On 21 Jul 2025, at 7:46, wang lian wrote:
> Add tests for process_madvise(), focusing on verifying behavior under
> various conditions including valid usage and error cases.
>
> Signed-off-by: wang lian <lianux...@gmail.com>
> Suggested-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
> Suggested-by: David Hildenbrand <da...@redhat.com>
> Suggested-by: Zi Yan <z...@nvidia.com>
> Suggested-by: Mark Brown <broo...@kernel.org>
> Acked-by: SeongJae Park <s...@kernel.org>
>
> ---
> Changelog v6:
> - Refactor child process and pidfd management to use the kselftest
> fixture's setup and teardown mechanism. This ensures that child
> processes are reliably terminated and file descriptors are closed, even
> when a test is aborted by an ASSERT or SKIP macro. This resolves the
> issue where a failed assertion could lead to a leaked child process.
>
> Changelog v5:
> https://lore.kernel.org/lkml/20250714122533.3135-1-lianux...@gmail.com/
> - Refactor the remote_collapse test to concentrate on its primary goal
> confirming the successful remote invocation of process_madvise() on a child
> process.
> - Split the validation logic for invalid pidfds out of the remote test and
> into two new
> (`exited_process_pidfd` and `bad_pidfd`).
> - Based mm-new branch, can ensure clean application
>
>
> Changelog v4:
> https://lore.kernel.org/lkml/20250710112249.58722-1-lianux...@gmail.com/
> - Refine resource cleanup logic in test teardown to be more robust.
> - Improve remote_collapse test to correctly handle different THP
> (Transparent Huge Page) policies ('always', 'madvise', 'never'),
> including handling race conditions with khugepaged.
> - Resolve build errors
>
> Changelog v3:
> https://lore.kernel.org/lkml/20250703044326.65061-1-lianux...@gmail.com/
> - Rebased onto the latest mm-stable branch to ensure clean application.
> - Refactor common signal handling logic into vm_util to reduce code
> duplication.
> - Improve test robustness and diagnostics based on community feedback.
> - Address minor code style and script corrections.
>
> Changelog v2:
> https://lore.kernel.org/lkml/20250630140957.4000-1-lianux...@gmail.com/
> - Drop MADV_DONTNEED tests based on feedback.
> - Focus solely on process_madvise() syscall.
> - Improve error handling and structure.
> - Add future-proof flag test.
> - Style and comment cleanups.
>
> -V1: https://lore.kernel.org/lkml/20250621133003.4733-1-lianux...@gmail.com/
> tools/testing/selftests/mm/.gitignore | 1 +
> tools/testing/selftests/mm/Makefile | 1 +
> tools/testing/selftests/mm/process_madv.c | 302 ++++++++++++++++++++++
> tools/testing/selftests/mm/run_vmtests.sh | 5 +
> 4 files changed, 309 insertions(+)
> create mode 100644 tools/testing/selftests/mm/process_madv.c
>
> diff --git a/tools/testing/selftests/mm/.gitignore
> b/tools/testing/selftests/mm/.gitignore
> index f2dafa0b700b..e7b23a8a05fe
> --- a/tools/testing/selftests/mm/.gitignore
> +++ b/tools/testing/selftests/mm/.gitignore
> @@ -21,6 +21,7 @@ on-fault-limit
> transhuge-stress
> pagemap_ioctl
> pfnmap
> +process_madv
> *.tmp*
> protection_keys
> protection_keys_32
> diff --git a/tools/testing/selftests/mm/Makefile
> b/tools/testing/selftests/mm/Makefile
> index ae6f994d3add..d13b3cef2a2b 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -85,6 +85,7 @@ TEST_GEN_FILES += mseal_test
> TEST_GEN_FILES += on-fault-limit
> TEST_GEN_FILES += pagemap_ioctl
> TEST_GEN_FILES += pfnmap
> +TEST_GEN_FILES += process_madv
> TEST_GEN_FILES += thuge-gen
> TEST_GEN_FILES += transhuge-stress
> TEST_GEN_FILES += uffd-stress
> diff --git a/tools/testing/selftests/mm/process_madv.c
> b/tools/testing/selftests/mm/process_madv.c
> new file mode 100644
> index 000000000000..8a83eac3bfab
> --- /dev/null
