On Mon, Oct 21, 2024 at 03:31:59PM -0600, Shuah Khan wrote: > On 10/20/24 10:20, 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 > > established (poisoned), cleared (remedied) and that touching poisoned pages > > result in SIGSEGV. We also assert that, in remedying a range, non-poison > > pages remain intact. > > > > We then examine different operations on regions containing poison markers > > behave to ensure correct behaviour: > > > > * Operations over multiple VMAs operate as expected. > > * Invoking MADV_GUARD_POISION / MADV_GUARD_REMEDY via process_madvise() in > > batches works correctly. > > * Ensuring that munmap() correctly tears down poison markers. > > * Using mprotect() to adjust protection bits does not in any way override > > or cause issues with poison markers. > > * Ensuring that splitting and merging VMAs around poison 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) does not remove poison markers. > > * Ensuring that mlock()'ing a range containing poison markers does not > > cause issues. > > * Ensuring that mremap() can move a poisoned range and retain poison > > markers. > > * Ensuring that mremap() can expand a poisoned range and retain poison > > markers (perhaps moving the range). > > * Ensuring that mremap() can shrink a poisoned range and retain poison > > markers. > > * Ensuring that forking a process correctly retains poison markers. > > * Ensuring that forking a VMA with VM_WIPEONFORK set behaves sanely. > > * Ensuring that lazyfree simply clears poison 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 > > poison markers. > > * Ensuring that madvise(..., MADV_COLD) and madvise(..., MADV_PAGEOUT) do > > not remove poison markers. > > > > If any test is unable to be run due to lack of permissions, that test is > > skipped. > > > > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> > > --- > > tools/testing/selftests/mm/.gitignore | 1 + > > tools/testing/selftests/mm/Makefile | 1 + > > tools/testing/selftests/mm/guard-pages.c | 1228 ++++++++++++++++++++++ > > 3 files changed, 1230 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..f67d2700d44a > > --- /dev/null > > +++ b/tools/testing/selftests/mm/guard-pages.c > > @@ -0,0 +1,1228 @@ > > +// 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) > > + > > Thank you. > > Reviewed-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> Thanks! :) > > thanks, > -- Shuah >
