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Systemd/src/basic/process-util.c
Lennart Poettering dfd14786b5 util-lib: save/restore errno in cleanup calls 
We should be careful with errno in cleanup functions, and not alter it
under any circumstances. In the safe_close cleanup handlers we are
already safe in that regard, but let's add similar protections on other
cleanup handlers that invoke system calls.

Why bother? Cleanup handlers insert code at function return in
non-obvious ways. Hence, code that sets errno and returns should not be
confused by us overrding the errno from a cleanup handler.

This is a paranoia fix only, I am not aware where this actually mattered
in real-life situations.
2018-01-10 17:21:15 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <linux/oom.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/personality.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <syslog.h>
#include <unistd.h>
#if HAVE_VALGRIND_VALGRIND_H
#include <valgrind/valgrind.h>
#endif
#include "alloc-util.h"
#include "architecture.h"
#include "escape.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "ioprio.h"
#include "log.h"
#include "macro.h"
#include "missing.h"
#include "process-util.h"
#include "raw-clone.h"
#include "signal-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "terminal-util.h"
#include "user-util.h"
#include "util.h"
int get_process_state(pid_t pid) {
const char *p;
char state;
int r;
_cleanup_free_ char *line = NULL;
assert(pid >= 0);
p = procfs_file_alloca(pid, "stat");
r = read_one_line_file(p, &line);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
p = strrchr(line, ')');
if (!p)
return -EIO;
p++;
if (sscanf(p, " %c", &state) != 1)
return -EIO;
return (unsigned char) state;
}
int get_process_comm(pid_t pid, char **name) {
const char *p;
int r;
assert(name);
assert(pid >= 0);
p = procfs_file_alloca(pid, "comm");
r = read_one_line_file(p, name);
if (r == -ENOENT)
return -ESRCH;
return r;
}
int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char **line) {
_cleanup_fclose_ FILE *f = NULL;
bool space = false;
char *k, *ans = NULL;
const char *p;
int c;
assert(line);
assert(pid >= 0);
/* Retrieves a process' command line. Replaces unprintable characters while doing so by whitespace (coalescing
* multiple sequential ones into one). If max_length is != 0 will return a string of the specified size at most
* (the trailing NUL byte does count towards the length here!), abbreviated with a "..." ellipsis. If
* comm_fallback is true and the process has no command line set (the case for kernel threads), or has a
* command line that resolves to the empty string will return the "comm" name of the process instead.
*
* Returns -ESRCH if the process doesn't exist, and -ENOENT if the process has no command line (and
* comm_fallback is false). Returns 0 and sets *line otherwise. */
p = procfs_file_alloca(pid, "cmdline");
f = fopen(p, "re");
if (!f) {
if (errno == ENOENT)
return -ESRCH;
return -errno;
}
(void) __fsetlocking(f, FSETLOCKING_BYCALLER);
if (max_length == 1) {
/* If there's only room for one byte, return the empty string */
ans = new0(char, 1);
if (!ans)
return -ENOMEM;
*line = ans;
return 0;
} else if (max_length == 0) {
size_t len = 0, allocated = 0;
while ((c = getc(f)) != EOF) {
if (!GREEDY_REALLOC(ans, allocated, len+3)) {
free(ans);
return -ENOMEM;
}
if (isprint(c)) {
if (space) {
ans[len++] = ' ';
space = false;
}
ans[len++] = c;
} else if (len > 0)
space = true;
}
if (len > 0)
ans[len] = '\0';
else
ans = mfree(ans);
} else {
bool dotdotdot = false;
size_t left;
ans = new(char, max_length);
if (!ans)
return -ENOMEM;
k = ans;
left = max_length;
while ((c = getc(f)) != EOF) {
if (isprint(c)) {
if (space) {
if (left <= 2) {
dotdotdot = true;
break;
}
