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Mon, 31 Aug 2026 14:52:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id qjZcOxKVlWraFQAAD6G6ig (envelope-from ); Mon, 31 Aug 2026 14:52:02 +0000 Date: Mon, 31 Aug 2026 16:52:06 +0200 From: Cyril Hrubis To: Andrea Cervesato Message-ID: References: <20260824-coredump-v3-1-6429da674718@suse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20260824-coredump-v3-1-6429da674718@suse.com> X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_DN_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:email, yuki.lan:mid, zram02.sh:url, linux.it:url, imap1.dmz-prg2.suse.org:helo, suse.com:email] X-Virus-Scanned: clamav-milter 1.0.9 at in-6.smtp.seeweb.it X-Virus-Status: Clean Subject: Re: [LTP] [PATCH v3] coredump01: New core_pattern specifiers test X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux Test Project Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" Hi! > LTP has no coverage for the core_pattern specifiers expansion, neither > for the pipe flavor of core_pattern, where the kernel spawns a user > space helper and writes the core dump into its standard input. > > The new test verifies that %e, %p and %s are expanded both in the core > file name and in the arguments of a piped helper, checking also that > the helper really receives an ELF core dump. > > Root is required to rewrite the system wide core_pattern, which is > restored by the test library on all exit paths. > > Signed-off-by: Andrea Cervesato > --- > Add a simple coredump01 test that simulate a coredump and verify that it > actually works. This is a small coverage that is missing inside LTP > testing suite. > --- > Changes in v3: > - check for CONFIG_COREDUMP=y > - Link to v2: https://lore.kernel.org/20260824-coredump-v2-1-42428acf5216@suse.com > > Changes in v2: > - fix CI agent spotted errors > - Link to v1: https://lore.kernel.org/20260820-coredump-v1-1-7ce51603cefb@suse.com > --- > runtest/kernel_misc | 1 + > testcases/kernel/Makefile | 1 + > testcases/kernel/coredump/.gitignore | 2 + > testcases/kernel/coredump/Makefile | 7 + > testcases/kernel/coredump/coredump01.c | 225 ++++++++++++++++++++++++++ > testcases/kernel/coredump/coredump01_helper.c | 66 ++++++++ > 6 files changed, 302 insertions(+) > > diff --git a/runtest/kernel_misc b/runtest/kernel_misc > index cc3562cb7..ecf9ee2a2 100644 > --- a/runtest/kernel_misc > +++ b/runtest/kernel_misc > @@ -17,3 +17,4 @@ zram02 zram02.sh > zram03 zram03 > umip_basic_test umip_basic_test > aslr01 aslr01 > +coredump01 coredump01 > diff --git a/testcases/kernel/Makefile b/testcases/kernel/Makefile > index ac816e4e8..6b303c14b 100644 > --- a/testcases/kernel/Makefile > +++ b/testcases/kernel/Makefile > @@ -19,6 +19,7 @@ SUBDIRS += lib > SUBDIRS += connectors \ > containers \ > controllers \ > + coredump \ > crypto \ > device-drivers \ > firmware \ > diff --git a/testcases/kernel/coredump/.gitignore b/testcases/kernel/coredump/.gitignore > new file mode 100644 > index 000000000..cd0b51700 > --- /dev/null > +++ b/testcases/kernel/coredump/.gitignore > @@ -0,0 +1,2 @@ > +/coredump01 > +/coredump01_helper > diff --git a/testcases/kernel/coredump/Makefile b/testcases/kernel/coredump/Makefile > new file mode 100644 > index 000000000..951a3e976 > --- /dev/null > +++ b/testcases/kernel/coredump/Makefile > @@ -0,0 +1,7 @@ > +# SPDX-License-Identifier: GPL-2.0-or-later > +# Copyright (c) 2026 Linux Test Project > + > +top_srcdir ?= ../../.. > + > +include $(top_srcdir)/include/mk/testcases.mk > +include $(top_srcdir)/include/mk/generic_leaf_target.mk > diff --git a/testcases/kernel/coredump/coredump01.c b/testcases/kernel/coredump/coredump01.c > new file mode 100644 > index 000000000..96a7252da > --- /dev/null > +++ b/testcases/kernel/coredump/coredump01.c > @@ -0,0 +1,225 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2026 Linux Test Project > + */ > + > +/*\ > + * Verify that the kernel expands the :manpage:`core(5)` specifiers %e > + * (executable name), %p (PID) and %s (signal number) when it creates a > + * core dump. > + * > + * Both flavors of ``/proc/sys/kernel/core_pattern`` are tested: > + * > + * - a plain file name, where the specifiers become part of the core file > + * name > + * - a pipe to a user space helper, where the specifiers are expanded in > + * the helper arguments and the core dump is written to the helper > + * standard input > + * > + * The test needs root because it rewrites the system wide core_pattern. > + * The original value is saved and restored by the test library on all > + * exit paths. > + * > + * [Algorithm] > + * > + * - Point core_pattern into the test temporary directory > + * - Fork a child which aborts itself to produce a core dump > + * - For the file pattern check that ``core...