_VARIANT(guard_regions) * variant)
+{
+ switch (variant->backing) {
+ case ANON_BACKED:
+ case SHMEM_BACKED:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static void *mmap_(FIXTURE_DATA(guard_regions) * self,
+ const FIXTURE_VARIANT(guard_regions) * variant,
+ void *addr, size_t length, int prot, int extra_flags,
+ off_t offset)
+{
+ int fd;
+ int flags = extra_flags;
+
+ switch (variant->backing) {
+ case ANON_BACKED:
+ flags |= MAP_PRIVATE | MAP_ANON;
+ fd = -1;
+ break;
+ case SHMEM_BACKED:
+ case LOCAL_FILE_BACKED:
+ flags |= MAP_SHARED;
+ fd = self->fd;
+ break;
+ default:
+ ksft_exit_fail();
+ break;
+ }
+
+ return mmap(addr, length, prot, flags, fd, offset);
+}
+
+static int userfaultfd(int flags)
+{
+ return syscall(SYS_userfaultfd, flags);
+}
+
+static void handle_fatal(int c)
+{
+ if (!signal_jump_set)
+ return;
+
+ siglongjmp(signal_jmp_buf, c);
+}
+
+static ssize_t sys_process_madvise(int pidfd, const struct iovec *iovec,
+ size_t n, int advice, unsigned int flags)
+{
+ return syscall(__NR_process_madvise, pidfd, iovec, n, advice, flags);
+}
+
+/*
+ * Enable our signal catcher and try to read/write the specified buffer. The
+ * return value indicates whether the read/write succeeds without a fatal
+ * signal.
+ */
+static bool try_access_buf(char *ptr, bool write)
+{
+ bool failed;
+
+ /* Tell signal handler to jump back here on fatal signal. */
+ signal_jump_set = true;
+ /* If a fatal signal arose, we will jump back here and failed is set. */
+ failed = sigsetjmp(signal_jmp_buf, 0) != 0;
+
+ if (!failed) {
+ if (write)
+ *ptr = 'x';
+ else
+ FORCE_READ(ptr);
+ }
+
+ signal_jump_set = false;
+ return !failed;
+}
+
+/* Try and read from a buffer, return true if no fatal signal. */
+static bool try_read_buf(char *ptr)
+{
+ return try_access_buf(ptr, false);
+}
+
+/* Try and write to a buffer, return true if no fatal signal. */
+static bool try_write_buf(char *ptr)
+{
+ return try_access_buf(ptr, true);
+}
+
+/*
+ * Try and BOTH read from AND write to a buffer, return true if BOTH operations
+ * succeed.
+ */
+static bool try_read_write_buf(char *ptr)
+{
+ return try_read_buf(ptr) && try_write_buf(ptr);
+}
+
+static void setup_sighandler(void)
+{
+ struct sigaction act = {
+ .sa_handler = &handle_fatal,
+ .sa_flags = SA_NODEFER,
+ };
+
+ sigemptyset(&act.sa_mask);
+ if (sigaction(SIGSEGV, &act, NULL))
+ ksft_exit_fail_perror("sigaction");
+}
+
+static void teardown_sighandler(void)
+{
+ struct sigaction act = {
+ .sa_handler = SIG_DFL,
+ .sa_flags = SA_NODEFER,
+ };
+
+ sigemptyset(&act.sa_mask);
+ sigaction(SIGSEGV, &act, NULL);
+}
+
+static int open_file(const char *prefix, char *path)
+{
+ int fd;
+
+ snprintf(path, PATH_MAX, "%sguard_regions_test_file_XXXXXX", prefix);
+ fd = mkstemp(path);
+ if (fd < 0)
+ ksft_exit_fail_perror("mkstemp");
+
+ return fd;
+}
+
+/* Establish a varying pattern in a buffer. */
+static void set_pattern(char *ptr, size_t num_pages, size_t page_size)
+{
+ size_t i;
+
+ for (i = 0; i < num_pages; i++) {
+ char *ptr2 = &ptr[i * page_size];
+
+ memset(ptr2, 'a' + (i % 26), page_size);
+ }
+}
+
+/*
+ * Check that a buffer contains the pattern set by set_pattern(), starting at a
+ * page offset of pgoff within the buffer.
+ */
+static bool check_pattern_offset(char *ptr, size_t num_pages, size_t page_size,
+ size_t pgoff)
+{
+ size_t i;
+
+ for (i = 0; i < num_pages * page_size; i++) {
+ size_t offset = pgoff * page_size + i;
+ char actual = ptr[offset];
+ char expected = 'a' + ((offset / page_size) % 26);
+
+ if (actual != expected)
+ return false;
+ }
+
+ return true;
+}
+
+/* Check that a buffer contains the pattern set by set_pattern(). */
+static bool check_pattern(char *ptr, size_t num_pages, size_t page_size)
+{
+ return check_pattern_offset(ptr, num_pages, page_size, 0);
+}
+
+/* Determine if a buffer contains only repetitions of a specified char. */
+static bool is_buf_eq(char *buf, size_t size, char chr)
+{
+ size_t i;
+
+ for (i = 0; i < size; i++) {
+ if (buf[i] != chr)
+ return false;
+ }
+
+ return true;
+}
+
+FIXTURE_SETUP(guard_regions)
+{
+ self->page_size = (unsigned long)sysconf(_SC_PAGESIZE);
+ setup_sighandler();
+
+ if (variant->backing == ANON_BACKED)
+ return;
+
+ self->fd = open_file(
+ variant->backing == SHMEM_BACKED ? "/tmp/" : "",
+ self->path);
+
+ /* We truncate file to at least 100 pages, tests can modify as needed. */
+ ASSERT_EQ(ftruncate(self->fd, 100 * self->page_size), 0);
+};
+
+FIXTURE_TEARDOWN_PARENT(guard_regions)
+{
+ teardown_sighandler();
+
+ if (variant->backing == ANON_BACKED)
+ return;
+
+ if (self->fd >= 0)
+ close(self->fd);
+
+ if (self->path[0] != '\0')
+ unlink(self->path);
+}
+
+TEST_F(guard_regions, basic)
+{
+ const unsigned long NUM_PAGES = 10;
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ ptr = mmap_(self, variant, NULL, NUM_PAGES * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Trivially assert we can touch the first page. */
+ ASSERT_TRUE(try_read_write_buf(ptr));
+
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Establish that 1st page SIGSEGV's. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+
+ /* Ensure we can touch everything else.*/
+ for (i = 1; i < NUM_PAGES; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Establish a guard page at the end of the mapping. */
+ ASSERT_EQ(madvise(&ptr[(NUM_PAGES - 1) * page_size], page_size,
+ MADV_GUARD_INSTALL), 0);
+
+ /* Check that both guard pages result in SIGSEGV. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[(NUM_PAGES - 1) * page_size]));
+
+ /* Remove the first guard page. */
+ ASSERT_FALSE(madvise(ptr, page_size, MADV_GUARD_REMOVE));
+
+ /* Make sure we can touch it. */
+ ASSERT_TRUE(try_read_write_buf(ptr));
+
+ /* Remove the last guard page. */
+ ASSERT_FALSE(madvise(&ptr[(NUM_PAGES - 1) * page_size], page_size,
+ MADV_GUARD_REMOVE));
+
+ /* Make sure we can touch it. */
+ ASSERT_TRUE(try_read_write_buf(&ptr[(NUM_PAGES - 1) * page_size]));
+
+ /*
+ * Test setting a _range_ of pages, namely the first 3. The first of
+ * these be faulted in, so this also tests that we can install guard
+ * pages over backed pages.
