Adding upstream version 241.upstream/241upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1405 insertions, 0 deletions

diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c
new file mode 100644
index 0000000..ecbb4bf
--- /dev/null
+++ b/src/coredump/coredump.c
@@ -0,0 +1,1405 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdio_ext.h>
+#include <sys/prctl.h>
+#include <sys/xattr.h>
+#include <unistd.h>
+
+#if HAVE_ELFUTILS
+#include <dwarf.h>
+#include <elfutils/libdwfl.h>
+#endif
+
+#include "sd-daemon.h"
+#include "sd-journal.h"
+#include "sd-login.h"
+#include "sd-messages.h"
+
+#include "acl-util.h"
+#include "alloc-util.h"
+#include "capability-util.h"
+#include "cgroup-util.h"
+#include "compress.h"
+#include "conf-parser.h"
+#include "copy.h"
+#include "coredump-vacuum.h"
+#include "dirent-util.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "io-util.h"
+#include "journal-importer.h"
+#include "log.h"
+#include "macro.h"
+#include "main-func.h"
+#include "missing.h"
+#include "mkdir.h"
+#include "parse-util.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "socket-util.h"
+#include "special.h"
+#include "stacktrace.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tmpfile-util.h"
+#include "user-util.h"
+#include "util.h"
+
+/* The maximum size up to which we process coredumps */
+#define PROCESS_SIZE_MAX ((uint64_t) (2LLU*1024LLU*1024LLU*1024LLU))
+
+/* The maximum size up to which we leave the coredump around on disk */
+#define EXTERNAL_SIZE_MAX PROCESS_SIZE_MAX
+
+/* The maximum size up to which we store the coredump in the journal */
+#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#define JOURNAL_SIZE_MAX ((size_t) (767LU*1024LU*1024LU))
+#else
+/* oss-fuzz limits memory usage. */
+#define JOURNAL_SIZE_MAX ((size_t) (10LU*1024LU*1024LU))
+#endif
+
+/* Make sure to not make this larger than the maximum journal entry
+ * size. See DATA_SIZE_MAX in journal-importer.h. */
+assert_cc(JOURNAL_SIZE_MAX <= DATA_SIZE_MAX);
+
+enum {
+        /* We use this as array indexes for a couple of special fields we use for
+         * naming coredump files, and attaching xattrs, and for indexing argv[].
+
+         * Our pattern for man:systectl(1) kernel.core_pattern is such that the
+         * kernel passes fields until CONTEXT_RLIMIT as arguments in argv[]. After
+         * that it gets complicated: the kernel passes "comm" as one or more fields
+         * starting at index CONTEXT_COMM (in other words, full "comm" is under index
+         * CONTEXT_COMM when it does not contain spaces, which is the common
+         * case). This mapping is not reversible, so we prefer to retrieve "comm"
+         * from /proc. We only fall back to argv[CONTEXT_COMM...] when that fails.
+         *
+         * In the internal context[] array, fields before CONTEXT_COMM are the
+         * strings from argv[], so they should not be freed. The strings at indices
+         * CONTEXT_COMM and higher are allocated by us and should be freed at the
+         * end.
+         */
+        CONTEXT_PID,
+        CONTEXT_UID,
+        CONTEXT_GID,
+        CONTEXT_SIGNAL,
+        CONTEXT_TIMESTAMP,
+        CONTEXT_RLIMIT,
+        CONTEXT_HOSTNAME,
+        CONTEXT_COMM,
+        CONTEXT_EXE,
+        CONTEXT_UNIT,
+        _CONTEXT_MAX
+};
+
+typedef enum CoredumpStorage {
+        COREDUMP_STORAGE_NONE,
+        COREDUMP_STORAGE_EXTERNAL,
+        COREDUMP_STORAGE_JOURNAL,
+        _COREDUMP_STORAGE_MAX,
+        _COREDUMP_STORAGE_INVALID = -1
+} CoredumpStorage;
+
+static const char* const coredump_storage_table[_COREDUMP_STORAGE_MAX] = {
+        [COREDUMP_STORAGE_NONE] = "none",
+        [COREDUMP_STORAGE_EXTERNAL] = "external",
+        [COREDUMP_STORAGE_JOURNAL] = "journal",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP(coredump_storage, CoredumpStorage);
+static DEFINE_CONFIG_PARSE_ENUM(config_parse_coredump_storage, coredump_storage, CoredumpStorage, "Failed to parse storage setting");
+
+static CoredumpStorage arg_storage = COREDUMP_STORAGE_EXTERNAL;
+static bool arg_compress = true;
+static uint64_t arg_process_size_max = PROCESS_SIZE_MAX;
+static uint64_t arg_external_size_max = EXTERNAL_SIZE_MAX;
+static uint64_t arg_journal_size_max = JOURNAL_SIZE_MAX;
+static uint64_t arg_keep_free = (uint64_t) -1;
+static uint64_t arg_max_use = (uint64_t) -1;
+
+static int parse_config(void) {
+        static const ConfigTableItem items[] = {
+                { "Coredump", "Storage",          config_parse_coredump_storage,  0, &arg_storage           },
+                { "Coredump", "Compress",         config_parse_bool,              0, &arg_compress          },
+                { "Coredump", "ProcessSizeMax",   config_parse_iec_uint64,        0, &arg_process_size_max  },
+                { "Coredump", "ExternalSizeMax",  config_parse_iec_uint64,        0, &arg_external_size_max },
+                { "Coredump", "JournalSizeMax",   config_parse_iec_size,          0, &arg_journal_size_max  },
+                { "Coredump", "KeepFree",         config_parse_iec_uint64,        0, &arg_keep_free         },
+                { "Coredump", "MaxUse",           config_parse_iec_uint64,        0, &arg_max_use           },
+                {}
+        };
+
+        return config_parse_many_nulstr(PKGSYSCONFDIR "/coredump.conf",
+                                        CONF_PATHS_NULSTR("systemd/coredump.conf.d"),
+                                        "Coredump\0",
+                                        config_item_table_lookup, items,
+                                        CONFIG_PARSE_WARN, NULL);
+}
+
+static uint64_t storage_size_max(void) {
+        if (arg_storage == COREDUMP_STORAGE_EXTERNAL)
+                return arg_external_size_max;
+        if (arg_storage == COREDUMP_STORAGE_JOURNAL)
+                return arg_journal_size_max;
+        assert(arg_storage == COREDUMP_STORAGE_NONE);
+        return 0;
+}
+
+static int fix_acl(int fd, uid_t uid) {
+
+#if HAVE_ACL
+        _cleanup_(acl_freep) acl_t acl = NULL;
