On Wed Oct 23, 2024 at 7:24 PM EEST, Lorenzo Stoakes wrote: > Utilise the kselftest harmness to implement tests for the guard page > implementation. > > We start by implement basic tests asserting that guard pages can be > installed, removed and that touching guard pages result in SIGSEGV. We also > assert that, in removing guard pages from a range, non-guard pages remain > intact. > > We then examine different operations on regions containing guard markers > behave to ensure correct behaviour: > > * Operations over multiple VMAs operate as expected. > * Invoking MADV_GUARD_INSTALL / MADV_GUARD_REMOVE via process_madvise() in > batches works correctly. > * Ensuring that munmap() correctly tears down guard markers. > * Using mprotect() to adjust protection bits does not in any way override > or cause issues with guard markers. > * Ensuring that splitting and merging VMAs around guard markers causes no > issue - i.e. that a marker which 'belongs' to one VMA can function just > as well 'belonging' to another. > * Ensuring that madvise(..., MADV_DONTNEED) and madvise(..., MADV_FREE) > do not remove guard markers. > * Ensuring that mlock()'ing a range containing guard markers does not > cause issues. > * Ensuring that mremap() can move a guard range and retain guard markers. > * Ensuring that mremap() can expand a guard range and retain guard > markers (perhaps moving the range). > * Ensuring that mremap() can shrink a guard range and retain guard markers. > * Ensuring that forking a process correctly retains guard markers. > * Ensuring that forking a VMA with VM_WIPEONFORK set behaves sanely. > * Ensuring that lazyfree simply clears guard markers. > * Ensuring that userfaultfd can co-exist with guard pages. > * Ensuring that madvise(..., MADV_POPULATE_READ) and > madvise(..., MADV_POPULATE_WRITE) error out when encountering > guard markers. > * Ensuring that madvise(..., MADV_COLD) and madvise(..., MADV_PAGEOUT) do > not remove guard markers. > > If any test is unable to be run due to lack of permissions, that test is > skipped. > > Reviewed-by: Shuah Khan <[email protected]> > Signed-off-by: Lorenzo Stoakes <[email protected]> > --- > tools/testing/selftests/mm/.gitignore | 1 + > tools/testing/selftests/mm/Makefile | 1 + > tools/testing/selftests/mm/guard-pages.c | 1239 ++++++++++++++++++++++ > 3 files changed, 1241 insertions(+) > create mode 100644 tools/testing/selftests/mm/guard-pages.c > > diff --git a/tools/testing/selftests/mm/.gitignore > b/tools/testing/selftests/mm/.gitignore > index 689bbd520296..8f01f4da1c0d 100644 > --- a/tools/testing/selftests/mm/.gitignore > +++ b/tools/testing/selftests/mm/.gitignore > @@ -54,3 +54,4 @@ droppable > hugetlb_dio > pkey_sighandler_tests_32 > pkey_sighandler_tests_64 > +guard-pages > diff --git a/tools/testing/selftests/mm/Makefile > b/tools/testing/selftests/mm/Makefile > index 02e1204971b0..15c734d6cfec 100644 > --- a/tools/testing/selftests/mm/Makefile > +++ b/tools/testing/selftests/mm/Makefile > @@ -79,6 +79,7 @@ TEST_GEN_FILES += hugetlb_fault_after_madv > TEST_GEN_FILES += hugetlb_madv_vs_map > TEST_GEN_FILES += hugetlb_dio > TEST_GEN_FILES += droppable > +TEST_GEN_FILES += guard-pages > > ifneq ($(ARCH),arm64) > TEST_GEN_FILES += soft-dirty > diff --git a/tools/testing/selftests/mm/guard-pages.c > b/tools/testing/selftests/mm/guard-pages.c > new file mode 100644 > index 000000000000..7db9c913e9db > --- /dev/null > +++ b/tools/testing/selftests/mm/guard-pages.c > @@ -0,0 +1,1239 @@ > +// 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/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> > + > +/* > + * 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) > + > +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 int pidfd_open(pid_t pid, unsigned int flags) > +{ > + return syscall(SYS_pidfd_open, pid, 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); > +} > + > +FIXTURE(guard_pages) > +{ > + unsigned long page_size; > +}; > + > +FIXTURE_SETUP(guard_pages) > +{ > + 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"); > + > + self->page_size = (unsigned long)sysconf(_SC_PAGESIZE); > +}; > + > +FIXTURE_TEARDOWN(guard_pages) > +{ > + struct sigaction act = { > + .sa_handler = SIG_DFL, > + .sa_flags = SA_NODEFER, > + }; > + > + sigemptyset(&act.sa_mask); > + sigaction(SIGSEGV, &act, NULL); > +} > + > +TEST_F(guard_pages, basic) > +{ > + const unsigned long NUM_PAGES = 10; > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + ptr = mmap(NULL, NUM_PAGES * page_size, PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANON, -1, 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_pages, 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(NULL, 100 * page_size, PROT_NONE, > + MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr_region, MAP_FAILED); > + > + /* Place a VMA of 10 pages size at the start of the region. */ > + ptr1 = mmap(ptr_region, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr1, MAP_FAILED); > + > + /* Place a VMA of 5 pages size 50 pages into the region. */ > + ptr2 = mmap(&ptr_region[50 * page_size], 5 * page_size, > + PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr2, MAP_FAILED); > + > + /* Place a VMA of 20 pages size at the end of the region. */ > + ptr3 = mmap(&ptr_region[80 * page_size], 20 * page_size, > + PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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(&ptr_region[10 * page_size], 40 * page_size, > + PROT_READ | PROT_WRITE | PROT_EXEC, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr, MAP_FAILED); > + ptr = mmap(&ptr_region[55 * page_size], 25 * page_size, > + PROT_READ | PROT_WRITE | PROT_EXEC, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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_pages, process_madvise) > +{ > + const unsigned long page_size = self->page_size; > + pid_t pid = getpid(); > + int pidfd = pidfd_open(pid, 0); > + char *ptr_region, *ptr1, *ptr2, *ptr3; > + ssize_t count; > + struct iovec vec[6]; > + > + ASSERT_NE(pidfd, -1); > + > + /* Reserve region to map over. */ > + ptr_region = mmap(NULL, 100 * page_size, PROT_NONE, > + MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr_region, MAP_FAILED); > + > + /* 10 pages offset 1 page into reserve region. */ > + ptr1 = mmap(&ptr_region[page_size], 10 * page_size, > + PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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(&ptr_region[50 * page_size], 5 * page_size, > + PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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(&ptr_region[79 * page_size], 20 * page_size, > + PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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 = process_madvise(pidfd, 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 = process_madvise(pidfd, 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); > + close(pidfd); > +} > + > +/* Assert that unmapping ranges does not leave guard markers behind. */ > +TEST_F(guard_pages, munmap) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr, *ptr_new1, *ptr_new2; > + > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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(ptr, page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr_new1, MAP_FAILED); > + ptr_new2 = mmap(&ptr[9 * page_size], page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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_pages, mprotect) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, split_merge) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr, *ptr_new; > + int i; > + > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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(&ptr[2 * page_size], page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr_new, MAP_FAILED); > + ptr_new = mmap(&ptr[5 * page_size], page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr_new, MAP_FAILED); > + ptr_new = mmap(&ptr[8 * page_size], page_size, PROT_READ | PROT_WRITE, > + MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 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_pages, dontneed) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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); > + /* Make sure we really did get reset to zero page. */ > + ASSERT_EQ(*curr, '\0'); > + } > + > + /* 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_pages, mlock) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, mremap_move) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr, *ptr_new; > + > + /* Map 5 pages. */ > + ptr = mmap(NULL, 5 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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(NULL, 5 * page_size, PROT_NONE, MAP_ANON | MAP_PRIVATE, > + -1, 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_pages, mremap_expand) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr, *ptr_new; > + > + /* Map 10 pages... */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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(NULL, 20 * page_size, PROT_NONE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, mremap_shrink) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + /* Map 5 pages. */ > + ptr = mmap(NULL, 5 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, fork) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + pid_t pid; > + int i; > + > + /* Map 10 pages. */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 0); > + ASSERT_NE(ptr, MAP_FAILED); > + > + /* Establish guard apges 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 that forking a process with VMAs that do have VM_WIPEONFORK set > + * behave as expected. > + */ > +TEST_F(guard_pages, fork_wipeonfork) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + pid_t pid; > + int i; > + > + /* Map 10 pages. */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, lazyfree) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + /* Map 10 pages. */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, populate) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + > + /* Map 10 pages. */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, cold_pageout) > +{ > + const unsigned long page_size = self->page_size; > + char *ptr; > + int i; > + > + /* Map 10 pages. */ > + ptr = mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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_pages, 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; > + > + /* 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(NULL, 10 * page_size, PROT_READ | PROT_WRITE, > + MAP_ANON | MAP_PRIVATE, -1, 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, ®), 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); > +} > + > +TEST_HARNESS_MAIN
Acked-by: Jarkko Sakkinen <[email protected]> Tested-by: Jarkko Sakkinen <[email protected]> BR, Jarkko