+ */
+ ASSERT_EQ(madvise(ptr, 3 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure they are all guard pages. */
+ for (i = 0; i < 3; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Make sure the rest are not. */
+ for (i = 3; i < NUM_PAGES; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Remove guard pages. */
+ ASSERT_EQ(madvise(ptr, NUM_PAGES * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Now make sure we can touch everything. */
+ for (i = 0; i < NUM_PAGES; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /*
+ * Now remove all guard pages, make sure we don't remove existing
+ * entries.
+ */
+ ASSERT_EQ(madvise(ptr, NUM_PAGES * page_size, MADV_GUARD_REMOVE), 0);
+
+ for (i = 0; i < NUM_PAGES * page_size; i += page_size) {
+ char chr = ptr[i];
+
+ ASSERT_EQ(chr, 'x');
+ }
+
+ ASSERT_EQ(munmap(ptr, NUM_PAGES * page_size), 0);
+}
+
+/* Assert that operations applied across multiple VMAs work as expected. */
+TEST_F(guard_regions, multi_vma)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr_region, *ptr, *ptr1, *ptr2, *ptr3;
+ int i;
+
+ /* Reserve a 100 page region over which we can install VMAs. */
+ ptr_region = mmap_(self, variant, NULL, 100 * page_size,
+ PROT_NONE, 0, 0);
+ ASSERT_NE(ptr_region, MAP_FAILED);
+
+ /* Place a VMA of 10 pages size at the start of the region. */
+ ptr1 = mmap_(self, variant, ptr_region, 10 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr1, MAP_FAILED);
+
+ /* Place a VMA of 5 pages size 50 pages into the region. */
+ ptr2 = mmap_(self, variant, &ptr_region[50 * page_size], 5 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr2, MAP_FAILED);
+
+ /* Place a VMA of 20 pages size at the end of the region. */
+ ptr3 = mmap_(self, variant, &ptr_region[80 * page_size], 20 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr3, MAP_FAILED);
+
+ /* Unmap gaps. */
+ ASSERT_EQ(munmap(&ptr_region[10 * page_size], 40 * page_size), 0);
+ ASSERT_EQ(munmap(&ptr_region[55 * page_size], 25 * page_size), 0);
+
+ /*
+ * We end up with VMAs like this:
+ *
+ * 0 10 .. 50 55 .. 80 100
+ * [---] [---] [---]
+ */
+
+ /*
+ * Now mark the whole range as guard pages and make sure all VMAs are as
+ * such.
+ */
+
+ /*
+ * madvise() is certifiable and lets you perform operations over gaps,
+ * everything works, but it indicates an error and errno is set to
+ * -ENOMEM. Also if anything runs out of memory it is set to
+ * -ENOMEM. You are meant to guess which is which.
+ */
+ ASSERT_EQ(madvise(ptr_region, 100 * page_size, MADV_GUARD_INSTALL), -1);
+ ASSERT_EQ(errno, ENOMEM);
+
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr1[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ for (i = 0; i < 5; i++) {
+ char *curr = &ptr2[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ for (i = 0; i < 20; i++) {
+ char *curr = &ptr3[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Now remove guar pages over range and assert the opposite. */
+
+ ASSERT_EQ(madvise(ptr_region, 100 * page_size, MADV_GUARD_REMOVE), -1);
+ ASSERT_EQ(errno, ENOMEM);
+
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr1[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ for (i = 0; i < 5; i++) {
+ char *curr = &ptr2[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ for (i = 0; i < 20; i++) {
+ char *curr = &ptr3[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Now map incompatible VMAs in the gaps. */
+ ptr = mmap_(self, variant, &ptr_region[10 * page_size], 40 * page_size,
+ PROT_READ | PROT_WRITE | PROT_EXEC, MAP_FIXED, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+ ptr = mmap_(self, variant, &ptr_region[55 * page_size], 25 * page_size,
+ PROT_READ | PROT_WRITE | PROT_EXEC, MAP_FIXED, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /*
+ * We end up with VMAs like this:
+ *
+ * 0 10 .. 50 55 .. 80 100
+ * [---][xxxx][---][xxxx][---]
+ *
+ * Where 'x' signifies VMAs that cannot be merged with those adjacent to
+ * them.
+ */
+
+ /* Multiple VMAs adjacent to one another should result in no error. */
+ ASSERT_EQ(madvise(ptr_region, 100 * page_size, MADV_GUARD_INSTALL), 0);
+ for (i = 0; i < 100; i++) {
+ char *curr = &ptr_region[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+ ASSERT_EQ(madvise(ptr_region, 100 * page_size, MADV_GUARD_REMOVE), 0);
+ for (i = 0; i < 100; i++) {
+ char *curr = &ptr_region[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr_region, 100 * page_size), 0);
+}
+
+/*
+ * Assert that batched operations performed using process_madvise() work as
+ * expected.