+        acl_entry_t entry;
+        acl_permset_t permset;
+        int r;
+
+        assert(fd >= 0);
+
+        if (uid_is_system(uid) || uid_is_dynamic(uid) || uid == UID_NOBODY)
+                return 0;
+
+        /* Make sure normal users can read (but not write or delete)
+         * their own coredumps */
+
+        acl = acl_get_fd(fd);
+        if (!acl)
+                return log_error_errno(errno, "Failed to get ACL: %m");
+
+        if (acl_create_entry(&acl, &entry) < 0 ||
+            acl_set_tag_type(entry, ACL_USER) < 0 ||
+            acl_set_qualifier(entry, &uid) < 0)
+                return log_error_errno(errno, "Failed to patch ACL: %m");
+
+        if (acl_get_permset(entry, &permset) < 0 ||
+            acl_add_perm(permset, ACL_READ) < 0)
+                return log_warning_errno(errno, "Failed to patch ACL: %m");
+
+        r = calc_acl_mask_if_needed(&acl);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to patch ACL: %m");
+
+        if (acl_set_fd(fd, acl) < 0)
+                return log_error_errno(errno, "Failed to apply ACL: %m");
+#endif
+
+        return 0;
+}
+
+static int fix_xattr(int fd, const char *context[_CONTEXT_MAX]) {
+
+        static const char * const xattrs[_CONTEXT_MAX] = {
+                [CONTEXT_PID] = "user.coredump.pid",
+                [CONTEXT_UID] = "user.coredump.uid",
+                [CONTEXT_GID] = "user.coredump.gid",
+                [CONTEXT_SIGNAL] = "user.coredump.signal",
+                [CONTEXT_TIMESTAMP] = "user.coredump.timestamp",
+                [CONTEXT_RLIMIT] = "user.coredump.rlimit",
+                [CONTEXT_HOSTNAME] = "user.coredump.hostname",
+                [CONTEXT_COMM] = "user.coredump.comm",
+                [CONTEXT_EXE] = "user.coredump.exe",
+        };
+
+        int r = 0;
+        unsigned i;
+
+        assert(fd >= 0);
+
+        /* Attach some metadata to coredumps via extended
+         * attributes. Just because we can. */
+
+        for (i = 0; i < _CONTEXT_MAX; i++) {
+                int k;
+
+                if (isempty(context[i]) || !xattrs[i])
+                        continue;
+
+                k = fsetxattr(fd, xattrs[i], context[i], strlen(context[i]), XATTR_CREATE);
+                if (k < 0 && r == 0)
+                        r = -errno;
+        }
+
+        return r;
+}
+
+#define filename_escape(s) xescape((s), "./ ")
+
+static const char *coredump_tmpfile_name(const char *s) {
+        return s ? s : "(unnamed temporary file)";
+}
+
+static int fix_permissions(
+                int fd,
+                const char *filename,
+                const char *target,
+                const char *context[_CONTEXT_MAX],
+                uid_t uid) {
+
+        int r;
+
+        assert(fd >= 0);
+        assert(target);
+        assert(context);
+
+        /* Ignore errors on these */
+        (void) fchmod(fd, 0640);
+        (void) fix_acl(fd, uid);
+        (void) fix_xattr(fd, context);
+
+        if (fsync(fd) < 0)
+                return log_error_errno(errno, "Failed to sync coredump %s: %m", coredump_tmpfile_name(filename));
+
+        (void) fsync_directory_of_file(fd);
+
+        r = link_tmpfile(fd, filename, target);
+        if (r < 0)
+                return log_error_errno(r, "Failed to move coredump %s into place: %m", target);
+
+        return 0;
+}
+
+static int maybe_remove_external_coredump(const char *filename, uint64_t size) {
+
+        /* Returns 1 if might remove, 0 if will not remove, < 0 on error. */
+
+        if (arg_storage == COREDUMP_STORAGE_EXTERNAL &&
+            size <= arg_external_size_max)
+                return 0;
+
+        if (!filename)
+                return 1;
+
+        if (unlink(filename) < 0 && errno != ENOENT)
+                return log_error_errno(errno, "Failed to unlink %s: %m", filename);
+
+        return 1;
+}
+
+static int make_filename(const char *context[_CONTEXT_MAX], char **ret) {
+        _cleanup_free_ char *c = NULL, *u = NULL, *p = NULL, *t = NULL;
+        sd_id128_t boot = {};
+        int r;
+
+        assert(context);
+
+        c = filename_escape(context[CONTEXT_COMM]);
+        if (!c)
+                return -ENOMEM;
+
+        u = filename_escape(context[CONTEXT_UID]);
+        if (!u)
+                return -ENOMEM;
+
+        r = sd_id128_get_boot(&boot);
+        if (r < 0)
+                return r;
+
+        p = filename_escape(context[CONTEXT_PID]);
+        if (!p)
+                return -ENOMEM;
+
+        t = filename_escape(context[CONTEXT_TIMESTAMP]);
+        if (!t)
+                return -ENOMEM;
+
+        if (asprintf(ret,
+                     "/var/lib/systemd/coredump/core.%s.%s." SD_ID128_FORMAT_STR ".%s.%s000000",
+                     c,
+                     u,
+                     SD_ID128_FORMAT_VAL(boot),
+                     p,
+                     t) < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
+static int save_external_coredump(
+                const char *context[_CONTEXT_MAX],
+                int input_fd,
+                char **ret_filename,
+                int *ret_node_fd,
+                int *ret_data_fd,
+                uint64_t *ret_size,
+                bool *ret_truncated) {
+
+        _cleanup_free_ char *fn = NULL, *tmp = NULL;
+        _cleanup_close_ int fd = -1;
+        uint64_t rlimit, process_limit, max_size;
+        struct stat st;
+        uid_t uid;
+        int r;
+
+        assert(context);
+        assert(ret_filename);
+        assert(ret_node_fd);
+        assert(ret_data_fd);
+        assert(ret_size);
+
+        r = parse_uid(context[CONTEXT_UID], &uid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse UID: %m");
+
+        r = safe_atou64(context[CONTEXT_RLIMIT], &rlimit);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse resource limit '%s': %m", context[CONTEXT_RLIMIT]);
+        if (rlimit < page_size()) {
+                /* Is coredumping disabled? Then don't bother saving/processing the coredump.