`` was created > + * - For the pipe pattern check the arguments the helper was called with > + * and that it received an ELF core dump on its standard input > + */ > + > +#include > +#include > +#include > + > +#include "tst_test.h" > +#include "tst_kconfig.h" > +#include "lapi/prctl.h" > + > +#define PATTERN_MAX 128 > +#define HELPER "coredump01_helper" > +#define HELPER_TIMEOUT 10 > + > +static char helper_dir[PATH_MAX]; > +static char cwd[PATH_MAX]; > + > +static void set_pattern(const char *fmt, ...) > +{ > + char pattern[PATTERN_MAX]; > + va_list va; > + int len; > + > + va_start(va, fmt); > + len = vsnprintf(pattern, sizeof(pattern), fmt, va); > + va_end(va); > + > + if (len >= PATTERN_MAX) > + tst_brk(TCONF, "core_pattern does not fit into %i bytes", PATTERN_MAX - 1); > + > + SAFE_FILE_PRINTF(PATH_KERN_CORE_PATTERN, "%s", pattern); > + > + tst_res(TINFO, "core_pattern is '%s'", pattern); Shouldn't we read the pattern back and make sure it's the same? > +} > + > +static pid_t crash_child(void) > +{ > + int status; > + pid_t pid; > + > + pid = SAFE_FORK(); > + if (!pid) > + abort(); > + > + SAFE_WAITPID(pid, &status, 0); > + > + if (!WIFSIGNALED(status) || !WCOREDUMP(status)) > + tst_brk(TFAIL, "Child did not dump core"); > + > + return pid; > +} > + > +static void verify_file_pattern(void) > +{ > + char dump[PATH_MAX + 32]; > + pid_t pid; > + > + tst_res(TINFO, "Testing file core_pattern"); > + > + set_pattern("%s/core.%%e.%%p.%%s", cwd); > + > + pid = crash_child(); > + > + snprintf(dump, sizeof(dump), "%s/core.coredump01.%d.%d", cwd, pid, SIGABRT); > + > + TST_EXP_PASS(access(dump, F_OK), "core.%%e.%%p.%%s expanded to core.coredump01.%d.%d", > + pid, SIGABRT); > +} > + > +/* PID 2 is kthreadd only if we can see the initial PID namespace */ > +static int have_init_pid_ns(void) > +{ > + char comm[16] = {0}; > + int fd, len; > + > + fd = open("/proc/2/comm", O_RDONLY); > + if (fd < 0) > + return 0; > + > + len = SAFE_READ(0, fd, comm, sizeof(comm) - 1); > + SAFE_CLOSE(fd); > + > + return len > 0 && !strncmp(comm, "kthreadd\n", 9); > +} > + > +/* > + * The kernel resolves @path the way /proc/2/root (kthreadd lives in the > + * initial namespaces) resolves it. > + */ > +static int same_in_init_mnt_ns(const char *path) > +{ > + char init_path[PATH_MAX + 32]; > + struct stat our_st, init_st; > + > + SAFE_STAT(path, &our_st); > + > + snprintf(init_path, sizeof(init_path), "/proc/2/root%s", path); > + > + if (stat(init_path, &init_st)) > + return 0; > + > + return init_st.st_dev == our_st.st_dev && init_st.st_ino == our_st.st_ino; > +} > + > +static void verify_pipe_pattern(void) > +{ > + char res[PATH_MAX + 32], exe[PATH_MAX], helper[PATH_MAX + 32]; > + struct tst_kconfig_var kconfig = TST_KCONFIG_INIT("CONFIG_STATIC_USERMODEHELPER"); > + int pid_seen, sig_seen, elf; > + long long bytes; > + pid_t pid; > + > + tst_kconfig_read(&kconfig, 1); > + if (kconfig.choice == 'y') { > + tst_res(TCONF, "CONFIG_STATIC_USERMODEHELPER is enabled, skipping pipe core_pattern"); > + return; > + } This should be read once in the test setup so that we do not parse .config on each -i iteration. > + snprintf(helper, sizeof(helper), "%s/%s", helper_dir, HELPER); > + > + /* > + * The kernel always execs the pipe helper in the initial mount > + * namespace (core(5)), no matter where the crashing process lives. > + * Skip unless both the helper and the result directory are the very > + * same objects there, otherwise the kernel would not find them and > + * the test would fail spuriously, e.g. inside a container. > + */ > + if (!have_init_pid_ns() || !same_in_init_mnt_ns(helper) || > + !same_in_init_mnt_ns(cwd)) { > + tst_res(TCONF, "Pipe helper or result dir not visible in the initial mount namespace"); > + return; > + } I'm not sure if these extensive tests aren't out of scope for the test. Is it common for tests to be executed in a mount namespace? > + tst_res(TINFO, "Testing pipe core_pattern"); > + > + set_pattern("|%s/%s %%e %%p %%s %s/res.