+ */
+TEST_F(guard_regions, process_madvise)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr_region, *ptr1, *ptr2, *ptr3;
+ ssize_t count;
+ struct iovec vec[6];
+
+ /* Reserve region to map over. */
+ ptr_region = mmap_(self, variant, NULL, 100 * page_size,
+ PROT_NONE, 0, 0);
+ ASSERT_NE(ptr_region, MAP_FAILED);
+
+ /*
+ * 10 pages offset 1 page into reserve region. We MAP_POPULATE so we
+ * overwrite existing entries and test this code path against
+ * overwriting existing entries.
+ */
+ ptr1 = mmap_(self, variant, &ptr_region[page_size], 10 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED | MAP_POPULATE, 0);
+ ASSERT_NE(ptr1, MAP_FAILED);
+ /* We want guard markers at start/end of each VMA. */
+ vec[0].iov_base = ptr1;
+ vec[0].iov_len = page_size;
+ vec[1].iov_base = &ptr1[9 * page_size];
+ vec[1].iov_len = page_size;
+
+ /* 5 pages offset 50 pages into reserve region. */
+ ptr2 = mmap_(self, variant, &ptr_region[50 * page_size], 5 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr2, MAP_FAILED);
+ vec[2].iov_base = ptr2;
+ vec[2].iov_len = page_size;
+ vec[3].iov_base = &ptr2[4 * page_size];
+ vec[3].iov_len = page_size;
+
+ /* 20 pages offset 79 pages into reserve region. */
+ ptr3 = mmap_(self, variant, &ptr_region[79 * page_size], 20 * page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr3, MAP_FAILED);
+ vec[4].iov_base = ptr3;
+ vec[4].iov_len = page_size;
+ vec[5].iov_base = &ptr3[19 * page_size];
+ vec[5].iov_len = page_size;
+
+ /* Free surrounding VMAs. */
+ ASSERT_EQ(munmap(ptr_region, page_size), 0);
+ ASSERT_EQ(munmap(&ptr_region[11 * page_size], 39 * page_size), 0);
+ ASSERT_EQ(munmap(&ptr_region[55 * page_size], 24 * page_size), 0);
+ ASSERT_EQ(munmap(&ptr_region[99 * page_size], page_size), 0);
+
+ /* Now guard in one step. */
+ count = sys_process_madvise(PIDFD_SELF, vec, 6, MADV_GUARD_INSTALL, 0);
+
+ /* OK we don't have permission to do this, skip. */
+ if (count == -1 && errno == EPERM)
+ ksft_exit_skip("No process_madvise() permissions, try running as root.\n");
+
+ /* Returns the number of bytes advised. */
+ ASSERT_EQ(count, 6 * page_size);
+
+ /* Now make sure the guarding was applied. */
+
+ ASSERT_FALSE(try_read_write_buf(ptr1));
+ ASSERT_FALSE(try_read_write_buf(&ptr1[9 * page_size]));
+
+ ASSERT_FALSE(try_read_write_buf(ptr2));
+ ASSERT_FALSE(try_read_write_buf(&ptr2[4 * page_size]));
+
+ ASSERT_FALSE(try_read_write_buf(ptr3));
+ ASSERT_FALSE(try_read_write_buf(&ptr3[19 * page_size]));
+
+ /* Now do the same with unguard... */
+ count = sys_process_madvise(PIDFD_SELF, vec, 6, MADV_GUARD_REMOVE, 0);
+
+ /* ...and everything should now succeed. */
+
+ ASSERT_TRUE(try_read_write_buf(ptr1));
+ ASSERT_TRUE(try_read_write_buf(&ptr1[9 * page_size]));
+
+ ASSERT_TRUE(try_read_write_buf(ptr2));
+ ASSERT_TRUE(try_read_write_buf(&ptr2[4 * page_size]));
+
+ ASSERT_TRUE(try_read_write_buf(ptr3));
+ ASSERT_TRUE(try_read_write_buf(&ptr3[19 * page_size]));
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr1, 10 * page_size), 0);
+ ASSERT_EQ(munmap(ptr2, 5 * page_size), 0);
+ ASSERT_EQ(munmap(ptr3, 20 * page_size), 0);
+}
+
+/* Assert that unmapping ranges does not leave guard markers behind. */
+TEST_F(guard_regions, munmap)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr, *ptr_new1, *ptr_new2;
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard first and last pages. */
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ ASSERT_EQ(madvise(&ptr[9 * page_size], page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Assert that they are guarded. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[9 * page_size]));
+
+ /* Unmap them. */
+ ASSERT_EQ(munmap(ptr, page_size), 0);
+ ASSERT_EQ(munmap(&ptr[9 * page_size], page_size), 0);
+
+ /* Map over them.*/
+ ptr_new1 = mmap_(self, variant, ptr, page_size, PROT_READ | PROT_WRITE,
+ MAP_FIXED, 0);
+ ASSERT_NE(ptr_new1, MAP_FAILED);
+ ptr_new2 = mmap_(self, variant, &ptr[9 * page_size], page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr_new2, MAP_FAILED);
+
+ /* Assert that they are now not guarded. */
+ ASSERT_TRUE(try_read_write_buf(ptr_new1));
+ ASSERT_TRUE(try_read_write_buf(ptr_new2));
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Assert that mprotect() operations have no bearing on guard markers. */
+TEST_F(guard_regions, mprotect)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard the middle of the range. */
+ ASSERT_EQ(madvise(&ptr[5 * page_size], 2 * page_size,
+ MADV_GUARD_INSTALL), 0);
+
+ /* Assert that it is indeed guarded. */
+ ASSERT_FALSE(try_read_write_buf(&ptr[5 * page_size]));
+ ASSERT_FALSE(try_read_write_buf(&ptr[6 * page_size]));
+
+ /* Now make these pages read-only. */
+ ASSERT_EQ(mprotect(&ptr[5 * page_size], 2 * page_size, PROT_READ), 0);
+
+ /* Make sure the range is still guarded. */
+ ASSERT_FALSE(try_read_buf(&ptr[5 * page_size]));
+ ASSERT_FALSE(try_read_buf(&ptr[6 * page_size]));
+
+ /* Make sure we can guard again without issue.*/
+ ASSERT_EQ(madvise(&ptr[5 * page_size], 2 * page_size,
+ MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the range is, yet again, still guarded. */
+ ASSERT_FALSE(try_read_buf(&ptr[5 * page_size]));
+ ASSERT_FALSE(try_read_buf(&ptr[6 * page_size]));
+
+ /* Now unguard the whole range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Make sure the whole range is readable. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Split and merge VMAs and make sure guard pages still behave. */
+TEST_F(guard_regions, split_merge)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr, *ptr_new;
+ int i;
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard the whole range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the whole range is guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Now unmap some pages in the range so we split. */
+ ASSERT_EQ(munmap(&ptr[2 * page_size], page_size), 0);
+ ASSERT_EQ(munmap(&ptr[5 * page_size], page_size), 0);