+                 * Anything below PAGE_SIZE cannot give a readable coredump (the kernel uses
+                 * ELF_EXEC_PAGESIZE which is not easily accessible, but is usually the same as PAGE_SIZE. */
+                return log_info_errno(SYNTHETIC_ERRNO(EBADSLT),
+                                      "Resource limits disable core dumping for process %s (%s).",
+                                      context[CONTEXT_PID], context[CONTEXT_COMM]);
+        }
+
+        process_limit = MAX(arg_process_size_max, storage_size_max());
+        if (process_limit == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EBADSLT),
+                                       "Limits for coredump processing and storage are both 0, not dumping core.");
+
+        /* Never store more than the process configured, or than we actually shall keep or process */
+        max_size = MIN(rlimit, process_limit);
+
+        r = make_filename(context, &fn);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine coredump file name: %m");
+
+        mkdir_p_label("/var/lib/systemd/coredump", 0755);
+
+        fd = open_tmpfile_linkable(fn, O_RDWR|O_CLOEXEC, &tmp);
+        if (fd < 0)
+                return log_error_errno(fd, "Failed to create temporary file for coredump %s: %m", fn);
+
+        r = copy_bytes(input_fd, fd, max_size, 0);
+        if (r < 0) {
+                log_error_errno(r, "Cannot store coredump of %s (%s): %m", context[CONTEXT_PID], context[CONTEXT_COMM]);
+                goto fail;
+        }
+        *ret_truncated = r == 1;
+        if (*ret_truncated)
+                log_struct(LOG_INFO,
+                           LOG_MESSAGE("Core file was truncated to %zu bytes.", max_size),
+                           "SIZE_LIMIT=%zu", max_size,
+                           "MESSAGE_ID=" SD_MESSAGE_TRUNCATED_CORE_STR);
+
+        if (fstat(fd, &st) < 0) {
+                log_error_errno(errno, "Failed to fstat core file %s: %m", coredump_tmpfile_name(tmp));
+                goto fail;
+        }
+
+        if (lseek(fd, 0, SEEK_SET) == (off_t) -1) {
+                log_error_errno(errno, "Failed to seek on %s: %m", coredump_tmpfile_name(tmp));
+                goto fail;
+        }
+
+#if HAVE_XZ || HAVE_LZ4
+        /* If we will remove the coredump anyway, do not compress. */
+        if (arg_compress && !maybe_remove_external_coredump(NULL, st.st_size)) {
+
+                _cleanup_free_ char *fn_compressed = NULL, *tmp_compressed = NULL;
+                _cleanup_close_ int fd_compressed = -1;
+
+                fn_compressed = strappend(fn, COMPRESSED_EXT);
+                if (!fn_compressed) {
+                        log_oom();
+                        goto uncompressed;
+                }
+
+                fd_compressed = open_tmpfile_linkable(fn_compressed, O_RDWR|O_CLOEXEC, &tmp_compressed);
+                if (fd_compressed < 0) {
+                        log_error_errno(fd_compressed, "Failed to create temporary file for coredump %s: %m", fn_compressed);
+                        goto uncompressed;
+                }
+
+                r = compress_stream(fd, fd_compressed, -1);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to compress %s: %m", coredump_tmpfile_name(tmp_compressed));
+                        goto fail_compressed;
+                }
+
+                r = fix_permissions(fd_compressed, tmp_compressed, fn_compressed, context, uid);
+                if (r < 0)
+                        goto fail_compressed;
+
+                /* OK, this worked, we can get rid of the uncompressed version now */
+                if (tmp)
+                        unlink_noerrno(tmp);
+
+                *ret_filename = TAKE_PTR(fn_compressed);     /* compressed */
+                *ret_node_fd = TAKE_FD(fd_compressed);      /* compressed */
+                *ret_data_fd = TAKE_FD(fd);                 /* uncompressed */
+                *ret_size = (uint64_t) st.st_size; /* uncompressed */
+
+                return 0;
+
+        fail_compressed:
+                if (tmp_compressed)
+                        (void) unlink(tmp_compressed);
+        }
+
+uncompressed:
+#endif
+
+        r = fix_permissions(fd, tmp, fn, context, uid);
+        if (r < 0)
+                goto fail;
+
+        *ret_filename = TAKE_PTR(fn);
+        *ret_data_fd = TAKE_FD(fd);
+        *ret_node_fd = -1;
+        *ret_size = (uint64_t) st.st_size;
+
+        return 0;
+
+fail:
+        if (tmp)
+                (void) unlink(tmp);
+        return r;
+}
+
+static int allocate_journal_field(int fd, size_t size, char **ret, size_t *ret_size) {
+        _cleanup_free_ char *field = NULL;
+        ssize_t n;
+
+        assert(fd >= 0);
+        assert(ret);
+        assert(ret_size);
+
+        if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
+                return log_warning_errno(errno, "Failed to seek: %m");
+
+        field = malloc(9 + size);
+        if (!field) {
+                log_warning("Failed to allocate memory for coredump, coredump will not be stored.");
+                return -ENOMEM;
+        }
+
+        memcpy(field, "COREDUMP=", 9);
+
+        n = read(fd, field + 9, size);
+        if (n < 0)
+                return log_error_errno((int) n, "Failed to read core data: %m");
+        if ((size_t) n < size)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO),
+                                       "Core data too short.");
+
+        *ret = TAKE_PTR(field);
+        *ret_size = size + 9;
+
+        return 0;
+}
+
+/* Joins /proc/[pid]/fd/ and /proc/[pid]/fdinfo/ into the following lines:
+ * 0:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ *
+ * 1:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ *
+ * 2:/dev/pts/23
+ * pos:    0
+ * flags:  0100002
+ * EOF
+ */
+static int compose_open_fds(pid_t pid, char **open_fds) {
+        _cleanup_closedir_ DIR *proc_fd_dir = NULL;
+        _cleanup_close_ int proc_fdinfo_fd = -1;
+        _cleanup_free_ char *buffer = NULL;
+        _cleanup_fclose_ FILE *stream = NULL;
+        const char *fddelim = "", *path;
+        struct dirent *dent = NULL;
+        size_t size = 0;
+        int r;
+
+        assert(pid >= 0);
+        assert(open_fds != NULL);
+
+        path = procfs_file_alloca(pid, "fd");
+        proc_fd_dir = opendir(path);
+        if (!proc_fd_dir)
+                return -errno;
+
+        proc_fdinfo_fd = openat(dirfd(proc_fd_dir), "../fdinfo", O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC|O_PATH);
+        if (proc_fdinfo_fd < 0)
+                return -errno;
+
+        stream = open_memstream(&buffer, &size);
+        if (!stream)
+                return -ENOMEM;
+
+        (void) __fsetlocking(stream, FSETLOCKING_BYCALLER);
+
+        FOREACH_DIRENT(dent, proc_fd_dir, return -errno) {