*(k++) = ' ';
left--;
space = false;
}
if (left <= 1) {
dotdotdot = true;
break;
}
*(k++) = (char) c;
left--;
} else if (k > ans)
space = true;
}
if (dotdotdot) {
if (max_length <= 4) {
k = ans;
left = max_length;
} else {
k = ans + max_length - 4;
left = 4;
/* Eat up final spaces */
while (k > ans && isspace(k[-1])) {
k--;
left++;
}
}
strncpy(k, "...", left-1);
k[left-1] = 0;
} else
*k = 0;
}
/* Kernel threads have no argv[] */
if (isempty(ans)) {
_cleanup_free_ char *t = NULL;
int h;
free(ans);
if (!comm_fallback)
return -ENOENT;
h = get_process_comm(pid, &t);
if (h < 0)
return h;
if (max_length == 0)
ans = strjoin("[", t, "]");
else {
size_t l;
l = strlen(t);
if (l + 3 <= max_length)
ans = strjoin("[", t, "]");
else if (max_length <= 6) {
ans = new(char, max_length);
if (!ans)
return -ENOMEM;
memcpy(ans, "[...]", max_length-1);
ans[max_length-1] = 0;
} else {
char *e;
t[max_length - 6] = 0;
/* Chop off final spaces */
e = strchr(t, 0);
while (e > t && isspace(e[-1]))
e--;
*e = 0;
ans = strjoin("[", t, "...]");
}
}
if (!ans)
return -ENOMEM;
}
*line = ans;
return 0;
}
int rename_process(const char name[]) {
static size_t mm_size = 0;
static char *mm = NULL;
bool truncated = false;
size_t l;
/* This is a like a poor man's setproctitle(). It changes the comm field, argv[0], and also the glibc's
* internally used name of the process. For the first one a limit of 16 chars applies; to the second one in
* many cases one of 10 (i.e. length of "/sbin/init") — however if we have CAP_SYS_RESOURCES it is unbounded;
* to the third one 7 (i.e. the length of "systemd". If you pass a longer string it will likely be
* truncated.
*
* Returns 0 if a name was set but truncated, > 0 if it was set but not truncated. */
if (isempty(name))
return -EINVAL; /* let's not confuse users unnecessarily with an empty name */
if (!is_main_thread())
return -EPERM; /* Let's not allow setting the process name from other threads than the main one, as we
* cache things without locking, and we make assumptions that PR_SET_NAME sets the
* process name that isn't correct on any other threads */
l = strlen(name);
/* First step, change the comm field. The main thread's comm is identical to the process comm. This means we
* can use PR_SET_NAME, which sets the thread name for the calling thread. */
if (prctl(PR_SET_NAME, name) < 0)
log_debug_errno(errno, "PR_SET_NAME failed: %m");
if (l > 15) /* Linux process names can be 15 chars at max */
truncated = true;
/* Second step, change glibc's ID of the process name. */
if (program_invocation_name) {
size_t k;
k = strlen(program_invocation_name);
strncpy(program_invocation_name, name, k);
if (l > k)
truncated = true;
}
/* Third step, completely replace the argv[] array the kernel maintains for us. This requires privileges, but
* has the advantage that the argv[] array is exactly what we want it to be, and not filled up with zeros at
* the end. This is the best option for changing /proc/self/cmdline. */
/* Let's not bother with this if we don't have euid == 0. Strictly speaking we should check for the
* CAP_SYS_RESOURCE capability which is independent of the euid. In our own code the capability generally is
* present only for euid == 0, hence let's use this as quick bypass check, to avoid calling mmap() if
* PR_SET_MM_ARG_{START,END} fails with EPERM later on anyway. After all geteuid() is dead cheap to call, but
* mmap() is not. */
if (geteuid() != 0)
log_debug("Skipping PR_SET_MM, as we don't have privileges.");
else if (mm_size < l+1) {
size_t nn_size;
char *nn;
nn_size = PAGE_ALIGN(l+1);
nn = mmap(NULL, nn_size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (nn == MAP_FAILED) {
log_debug_errno(errno, "mmap() failed: %m");
goto use_saved_argv;
}
strncpy(nn, name, nn_size);