+ ASSERT_EQ(munmap(&ptr[8 * page_size], page_size), 0);
+
+ /* Make sure the remaining ranges are guarded post-split. */
+ for (i = 0; i < 2; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+ for (i = 2; i < 5; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+ for (i = 6; i < 8; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+ for (i = 9; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Now map them again - the unmap will have cleared the guards. */
+ ptr_new = mmap_(self, variant, &ptr[2 * page_size], page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr_new, MAP_FAILED);
+ ptr_new = mmap_(self, variant, &ptr[5 * page_size], page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr_new, MAP_FAILED);
+ ptr_new = mmap_(self, variant, &ptr[8 * page_size], page_size,
+ PROT_READ | PROT_WRITE, MAP_FIXED, 0);
+ ASSERT_NE(ptr_new, MAP_FAILED);
+
+ /* Now make sure guard pages are established. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_write_buf(curr);
+ bool expect_true = i == 2 || i == 5 || i == 8;
+
+ ASSERT_TRUE(expect_true ? result : !result);
+ }
+
+ /* Now guard everything again. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the whole range is guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Now split the range into three. */
+ ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ), 0);
+ ASSERT_EQ(mprotect(&ptr[7 * page_size], 3 * page_size, PROT_READ), 0);
+
+ /* Make sure the whole range is guarded for read. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_buf(curr));
+ }
+
+ /* Now reset protection bits so we merge the whole thing. */
+ ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ | PROT_WRITE), 0);
+ ASSERT_EQ(mprotect(&ptr[7 * page_size], 3 * page_size,
+ PROT_READ | PROT_WRITE), 0);
+
+ /* Make sure the whole range is still guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Split range into 3 again... */
+ ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ), 0);
+ ASSERT_EQ(mprotect(&ptr[7 * page_size], 3 * page_size, PROT_READ), 0);
+
+ /* ...and unguard the whole range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Make sure the whole range is remedied for read. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_buf(curr));
+ }
+
+ /* Merge them again. */
+ ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ | PROT_WRITE), 0);
+ ASSERT_EQ(mprotect(&ptr[7 * page_size], 3 * page_size,
+ PROT_READ | PROT_WRITE), 0);
+
+ /* Now ensure the merged range is remedied for read/write. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Assert that MADV_DONTNEED does not remove guard markers. */
+TEST_F(guard_regions, dontneed)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Back the whole range. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ *curr = 'y';
+ }
+
+ /* Guard every other page. */
+ for (i = 0; i < 10; i += 2) {
+ char *curr = &ptr[i * page_size];
+ int res = madvise(curr, page_size, MADV_GUARD_INSTALL);
+
+ ASSERT_EQ(res, 0);
+ }
+
+ /* Indicate that we don't need any of the range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_DONTNEED), 0);
+
+ /* Check to ensure guard markers are still in place. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_buf(curr);
+
+ if (i % 2 == 0) {
+ ASSERT_FALSE(result);
+ } else {
+ ASSERT_TRUE(result);
+ switch (variant->backing) {
+ case ANON_BACKED:
+ /* If anon, then we get a zero page. */
+ ASSERT_EQ(*curr, '\0');
+ break;
+ default:
+ /* Otherwise, we get the file data. */
+ ASSERT_EQ(*curr, 'y');
+ break;
+ }
+ }
+
+ /* Now write... */
+ result = try_write_buf(&ptr[i * page_size]);
+
+ /* ...and make sure same result. */
+ ASSERT_TRUE(i % 2 != 0 ? result : !result);
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Assert that mlock()'ed pages work correctly with guard markers. */
+TEST_F(guard_regions, mlock)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Populate. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ *curr = 'y';
+ }
+
+ /* Lock. */
+ ASSERT_EQ(mlock(ptr, 10 * page_size), 0);
+
+ /* Now try to guard, should fail with EINVAL. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), -1);
+ ASSERT_EQ(errno, EINVAL);
+
+ /* OK unlock. */
+ ASSERT_EQ(munlock(ptr, 10 * page_size), 0);
+
+ /* Guard first half of range, should now succeed. */
+ ASSERT_EQ(madvise(ptr, 5 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure guard works. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_write_buf(curr);
+
+ if (i < 5) {
+ ASSERT_FALSE(result);
+ } else {
+ ASSERT_TRUE(result);
+ ASSERT_EQ(*curr, 'x');
+ }
+ }
+
+ /*
+ * Now lock the latter part of the range. We can't lock the guard pages,
+ * as this would result in the pages being populated and the guarding
+ * would cause this to error out.
+ */
+ ASSERT_EQ(mlock(&ptr[5 * page_size], 5 * page_size), 0);
+
+ /*
+ * Now remove guard pages, we permit mlock()'d ranges to have guard
+ * pages removed as it is a non-destructive operation.
+ */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Now check that no guard pages remain. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Assert that moving, extending and shrinking memory via mremap() retains
+ * guard markers where possible.
+ *
+ * - Moving a mapping alone should retain markers as they are.
+ */
+TEST_F(guard_regions, mremap_move)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr, *ptr_new;
+
+ /* Map 5 pages. */
+ ptr = mmap_(self, variant, NULL, 5 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Place guard markers at both ends of the 5 page span. */
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ ASSERT_EQ(madvise(&ptr[4 * page_size], page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the guard pages are in effect. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[4 * page_size]));
+
+ /* Map a new region we will move this range into. Doing this ensures
+ * that we have reserved a range to map into.