+                _cleanup_fclose_ FILE *fdinfo = NULL;
+                _cleanup_free_ char *fdname = NULL;
+                int fd;
+
+                r = readlinkat_malloc(dirfd(proc_fd_dir), dent->d_name, &fdname);
+                if (r < 0)
+                        return r;
+
+                fprintf(stream, "%s%s:%s\n", fddelim, dent->d_name, fdname);
+                fddelim = "\n";
+
+                /* Use the directory entry from /proc/[pid]/fd with /proc/[pid]/fdinfo */
+                fd = openat(proc_fdinfo_fd, dent->d_name, O_NOFOLLOW|O_CLOEXEC|O_RDONLY);
+                if (fd < 0)
+                        continue;
+
+                fdinfo = fdopen(fd, "r");
+                if (!fdinfo) {
+                        safe_close(fd);
+                        continue;
+                }
+
+                for (;;) {
+                        _cleanup_free_ char *line = NULL;
+
+                        r = read_line(fdinfo, LONG_LINE_MAX, &line);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                break;
+
+                        fputs(line, stream);
+                        fputc('\n', stream);
+                }
+        }
+
+        errno = 0;
+        stream = safe_fclose(stream);
+
+        if (errno > 0)
+                return -errno;
+
+        *open_fds = TAKE_PTR(buffer);
+
+        return 0;
+}
+
+static int get_process_ns(pid_t pid, const char *namespace, ino_t *ns) {
+        const char *p;
+        struct stat stbuf;
+        _cleanup_close_ int proc_ns_dir_fd;
+
+        p = procfs_file_alloca(pid, "ns");
+
+        proc_ns_dir_fd = open(p, O_DIRECTORY | O_CLOEXEC | O_RDONLY);
+        if (proc_ns_dir_fd < 0)
+                return -errno;
+
+        if (fstatat(proc_ns_dir_fd, namespace, &stbuf, /* flags */0) < 0)
+                return -errno;
+
+        *ns = stbuf.st_ino;
+        return 0;
+}
+
+static int get_mount_namespace_leader(pid_t pid, pid_t *container_pid) {
+        pid_t cpid = pid, ppid = 0;
+        ino_t proc_mntns;
+        int r = 0;
+
+        r = get_process_ns(pid, "mnt", &proc_mntns);
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                ino_t parent_mntns;
+
+                r = get_process_ppid(cpid, &ppid);
+                if (r < 0)
+                        return r;
+
+                r = get_process_ns(ppid, "mnt", &parent_mntns);
+                if (r < 0)
+                        return r;
+
+                if (proc_mntns != parent_mntns)
+                        break;
+
+                if (ppid == 1)
+                        return -ENOENT;
+
+                cpid = ppid;
+        }
+
+        *container_pid = ppid;
+        return 0;
+}
+
+/* Returns 1 if the parent was found.
+ * Returns 0 if there is not a process we can call the pid's
+ * container parent (the pid's process isn't 'containerized').
+ * Returns a negative number on errors.
+ */
+static int get_process_container_parent_cmdline(pid_t pid, char** cmdline) {
+        int r = 0;
+        pid_t container_pid;
+        const char *proc_root_path;
+        struct stat root_stat, proc_root_stat;
+
+        /* To compare inodes of / and /proc/[pid]/root */
+        if (stat("/", &root_stat) < 0)
+                return -errno;
+
+        proc_root_path = procfs_file_alloca(pid, "root");
+        if (stat(proc_root_path, &proc_root_stat) < 0)
+                return -errno;
+
+        /* The process uses system root. */
+        if (proc_root_stat.st_ino == root_stat.st_ino) {
+                *cmdline = NULL;
+                return 0;
+        }
+
+        r = get_mount_namespace_leader(pid, &container_pid);
+        if (r < 0)
+                return r;
+
+        r = get_process_cmdline(container_pid, 0, false, cmdline);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int change_uid_gid(const char *context[]) {
+        uid_t uid;
+        gid_t gid;
+        int r;
+
+        r = parse_uid(context[CONTEXT_UID], &uid);
+        if (r < 0)
+                return r;
+
+        if (uid <= SYSTEM_UID_MAX) {
+                const char *user = "systemd-coredump";
+
+                r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
+                if (r < 0) {
+                        log_warning_errno(r, "Cannot resolve %s user. Proceeding to dump core as root: %m", user);
+                        uid = gid = 0;
+                }
+        } else {
+                r = parse_gid(context[CONTEXT_GID], &gid);
+                if (r < 0)
+                        return r;
+        }
+
+        return drop_privileges(uid, gid, 0);
+}
+
+static bool is_journald_crash(const char *context[_CONTEXT_MAX]) {
+        assert(context);
+
+        return streq_ptr(context[CONTEXT_UNIT], SPECIAL_JOURNALD_SERVICE);
+}
+
+static bool is_pid1_crash(const char *context[_CONTEXT_MAX]) {
+        assert(context);
+
+        return streq_ptr(context[CONTEXT_UNIT], SPECIAL_INIT_SCOPE) ||
+                streq_ptr(context[CONTEXT_PID], "1");
+}
+
+#define SUBMIT_COREDUMP_FIELDS 4
+
+static int submit_coredump(
+                const char *context[_CONTEXT_MAX],
+                struct iovec *iovec,
+                size_t n_iovec_allocated,
+                size_t n_iovec,
+                int input_fd) {
+
+        _cleanup_close_ int coredump_fd = -1, coredump_node_fd = -1;
+        _cleanup_free_ char *core_message = NULL, *filename = NULL, *coredump_data = NULL;
+        uint64_t coredump_size = UINT64_MAX;
+        bool truncated = false, journald_crash;
+        int r;
+
+        assert(context);
+        assert(iovec);
+        assert(n_iovec_allocated >= n_iovec + SUBMIT_COREDUMP_FIELDS);
+        assert(input_fd >= 0);
+
+        journald_crash = is_journald_crash(context);
+
+        /* Vacuum before we write anything again */
+        (void) coredump_vacuum(-1, arg_keep_free, arg_max_use);
+
+        /* Always stream the coredump to disk, if that's possible */
+        r = save_external_coredump(context, input_fd,
+                                   &filename, &coredump_node_fd, &coredump_fd, &coredump_size, &truncated);
+        if (r < 0)
+                /* Skip whole core dumping part */
+                goto log;
+
+        /* If we don't want to keep the coredump on disk, remove it now, as later on we will lack the privileges for
+         * it. However, we keep the fd to it, so that we can still process it and log it. */
+        r = maybe_remove_external_coredump(filename, coredump_size);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                const char *coredump_filename;
+
+                coredump_filename = strjoina("COREDUMP_FILENAME=", filename);
+                iovec[n_iovec++] = IOVEC_MAKE_STRING(coredump_filename);
+        } else if (arg_storage == COREDUMP_STORAGE_EXTERNAL)