/* Now, let's tell the kernel about this new memory */
if (prctl(PR_SET_MM, PR_SET_MM_ARG_START, (unsigned long) nn, 0, 0) < 0) {
log_debug_errno(errno, "PR_SET_MM_ARG_START failed, proceeding without: %m");
(void) munmap(nn, nn_size);
goto use_saved_argv;
}
/* And update the end pointer to the new end, too. If this fails, we don't really know what to do, it's
* pretty unlikely that we can rollback, hence we'll just accept the failure, and continue. */
if (prctl(PR_SET_MM, PR_SET_MM_ARG_END, (unsigned long) nn + l + 1, 0, 0) < 0)
log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m");
if (mm)
(void) munmap(mm, mm_size);
mm = nn;
mm_size = nn_size;
} else {
strncpy(mm, name, mm_size);
/* Update the end pointer, continuing regardless of any failure. */
if (prctl(PR_SET_MM, PR_SET_MM_ARG_END, (unsigned long) mm + l + 1, 0, 0) < 0)
log_debug_errno(errno, "PR_SET_MM_ARG_END failed, proceeding without: %m");
}
use_saved_argv:
/* Fourth step: in all cases we'll also update the original argv[], so that our own code gets it right too if
* it still looks here */
if (saved_argc > 0) {
int i;
if (saved_argv[0]) {
size_t k;
k = strlen(saved_argv[0]);
strncpy(saved_argv[0], name, k);
if (l > k)
truncated = true;
}
for (i = 1; i < saved_argc; i++) {
if (!saved_argv[i])
break;
memzero(saved_argv[i], strlen(saved_argv[i]));
}
}
return !truncated;
}
int is_kernel_thread(pid_t pid) {
const char *p;
size_t count;
char c;
bool eof;
FILE *f;
if (IN_SET(pid, 0, 1) || pid == getpid_cached()) /* pid 1, and we ourselves certainly aren't a kernel thread */
return 0;
assert(pid > 1);
p = procfs_file_alloca(pid, "cmdline");
f = fopen(p, "re");
if (!f) {
if (errno == ENOENT)
return -ESRCH;
return -errno;
}
(void) __fsetlocking(f, FSETLOCKING_BYCALLER);
count = fread(&c, 1, 1, f);
eof = feof(f);
fclose(f);
/* Kernel threads have an empty cmdline */
if (count <= 0)
return eof ? 1 : -errno;
return 0;
}
int get_process_capeff(pid_t pid, char **capeff) {
const char *p;
int r;
assert(capeff);
assert(pid >= 0);
p = procfs_file_alloca(pid, "status");
r = get_proc_field(p, "CapEff", WHITESPACE, capeff);
if (r == -ENOENT)
return -ESRCH;
return r;
}
static int get_process_link_contents(const char *proc_file, char **name) {
int r;
assert(proc_file);
assert(name);
r = readlink_malloc(proc_file, name);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
return 0;
}
int get_process_exe(pid_t pid, char **name) {
const char *p;
char *d;
int r;
assert(pid >= 0);
p = procfs_file_alloca(pid, "exe");
r = get_process_link_contents(p, name);
if (r < 0)
return r;
d = endswith(*name, " (deleted)");
if (d)
*d = '\0';
return 0;
}
static int get_process_id(pid_t pid, const char *field, uid_t *uid) {
_cleanup_fclose_ FILE *f = NULL;
char line[LINE_MAX];
const char *p;
assert(field);
assert(uid);
if (pid < 0)
return -EINVAL;
p = procfs_file_alloca(pid, "status");
f = fopen(p, "re");
if (!f) {
if (errno == ENOENT)
return -ESRCH;
return -errno;
}
(void) __fsetlocking(f, FSETLOCKING_BYCALLER);
FOREACH_LINE(line, f, return -errno) {
char *l;
l = strstrip(line);
if (startswith(l, field)) {
l += strlen(field);
l += strspn(l, WHITESPACE);
l[strcspn(l, WHITESPACE)] = 0;
return parse_uid(l, uid);
}
}
return -EIO;
}
int get_process_uid(pid_t pid, uid_t *uid) {
if (pid == 0 || pid == getpid_cached()) {
*uid = getuid();
return 0;
}
return get_process_id(pid, "Uid:", uid);
}
int get_process_gid(pid_t pid, gid_t *gid) {
if (pid == 0 || pid == getpid_cached()) {
*gid = getgid();
return 0;
}
assert_cc(sizeof(uid_t) == sizeof(gid_t));
return get_process_id(pid, "Gid:", gid);
}
int get_process_cwd(pid_t pid, char **cwd) {
const char *p;
assert(pid >= 0);
p = procfs_file_alloca(pid, "cwd");
return get_process_link_contents(p, cwd);
}
int get_process_root(pid_t pid, char **root) {