+ */
+ ptr_new = mmap_(self, variant, NULL, 5 * page_size, PROT_NONE, 0, 0);
+ ASSERT_NE(ptr_new, MAP_FAILED);
+
+ ASSERT_EQ(mremap(ptr, 5 * page_size, 5 * page_size,
+ MREMAP_MAYMOVE | MREMAP_FIXED, ptr_new), ptr_new);
+
+ /* Make sure the guard markers are retained. */
+ ASSERT_FALSE(try_read_write_buf(ptr_new));
+ ASSERT_FALSE(try_read_write_buf(&ptr_new[4 * page_size]));
+
+ /*
+ * Clean up - we only need reference the new pointer as we overwrote the
+ * PROT_NONE range and moved the existing one.
+ */
+ munmap(ptr_new, 5 * page_size);
+}
+
+/*
+ * Assert that moving, extending and shrinking memory via mremap() retains
+ * guard markers where possible.
+ *
+ * Expanding should retain guard pages, only now in different position. The user
+ * will have to remove guard pages manually to fix up (they'd have to do the
+ * same if it were a PROT_NONE mapping).
+ */
+TEST_F(guard_regions, mremap_expand)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr, *ptr_new;
+
+ /* Map 10 pages... */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+ /* ...But unmap the last 5 so we can ensure we can expand into them. */
+ ASSERT_EQ(munmap(&ptr[5 * page_size], 5 * page_size), 0);
+
+ /* Place guard markers at both ends of the 5 page span. */
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ ASSERT_EQ(madvise(&ptr[4 * page_size], page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the guarding is in effect. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[4 * page_size]));
+
+ /* Now expand to 10 pages. */
+ ptr = mremap(ptr, 5 * page_size, 10 * page_size, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /*
+ * Make sure the guard markers are retained in their original positions.
+ */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[4 * page_size]));
+
+ /* Reserve a region which we can move to and expand into. */
+ ptr_new = mmap_(self, variant, NULL, 20 * page_size, PROT_NONE, 0, 0);
+ ASSERT_NE(ptr_new, MAP_FAILED);
+
+ /* Now move and expand into it. */
+ ptr = mremap(ptr, 10 * page_size, 20 * page_size,
+ MREMAP_MAYMOVE | MREMAP_FIXED, ptr_new);
+ ASSERT_EQ(ptr, ptr_new);
+
+ /*
+ * Again, make sure the guard markers are retained in their original positions.
+ */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[4 * page_size]));
+
+ /*
+ * A real user would have to remove guard markers, but would reasonably
+ * expect all characteristics of the mapping to be retained, including
+ * guard markers.
+ */
+
+ /* Cleanup. */
+ munmap(ptr, 20 * page_size);
+}
+/*
+ * Assert that moving, extending and shrinking memory via mremap() retains
+ * guard markers where possible.
+ *
+ * Shrinking will result in markers that are shrunk over being removed. Again,
+ * if the user were using a PROT_NONE mapping they'd have to manually fix this
+ * up also so this is OK.
+ */
+TEST_F(guard_regions, mremap_shrink)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ /* Map 5 pages. */
+ ptr = mmap_(self, variant, NULL, 5 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Place guard markers at both ends of the 5 page span. */
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ ASSERT_EQ(madvise(&ptr[4 * page_size], page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Make sure the guarding is in effect. */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+ ASSERT_FALSE(try_read_write_buf(&ptr[4 * page_size]));
+
+ /* Now shrink to 3 pages. */
+ ptr = mremap(ptr, 5 * page_size, 3 * page_size, MREMAP_MAYMOVE);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* We expect the guard marker at the start to be retained... */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+
+ /* ...But remaining pages will not have guard markers. */
+ for (i = 1; i < 3; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /*
+ * As with expansion, a real user would have to remove guard pages and
+ * fixup. But you'd have to do similar manual things with PROT_NONE
+ * mappings too.
+ */
+
+ /*
+ * If we expand back to the original size, the end marker will, of
+ * course, no longer be present.
+ */
+ ptr = mremap(ptr, 3 * page_size, 5 * page_size, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Again, we expect the guard marker at the start to be retained... */
+ ASSERT_FALSE(try_read_write_buf(ptr));
+
+ /* ...But remaining pages will not have guard markers. */
+ for (i = 1; i < 5; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ munmap(ptr, 5 * page_size);
+}
+
+/*
+ * Assert that forking a process with VMAs that do not have VM_WIPEONFORK set
+ * retain guard pages.
+ */
+TEST_F(guard_regions, fork)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ pid_t pid;
+ int i;
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Establish guard pages in the first 5 pages. */
+ ASSERT_EQ(madvise(ptr, 5 * page_size, MADV_GUARD_INSTALL), 0);
+
+ pid = fork();
+ ASSERT_NE(pid, -1);
+ if (!pid) {
+ /* This is the child process now. */
+
+ /* Assert that the guarding is in effect. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_write_buf(curr);
+
+ ASSERT_TRUE(i >= 5 ? result : !result);
+ }
+
+ /* Now unguard the range.*/
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ exit(0);
+ }
+
+ /* Parent process. */
+
+ /* Parent simply waits on child. */
+ waitpid(pid, NULL, 0);
+
+ /* Child unguard does not impact parent page table state. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_write_buf(curr);
+
+ ASSERT_TRUE(i >= 5 ? result : !result);
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Assert expected behaviour after we fork populated ranges of anonymous memory
+ * and then guard and unguard the range.
+ */
+TEST_F(guard_regions, fork_cow)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ pid_t pid;
+ int i;
+
+ if (variant->backing != ANON_BACKED)
+ SKIP(return, "CoW only supported on anon mappings");
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Populate range. */
+ for (i = 0; i < 10 * page_size; i++) {
+ char chr = 'a' + (i % 26);
+
+ ptr[i] = chr;
+ }
+
+ pid = fork();
+ ASSERT_NE(pid, -1);
+ if (!pid) {
+ /* This is the child process now. */
+
+ /* Ensure the range is as expected. */
+ for (i = 0; i < 10 * page_size; i++) {
+ char expected = 'a' + (i % 26);
+ char actual = ptr[i];
+
+ ASSERT_EQ(actual, expected);
+ }
+
+ /* Establish guard pages across the whole range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+ /* Remove it. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /*
+ * By removing the guard pages, the page tables will be
+ * cleared. Assert that we are looking at the zero page now.
