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systemctl-whoami: use pidfd to refer to processes

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While at it, rephrase the output a bit. Before this commit, if
the pid doesn't exist, we output something hard to interpret -
"Failed to get unit for ourselves".
This commit is contained in:
Mike Yuan 2023-11-25 22:10:16 +08:00 committed by Luca Boccassi
parent cbc51d0cf4
commit fb45185d98
1 changed files with 134 additions and 30 deletions
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164
src/systemctl/systemctl-whoami.c
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@ -1,24 +1,39 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "bus-common-errors.h"
#include "bus-error.h"
#include "bus-locator.h"
#include "format-util.h"
#include "parse-util.h"
#include "pidref.h"
#include "process-util.h"
#include "systemctl.h"
#include "systemctl-util.h"
#include "systemctl-whoami.h"
#include "parse-util.h"
static int lookup_pid(sd_bus *bus, pid_t pid) {
static int get_unit_by_pid(sd_bus *bus, pid_t pid, char **ret) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
_cleanup_free_ char *unit = NULL;
const char *path;
int r;
r = bus_call_method(bus, bus_systemd_mgr, "GetUnitByPID", &error, &reply, "u", (uint32_t) pid);
if (r < 0)
return log_error_errno(r, "Failed to get unit for ourselves: %s", bus_error_message(&error, r));
assert(bus);
assert(pid >= 0); /* 0 is accepted by GetUnitByPID for querying our own process. */
assert(ret);
r = sd_bus_message_read(reply, "o", &path);
r = bus_call_method(bus, bus_systemd_mgr, "GetUnitByPID", &error, &reply, "u", (uint32_t) pid);
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_NO_UNIT_FOR_PID))
return log_error_errno(r, "%s", bus_error_message(&error, r));
return log_error_errno(r,
"Failed to get unit that PID " PID_FMT " belongs to: %s",
pid > 0 ? pid : getpid_cached(),
bus_error_message(&error, r));
}
r = sd_bus_message_read_basic(reply, 'o', &path);
if (r < 0)
return bus_log_parse_error(r);
@ -26,7 +41,103 @@ static int lookup_pid(sd_bus *bus, pid_t pid) {
if (r < 0)
return log_error_errno(r, "Failed to extract unit name from D-Bus object path '%s': %m", path);
printf("%s\n", unit);
*ret = TAKE_PTR(unit);
return 0;
}
static int lookup_pidfd(sd_bus *bus, const PidRef *pid, char **ret) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
const char *unit;
int r;
assert(bus);
assert(pidref_is_set(pid));
assert(ret);
if (pid->fd < 0)
return -EOPNOTSUPP;
r = bus_call_method(bus, bus_systemd_mgr, "GetUnitByPIDFD", &error, &reply, "h", pid->fd);
if (r < 0) {
if (sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD))
return -EOPNOTSUPP;
if (sd_bus_error_has_names(&error, BUS_ERROR_NO_UNIT_FOR_PID, BUS_ERROR_NO_SUCH_PROCESS))
return log_error_errno(r, "%s", bus_error_message(&error, r));
return log_error_errno(r,
"Failed to get unit that PID " PID_FMT " belongs to: %s",
pid->pid, bus_error_message(&error, r));
}
r = sd_bus_message_read(reply, "os", NULL, &unit);
if (r < 0)
return bus_log_parse_error(r);
char *u = strdup(unit);
if (!u)
return log_oom();
*ret = TAKE_PTR(u);
return 0;
}
static int lookup_pid(sd_bus *bus, const char *pidstr) {
_cleanup_free_ char *unit = NULL;
int r;
assert(bus);
assert(pidstr);
if (arg_transport == BUS_TRANSPORT_LOCAL) {
static bool use_pidfd = true;
_cleanup_(pidref_done) PidRef pid = PIDREF_NULL;
r = pidref_set_pidstr(&pid, pidstr);
if (r < 0)
return log_error_errno(r,
r == -ESRCH ?
"PID %s doesn't exist or is already gone." :
"Failed to create reference to PID %s: %m",
pidstr);
if (use_pidfd) {
r = lookup_pidfd(bus, &pid, &unit);
if (r == -EOPNOTSUPP) {
use_pidfd = false;
log_debug_errno(r, "Unable to look up process using pidfd, ignoring.");
} else if (r < 0)
return r;
}
if (!use_pidfd) {
assert(!unit);
r = get_unit_by_pid(bus, pid.pid, &unit);
if (r < 0)
return r;
r = pidref_verify(&pid);
if (r < 0)
return log_error_errno(r,
"Failed to verify our reference to PID " PID_FMT ": %m",
pid.pid);
}
} else {
pid_t pid;
r = parse_pid(pidstr, &pid);
if (r < 0)
return log_error_errno(r, "Failed to parse PID %s: %m", pidstr);
r = get_unit_by_pid(bus, pid, &unit);
if (r < 0)
return r;
}
puts(unit);
return 0;
}
@ -38,33 +149,26 @@ int verb_whoami(int argc, char *argv[], void *userdata) {
if (r < 0)
return r;
char **pids = strv_skip(argv, 1);
if (strv_isempty(pids)) {
if (argc <= 1) {
_cleanup_free_ char *unit = NULL;
if (arg_transport != BUS_TRANSPORT_LOCAL)
return log_error_errno(SYNTHETIC_ERRNO(EREMOTE), "Refusing to look up local PID on remote host.");
return log_error_errno(SYNTHETIC_ERRNO(EREMOTE), "Refusing to look up our local PID on remote host.");
return lookup_pid(bus, 0);
} else {
int ret = 0;
/* Our own process can never go away while querying, hence no need to open pidfd. */
STRV_FOREACH(p, pids) {
pid_t pid;
r = get_unit_by_pid(bus, 0, &unit);
if (r < 0)
return r;
r = parse_pid(*p, &pid);
if (r < 0) {
log_error_errno(r, "Failed to parse PID: %s", *p);
if (ret >= 0)
ret = r;
continue;
}
r = lookup_pid(bus, pid);
if (r < 0 && ret >= 0)
ret = r;
}
return ret;
puts(unit);
return 0;
}
r = 0;
STRV_FOREACH(pid, strv_skip(argv, 1))
RET_GATHER(r, lookup_pid(bus, *pid));
return r;
}