const char *p;
assert(pid >= 0);
p = procfs_file_alloca(pid, "root");
return get_process_link_contents(p, root);
}
int get_process_environ(pid_t pid, char **env) {
_cleanup_fclose_ FILE *f = NULL;
_cleanup_free_ char *outcome = NULL;
int c;
const char *p;
size_t allocated = 0, sz = 0;
assert(pid >= 0);
assert(env);
p = procfs_file_alloca(pid, "environ");
f = fopen(p, "re");
if (!f) {
if (errno == ENOENT)
return -ESRCH;
return -errno;
}
(void) __fsetlocking(f, FSETLOCKING_BYCALLER);
while ((c = fgetc(f)) != EOF) {
if (!GREEDY_REALLOC(outcome, allocated, sz + 5))
return -ENOMEM;
if (c == '\0')
outcome[sz++] = '\n';
else
sz += cescape_char(c, outcome + sz);
}
if (!outcome) {
outcome = strdup("");
if (!outcome)
return -ENOMEM;
} else
outcome[sz] = '\0';
*env = outcome;
outcome = NULL;
return 0;
}
int get_process_ppid(pid_t pid, pid_t *_ppid) {
int r;
_cleanup_free_ char *line = NULL;
long unsigned ppid;
const char *p;
assert(pid >= 0);
assert(_ppid);
if (pid == 0 || pid == getpid_cached()) {
*_ppid = getppid();
return 0;
}
p = procfs_file_alloca(pid, "stat");
r = read_one_line_file(p, &line);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
/* Let's skip the pid and comm fields. The latter is enclosed
* in () but does not escape any () in its value, so let's
* skip over it manually */
p = strrchr(line, ')');
if (!p)
return -EIO;
p++;
if (sscanf(p, " "
"%*c " /* state */
"%lu ", /* ppid */
&ppid) != 1)
return -EIO;
if ((long unsigned) (pid_t) ppid != ppid)
return -ERANGE;
*_ppid = (pid_t) ppid;
return 0;
}
int wait_for_terminate(pid_t pid, siginfo_t *status) {
siginfo_t dummy;
assert(pid >= 1);
if (!status)
status = &dummy;
for (;;) {
zero(*status);
if (waitid(P_PID, pid, status, WEXITED) < 0) {
if (errno == EINTR)
continue;
return negative_errno();
}
return 0;
}
}
/*
* Return values:
* < 0 : wait_for_terminate() failed to get the state of the
* process, the process was terminated by a signal, or
* failed for an unknown reason.
* >=0 : The process terminated normally, and its exit code is
* returned.
*
* That is, success is indicated by a return value of zero, and an
* error is indicated by a non-zero value.
*
* A warning is emitted if the process terminates abnormally,
* and also if it returns non-zero unless check_exit_code is true.
*/
int wait_for_terminate_and_check(const char *name, pid_t pid, WaitFlags flags) {
_cleanup_free_ char *buffer = NULL;
siginfo_t status;
int r, prio;
assert(pid > 1);
if (!name) {
r = get_process_comm(pid, &buffer);
if (r < 0)
log_debug_errno(r, "Failed to acquire process name of " PID_FMT ", ignoring: %m", pid);
else
name = buffer;
}
prio = flags & WAIT_LOG_ABNORMAL ? LOG_ERR : LOG_DEBUG;
r = wait_for_terminate(pid, &status);
if (r < 0)
return log_full_errno(prio, r, "Failed to wait for %s: %m", strna(name));
if (status.si_code == CLD_EXITED) {
if (status.si_status != EXIT_SUCCESS)
log_full(flags & WAIT_LOG_NON_ZERO_EXIT_STATUS ? LOG_ERR : LOG_DEBUG,
"%s failed with exit status %i.", strna(name), status.si_status);
else
log_debug("%s succeeded.", name);
return status.si_status;
} else if (IN_SET(status.si_code, CLD_KILLED, CLD_DUMPED)) {
log_full(prio, "%s terminated by signal %s.", strna(name), signal_to_string(status.si_status));
return -EPROTO;
}
log_full(prio, "%s failed due to unknown reason.", strna(name));
return -EPROTO;
}
/*
* Return values:
* < 0 : wait_for_terminate_with_timeout() failed to get the state of the
* process, the process timed out, the process was terminated by a
* signal, or failed for an unknown reason.
* >=0 : The process terminated normally with no failures.
*
* Success is indicated by a return value of zero, a timeout is indicated
* by ETIMEDOUT, and all other child failure states are indicated by error
* is indicated by a non-zero value.