+                log_info("The core will not be stored: size %"PRIu64" is greater than %"PRIu64" (the configured maximum)",
+                         coredump_size, arg_external_size_max);
+
+        /* Vacuum again, but exclude the coredump we just created */
+        (void) coredump_vacuum(coredump_node_fd >= 0 ? coredump_node_fd : coredump_fd, arg_keep_free, arg_max_use);
+
+        /* Now, let's drop privileges to become the user who owns the segfaulted process and allocate the coredump
+         * memory under the user's uid. This also ensures that the credentials journald will see are the ones of the
+         * coredumping user, thus making sure the user gets access to the core dump. Let's also get rid of all
+         * capabilities, if we run as root, we won't need them anymore. */
+        r = change_uid_gid(context);
+        if (r < 0)
+                return log_error_errno(r, "Failed to drop privileges: %m");
+
+#if HAVE_ELFUTILS
+        /* Try to get a strack trace if we can */
+        if (coredump_size <= arg_process_size_max) {
+                _cleanup_free_ char *stacktrace = NULL;
+
+                r = coredump_make_stack_trace(coredump_fd, context[CONTEXT_EXE], &stacktrace);
+                if (r >= 0)
+                        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
+                                               " (", context[CONTEXT_COMM], ") of user ",
+                                               context[CONTEXT_UID], " dumped core.",
+                                               journald_crash ? "\nCoredump diverted to " : "",
+                                               journald_crash ? filename : "",
+                                               "\n\n", stacktrace);
+                else if (r == -EINVAL)
+                        log_warning("Failed to generate stack trace: %s", dwfl_errmsg(dwfl_errno()));
+                else
+                        log_warning_errno(r, "Failed to generate stack trace: %m");
+        } else
+                log_debug("Not generating stack trace: core size %"PRIu64" is greater than %"PRIu64" (the configured maximum)",
+                          coredump_size, arg_process_size_max);
+
+        if (!core_message)
+#endif
+log:
+        core_message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
+                               " (", context[CONTEXT_COMM], ") of user ",
+                               context[CONTEXT_UID], " dumped core.",
+                               journald_crash && filename ? "\nCoredump diverted to " : NULL,
+                               journald_crash && filename ? filename : NULL);
+        if (!core_message)
+                return log_oom();
+
+        if (journald_crash) {
+                /* We cannot log to the journal, so just print the message.
+                 * The target was set previously to something safe. */
+                assert(startswith(core_message, "MESSAGE="));
+                log_dispatch(LOG_ERR, 0, core_message + strlen("MESSAGE="));
+                return 0;
+        }
+
+        iovec[n_iovec++] = IOVEC_MAKE_STRING(core_message);
+
+        if (truncated)
+                iovec[n_iovec++] = IOVEC_MAKE_STRING("COREDUMP_TRUNCATED=1");
+
+        /* Optionally store the entire coredump in the journal */
+        if (arg_storage == COREDUMP_STORAGE_JOURNAL) {
+                if (coredump_size <= arg_journal_size_max) {
+                        size_t sz = 0;
+
+                        /* Store the coredump itself in the journal */
+
+                        r = allocate_journal_field(coredump_fd, (size_t) coredump_size, &coredump_data, &sz);
+                        if (r >= 0)
+                                iovec[n_iovec++] = IOVEC_MAKE(coredump_data, sz);
+                        else
+                                log_warning_errno(r, "Failed to attach the core to the journal entry: %m");
+                } else
+                        log_info("The core will not be stored: size %"PRIu64" is greater than %"PRIu64" (the configured maximum)",
+                                 coredump_size, arg_journal_size_max);
+        }
+
+        assert(n_iovec <= n_iovec_allocated);
+
+        r = sd_journal_sendv(iovec, n_iovec);
+        if (r < 0)
+                return log_error_errno(r, "Failed to log coredump: %m");
+
+        return 0;
+}
+
+static void map_context_fields(const struct iovec *iovec, const char* context[]) {
+
+        static const char * const context_field_names[] = {
+                [CONTEXT_PID] = "COREDUMP_PID=",
+                [CONTEXT_UID] = "COREDUMP_UID=",
+                [CONTEXT_GID] = "COREDUMP_GID=",
+                [CONTEXT_SIGNAL] = "COREDUMP_SIGNAL=",
+                [CONTEXT_TIMESTAMP] = "COREDUMP_TIMESTAMP=",
+                [CONTEXT_RLIMIT] = "COREDUMP_RLIMIT=",
+                [CONTEXT_HOSTNAME] = "COREDUMP_HOSTNAME=",
+                [CONTEXT_COMM] = "COREDUMP_COMM=",
+                [CONTEXT_EXE] = "COREDUMP_EXE=",
+        };
+
+        unsigned i;
+
+        assert(iovec);
+        assert(context);
+
+        for (i = 0; i < ELEMENTSOF(context_field_names); i++) {
+                char *p;
+
+                if (!context_field_names[i])
+                        continue;
+
+                p = memory_startswith(iovec->iov_base, iovec->iov_len, context_field_names[i]);
+                if (!p)
+                        continue;
+
+                /* Note that these strings are NUL terminated, because we made sure that a trailing NUL byte is in the
+                 * buffer, though not included in the iov_len count. (see below) */
+                context[i] = p;
+                break;
+        }
+}
+
+static int process_socket(int fd) {
+        _cleanup_close_ int coredump_fd = -1;
+        struct iovec *iovec = NULL;
+        size_t n_iovec = 0, n_allocated = 0, i, k;
+        const char *context[_CONTEXT_MAX] = {};
+        int r;
+
+        assert(fd >= 0);
+
+        log_setup_service();
+
+        log_debug("Processing coredump received on stdin...");
+
+        for (;;) {
+                union {
+                        struct cmsghdr cmsghdr;
+                        uint8_t buf[CMSG_SPACE(sizeof(int))];
+                } control = {};
+                struct msghdr mh = {
+                        .msg_control = &control,
+                        .msg_controllen = sizeof(control),
+                        .msg_iovlen = 1,
+                };
+                ssize_t n;
+                ssize_t l;
+
+                if (!GREEDY_REALLOC(iovec, n_allocated, n_iovec + SUBMIT_COREDUMP_FIELDS)) {
+                        r = log_oom();
+                        goto finish;
+                }
+
+                l = next_datagram_size_fd(fd);
+                if (l < 0) {