+ */
+ for (i = 0; i < 10 * page_size; i++) {
+ char actual = ptr[i];
+
+ ASSERT_EQ(actual, '\0');
+ }
+
+ exit(0);
+ }
+
+ /* Parent process. */
+
+ /* Parent simply waits on child. */
+ waitpid(pid, NULL, 0);
+
+ /* Ensure the range is unchanged in parent anon range. */
+ for (i = 0; i < 10 * page_size; i++) {
+ char expected = 'a' + (i % 26);
+ char actual = ptr[i];
+
+ ASSERT_EQ(actual, expected);
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Assert that forking a process with VMAs that do have VM_WIPEONFORK set
+ * behave as expected.
+ */
+TEST_F(guard_regions, fork_wipeonfork)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ pid_t pid;
+ int i;
+
+ if (variant->backing != ANON_BACKED)
+ SKIP(return, "Wipe on fork only supported on anon mappings");
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Mark wipe on fork. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_WIPEONFORK), 0);
+
+ /* Guard the first 5 pages. */
+ ASSERT_EQ(madvise(ptr, 5 * page_size, MADV_GUARD_INSTALL), 0);
+
+ pid = fork();
+ ASSERT_NE(pid, -1);
+ if (!pid) {
+ /* This is the child process now. */
+
+ /* Guard will have been wiped. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_write_buf(curr));
+ }
+
+ exit(0);
+ }
+
+ /* Parent process. */
+
+ waitpid(pid, NULL, 0);
+
+ /* Guard markers should be in effect.*/
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+ bool result = try_read_write_buf(curr);
+
+ ASSERT_TRUE(i >= 5 ? result : !result);
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Ensure that MADV_FREE retains guard entries as expected. */
+TEST_F(guard_regions, lazyfree)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing != ANON_BACKED)
+ SKIP(return, "MADV_FREE only supported on anon mappings");
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Ensure guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Lazyfree range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_FREE), 0);
+
+ /* This should leave the guard markers in place. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Ensure that MADV_POPULATE_READ, MADV_POPULATE_WRITE behave as expected. */
+TEST_F(guard_regions, populate)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Populate read should error out... */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_POPULATE_READ), -1);
+ ASSERT_EQ(errno, EFAULT);
+
+ /* ...as should populate write. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_POPULATE_WRITE), -1);
+ ASSERT_EQ(errno, EFAULT);
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Ensure that MADV_COLD, MADV_PAGEOUT do not remove guard markers. */
+TEST_F(guard_regions, cold_pageout)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Guard range. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* Ensured guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Now mark cold. This should have no impact on guard markers. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_COLD), 0);
+
+ /* Should remain guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* OK, now page out. This should equally, have no effect on markers. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_PAGEOUT), 0);
+
+ /* Should remain guarded. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/* Ensure that guard pages do not break userfaultd. */
+TEST_F(guard_regions, uffd)
+{
+ const unsigned long page_size = self->page_size;
+ int uffd;
+ char *ptr;
+ int i;
+ struct uffdio_api api = {
+ .api = UFFD_API,
+ .features = 0,
+ };
+ struct uffdio_register reg;
+ struct uffdio_range range;
+
+ if (!is_anon_backed(variant))
+ SKIP(return, "uffd only works on anon backing");
+
+ /* Set up uffd. */
+ uffd = userfaultfd(0);
+ if (uffd == -1 && errno == EPERM)
+ ksft_exit_skip("No userfaultfd permissions, try running as root.\n");
+ ASSERT_NE(uffd, -1);
+
+ ASSERT_EQ(ioctl(uffd, UFFDIO_API, &api), 0);
+
+ /* Map 10 pages. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Register the range with uffd. */
+ range.start = (unsigned long)ptr;
+ range.len = 10 * page_size;
+ reg.range = range;
+ reg.mode = UFFDIO_REGISTER_MODE_MISSING;
+ ASSERT_EQ(ioctl(uffd, UFFDIO_REGISTER, &reg), 0);
+
+ /* Guard the range. This should not trigger the uffd. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /* The guarding should behave as usual with no uffd intervention. */
+ for (i = 0; i < 10; i++) {
+ char *curr = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_read_write_buf(curr));
+ }
+
+ /* Cleanup. */
+ ASSERT_EQ(ioctl(uffd, UFFDIO_UNREGISTER, &range), 0);
+ close(uffd);
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Mark a region within a file-backed mapping using MADV_SEQUENTIAL so we
+ * aggressively read-ahead, then install guard regions and assert that it
+ * behaves correctly.
+ *
+ * We page out using MADV_PAGEOUT before checking guard regions so we drop page
+ * cache folios, meaning we maximise the possibility of some broken readahead.
+ */
+TEST_F(guard_regions, madvise_sequential)
+{
+ char *ptr;
+ int i;
+ const unsigned long page_size = self->page_size;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "MADV_SEQUENTIAL meaningful only for file-backed");
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Establish a pattern of data in the file. */
+ set_pattern(ptr, 10, page_size);
+ ASSERT_TRUE(check_pattern(ptr, 10, page_size));
+
+ /* Mark it as being accessed sequentially. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_SEQUENTIAL), 0);
+
+ /* Mark every other page a guard page. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr2 = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr2, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Now page it out. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_PAGEOUT), 0);
+
+ /* Now make sure pages are as expected. */
+ for (i = 0; i < 10; i++) {
+ char *chrp = &ptr[i * page_size];
+
+ if (i % 2 == 0) {
+ bool result = try_read_write_buf(chrp);
+
+ ASSERT_FALSE(result);
+ } else {
+ ASSERT_EQ(*chrp, 'a' + i);
+ }
+ }
+
+ /* Now remove guard pages. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Now make sure all data is as expected. */
+ if (!check_pattern(ptr, 10, page_size))
+ ASSERT_TRUE(false);
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Check that file-backed mappings implement guard regions with MAP_PRIVATE
+ * correctly.
