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coredump: process special crashes in an (almost) normal way
We would only log a terse message when pid1 or systemd-journald crashed. It seems better to reuse the normal code paths as much as possible, with the following differences: - if pid1 crashes, we cannot launch the helper, so we don't analyze the coredump, just write it to file directly from the helper invoked by the kernel; - if journald crashes, we can produce the backtrace, but we don't log full structured messages. With comparison to previous code, advantages are: - we go through most of the steps, so for example vacuuming is performed, - we gather and log more data. In particular for journald and pid1 crashes we generate a backtrace, and for pid1 crashes we record the metadata (fdinfo, maps, etc.), - coredumpctl shows pid1 crashes. A disavantage (inefficiency) is that we gather metadata for journald crashes which is then ignored because _TRANSPORT=kernel does not support structued messages. Messages for the systemd-journald "crash" have _TRANSPORT=kernel, and _TRANSPORT=journal for the pid1 "crash". Feb 26 16:27:55 systemd[1]: systemd-journald.service: Main process exited, code=dumped, status=11/SEGV Feb 26 16:27:55 systemd[1]: systemd-journald.service: Unit entered failed state. Feb 26 16:37:54 systemd-coredump[18801]: Process 18729 (systemd-journal) of user 0 dumped core. Feb 26 16:37:54 systemd-coredump[18801]: Coredump diverted to /var/lib/systemd/coredump/core.systemd-journal.0.36c14bf3c6ce4c38914f441038990979.18729.1488145074000000.lz4 Feb 26 16:37:54 systemd-coredump[18801]: Stack trace of thread 18729: Feb 26 16:37:54 systemd-coredump[18801]: #0 0x00007f46d6a06b8d fsync (libpthread.so.0) Feb 26 16:37:54 systemd-coredump[18801]: #1 0x00007f46d71bfc47 journal_file_set_online (libsystemd-shared-233.so) Feb 26 16:37:54 systemd-coredump[18801]: #2 0x00007f46d71c1c31 journal_file_append_object (libsystemd-shared-233.so) Feb 26 16:37:54 systemd-coredump[18801]: #3 0x00007f46d71c3405 journal_file_append_data (libsystemd-shared-233.so) Feb 26 16:37:54 systemd-coredump[18801]: #4 0x00007f46d71c4b7c journal_file_append_entry (libsystemd-shared-233.so) Feb 26 16:37:54 systemd-coredump[18801]: #5 0x00005577688cf056 write_to_journal (systemd-journald) Feb 26 16:37:54 systemd-coredump[18801]: #6 0x00005577688d2e98 dispatch_message_real (systemd-journald) Feb 26 16:37:54 kernel: systemd-coredum: 9 output lines suppressed due to ratelimiting Feb 26 16:37:54 systemd-journald[18810]: Journal started Feb 26 16:50:59 systemd-coredump[19229]: Due to PID 1 having crashed coredump collection will now be turned off. Feb 26 16:51:00 systemd[1]: Caught <SEGV>, dumped core as pid 19228. Feb 26 16:51:00 systemd[1]: Freezing execution. Feb 26 16:51:00 systemd-coredump[19229]: Process 19228 (systemd) of user 0 dumped core. Stack trace of thread 19228: #0 0x00007fab82075c47 kill (libc.so.6) #1 0x000055fdf7c38b6b crash (systemd) #2 0x00007fab824175c0 __restore_rt (libpthread.so.0) #3 0x00007fab82148573 epoll_wait (libc.so.6) #4 0x00007fab8366f84a sd_event_wait (libsystemd-shared-233.so) #5 0x00007fab836701de sd_event_run (libsystemd-shared-233.so) #6 0x000055fdf7c4a380 manager_loop (systemd) #7 0x000055fdf7c402c2 main (systemd) #8 0x00007fab82060401 __libc_start_main (libc.so.6) #9 0x000055fdf7c3818a _start (systemd) Poor machine ;)
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
parent
cc4419ed92
commit
92e92d71fa
@ -102,6 +102,7 @@ enum {
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CONTEXT_RLIMIT,
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CONTEXT_COMM,
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CONTEXT_EXE,
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CONTEXT_UNIT,
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_CONTEXT_MAX
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};
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@ -706,7 +707,7 @@ static int submit_coredump(
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_cleanup_close_ int coredump_fd = -1, coredump_node_fd = -1;
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_cleanup_free_ char *core_message = NULL, *filename = NULL, *coredump_data = NULL;
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uint64_t coredump_size = UINT64_MAX;
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bool truncated = false;
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bool truncated = false, journald_crash;
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int r;
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assert(context);
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@ -714,6 +715,8 @@ static int submit_coredump(
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assert(n_iovec_allocated >= n_iovec + SUBMIT_COREDUMP_FIELDS);
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assert(input_fd >= 0);
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journald_crash = streq_ptr(context[CONTEXT_UNIT], SPECIAL_JOURNALD_SERVICE);
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/* Vacuum before we write anything again */
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(void) coredump_vacuum(-1, arg_keep_free, arg_max_use);
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@ -758,8 +761,10 @@ static int submit_coredump(
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if (r >= 0)
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core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
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" (", context[CONTEXT_COMM], ") of user ",
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context[CONTEXT_UID], " dumped core.\n\n",
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stacktrace);
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context[CONTEXT_UID], " dumped core.",
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journald_crash ? "\nCoredump diverted to " : "",
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journald_crash ? filename : "",
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"\n\n", stacktrace);
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else if (r == -EINVAL)
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log_warning("Failed to generate stack trace: %s", dwfl_errmsg(dwfl_errno()));
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else
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@ -771,9 +776,21 @@ static int submit_coredump(
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if (!core_message)
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#endif
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log:
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core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID], " (",
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context[CONTEXT_COMM], ") of user ",
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context[CONTEXT_UID], " dumped core.");
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core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
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" (", context[CONTEXT_COMM], ") of user ",
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context[CONTEXT_UID], " dumped core.",
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journald_crash ? "\nCoredump diverted to " : NULL,
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journald_crash ? filename : NULL);
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if (!core_message)
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return log_oom();
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if (journald_crash) {
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/* We cannot log to the journal, so just print the MESSAGE.