%%p", helper_dir, HELPER, cwd); > + > + pid = crash_child(); > + > + snprintf(res, sizeof(res), "%s/res.%d", cwd, pid); > + > + /* the kernel spawns the helper asynchronously */ > + if (TST_RETRY_FN_EXP_BACKOFF(access(res, F_OK), TST_RETVAL_EQ0, HELPER_TIMEOUT)) { > + tst_res(TFAIL, "%s did not report any core dump", HELPER); > + return; > + } > + > + SAFE_FILE_SCANF(res, "exe=%15s pid=%d sig=%d bytes=%lld elf=%d", > + exe, &pid_seen, &sig_seen, &bytes, &elf); > + > + TST_EXP_EQ_STR(exe, "coredump01"); > + TST_EXP_EQ_LI(pid_seen, pid); > + TST_EXP_EQ_LI(sig_seen, SIGABRT); > + TST_EXP_EXPR(elf && bytes > 0, "%s read %lli bytes of ELF core dump", HELPER, bytes); > +} > + > +static void run(unsigned int n) > +{ > + if (n) > + verify_pipe_pattern(); > + else > + verify_file_pattern(); > +} > + > +static void setup(void) > +{ > + struct rlimit rl = {RLIM_INFINITY, RLIM_INFINITY}; > + ssize_t len; > + > + SAFE_SETRLIMIT(RLIMIT_CORE, &rl); > + > + SAFE_PRCTL(PR_SET_DUMPABLE, 1, 0, 0, 0); > + > + SAFE_GETCWD(cwd, sizeof(cwd)); > + > + len = SAFE_READLINK("/proc/self/exe", helper_dir, sizeof(helper_dir) - 1); > + helper_dir[len] = '\0'; > + *strrchr(helper_dir, '/') = '\0'; This looks like a hack. We do have tst_get_path() that could be used to resolve the helper absolute path instead. > +} > + > +static struct tst_test test = { > + .test = run, > + .tcnt = 2, > + .setup = setup, > + .needs_root = 1, > + .needs_tmpdir = 1, > + .forks_child = 1, > + .needs_kconfigs = (const char* []) { > + "CONFIG_COREDUMP=y", > + NULL, > + }, > + .save_restore = (const struct tst_path_val[]) { > + {PATH_KERN_CORE_PATTERN, NULL, TST_SR_TCONF}, > + {} > + }, > +}; > diff --git a/testcases/kernel/coredump/coredump01_helper.c b/testcases/kernel/coredump/coredump01_helper.c > new file mode 100644 > index 000000000..41091b428 > --- /dev/null > +++ b/testcases/kernel/coredump/coredump01_helper.c > @@ -0,0 +1,66 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2026 Linux Test Project > + */ > + > +/* > + * Core dump collector for the piped core_pattern tested by coredump01. > + * > + * Avoiding the LTP API here is correct, since the kernel spawns the helper > + * through ``call_usermodehelper()`` without the LTP IPC environment. > + * > + * The helper is called as: > + * > + * coredump01_helper > + * > + * and stores what it received in the result file, which is published with > + * :manpage:`rename()` so that the polling test never reads a partial line. > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +int main(int argc, char *argv[]) > +{ > + char buf[4096], tmp[PATH_MAX], magic[4]; > + long long bytes = 0; > + ssize_t rval, i; > + int fd, elf = 0; > + > + if (argc < 5) > + return 1; > + > + /* > + * A core dump embeds the ELF images it has mapped, so the magic is > + * only meaningful at the very beginning of the stream. Collect it > + * across reads, since a pipe read can return less than 4 bytes. > + */ > + while ((rval = read(STDIN_FILENO, buf, sizeof(buf))) > 0) { > + for (i = 0; i < rval && bytes + i < 4; i++) > + magic[bytes + i] = buf[i]; > + > + bytes += rval; > + } > + > + if (rval < 0) > + return 1; > + > + if (bytes >= 4 && !memcmp(magic, "\177ELF", 4)) > + elf = 1; > + > + snprintf(tmp, sizeof(tmp), "%s.tmp", argv[4]); > + > + fd = open(tmp, O_WRONLY | O_CREAT | O_TRUNC, 0644); > + if (fd < 0) > + return 1; > + > + dprintf(fd, "exe=%s pid=%s sig=%s bytes=%lld elf=%d\n", > + argv[1], argv[2], argv[3], bytes, elf); > + > + close(fd); > + > + return rename(tmp, argv[4]) ? 1 : 0; > +} > > --- > base-commit: e62b1a4731f9c458d65c2659d2f8bb58b93e6d6d > change-id: 20260820-coredump-22fc731bde08 > > Best regards, > -- > Andrea Cervesato > > > -- > Mailing list info: https://lists.linux.it/listinfo/ltp -- Cyril Hrubis chrubis@suse.cz -- Mailing list info: https://lists.linux.it/listinfo/ltp