+ */
+TEST_F(guard_regions, map_private)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr_shared, *ptr_private;
+ int i;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "MAP_PRIVATE test specific to file-backed");
+
+ ptr_shared = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr_shared, MAP_FAILED);
+
+ /* Manually mmap(), do not use mmap_() wrapper so we can force MAP_PRIVATE. */
+ ptr_private = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, self->fd, 0);
+ ASSERT_NE(ptr_private, MAP_FAILED);
+
+ /* Set pattern in shared mapping. */
+ set_pattern(ptr_shared, 10, page_size);
+
+ /* Install guard regions in every other page in the shared mapping. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr = &ptr_shared[i * page_size];
+
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ for (i = 0; i < 10; i++) {
+ /* Every even shared page should be guarded. */
+ ASSERT_EQ(try_read_buf(&ptr_shared[i * page_size]), i % 2 != 0);
+ /* Private mappings should always be readable. */
+ ASSERT_TRUE(try_read_buf(&ptr_private[i * page_size]));
+ }
+
+ /* Install guard regions in every other page in the private mapping. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr = &ptr_private[i * page_size];
+
+ ASSERT_EQ(madvise(ptr, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ for (i = 0; i < 10; i++) {
+ /* Every even shared page should be guarded. */
+ ASSERT_EQ(try_read_buf(&ptr_shared[i * page_size]), i % 2 != 0);
+ /* Every odd private page should be guarded. */
+ ASSERT_EQ(try_read_buf(&ptr_private[i * page_size]), i % 2 != 0);
+ }
+
+ /* Remove guard regions from shared mapping. */
+ ASSERT_EQ(madvise(ptr_shared, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ for (i = 0; i < 10; i++) {
+ /* Shared mappings should always be readable. */
+ ASSERT_TRUE(try_read_buf(&ptr_shared[i * page_size]));
+ /* Every even private page should be guarded. */
+ ASSERT_EQ(try_read_buf(&ptr_private[i * page_size]), i % 2 != 0);
+ }
+
+ /* Remove guard regions from private mapping. */
+ ASSERT_EQ(madvise(ptr_private, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ for (i = 0; i < 10; i++) {
+ /* Shared mappings should always be readable. */
+ ASSERT_TRUE(try_read_buf(&ptr_shared[i * page_size]));
+ /* Private mappings should always be readable. */
+ ASSERT_TRUE(try_read_buf(&ptr_private[i * page_size]));
+ }
+
+ /* Ensure patterns are intact. */
+ ASSERT_TRUE(check_pattern(ptr_shared, 10, page_size));
+ ASSERT_TRUE(check_pattern(ptr_private, 10, page_size));
+
+ /* Now write out every other page to MAP_PRIVATE. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr = &ptr_private[i * page_size];
+
+ memset(ptr, 'a' + i, page_size);
+ }
+
+ /*
+ * At this point the mapping is:
+ *
+ * 0123456789
+ * SPSPSPSPSP
+ *
+ * Where S = shared, P = private mappings.
+ */
+
+ /* Now mark the beginning of the mapping guarded. */
+ ASSERT_EQ(madvise(ptr_private, 5 * page_size, MADV_GUARD_INSTALL), 0);
+
+ /*
+ * This renders the mapping:
+ *
+ * 0123456789
+ * xxxxxPSPSP
+ */
+
+ for (i = 0; i < 10; i++) {
+ char *ptr = &ptr_private[i * page_size];
+
+ /* Ensure guard regions as expected. */
+ ASSERT_EQ(try_read_buf(ptr), i >= 5);
+ /* The shared mapping should always succeed. */
+ ASSERT_TRUE(try_read_buf(&ptr_shared[i * page_size]));
+ }
+
+ /* Remove the guard regions altogether. */
+ ASSERT_EQ(madvise(ptr_private, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /*
+ *
+ * We now expect the mapping to be:
+ *
+ * 0123456789
+ * SSSSSPSPSP
+ *
+ * As we removed guard regions, the private pages from the first 5 will
+ * have been zapped, so on fault will reestablish the shared mapping.
+ */
+
+ for (i = 0; i < 10; i++) {
+ char *ptr = &ptr_private[i * page_size];
+
+ /*
+ * Assert that shared mappings in the MAP_PRIVATE mapping match
+ * the shared mapping.
+ */
+ if (i < 5 || i % 2 == 0) {
+ char *ptr_s = &ptr_shared[i * page_size];
+
+ ASSERT_EQ(memcmp(ptr, ptr_s, page_size), 0);
+ continue;
+ }
+
+ /* Everything else is a private mapping. */
+ ASSERT_TRUE(is_buf_eq(ptr, page_size, 'a' + i));
+ }
+
+ ASSERT_EQ(munmap(ptr_shared, 10 * page_size), 0);
+ ASSERT_EQ(munmap(ptr_private, 10 * page_size), 0);
+}
+
+/* Test that guard regions established over a read-only mapping function correctly. */
+TEST_F(guard_regions, readonly_file)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "Read-only test specific to file-backed");
+
+ /* Map shared so we can populate with pattern, populate it, unmap. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+ set_pattern(ptr, 10, page_size);
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+ /* Close the fd so we can re-open read-only. */
+ ASSERT_EQ(close(self->fd), 0);
+
+ /* Re-open read-only. */
+ self->fd = open(self->path, O_RDONLY);
+ ASSERT_NE(self->fd, -1);
+ /* Re-map read-only. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Mark every other page guarded. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_pg = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_pg, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Assert that the guard regions are in place.*/
+ for (i = 0; i < 10; i++) {
+ char *ptr_pg = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_pg), i % 2 != 0);
+ }
+
+ /* Remove guard regions. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Ensure the data is as expected. */
+ ASSERT_TRUE(check_pattern(ptr, 10, page_size));
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+TEST_F(guard_regions, fault_around)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "Fault-around test specific to file-backed");
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Establish a pattern in the backing file. */
+ set_pattern(ptr, 10, page_size);
+
+ /*
+ * Now drop it from the page cache so we get major faults when next we
+ * map it.
+ */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_PAGEOUT), 0);
+
+ /* Unmap and remap 'to be sure'. */
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Now make every even page guarded. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Now fault in every odd page. This should trigger fault-around. */
+ for (i = 1; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_buf(ptr_p));
+ }
+
+ /* Finally, ensure that guard regions are intact as expected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_p), i % 2 != 0);
+ }
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+TEST_F(guard_regions, truncation)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "Truncation test specific to file-backed");
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /*
+ * Establish a pattern in the backing file, just so there is data
+ * there.
