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Message-ID: <CAJqdLroCjAwveicSftrf9BjCSZUdR3X_oG3pvkV-_cWuP4qfAA@mail.gmail.com>
Date: Tue, 4 Nov 2025 10:13:08 +0100
From: Alexander Mikhalitsyn <alexander@...alicyn.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
Amir Goldstein <amir73il@...il.com>, Aleksa Sarai <cyphar@...har.com>,
Yu Watanabe <watanabe.yu+github@...il.com>, Josef Bacik <josef@...icpanda.com>,
Jeff Layton <jlayton@...nel.org>, Jann Horn <jannh@...gle.com>,
Luca Boccassi <luca.boccassi@...il.com>, linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
Lennart Poettering <lennart@...ttering.net>, Mike Yuan <me@...dnzj.com>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>
Subject: Re: [PATCH 17/22] selftests/coredump: add debug logging to test helpers
Am Di., 28. Okt. 2025 um 09:47 Uhr schrieb Christian Brauner
<brauner@...nel.org>:
>
> so we can easily figure out why something failed.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> ---
> .../selftests/coredump/coredump_test_helpers.c | 55 +++++++++++++++++-----
> 1 file changed, 44 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c
> index 116c797090a1..65deb3cfbe1b 100644
> --- a/tools/testing/selftests/coredump/coredump_test_helpers.c
> +++ b/tools/testing/selftests/coredump/coredump_test_helpers.c
> @@ -131,17 +131,26 @@ int get_peer_pidfd(int fd)
> int ret = getsockopt(fd, SOL_SOCKET, SO_PEERPIDFD, &fd_peer_pidfd,
> &fd_peer_pidfd_len);
> if (ret < 0) {
> - fprintf(stderr, "%m - Failed to retrieve peer pidfd for coredump socket connection\n");
> + fprintf(stderr, "get_peer_pidfd: getsockopt(SO_PEERPIDFD) failed: %m\n");
> return -1;
> }
> + fprintf(stderr, "get_peer_pidfd: successfully retrieved pidfd %d\n", fd_peer_pidfd);
> return fd_peer_pidfd;
> }
>
> bool get_pidfd_info(int fd_peer_pidfd, struct pidfd_info *info)
> {
> + int ret;
> memset(info, 0, sizeof(*info));
> info->mask = PIDFD_INFO_EXIT | PIDFD_INFO_COREDUMP | PIDFD_INFO_COREDUMP_SIGNAL;
> - return ioctl(fd_peer_pidfd, PIDFD_GET_INFO, info) == 0;
> + ret = ioctl(fd_peer_pidfd, PIDFD_GET_INFO, info);
> + if (ret < 0) {
> + fprintf(stderr, "get_pidfd_info: ioctl(PIDFD_GET_INFO) failed: %m\n");
> + return false;
> + }
> + fprintf(stderr, "get_pidfd_info: mask=0x%llx, coredump_mask=0x%x, coredump_signal=%d\n",
> + (unsigned long long)info->mask, info->coredump_mask, info->coredump_signal);
> + return true;
> }
>
> /* Protocol helper functions */
> @@ -198,14 +207,23 @@ bool read_coredump_req(int fd, struct coredump_req *req)
>
> /* Peek the size of the coredump request. */
> ret = recv(fd, req, field_size, MSG_PEEK | MSG_WAITALL);
> - if (ret != field_size)
> + if (ret != field_size) {
> + fprintf(stderr, "read_coredump_req: peek failed (got %zd, expected %zu): %m\n",
> + ret, field_size);
> return false;
> + }
> kernel_size = req->size;
>
> - if (kernel_size < COREDUMP_ACK_SIZE_VER0)
> + if (kernel_size < COREDUMP_ACK_SIZE_VER0) {
> + fprintf(stderr, "read_coredump_req: kernel_size %zu < min %d\n",
> + kernel_size, COREDUMP_ACK_SIZE_VER0);
> return false;
> - if (kernel_size >= PAGE_SIZE)
> + }
> + if (kernel_size >= PAGE_SIZE) {
> + fprintf(stderr, "read_coredump_req: kernel_size %zu >= PAGE_SIZE %d\n",
> + kernel_size, PAGE_SIZE);
> return false;
> + }
>
> /* Use the minimum of user and kernel size to read the full request. */
> user_size = sizeof(struct coredump_req);
> @@ -295,25 +313,35 @@ void process_coredump_worker(int fd_coredump, int fd_peer_pidfd, int fd_core_fil
>
> /* Set socket to non-blocking mode for edge-triggered epoll */
> flags = fcntl(fd_coredump, F_GETFL, 0);
> - if (flags < 0)
> + if (flags < 0) {
> + fprintf(stderr, "Worker: fcntl(F_GETFL) failed: %m\n");
> goto out;
> - if (fcntl(fd_coredump, F_SETFL, flags | O_NONBLOCK) < 0)
> + }
> + if (fcntl(fd_coredump, F_SETFL, flags | O_NONBLOCK) < 0) {
> + fprintf(stderr, "Worker: fcntl(F_SETFL, O_NONBLOCK) failed: %m\n");
> goto out;
> + }
>
> epfd = epoll_create1(0);
> - if (epfd < 0)
> + if (epfd < 0) {
> + fprintf(stderr, "Worker: epoll_create1() failed: %m\n");
> goto out;
> + }
>
> ev.events = EPOLLIN | EPOLLRDHUP | EPOLLET;
> ev.data.fd = fd_coredump;
> - if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd_coredump, &ev) < 0)
> + if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd_coredump, &ev) < 0) {
> + fprintf(stderr, "Worker: epoll_ctl(EPOLL_CTL_ADD) failed: %m\n");
> goto out;
> + }
>
> for (;;) {
> struct epoll_event events[1];
> int n = epoll_wait(epfd, events, 1, -1);
> - if (n < 0)
> + if (n < 0) {
> + fprintf(stderr, "Worker: epoll_wait() failed: %m\n");
> break;
> + }
>
> if (events[0].events & (EPOLLIN | EPOLLRDHUP)) {
> for (;;) {
> @@ -322,19 +350,24 @@ void process_coredump_worker(int fd_coredump, int fd_peer_pidfd, int fd_core_fil
> if (bytes_read < 0) {
> if (errno == EAGAIN || errno == EWOULDBLOCK)
> break;
> + fprintf(stderr, "Worker: read() failed: %m\n");
> goto out;
> }
> if (bytes_read == 0)
> goto done;
> ssize_t bytes_write = write(fd_core_file, buffer, bytes_read);
> - if (bytes_write != bytes_read)
> + if (bytes_write != bytes_read) {
> + fprintf(stderr, "Worker: write() failed (read=%zd, write=%zd): %m\n",
> + bytes_read, bytes_write);
> goto out;
> + }
> }
> }
> }
>
> done:
> exit_code = EXIT_SUCCESS;
> + fprintf(stderr, "Worker: completed successfully\n");
> out:
> if (epfd >= 0)
> close(epfd);
>
> --
> 2.47.3
>
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