+                        r = log_error_errno(l, "Failed to determine datagram size to read: %m");
+                        goto finish;
+                }
+
+                assert(l >= 0);
+
+                iovec[n_iovec].iov_len = l;
+                iovec[n_iovec].iov_base = malloc(l + 1);
+                if (!iovec[n_iovec].iov_base) {
+                        r = log_oom();
+                        goto finish;
+                }
+
+                mh.msg_iov = iovec + n_iovec;
+
+                n = recvmsg(fd, &mh, MSG_CMSG_CLOEXEC);
+                if (n < 0)  {
+                        free(iovec[n_iovec].iov_base);
+                        r = log_error_errno(errno, "Failed to receive datagram: %m");
+                        goto finish;
+                }
+
+                if (n == 0) {
+                        struct cmsghdr *cmsg, *found = NULL;
+                        /* The final zero-length datagram carries the file descriptor and tells us that we're done. */
+
+                        free(iovec[n_iovec].iov_base);
+
+                        CMSG_FOREACH(cmsg, &mh) {
+                                if (cmsg->cmsg_level == SOL_SOCKET &&
+                                    cmsg->cmsg_type == SCM_RIGHTS &&
+                                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
+                                        assert(!found);
+                                        found = cmsg;
+                                }
+                        }
+
+                        if (!found) {
+                                log_error("Coredump file descriptor missing.");
+                                r = -EBADMSG;
+                                goto finish;
+                        }
+
+                        assert(coredump_fd < 0);
+                        coredump_fd = *(int*) CMSG_DATA(found);
+                        break;
+                }
+
+                /* Add trailing NUL byte, in case these are strings */
+                ((char*) iovec[n_iovec].iov_base)[n] = 0;
+                iovec[n_iovec].iov_len = (size_t) n;
+
+                cmsg_close_all(&mh);
+                map_context_fields(iovec + n_iovec, context);
+                n_iovec++;
+        }
+
+        if (!GREEDY_REALLOC(iovec, n_allocated, n_iovec + SUBMIT_COREDUMP_FIELDS)) {
+                r = log_oom();
+                goto finish;
+        }
+
+        /* Make sure we got all data we really need */
+        assert(context[CONTEXT_PID]);
+        assert(context[CONTEXT_UID]);
+        assert(context[CONTEXT_GID]);
+        assert(context[CONTEXT_SIGNAL]);
+        assert(context[CONTEXT_TIMESTAMP]);
+        assert(context[CONTEXT_RLIMIT]);
+        assert(context[CONTEXT_HOSTNAME]);
+        assert(context[CONTEXT_COMM]);
+        assert(coredump_fd >= 0);
+
+        /* Small quirk: the journal fields contain the timestamp padded with six zeroes, so that the kernel-supplied 1s
+         * granularity timestamps becomes 1µs granularity, i.e. the granularity systemd usually operates in. Since we
+         * are reconstructing the original kernel context, we chop this off again, here. */
+        k = strlen(context[CONTEXT_TIMESTAMP]);
+        if (k > 6)
+                context[CONTEXT_TIMESTAMP] = strndupa(context[CONTEXT_TIMESTAMP], k - 6);
+
+        r = submit_coredump(context, iovec, n_allocated, n_iovec, coredump_fd);
+
+finish:
+        for (i = 0; i < n_iovec; i++)
+                free(iovec[i].iov_base);
+        free(iovec);
+
+        return r;
+}
+
+static int send_iovec(const struct iovec iovec[], size_t n_iovec, int input_fd) {
+
+        static const union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/coredump",
+        };
+        _cleanup_close_ int fd = -1;
+        size_t i;
+        int r;
+
+        assert(iovec || n_iovec <= 0);
+        assert(input_fd >= 0);
+
+        fd = socket(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
+        if (fd < 0)
+                return log_error_errno(errno, "Failed to create coredump socket: %m");
+
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
+                return log_error_errno(errno, "Failed to connect to coredump service: %m");
+
+        for (i = 0; i < n_iovec; i++) {
+                struct msghdr mh = {
+                        .msg_iov = (struct iovec*) iovec + i,
+                        .msg_iovlen = 1,
+                };
+                struct iovec copy[2];
+
+                for (;;) {
+                        if (sendmsg(fd, &mh, MSG_NOSIGNAL) >= 0)
+                                break;
+
+                        if (errno == EMSGSIZE && mh.msg_iov[0].iov_len > 0) {
+                                /* This field didn't fit? That's a pity. Given that this is just metadata,
+                                 * let's truncate the field at half, and try again. We append three dots, in
+                                 * order to show that this is truncated. */
+
+                                if (mh.msg_iov != copy) {
+                                        /* We don't want to modify the caller's iovec, hence let's create our
+                                         * own array, consisting of two new iovecs, where the first is a
+                                         * (truncated) copy of what we want to send, and the second one
+                                         * contains the trailing dots. */
+                                        copy[0] = iovec[i];
+                                        copy[1] = (struct iovec) {
+                                                .iov_base = (char[]) { '.', '.', '.' },
+                                                .iov_len = 3,
+                                        };
+
+                                        mh.msg_iov = copy;
+                                        mh.msg_iovlen = 2;
+                                }
+
+                                copy[0].iov_len /= 2; /* halve it, and try again */
+                                continue;
+                        }
+
+                        return log_error_errno(errno, "Failed to send coredump datagram: %m");
+                }
+        }
+
+        r = send_one_fd(fd, input_fd, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to send coredump fd: %m");
+
+        return 0;
+}
+
+static char* set_iovec_field_free(struct iovec *iovec, size_t *n_iovec, const char *field, char *value) {
+        char *x;
+
+        x = set_iovec_string_field(iovec, n_iovec, field, value);
+        free(value);
+        return x;
+}
+
+static int gather_pid_metadata(
+                char* context[_CONTEXT_MAX],
+                char **comm_fallback,
+                struct iovec *iovec, size_t *n_iovec) {
+
+        /* We need 27 empty slots in iovec!