*/
int wait_for_terminate_with_timeout(pid_t pid, usec_t timeout) {
sigset_t mask;
int r;
usec_t until;
assert_se(sigemptyset(&mask) == 0);
assert_se(sigaddset(&mask, SIGCHLD) == 0);
/* Drop into a sigtimewait-based timeout. Waiting for the
* pid to exit. */
until = now(CLOCK_MONOTONIC) + timeout;
for (;;) {
usec_t n;
siginfo_t status = {};
struct timespec ts;
n = now(CLOCK_MONOTONIC);
if (n >= until)
break;
r = sigtimedwait(&mask, NULL, timespec_store(&ts, until - n)) < 0 ? -errno : 0;
/* Assuming we woke due to the child exiting. */
if (waitid(P_PID, pid, &status, WEXITED|WNOHANG) == 0) {
if (status.si_pid == pid) {
/* This is the correct child.*/
if (status.si_code == CLD_EXITED)
return (status.si_status == 0) ? 0 : -EPROTO;
else
return -EPROTO;
}
}
/* Not the child, check for errors and proceed appropriately */
if (r < 0) {
switch (r) {
case -EAGAIN:
/* Timed out, child is likely hung. */
return -ETIMEDOUT;
case -EINTR:
/* Received a different signal and should retry */
continue;
default:
/* Return any unexpected errors */
return r;
}
}
}
return -EPROTO;
}
void sigkill_wait(pid_t pid) {
assert(pid > 1);
if (kill(pid, SIGKILL) > 0)
(void) wait_for_terminate(pid, NULL);
}
void sigkill_waitp(pid_t *pid) {
PROTECT_ERRNO;
if (!pid)
return;
if (*pid <= 1)
return;
sigkill_wait(*pid);
}
int kill_and_sigcont(pid_t pid, int sig) {
int r;
r = kill(pid, sig) < 0 ? -errno : 0;
/* If this worked, also send SIGCONT, unless we already just sent a SIGCONT, or SIGKILL was sent which isn't
* affected by a process being suspended anyway. */
if (r >= 0 && !IN_SET(sig, SIGCONT, SIGKILL))
(void) kill(pid, SIGCONT);
return r;
}
int getenv_for_pid(pid_t pid, const char *field, char **_value) {
_cleanup_fclose_ FILE *f = NULL;
char *value = NULL;
int r;
bool done = false;
size_t l;
const char *path;
assert(pid >= 0);
assert(field);
assert(_value);
path = procfs_file_alloca(pid, "environ");
f = fopen(path, "re");
if (!f) {
if (errno == ENOENT)
return -ESRCH;
return -errno;
}
(void) __fsetlocking(f, FSETLOCKING_BYCALLER);
l = strlen(field);
r = 0;
do {
char line[LINE_MAX];
unsigned i;
for (i = 0; i < sizeof(line)-1; i++) {
int c;
c = getc(f);
if (_unlikely_(c == EOF)) {
done = true;
break;
} else if (c == 0)
break;
line[i] = c;
}
line[i] = 0;
if (strneq(line, field, l) && line[l] == '=') {
value = strdup(line + l + 1);
if (!value)
return -ENOMEM;
r = 1;
break;
}
} while (!done);
*_value = value;
return r;
}
bool pid_is_unwaited(pid_t pid) {
/* Checks whether a PID is still valid at all, including a zombie */
if (pid < 0)
return false;
if (pid <= 1) /* If we or PID 1 would be dead and have been waited for, this code would not be running */
return true;
if (pid == getpid_cached())
return true;
if (kill(pid, 0) >= 0)
return true;
return errno != ESRCH;
}
bool pid_is_alive(pid_t pid) {
int r;
/* Checks whether a PID is still valid and not a zombie */
if (pid < 0)
return false;
if (pid <= 1) /* If we or PID 1 would be a zombie, this code would not be running */
return true;
if (pid == getpid_cached())
return true;
r = get_process_state(pid);
if (IN_SET(r, -ESRCH, 'Z'))
return false;
return true;
}
int pid_from_same_root_fs(pid_t pid) {
const char *root;
if (pid < 0)
return false;
if (pid == 0 || pid == getpid_cached())
return true;
root = procfs_file_alloca(pid, "root");
return files_same(root, "/proc/1/root", 0);
}
bool is_main_thread(void) {
static thread_local int cached = 0;
if (_unlikely_(cached == 0))
cached = getpid_cached() == gettid() ? 1 : -1;
return cached > 0;
}
noreturn void freeze(void) {
log_close();
/* Make sure nobody waits for us on a socket anymore */
close_all_fds(NULL, 0);
sync();
for (;;)
pause();
}
bool oom_score_adjust_is_valid(int oa) {
return oa >= OOM_SCORE_ADJ_MIN && oa <= OOM_SCORE_ADJ_MAX;
}
unsigned long personality_from_string(const char *p) {
int architecture;
if (!p)
return PERSONALITY_INVALID;
/* Parse a personality specifier. We use our own identifiers that indicate specific ABIs, rather than just
* hints regarding the register size, since we want to keep things open for multiple locally supported ABIs for
* the same register size. */
architecture = architecture_from_string(p);
if (architecture < 0)
return PERSONALITY_INVALID;
if (architecture == native_architecture())
return PER_LINUX;
#ifdef SECONDARY_ARCHITECTURE
if (architecture == SECONDARY_ARCHITECTURE)
return PER_LINUX32;
#endif
return PERSONALITY_INVALID;
}
const char* personality_to_string(unsigned long p) {
int architecture = _ARCHITECTURE_INVALID;
if (p == PER_LINUX)
architecture = native_architecture();
#ifdef SECONDARY_ARCHITECTURE
else if (p == PER_LINUX32)
architecture = SECONDARY_ARCHITECTURE;
#endif
if (architecture < 0)
return NULL;
return architecture_to_string(architecture);
}
int safe_personality(unsigned long p) {
int ret;
/* So here's the deal, personality() is weirdly defined by glibc. In some cases it returns a failure via errno,
* and in others as negative return value containing an errno-like value. Let's work around this: this is a
* wrapper that uses errno if it is set, and uses the return value otherwise. And then it sets both errno and
* the return value indicating the same issue, so that we are definitely on the safe side.