> +++ b/tools/testing/selftests/mm/process_madv.c
> @@ -0,0 +1,302 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#define _GNU_SOURCE
> +#include "../kselftest_harness.h"
> +#include <errno.h>
> +#include <setjmp.h>
> +#include <signal.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <linux/mman.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +#include <sched.h>
> +#include "vm_util.h"
> +
> +#include "../pidfd/pidfd.h"
> +
> +FIXTURE(process_madvise)
> +{
> + unsigned long page_size;
> + pid_t child_pid;
> + int remote_pidfd;
> + int pidfd;
> +};
> +
> +FIXTURE_SETUP(process_madvise)
> +{
> + self->page_size = (unsigned long)sysconf(_SC_PAGESIZE);
> + self->pidfd = PIDFD_SELF;
> + self->remote_pidfd = -1;
> + self->child_pid = -1;
> +};
> +
> +FIXTURE_TEARDOWN_PARENT(process_madvise)
> +{
> + /* This teardown is guaranteed to run, even if tests SKIP or ASSERT */
> + if (self->child_pid > 0) {
> + kill(self->child_pid, SIGKILL);
> + waitpid(self->child_pid, NULL, 0);
> + }
> +
> + if (self->remote_pidfd >= 0)
> + close(self->remote_pidfd);
> +}
> +
> +static ssize_t sys_process_madvise(int pidfd, const struct iovec *iovec,
> + size_t vlen, int advice, unsigned int flags)
> +{
> + return syscall(__NR_process_madvise, pidfd, iovec, vlen, advice, flags);
> +}
> +
> +/*
> + * This test uses PIDFD_SELF to target the current process. The main
> + * goal is to verify the basic behavior of process_madvise() with
> + * a vector of non-contiguous memory ranges, not its cross-process
> + * capabilities.
> + */
> +TEST_F(process_madvise, basic)
> +{
> + const unsigned long pagesize = self->page_size;
> + const int madvise_pages = 4;
> + struct iovec vec[madvise_pages];
> + int pidfd = self->pidfd;
> + ssize_t ret;
> + char *map;
> +
> + /*
> + * Create a single large mapping. We will pick pages from this
> + * mapping to advise on. This ensures we test non-contiguous iovecs.
> + */
> + map = mmap(NULL, pagesize * 10, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + if (map == MAP_FAILED)
> + SKIP(return, "mmap failed, not enough memory.\n");
> +
> + /* Fill the entire region with a known pattern. */
> + memset(map, 'A', pagesize * 10);
> +
> + /*
> + * Setup the iovec to point to 4 non-contiguous pages
> + * within the mapping.
> + */
> + vec[0].iov_base = &map[0 * pagesize];
> + vec[0].iov_len = pagesize;
> + vec[1].iov_base = &map[3 * pagesize];
> + vec[1].iov_len = pagesize;
> + vec[2].iov_base = &map[5 * pagesize];
> + vec[2].iov_len = pagesize;
> + vec[3].iov_base = &map[8 * pagesize];
> + vec[3].iov_len = pagesize;
> +
> + ret = sys_process_madvise(pidfd, vec, madvise_pages, MADV_DONTNEED, 0);
> + if (ret == -1 && errno == EPERM)
> + SKIP(return,
> + "process_madvise() unsupported or permission denied,
> try running as root.\n");
> + else if (errno == EINVAL)
> + SKIP(return,
> + "process_madvise() unsupported or parameter invalid,
> please check arguments.\n");
> +
> + /* The call should succeed and report the total bytes processed. */
> + ASSERT_EQ(ret, madvise_pages * pagesize);
> +
> + /* Check that advised pages are now zero. */
> + for (int i = 0; i < madvise_pages; i++) {
> + char *advised_page = (char *)vec[i].iov_base;
> +
> + /* Content must be 0, not 'A'. */
> + ASSERT_EQ(*advised_page, '\0');
> + }
> +
> + /* Check that an un-advised page in between is still 'A'. */
> + char *unadvised_page = &map[1 * pagesize];
> +
> + for (int i = 0; i < pagesize; i++)
> + ASSERT_EQ(unadvised_page[i], 'A');
> +
> + /* Cleanup. */
> + ASSERT_EQ(munmap(map, pagesize * 10), 0);
> +}
> +
> +/*
> + * This test deterministically validates process_madvise() with MADV_COLLAPSE
> + * on a remote process, other advices are difficult to verify reliably.