+         *
+         * Note that if we fail on oom later on, we do not roll-back changes to the iovec structure. (It remains valid,
+         * with the first n_iovec fields initialized.) */
+
+        uid_t owner_uid;
+        pid_t pid;
+        char *t;
+        const char *p;
+        int r, signo;
+
+        r = parse_pid(context[CONTEXT_PID], &pid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse PID \"%s\": %m", context[CONTEXT_PID]);
+
+        r = get_process_comm(pid, &context[CONTEXT_COMM]);
+        if (r < 0) {
+                log_warning_errno(r, "Failed to get COMM, falling back to the command line: %m");
+                context[CONTEXT_COMM] = strv_join(comm_fallback, " ");
+                if (!context[CONTEXT_COMM])
+                        return log_oom();
+        }
+
+        r = get_process_exe(pid, &context[CONTEXT_EXE]);
+        if (r < 0)
+                log_warning_errno(r, "Failed to get EXE, ignoring: %m");
+
+        if (cg_pid_get_unit(pid, &context[CONTEXT_UNIT]) >= 0) {
+                if (!is_journald_crash((const char**) context)) {
+                        /* OK, now we know it's not the journal, hence we can make use of it now. */
+                        log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
+                        log_open();
+                }
+
+                /* If this is PID 1 disable coredump collection, we'll unlikely be able to process it later on. */
+                if (is_pid1_crash((const char**) context)) {
+                        log_notice("Due to PID 1 having crashed coredump collection will now be turned off.");
+                        disable_coredumps();
+                }
+
+                set_iovec_string_field(iovec, n_iovec, "COREDUMP_UNIT=", context[CONTEXT_UNIT]);
+        }
+
+        if (cg_pid_get_user_unit(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_USER_UNIT=", t);
+
+        /* The next few are mandatory */
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_PID=", context[CONTEXT_PID]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_UID=", context[CONTEXT_UID]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_GID=", context[CONTEXT_GID]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_SIGNAL=", context[CONTEXT_SIGNAL]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_RLIMIT=", context[CONTEXT_RLIMIT]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_HOSTNAME=", context[CONTEXT_HOSTNAME]))
+                return log_oom();
+
+        if (!set_iovec_string_field(iovec, n_iovec, "COREDUMP_COMM=", context[CONTEXT_COMM]))
+                return log_oom();
+
+        if (context[CONTEXT_EXE] &&
+            !set_iovec_string_field(iovec, n_iovec, "COREDUMP_EXE=", context[CONTEXT_EXE]))
+                return log_oom();
+
+        if (sd_pid_get_session(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_SESSION=", t);
+
+        if (sd_pid_get_owner_uid(pid, &owner_uid) >= 0) {
+                r = asprintf(&t, "COREDUMP_OWNER_UID=" UID_FMT, owner_uid);
+                if (r > 0)
+                        iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(t);
+        }
+
+        if (sd_pid_get_slice(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_SLICE=", t);
+
+        if (get_process_cmdline(pid, 0, false, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_CMDLINE=", t);
+
+        if (cg_pid_get_path_shifted(pid, NULL, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_CGROUP=", t);
+
+        if (compose_open_fds(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_OPEN_FDS=", t);
+
+        p = procfs_file_alloca(pid, "status");
+        if (read_full_file(p, &t, NULL) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_PROC_STATUS=", t);
+
+        p = procfs_file_alloca(pid, "maps");
+        if (read_full_file(p, &t, NULL) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_PROC_MAPS=", t);
+
+        p = procfs_file_alloca(pid, "limits");
+        if (read_full_file(p, &t, NULL) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_PROC_LIMITS=", t);
+
+        p = procfs_file_alloca(pid, "cgroup");
+        if (read_full_file(p, &t, NULL) >=0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_PROC_CGROUP=", t);
+
+        p = procfs_file_alloca(pid, "mountinfo");
+        if (read_full_file(p, &t, NULL) >=0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_PROC_MOUNTINFO=", t);
+
+        if (get_process_cwd(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_CWD=", t);
+
+        if (get_process_root(pid, &t) >= 0) {
+                bool proc_self_root_is_slash;
+
+                proc_self_root_is_slash = strcmp(t, "/") == 0;
+
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_ROOT=", t);
+
+                /* If the process' root is "/", then there is a chance it has
+                 * mounted own root and hence being containerized. */
+                if (proc_self_root_is_slash && get_process_container_parent_cmdline(pid, &t) > 0)
+                        set_iovec_field_free(iovec, n_iovec, "COREDUMP_CONTAINER_CMDLINE=", t);
+        }
+
+        if (get_process_environ(pid, &t) >= 0)
+                set_iovec_field_free(iovec, n_iovec, "COREDUMP_ENVIRON=", t);
+
+        t = strjoin("COREDUMP_TIMESTAMP=", context[CONTEXT_TIMESTAMP], "000000");
+        if (t)
+                iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(t);
+
+        if (safe_atoi(context[CONTEXT_SIGNAL], &signo) >= 0 && SIGNAL_VALID(signo))
+                set_iovec_string_field(iovec, n_iovec, "COREDUMP_SIGNAL_NAME=SIG", signal_to_string(signo));
+
+        return 0; /* we successfully acquired all metadata */
+}
+
+static int process_kernel(int argc, char* argv[]) {
+
+        char* context[_CONTEXT_MAX] = {};
+        struct iovec iovec[29 + SUBMIT_COREDUMP_FIELDS];
+        size_t i, n_iovec, n_to_free = 0;
+        int r;
+
+        log_debug("Processing coredump received from the kernel...");
+
+        if (argc < CONTEXT_COMM + 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Not enough arguments passed by the kernel (%i, expected %i).",
+                                       argc - 1, CONTEXT_COMM + 1 - 1);
+
+        context[CONTEXT_PID]       = argv[1 + CONTEXT_PID];
+        context[CONTEXT_UID]       = argv[1 + CONTEXT_UID];
+        context[CONTEXT_GID]       = argv[1 + CONTEXT_GID];