*
* See https://github.com/systemd/systemd/issues/6737 */
errno = 0;
ret = personality(p);
if (ret < 0) {
if (errno != 0)
return -errno;
errno = -ret;
}
return ret;
}
int opinionated_personality(unsigned long *ret) {
int current;
/* Returns the current personality, or PERSONALITY_INVALID if we can't determine it. This function is a bit
* opinionated though, and ignores all the finer-grained bits and exotic personalities, only distinguishing the
* two most relevant personalities: PER_LINUX and PER_LINUX32. */
current = safe_personality(PERSONALITY_INVALID);
if (current < 0)
return current;
if (((unsigned long) current & 0xffff) == PER_LINUX32)
*ret = PER_LINUX32;
else
*ret = PER_LINUX;
return 0;
}
void valgrind_summary_hack(void) {
#if HAVE_VALGRIND_VALGRIND_H
if (getpid_cached() == 1 && RUNNING_ON_VALGRIND) {
pid_t pid;
pid = raw_clone(SIGCHLD);
if (pid < 0)
log_emergency_errno(errno, "Failed to fork off valgrind helper: %m");
else if (pid == 0)
exit(EXIT_SUCCESS);
else {
log_info("Spawned valgrind helper as PID "PID_FMT".", pid);
(void) wait_for_terminate(pid, NULL);
}
}
#endif
}
int pid_compare_func(const void *a, const void *b) {
const pid_t *p = a, *q = b;
/* Suitable for usage in qsort() */
if (*p < *q)
return -1;
if (*p > *q)
return 1;
return 0;
}
int ioprio_parse_priority(const char *s, int *ret) {
int i, r;
assert(s);
assert(ret);
r = safe_atoi(s, &i);
if (r < 0)
return r;
if (!ioprio_priority_is_valid(i))
return -EINVAL;
*ret = i;
return 0;
}
/* The cached PID, possible values:
*
* == UNSET [0] → cache not initialized yet
* == BUSY [-1] → some thread is initializing it at the moment
* any other → the cached PID
*/
#define CACHED_PID_UNSET ((pid_t) 0)
#define CACHED_PID_BUSY ((pid_t) -1)
static pid_t cached_pid = CACHED_PID_UNSET;
void reset_cached_pid(void) {
/* Invoked in the child after a fork(), i.e. at the first moment the PID changed */
cached_pid = CACHED_PID_UNSET;
}
/* We use glibc __register_atfork() + __dso_handle directly here, as they are not included in the glibc
* headers. __register_atfork() is mostly equivalent to pthread_atfork(), but doesn't require us to link against
* libpthread, as it is part of glibc anyway. */
extern int __register_atfork(void (*prepare) (void), void (*parent) (void), void (*child) (void), void * __dso_handle);
extern void* __dso_handle __attribute__ ((__weak__));
pid_t getpid_cached(void) {
pid_t current_value;
/* getpid_cached() is much like getpid(), but caches the value in local memory, to avoid having to invoke a
* system call each time. This restores glibc behaviour from before 2.24, when getpid() was unconditionally
* cached. Starting with 2.24 getpid() started to become prohibitively expensive when used for detecting when
* objects were used across fork()s. With this caching the old behaviour is somewhat restored.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=1443976
* https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c579f48edba88380635ab98cb612030e3ed8691e
*/
current_value = __sync_val_compare_and_swap(&cached_pid, CACHED_PID_UNSET, CACHED_PID_BUSY);
switch (current_value) {
case CACHED_PID_UNSET: { /* Not initialized yet, then do so now */
pid_t new_pid;
new_pid = getpid();
if (__register_atfork(NULL, NULL, reset_cached_pid, __dso_handle) != 0) {
/* OOM? Let's try again later */
cached_pid = CACHED_PID_UNSET;
return new_pid;
}
cached_pid = new_pid;
return new_pid;
}
case CACHED_PID_BUSY: /* Somebody else is currently initializing */