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* The target was set previously to something safe. */
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log_struct(LOG_ERR, core_message, NULL);
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return 0;
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}
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if (core_message)
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IOVEC_SET_STRING(iovec[n_iovec++], core_message);
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@ -810,15 +827,15 @@ log:
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static void map_context_fields(const struct iovec *iovec, const char* context[]) {
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static const char * const context_field_names[_CONTEXT_MAX] = {
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static const char * const context_field_names[] = {
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[CONTEXT_PID] = "COREDUMP_PID=",
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[CONTEXT_UID] = "COREDUMP_UID=",
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[CONTEXT_GID] = "COREDUMP_GID=",
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[CONTEXT_SIGNAL] = "COREDUMP_SIGNAL=",
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[CONTEXT_TIMESTAMP] = "COREDUMP_TIMESTAMP=",
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[CONTEXT_RLIMIT] = "COREDUMP_RLIMIT=",
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[CONTEXT_COMM] = "COREDUMP_COMM=",
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[CONTEXT_EXE] = "COREDUMP_EXE=",
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[CONTEXT_RLIMIT] = "COREDUMP_RLIMIT=",
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};
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unsigned i;
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@ -826,9 +843,12 @@ static void map_context_fields(const struct iovec *iovec, const char* context[])
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assert(iovec);
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assert(context);
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for (i = 0; i < _CONTEXT_MAX; i++) {
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for (i = 0; i < ELEMENTSOF(context_field_names); i++) {
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size_t l;
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if (!context_field_names[i])
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continue;
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l = strlen(context_field_names[i]);
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if (iovec->iov_len < l)
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continue;
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@ -1033,35 +1053,6 @@ static int send_iovec(const struct iovec iovec[], size_t n_iovec, int input_fd)
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return 0;
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}
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static int process_special_crash(const char *context[], int input_fd) {
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_cleanup_close_ int coredump_fd = -1, coredump_node_fd = -1;
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_cleanup_free_ char *filename = NULL;
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uint64_t coredump_size;
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bool truncated;
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int r;
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assert(context);
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assert(input_fd >= 0);
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/* If we are pid1 or journald, we cut things short, don't write to the journal, but still create a coredump. */
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if (arg_storage != COREDUMP_STORAGE_NONE)
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arg_storage = COREDUMP_STORAGE_EXTERNAL;
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r = save_external_coredump(context, input_fd,
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&filename, &coredump_node_fd, &coredump_fd, &coredump_size, &truncated);
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if (r < 0)
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return r;
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r = maybe_remove_external_coredump(filename, coredump_size);
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if (r < 0)
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return r;
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log_notice("Detected coredump of the journal daemon or PID 1, diverted to %s.", filename);
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return 0;
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}
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static char* set_iovec_field(struct iovec iovec[27], size_t *n_iovec, const char *field, const char *value) {
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char *x;
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@ -1079,7 +1070,7 @@ static char* set_iovec_field_free(struct iovec iovec[27], size_t *n_iovec, const
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return x;
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}
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static int gather_pid_metadata_and_process_special_crash(
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static int gather_pid_metadata(
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char* context[_CONTEXT_MAX],
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char **comm_fallback,
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struct iovec *iovec, size_t *n_iovec) {
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@ -1111,32 +1102,22 @@ static int gather_pid_metadata_and_process_special_crash(
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if (r < 0)
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log_warning_errno(r, "Failed to get EXE, ignoring: %m");
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if (cg_pid_get_unit(pid, &t) >= 0) {
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if (cg_pid_get_unit(pid, &context[CONTEXT_UNIT]) >= 0) {
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if (!streq(context[CONTEXT_UNIT], SPECIAL_JOURNALD_SERVICE)) {
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/* OK, now we know it's not the journal, hence we can make use of it now. */
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log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
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log_open();
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}
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/* If this is PID 1 disable coredump collection, we'll unlikely be able to process it later on. */
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if (streq(t, SPECIAL_INIT_SCOPE)) {
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if (streq(context[CONTEXT_UNIT], SPECIAL_INIT_SCOPE)) {
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log_notice("Due to PID 1 having crashed coredump collection will now be turned off.");
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(void) write_string_file("/proc/sys/kernel/core_pattern", "|/bin/false", 0);
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}
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/* Let's avoid dead-locks when processing journald and init crashes, as socket activation and logging
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* are unlikely to work then. */