> + *
> + * The test verifies that a memory region in a child process,
> + * focus on process_madv remote result, only check addresses and lengths.
> + * The correctness of the MADV_COLLAPSE can be found in the relevant test
> examples in khugepaged.
> + */
> +TEST_F(process_madvise, remote_collapse)
> +{
> + const unsigned long pagesize = self->page_size;
> + long huge_page_size;
> + int pipe_info[2];
> + ssize_t ret;
> + struct iovec vec;
> +
> + struct child_info {
> + pid_t pid;
> + void *map_addr;
> + } info;
> +
> + huge_page_size = default_huge_page_size();
You should use read_pmd_pagesize() here, since default_huge_page_size()
is used for hugetlb. See Documentation/admin-guide/mm/hugetlbpage.rst.
MADV_COLLAPSE is for THP. The test passes if HugeTLB size is 2M and
fails otherwise.
> + if (huge_page_size <= 0)
> + SKIP(return, "Could not determine a valid huge page size.\n");
> +
> + ASSERT_EQ(pipe(pipe_info), 0);
> +
> + self->child_pid = fork();
> + ASSERT_NE(self->child_pid, -1);
> +
> + if (self->child_pid == 0) {
> + char *map;
> + size_t map_size = 2 * huge_page_size;
> +
> + close(pipe_info[0]);
> +
> + map = mmap(NULL, map_size, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + ASSERT_NE(map, MAP_FAILED);
> +
> + /* Fault in as small pages */
> + for (size_t i = 0; i < map_size; i += pagesize)
> + map[i] = 'A';
> +
> + /* Send info and pause */
> + info.pid = getpid();
> + info.map_addr = map;
> + ret = write(pipe_info[1], &info, sizeof(info));
> + ASSERT_EQ(ret, sizeof(info));
> + close(pipe_info[1]);
> +
> + pause();
> + exit(0);
> + }
> +
> + close(pipe_info[1]);
> +
> + /* Receive child info */
> + ret = read(pipe_info[0], &info, sizeof(info));
> + if (ret <= 0) {
> + waitpid(self->child_pid, NULL, 0);
> + SKIP(return, "Failed to read child info from pipe.\n");
> + }
> + ASSERT_EQ(ret, sizeof(info));
> + close(pipe_info[0]);
> + self->child_pid = info.pid;
> +
> + self->remote_pidfd = syscall(__NR_pidfd_open, self->child_pid, 0);
> + ASSERT_GE(self->remote_pidfd, 0);
> +
> + vec.iov_base = info.map_addr;
> + vec.iov_len = huge_page_size;
> +
> + ret = sys_process_madvise(self->remote_pidfd, &vec, 1, MADV_COLLAPSE,
> 0);
> + if (ret == -1) {
> + if (errno == EINVAL)
> + SKIP(return, "PROCESS_MADV_ADVISE is not supported.\n");
> + else if (errno == EPERM)
> + SKIP(return,
> + "No process_madvise() permissions, try
> running as root.\n");
> + return;
> + }
> +
> + ASSERT_EQ(ret, huge_page_size);
> +}
> +
> +/*
> + * Test process_madvise() with a pidfd for a process that has already
> + * exited to ensure correct error handling.
> + */
> +TEST_F(process_madvise, exited_process_pidfd)
> +{
> + struct iovec vec;
> + ssize_t ret;
> + int pidfd;
> +
> + vec.iov_base = (void *)0x1234;
> + vec.iov_len = 4096;
Here an invalid address range is provided, since pid is checked before
address ranges are checked.
BTW, the size of iovec array cannot be bigger than IOV_MAX. It might be
worth testing as well, if you want to.
With default_huge_page_size() -> read_pmd_pagesize() fix, feel free to
add:
Reviewed-by: Zi Yan <z...@nvidia.com>
Tested-by: Zi Yan <z...@nvidia.com>
I am able to compile and run the test on arm64. Thanks.
Best Regards,
Yan, Zi