return getpid();
default: /* Properly initialized */
return current_value;
}
}
int must_be_root(void) {
if (geteuid() == 0)
return 0;
log_error("Need to be root.");
return -EPERM;
}
int safe_fork_full(
const char *name,
const int except_fds[],
size_t n_except_fds,
ForkFlags flags,
pid_t *ret_pid) {
pid_t original_pid, pid;
sigset_t saved_ss, ss;
bool block_signals = false;
int prio, r;
/* A wrapper around fork(), that does a couple of important initializations in addition to mere forking. Always
* returns the child's PID in *ret_pid. Returns == 0 in the child, and > 0 in the parent. */
prio = flags & FORK_LOG ? LOG_ERR : LOG_DEBUG;
original_pid = getpid_cached();
if (flags & (FORK_RESET_SIGNALS|FORK_DEATHSIG)) {
/* We temporarily block all signals, so that the new child has them blocked initially. This way, we can
* be sure that SIGTERMs are not lost we might send to the child. */
if (sigfillset(&ss) < 0)
return log_full_errno(prio, errno, "Failed to reset signal set: %m");
block_signals = true;
} else if (flags & FORK_WAIT) {
/* Let's block SIGCHLD at least, so that we can safely watch for the child process */
if (sigemptyset(&ss) < 0)
return log_full_errno(prio, errno, "Failed to clear signal set: %m");
if (sigaddset(&ss, SIGCHLD) < 0)
return log_full_errno(prio, errno, "Failed to add SIGCHLD to signal set: %m");
block_signals = true;
}
if (block_signals)
if (sigprocmask(SIG_SETMASK, &ss, &saved_ss) < 0)
return log_full_errno(prio, errno, "Failed to set signal mask: %m");
if (flags & FORK_NEW_MOUNTNS)
pid = raw_clone(SIGCHLD|CLONE_NEWNS);
else
pid = fork();
if (pid < 0) {
r = -errno;
if (block_signals) /* undo what we did above */
(void) sigprocmask(SIG_SETMASK, &saved_ss, NULL);
return log_full_errno(prio, r, "Failed to fork: %m");
}
if (pid > 0) {
/* We are in the parent process */
log_debug("Successfully forked off '%s' as PID " PID_FMT ".", strna(name), pid);
if (flags & FORK_WAIT) {
r = wait_for_terminate_and_check(name, pid, (flags & FORK_LOG ? WAIT_LOG : 0));
if (r < 0)
return r;
if (r != EXIT_SUCCESS) /* exit status > 0 should be treated as failure, too */
return -EPROTO;
}
if (block_signals) /* undo what we did above */
(void) sigprocmask(SIG_SETMASK, &saved_ss, NULL);
if (ret_pid)
*ret_pid = pid;
return 1;
}
/* We are in the child process */
if (flags & FORK_REOPEN_LOG) {
/* Close the logs if requested, before we log anything. And make sure we reopen it if needed. */
log_close();
log_set_open_when_needed(true);
}
if (name) {
r = rename_process(name);
if (r < 0)
log_full_errno(flags & FORK_LOG ? LOG_WARNING : LOG_DEBUG,
r, "Failed to rename process, ignoring: %m");
}
if (flags & FORK_DEATHSIG)
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0) {
log_full_errno(prio, errno, "Failed to set death signal: %m");
_exit(EXIT_FAILURE);
}
if (flags & FORK_RESET_SIGNALS) {
r = reset_all_signal_handlers();
if (r < 0) {
log_full_errno(prio, r, "Failed to reset signal handlers: %m");
_exit(EXIT_FAILURE);
}
/* This implicitly undoes the signal mask stuff we did before the fork()ing above */
r = reset_signal_mask();
if (r < 0) {
log_full_errno(prio, r, "Failed to reset signal mask: %m");
_exit(EXIT_FAILURE);
}
} else if (block_signals) { /* undo what we did above */
if (sigprocmask(SIG_SETMASK, &saved_ss, NULL) < 0) {
log_full_errno(prio, errno, "Failed to restore signal mask: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_DEATHSIG) {
pid_t ppid;
