diff -Naur a/misc-utils/kill.1.adoc b/misc-utils/kill.1.adoc --- a/misc-utils/kill.1.adoc 2022-02-13 23:49:01.403480088 -0800 +++ b/misc-utils/kill.1.adoc 2022-12-07 16:37:26.037765934 -0800 @@ -62,6 +62,8 @@ Do not restrict the command-name-to-PID conversion to processes with the same UID as the present process. *-p*, *--pid*:: Only print the process ID (PID) of the named processes, do not send any signals. +*-r*, *--require-handler*:: +Do not send the signal if it is not caught in userspace by the signalled process. *--verbose*:: Print PID(s) that will be signaled with *kill* along with the signal. *-q*, *--queue* _value_:: diff -Naur a/misc-utils/kill.c b/misc-utils/kill.c --- a/misc-utils/kill.c 2022-02-13 23:49:01.403480088 -0800 +++ b/misc-utils/kill.c 2022-12-07 16:38:05.231013950 -0800 @@ -93,6 +93,7 @@ check_all:1, do_kill:1, do_pid:1, + require_handler:1, use_sigval:1, #ifdef UL_HAVE_PIDFD timeout:1, @@ -210,6 +211,7 @@ fputs(_(" -p, --pid print pids without signaling them\n"), out); fputs(_(" -l, --list[=] list signal names, or convert a signal number to a name\n"), out); fputs(_(" -L, --table list signal names and numbers\n"), out); + fputs(_(" -r, --require-handler do not send signal if signal handler is not present\n"), out); fputs(_(" --verbose print pids that will be signaled\n"), out); fputs(USAGE_SEPARATOR, out); @@ -300,6 +302,10 @@ print_all_signals(stdout, 1); exit(EXIT_SUCCESS); } + if (!strcmp(arg, "-r") || !strcmp(arg, "--require-handler")) { + ctl->require_handler = 1; + continue; + } if (!strcmp(arg, "-p") || !strcmp(arg, "--pid")) { ctl->do_pid = 1; if (ctl->do_kill) @@ -446,6 +452,32 @@ return rc; } +static int check_signal_handler(const struct kill_control *ctl) +{ + uintmax_t sigcgt = 0; + int rc = 0, has_hnd = 0; + struct path_cxt *pc; + + if (!ctl->require_handler) + return 1; + + pc = ul_new_procfs_path(ctl->pid, NULL); + if (!pc) + return -ENOMEM; + + rc = procfs_process_get_stat_nth(pc, 34, &sigcgt); + if (rc) + return -EINVAL; + + ul_unref_path(pc); + + has_hnd = ((1UL << (ctl->numsig - 1)) & sigcgt) != 0; + if (ctl->verbose && !has_hnd) + printf(_("not signalling pid %d, it has no userspace handler for signal %d\n"), ctl->pid, ctl->numsig); + + return has_hnd; +} + int main(int argc, char **argv) { struct kill_control ctl = { .numsig = SIGTERM }; @@ -468,6 +500,8 @@ errno = 0; ctl.pid = strtol(ctl.arg, &ep, 10); if (errno == 0 && ep && *ep == '\0' && ctl.arg < ep) { + if (check_signal_handler(&ctl) <= 0) + continue; if (kill_verbose(&ctl) != 0) nerrs++; ct++; @@ -482,6 +516,8 @@ proc_processes_filter_by_name(ps, ctl.arg); while (proc_next_pid(ps, &ctl.pid) == 0) { + if (check_signal_handler(&ctl) <= 0) + continue; if (kill_verbose(&ctl) != 0) nerrs++; ct++;