Re: [PATCH 3/6] selftests/liveupdate: add test for memfd content preservation

[Mike Rapoport <rppt@kernel.org>]

On Mon, Mar 09, 2026 at 11:54:36AM +0000, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> Add a selftest that makes sure the contents of a memfd are correctly
> preserved across a live update. In stage 1, create a memfd and fill it
> with random data, and preserve it. Save the random data to the file
> system. This will be used by stage 2 to verify the contents are correct.

There's a small caveat here, as some CI systems put selftests in tmpfs, so
creating a file there won't really help.
I think there should be a skip if the test runs of tmpfs. 
 
> In stage 2, retrieve the memfd and compare its contents with the
> contents saved on the file system.
> 
> Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
> ---
>  tools/testing/selftests/liveupdate/Makefile   |  1 +
>  .../testing/selftests/liveupdate/luo_memfd.c  | 61 +++++++++++++++++++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
> index 051daae55eec..8e2eb6500c07 100644
> --- a/tools/testing/selftests/liveupdate/Makefile
> +++ b/tools/testing/selftests/liveupdate/Makefile
> @@ -13,6 +13,7 @@ TEST_FILES += do_kexec.sh
>  include ../lib.mk
>  
>  CFLAGS += $(KHDR_INCLUDES)
> +CFLAGS += -I$(top_srcdir)/tools/include
>  CFLAGS += -Wall -O2 -Wno-unused-function
>  CFLAGS += -MD
>  
> diff --git a/tools/testing/selftests/liveupdate/luo_memfd.c b/tools/testing/selftests/liveupdate/luo_memfd.c
> index b779eee18387..52b5f6b16e19 100644
> --- a/tools/testing/selftests/liveupdate/luo_memfd.c
> +++ b/tools/testing/selftests/liveupdate/luo_memfd.c
> @@ -3,6 +3,9 @@
>  /*
>   * Copyright (c) 2026, Google LLC.
>   * Pratyush Yadav (Google) <pratyush@kernel.org>
> + *
> + * Copyright (C) 2025 Amazon.com Inc. or its affiliates.
> + * Pratyush Yadav <ptyadav@amazon.de>
>   */
>  
>  /*
> @@ -11,11 +14,14 @@
>  
>  #include <errno.h>
>  #include <fcntl.h>
> +#include <stdlib.h>
>  #include <string.h>
>  #include <sys/ioctl.h>
> +#include <sys/mman.h>
>  #include <unistd.h>
>  
>  #include <linux/liveupdate.h>
> +#include <linux/sizes.h>
>  
>  #include "../kselftest.h"
>  #include "../kselftest_harness.h"
> @@ -25,9 +31,64 @@
>  #define STATE_SESSION_NAME "luo-state"
>  #define STATE_MEMFD_TOKEN 1
>  
> +#define MEMFD_DATA_SESSION_NAME "memfd_data_session"
> +#define MEMFD_DATA_TOKEN 1
> +#define MEMFD_DATA_BUFFER_SIZE SZ_1M
> +#define RANDOM_DATA_FILE "luo_random_data.bin"

Reads to me like a random file containing data :)
Something like FILESYSTEM_DATA_COPY would better express the meaning.

> +
>  #define LIVEUPDATE_DEV "/dev/liveupdate"
>  static int luo_fd = -1, stage;
>  
> +/*
> + * Test that a memfd with its data is preserved across live update.
> + */
> +TEST(memfd_data)
> +{
> +	int fd, session;
> +	char *buffer;
> +	struct liveupdate_session_preserve_fd preserve_arg = { .size = sizeof(preserve_arg) };
> +	struct liveupdate_session_retrieve_fd retrieve_arg = { .size = sizeof(retrieve_arg) };
> +
> +	buffer = malloc(MEMFD_DATA_BUFFER_SIZE);
> +	ASSERT_NE(buffer, NULL);
> +
> +	switch (stage) {
> +	case 1:

Can we please move each state to a helper function?

> +		session = luo_create_session(luo_fd, MEMFD_DATA_SESSION_NAME);
> +		ASSERT_GE(session, 0);
> +
> +		fd = create_random_memfd("memfd_data", buffer, MEMFD_DATA_BUFFER_SIZE);
> +		ASSERT_GE(fd, 0);
> +
> +		ASSERT_EQ(save_test_data(RANDOM_DATA_FILE, buffer, MEMFD_DATA_BUFFER_SIZE), 0);
> +
> +		preserve_arg.fd = fd;
> +		preserve_arg.token = MEMFD_DATA_TOKEN;
> +		ASSERT_GE(ioctl(session, LIVEUPDATE_SESSION_PRESERVE_FD, &preserve_arg), 0);
> +
> +		daemonize_and_wait();
> +		break;
> +	case 2:
> +		session = luo_retrieve_session(luo_fd, MEMFD_DATA_SESSION_NAME);
> +		ASSERT_GE(session, 0);
> +
> +		ASSERT_EQ(load_test_data(RANDOM_DATA_FILE, buffer, MEMFD_DATA_BUFFER_SIZE), 0);
> +
> +		retrieve_arg.token = MEMFD_DATA_TOKEN;
> +		ASSERT_GE(ioctl(session, LIVEUPDATE_SESSION_RETRIEVE_FD, &retrieve_arg), 0);
> +		fd = retrieve_arg.fd;
> +		ASSERT_GE(fd, 0);
> +
> +		ASSERT_EQ(verify_fd_content(fd, buffer, MEMFD_DATA_BUFFER_SIZE), 0);
> +
> +		ASSERT_EQ(luo_session_finish(session), 0);
> +		break;


> +	default:
> +		TH_LOG("Unknown stage %d\n", stage);
> +		ASSERT_FALSE(true);
> +	}
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	int session, expected_stage = 0;
> -- 
> 2.53.0.473.g4a7958ca14-goog
> 

-- 
Sincerely yours,
Mike.