+ */
+ set_pattern(ptr, 10, page_size);
+
+ /* Now make every even page guarded. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Now assert things are as expected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_write_buf(ptr_p), i % 2 != 0);
+ }
+
+ /* Now truncate to actually used size (initialised to 100). */
+ ASSERT_EQ(ftruncate(self->fd, 10 * page_size), 0);
+
+ /* Here the guard regions will remain intact. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_write_buf(ptr_p), i % 2 != 0);
+ }
+
+ /* Now truncate to half the size, then truncate again to the full size. */
+ ASSERT_EQ(ftruncate(self->fd, 5 * page_size), 0);
+ ASSERT_EQ(ftruncate(self->fd, 10 * page_size), 0);
+
+ /* Again, guard pages will remain intact. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_write_buf(ptr_p), i % 2 != 0);
+ }
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+TEST_F(guard_regions, hole_punch)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing == ANON_BACKED)
+ SKIP(return, "Truncation test specific to file-backed");
+
+ /* Establish pattern in mapping. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+ set_pattern(ptr, 10, page_size);
+
+ /* Install a guard region in the middle of the mapping. */
+ ASSERT_EQ(madvise(&ptr[3 * page_size], 4 * page_size,
+ MADV_GUARD_INSTALL), 0);
+
+ /*
+ * The buffer will now be:
+ *
+ * 0123456789
+ * ***xxxx***
+ *
+ * Where * is data and x is the guard region.
+ */
+
+ /* Ensure established. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_p), i < 3 || i >= 7);
+ }
+
+ /* Now hole punch the guarded region. */
+ ASSERT_EQ(madvise(&ptr[3 * page_size], 4 * page_size,
+ MADV_REMOVE), 0);
+
+ /* Ensure guard regions remain. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_p), i < 3 || i >= 7);
+ }
+
+ /* Now remove guard region throughout. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Check that the pattern exists in non-hole punched region. */
+ ASSERT_TRUE(check_pattern(ptr, 3, page_size));
+ /* Check that hole punched region is zeroed. */
+ ASSERT_TRUE(is_buf_eq(&ptr[3 * page_size], 4 * page_size, '\0'));
+ /* Check that the pattern exists in the remainder of the file. */
+ ASSERT_TRUE(check_pattern_offset(ptr, 3, page_size, 7));
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Ensure that a memfd works correctly with guard regions, that we can write
+ * seal it then open the mapping read-only and still establish guard regions
+ * within, remove those guard regions and have everything work correctly.
+ */
+TEST_F(guard_regions, memfd_write_seal)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (variant->backing != SHMEM_BACKED)
+ SKIP(return, "memfd write seal test specific to shmem");
+
+ /* OK, we need a memfd, so close existing one. */
+ ASSERT_EQ(close(self->fd), 0);
+
+ /* Create and truncate memfd. */
+ self->fd = memfd_create("guard_regions_memfd_seals_test",
+ MFD_ALLOW_SEALING);
+ ASSERT_NE(self->fd, -1);
+ ASSERT_EQ(ftruncate(self->fd, 10 * page_size), 0);
+
+ /* Map, set pattern, unmap. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+ set_pattern(ptr, 10, page_size);
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+
+ /* Write-seal the memfd. */
+ ASSERT_EQ(fcntl(self->fd, F_ADD_SEALS, F_SEAL_WRITE), 0);
+
+ /* Now map the memfd readonly. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Ensure pattern is as expected. */
+ ASSERT_TRUE(check_pattern(ptr, 10, page_size));
+
+ /* Now make every even page guarded. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Now assert things are as expected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_p), i % 2 != 0);
+ }
+
+ /* Now remove guard regions. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Ensure pattern is as expected. */
+ ASSERT_TRUE(check_pattern(ptr, 10, page_size));
+
+ /* Ensure write seal intact. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_FALSE(try_write_buf(ptr_p));
+ }
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+
+/*
+ * Since we are now permitted to establish guard regions in read-only anonymous
+ * mappings, for the sake of thoroughness, though it probably has no practical
+ * use, test that guard regions function with a mapping to the anonymous zero
+ * page.
+ */
+TEST_F(guard_regions, anon_zeropage)
+{
+ const unsigned long page_size = self->page_size;
+ char *ptr;
+ int i;
+
+ if (!is_anon_backed(variant))
+ SKIP(return, "anon zero page test specific to anon/shmem");
+
+ /* Obtain a read-only i.e. anon zero page mapping. */
+ ptr = mmap_(self, variant, NULL, 10 * page_size, PROT_READ, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Now make every even page guarded. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Now assert things are as expected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(try_read_buf(ptr_p), i % 2 != 0);
+ }
+
+ /* Now remove all guard regions. */
+ ASSERT_EQ(madvise(ptr, 10 * page_size, MADV_GUARD_REMOVE), 0);
+
+ /* Now assert things are as expected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_TRUE(try_read_buf(ptr_p));
+ }
+
+ /* Ensure zero page...*/
+ ASSERT_TRUE(is_buf_eq(ptr, 10 * page_size, '\0'));
+
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+/*
+ * Assert that /proc/$pid/pagemap correctly identifies guard region ranges.
+ */
+TEST_F(guard_regions, pagemap)
+{
+ const unsigned long page_size = self->page_size;
+ int proc_fd;
+ char *ptr;
+ int i;
+
+ proc_fd = open("/proc/self/pagemap", O_RDONLY);
+ ASSERT_NE(proc_fd, -1);
+
+ ptr = mmap_(self, variant, NULL, 10 * page_size,
+ PROT_READ | PROT_WRITE, 0, 0);
+ ASSERT_NE(ptr, MAP_FAILED);
+
+ /* Read from pagemap, and assert no guard regions are detected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+ unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
+ unsigned long masked = entry & PM_GUARD_REGION;
+
+ ASSERT_EQ(masked, 0);
+ }
+
+ /* Install a guard region in every other page. */
+ for (i = 0; i < 10; i += 2) {
+ char *ptr_p = &ptr[i * page_size];
+
+ ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+ }
+
+ /* Re-read from pagemap, and assert guard regions are detected. */
+ for (i = 0; i < 10; i++) {
+ char *ptr_p = &ptr[i * page_size];
+ unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
+ unsigned long masked = entry & PM_GUARD_REGION;
+
+ ASSERT_EQ(masked, i % 2 == 0 ? PM_GUARD_REGION : 0);
+ }
+
+ ASSERT_EQ(close(proc_fd), 0);
+ ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
+TEST_HARNESS_MAIN
generated by cgit (git 2.34.1) at 2025-04-04 11:48:00 +0000