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if (STR_IN_SET(t, SPECIAL_JOURNALD_SERVICE, SPECIAL_INIT_SCOPE)) {
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free(t);
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r = process_special_crash((const char**) context, STDIN_FILENO);
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if (r < 0)
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return r;
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return 1; /* > 0 means: we have already processed it, because it's a special crash */
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}
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set_iovec_field_free(iovec, n_iovec, "COREDUMP_UNIT=", t);
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set_iovec_field(iovec, n_iovec, "COREDUMP_UNIT=", context[CONTEXT_UNIT]);
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}
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/* OK, now we know it's not the journal, hence we can make use of it now. */
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log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
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log_open();
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if (cg_pid_get_user_unit(pid, &t) >= 0)
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set_iovec_field_free(iovec, n_iovec, "COREDUMP_USER_UNIT=", t);
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@ -1230,13 +1211,13 @@ static int gather_pid_metadata_and_process_special_crash(
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if (safe_atoi(context[CONTEXT_SIGNAL], &signo) >= 0 && SIGNAL_VALID(signo))
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set_iovec_field(iovec, n_iovec, "COREDUMP_SIGNAL_NAME=SIG", signal_to_string(signo));
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return 0; /* == 0 means: we successfully acquired all metadata */
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return 0; /* we successfully acquired all metadata */
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}
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static int process_kernel(int argc, char* argv[]) {
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char* context[_CONTEXT_MAX] = {};
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struct iovec iovec[28];
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struct iovec iovec[28 + SUBMIT_COREDUMP_FIELDS];
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size_t i, n_iovec, n_to_free = 0;
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int r;
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@ -1254,9 +1235,8 @@ static int process_kernel(int argc, char* argv[]) {
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context[CONTEXT_TIMESTAMP] = argv[1 + CONTEXT_TIMESTAMP];
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context[CONTEXT_RLIMIT] = argv[1 + CONTEXT_RLIMIT];
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r = gather_pid_metadata_and_process_special_crash(context, argv + 1 + CONTEXT_COMM, iovec, &n_to_free);
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if (r != 0)
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/* Error, or a a special crash, which has already been processed. */
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r = gather_pid_metadata(context, argv + 1 + CONTEXT_COMM, iovec, &n_to_free);
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if (r < 0)
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goto finish;
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n_iovec = n_to_free;
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@ -1268,15 +1248,23 @@ static int process_kernel(int argc, char* argv[]) {
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assert(n_iovec <= ELEMENTSOF(iovec));
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r = send_iovec(iovec, n_iovec, STDIN_FILENO);
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if (STRPTR_IN_SET(context[CONTEXT_UNIT],
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SPECIAL_JOURNALD_SERVICE,
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SPECIAL_INIT_SCOPE))
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r = submit_coredump((const char**) context,
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iovec, ELEMENTSOF(iovec), n_iovec,
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STDIN_FILENO);
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else
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r = send_iovec(iovec, n_iovec, STDIN_FILENO);
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finish:
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for (i = 0; i < n_to_free; i++)
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free(iovec[i].iov_base);
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/* Those fields are allocated by gather_pid_metadata_and_process_special_crash */
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/* Those fields are allocated by gather_pid_metadata */
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free(context[CONTEXT_COMM]);
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free(context[CONTEXT_EXE]);
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free(context[CONTEXT_UNIT]);
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return r;
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}
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@ -1305,12 +1293,13 @@ static int process_backtrace(int argc, char *argv[]) {
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context[CONTEXT_TIMESTAMP] = argv[2 + CONTEXT_TIMESTAMP];
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context[CONTEXT_RLIMIT] = argv[2 + CONTEXT_RLIMIT];
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n_allocated = 33; /* 25 metadata, 2 static, +unknown input, rounded up */
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n_allocated = 33 + COREDUMP_STORAGE_EXTERNAL;
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/* 25 metadata, 2 static, +unknown input, 4 storage, rounded up */
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iovec = new(struct iovec, n_allocated);
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if (!iovec)
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return log_oom();
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r = gather_pid_metadata_and_process_special_crash(context, argv + 2 + CONTEXT_COMM, iovec, &n_to_free);
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r = gather_pid_metadata(context, argv + 2 + CONTEXT_COMM, iovec, &n_to_free);
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if (r < 0)
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goto finish;
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if (r > 0) {
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@ -1364,9 +1353,10 @@ static int process_backtrace(int argc, char *argv[]) {
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for (i = 0; i < n_to_free; i++)
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free(iovec[i].iov_base);
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/* Those fields are allocated by gather_pid_metadata_and_process_special_crash */
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/* Those fields are allocated by gather_pid_metadata */
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free(context[CONTEXT_COMM]);
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free(context[CONTEXT_EXE]);
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free(context[CONTEXT_UNIT]);
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return r;
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}
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