+        context[CONTEXT_SIGNAL]    = argv[1 + CONTEXT_SIGNAL];
+        context[CONTEXT_TIMESTAMP] = argv[1 + CONTEXT_TIMESTAMP];
+        context[CONTEXT_RLIMIT]    = argv[1 + CONTEXT_RLIMIT];
+        context[CONTEXT_HOSTNAME]  = argv[1 + CONTEXT_HOSTNAME];
+
+        r = gather_pid_metadata(context, argv + 1 + CONTEXT_COMM, iovec, &n_to_free);
+        if (r < 0)
+                goto finish;
+
+        n_iovec = n_to_free;
+
+        iovec[n_iovec++] = IOVEC_MAKE_STRING("MESSAGE_ID=" SD_MESSAGE_COREDUMP_STR);
+
+        assert_cc(2 == LOG_CRIT);
+        iovec[n_iovec++] = IOVEC_MAKE_STRING("PRIORITY=2");
+
+        assert(n_iovec <= ELEMENTSOF(iovec));
+
+        if (is_journald_crash((const char**) context) || is_pid1_crash((const char**) context))
+                r = submit_coredump((const char**) context,
+                                    iovec, ELEMENTSOF(iovec), n_iovec,
+                                    STDIN_FILENO);
+        else
+                r = send_iovec(iovec, n_iovec, STDIN_FILENO);
+
+ finish:
+        for (i = 0; i < n_to_free; i++)
+                free(iovec[i].iov_base);
+
+        /* Those fields are allocated by gather_pid_metadata */
+        free(context[CONTEXT_COMM]);
+        free(context[CONTEXT_EXE]);
+        free(context[CONTEXT_UNIT]);
+
+        return r;
+}
+
+static int process_backtrace(int argc, char *argv[]) {
+        char *context[_CONTEXT_MAX] = {};
+        _cleanup_free_ char *message = NULL;
+        _cleanup_free_ struct iovec *iovec = NULL;
+        size_t n_iovec, n_allocated, n_to_free = 0, i;
+        int r;
+        JournalImporter importer = {
+                .fd = STDIN_FILENO,
+        };
+
+        log_debug("Processing backtrace on stdin...");
+
+        if (argc < CONTEXT_COMM + 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Not enough arguments passed (%i, expected %i).",
+                                       argc - 1, CONTEXT_COMM + 1 - 1);
+
+        context[CONTEXT_PID]       = argv[2 + CONTEXT_PID];
+        context[CONTEXT_UID]       = argv[2 + CONTEXT_UID];
+        context[CONTEXT_GID]       = argv[2 + CONTEXT_GID];
+        context[CONTEXT_SIGNAL]    = argv[2 + CONTEXT_SIGNAL];
+        context[CONTEXT_TIMESTAMP] = argv[2 + CONTEXT_TIMESTAMP];
+        context[CONTEXT_RLIMIT]    = argv[2 + CONTEXT_RLIMIT];
+        context[CONTEXT_HOSTNAME]  = argv[2 + CONTEXT_HOSTNAME];
+
+        n_allocated = 34 + COREDUMP_STORAGE_EXTERNAL;
+        /* 26 metadata, 2 static, +unknown input, 4 storage, rounded up */
+        iovec = new(struct iovec, n_allocated);
+        if (!iovec)
+                return log_oom();
+
+        r = gather_pid_metadata(context, argv + 2 + CONTEXT_COMM, iovec, &n_to_free);
+        if (r < 0)
+                goto finish;
+        if (r > 0) {
+                /* This was a special crash, and has already been processed. */
+                r = 0;
+                goto finish;
+        }
+        n_iovec = n_to_free;
+
+        for (;;) {
+                r = journal_importer_process_data(&importer);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to parse journal entry on stdin: %m");
+                        goto finish;
+                }
+                if (r == 1 ||                        /* complete entry */
+                    journal_importer_eof(&importer)) /* end of data */
+                        break;
+        }
+
+        if (!GREEDY_REALLOC(iovec, n_allocated, n_iovec + importer.iovw.count + 2))
+                return log_oom();
+
+        if (journal_importer_eof(&importer)) {
+                log_warning("Did not receive a full journal entry on stdin, ignoring message sent by reporter");
+
+                message = strjoin("MESSAGE=Process ", context[CONTEXT_PID],
+                                  " (", context[CONTEXT_COMM], ")"
+                                  " of user ", context[CONTEXT_UID],
+                                  " failed with ", context[CONTEXT_SIGNAL]);
+                if (!message) {
+                        r = log_oom();
+                        goto finish;
+                }
+                iovec[n_iovec++] = IOVEC_MAKE_STRING(message);
+        } else {
+                for (i = 0; i < importer.iovw.count; i++)
+                        iovec[n_iovec++] = importer.iovw.iovec[i];
+        }
+
+        iovec[n_iovec++] = IOVEC_MAKE_STRING("MESSAGE_ID=" SD_MESSAGE_BACKTRACE_STR);
+        assert_cc(2 == LOG_CRIT);
+        iovec[n_iovec++] = IOVEC_MAKE_STRING("PRIORITY=2");
+
+        assert(n_iovec <= n_allocated);
+
+        r = sd_journal_sendv(iovec, n_iovec);
+        if (r < 0)
+                log_error_errno(r, "Failed to log backtrace: %m");
+
+ finish:
+        for (i = 0; i < n_to_free; i++)
+                free(iovec[i].iov_base);
+
+        /* Those fields are allocated by gather_pid_metadata */
+        free(context[CONTEXT_COMM]);
+        free(context[CONTEXT_EXE]);
+        free(context[CONTEXT_UNIT]);
+
+        return r;
+}
+
+static int run(int argc, char *argv[]) {
+        int r;
+
+        /* First, log to a safe place, since we don't know what crashed and it might
+         * be journald which we'd rather not log to then. */
+
+        log_set_target(LOG_TARGET_KMSG);
+        log_open();
+
+        /* Make sure we never enter a loop */
+        (void) prctl(PR_SET_DUMPABLE, 0);
+
+        /* Ignore all parse errors */
+        (void) parse_config();
+
+        log_debug("Selected storage '%s'.", coredump_storage_to_string(arg_storage));
+        log_debug("Selected compression %s.", yes_no(arg_compress));
+
+        r = sd_listen_fds(false);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine the number of file descriptors: %m");
+
+        /* If we got an fd passed, we are running in coredumpd mode. Otherwise we
+         * are invoked from the kernel as coredump handler. */
+        if (r == 0) {
+                if (streq_ptr(argv[1], "--backtrace"))
+                        return process_backtrace(argc, argv);
+                else
+                        return process_kernel(argc, argv);
+        } else if (r == 1)
+                return process_socket(SD_LISTEN_FDS_START);
+
+        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                               "Received unexpected number of file descriptors.");
+}
+
+DEFINE_MAIN_FUNCTION(run);