/* Let's see if the parent PID is still the one we started from? If not, then the parent
* already died by the time we set PR_SET_PDEATHSIG, hence let's emulate the effect */
ppid = getppid();
if (ppid == 0)
/* Parent is in a differn't PID namespace. */;
else if (ppid != original_pid) {
log_debug("Parent died early, raising SIGTERM.");
(void) raise(SIGTERM);
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_CLOSE_ALL_FDS) {
/* Close the logs here in case it got reopened above, as close_all_fds() would close them for us */
log_close();
r = close_all_fds(except_fds, n_except_fds);
if (r < 0) {
log_full_errno(prio, r, "Failed to close all file descriptors: %m");
_exit(EXIT_FAILURE);
}
}
/* When we were asked to reopen the logs, do so again now */
if (flags & FORK_REOPEN_LOG) {
log_open();
log_set_open_when_needed(false);
}
if (flags & FORK_NULL_STDIO) {
r = make_null_stdio();
if (r < 0) {
log_full_errno(prio, r, "Failed to connect stdin/stdout to /dev/null: %m");
_exit(EXIT_FAILURE);
}
}
if (ret_pid)
*ret_pid = getpid_cached();
return 0;
}
int fork_agent(const char *name, const int except[], unsigned n_except, pid_t *ret_pid, const char *path, ...) {
bool stdout_is_tty, stderr_is_tty;
unsigned n, i;
va_list ap;
char **l;
int r;
assert(path);
/* Spawns a temporary TTY agent, making sure it goes away when we go away */
r = safe_fork_full(name, except, n_except, FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_CLOSE_ALL_FDS, ret_pid);
if (r < 0)
return r;
if (r > 0)
return 0;
/* In the child: */
stdout_is_tty = isatty(STDOUT_FILENO);
stderr_is_tty = isatty(STDERR_FILENO);
if (!stdout_is_tty || !stderr_is_tty) {
int fd;
/* Detach from stdout/stderr. and reopen
* /dev/tty for them. This is important to
* ensure that when systemctl is started via
* popen() or a similar call that expects to
* read EOF we actually do generate EOF and
* not delay this indefinitely by because we
* keep an unused copy of stdin around. */
fd = open("/dev/tty", O_WRONLY);
if (fd < 0) {
log_error_errno(errno, "Failed to open /dev/tty: %m");
_exit(EXIT_FAILURE);
}
if (!stdout_is_tty && dup2(fd, STDOUT_FILENO) < 0) {
log_error_errno(errno, "Failed to dup2 /dev/tty: %m");
_exit(EXIT_FAILURE);
}
if (!stderr_is_tty && dup2(fd, STDERR_FILENO) < 0) {
log_error_errno(errno, "Failed to dup2 /dev/tty: %m");
_exit(EXIT_FAILURE);
}
if (fd > STDERR_FILENO)
close(fd);
}
/* Count arguments */
va_start(ap, path);
for (n = 0; va_arg(ap, char*); n++)
;
va_end(ap);
/* Allocate strv */
l = alloca(sizeof(char *) * (n + 1));
/* Fill in arguments */
va_start(ap, path);
for (i = 0; i <= n; i++)
l[i] = va_arg(ap, char*);
va_end(ap);
execv(path, l);
_exit(EXIT_FAILURE);
}
static const char *const ioprio_class_table[] = {
[IOPRIO_CLASS_NONE] = "none",
[IOPRIO_CLASS_RT] = "realtime",
[IOPRIO_CLASS_BE] = "best-effort",
[IOPRIO_CLASS_IDLE] = "idle"
};
DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(ioprio_class, int, INT_MAX);
static const char *const sigchld_code_table[] = {
[CLD_EXITED] = "exited",
[CLD_KILLED] = "killed",
[CLD_DUMPED] = "dumped",
[CLD_TRAPPED] = "trapped",
[CLD_STOPPED] = "stopped",
[CLD_CONTINUED] = "continued",
};
DEFINE_STRING_TABLE_LOOKUP(sigchld_code, int);
static const char* const sched_policy_table[] = {
[SCHED_OTHER] = "other",
[SCHED_BATCH] = "batch",
[SCHED_IDLE] = "idle",
[SCHED_FIFO] = "fifo",
[SCHED_RR] = "rr"
};
DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(sched_policy, int, INT_MAX);
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