linux-kernel - Re: [PATCH v2] selftests/mm: Add process

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Message-ID: <1d67a048-00c0-4d2b-96ec-5e8d6d672dbd@redhat.com>
Date: Tue, 1 Jul 2025 15:18:32 +0200
From: David Hildenbrand <david@...hat.com>
To: wang lian <lianux.mm@...il.com>, linux-mm@...ck.org,
 akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com
Cc: Liam.Howlett@...cle.com, brauner@...nel.org, gkwang@...x-info.com,
 jannh@...gle.com, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, p1ucky0923@...il.com, ryncsn@...il.com,
 shuah@...nel.org, sj@...nel.org, vbabka@...e.cz, zijing.zhang@...ton.me
Subject: Re: [PATCH v2] selftests/mm: Add process_madvise() tests

On 30.06.25 16:09, wang lian wrote:
> This patch adds tests for the process_madvise(), focusing on
> verifying behavior under various conditions including valid
> usage and error cases.
> 
> Signed-off-by: wang lian<lianux.mm@...il.com>
> Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Suggested-by: David Hildenbrand <david@...hat.com>
> ---
> 
> Changelog v2:
> - 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
> 
>   tools/testing/selftests/mm/.gitignore     |   1 +
>   tools/testing/selftests/mm/Makefile       |   1 +
>   tools/testing/selftests/mm/process_madv.c | 414 ++++++++++++++++++++++
>   tools/testing/selftests/mm/run_vmtests.sh |   5 +
>   4 files changed, 421 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 911f39d634be..a8c3be02188c 100644
> --- a/tools/testing/selftests/mm/.gitignore
> +++ b/tools/testing/selftests/mm/.gitignore
> @@ -42,6 +42,7 @@ memfd_secret
>   hugetlb_dio
>   pkey_sighandler_tests_32
>   pkey_sighandler_tests_64
> +process_madv
>   soft-dirty
>   split_huge_page_test
>   ksm_tests
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index 2352252f3914..725612e09582 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -86,6 +86,7 @@ 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..73999c8e3570
> --- /dev/null
> +++ b/tools/testing/selftests/mm/process_madv.c
> @@ -0,0 +1,414 @@
> +// 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 <sys/mman.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +#include <sched.h>
> +#include <sys/pidfd.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)

Instead of copying that, it should probably be moved to vm_util.h.

Essentially, also the comments for signal_jump_set are copy-pasted from 
guard-regions.c. Is there a way to avoid that?

For example, we could place stuff like signal_jump_set in vm_util.c instead.

> +
> +static void handle_fatal(int c)
> +{
> +	if (!signal_jump_set)
> +		return;
> +
> +	siglongjmp(signal_jmp_buf, c);
> +}

Also copy-pasted.

> +
> +FIXTURE(process_madvise)
> +{
> +	int pidfd;
> +	int flag;
> +};
> +
> +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);
> +}

These two as well.

Let's avoid that much copy-pasting.

-- 
Cheers,

David / dhildenb