LXR busybox/libbb/find_pid_by

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Utility routines.
   4 *
   5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   6 *
   7 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
   8 */
   9
  10#include "libbb.h"
  11
  12/*
  13In Linux we have three ways to determine "process name":
  141. /proc/PID/stat has "...(name)...", among other things. It's so-called "comm" field.
  152. /proc/PID/cmdline's first NUL-terminated string. It's argv[0] from exec syscall.
  163. /proc/PID/exe symlink. Points to the running executable file.
  17
  18kernel threads:
  19 comm: thread name
  20 cmdline: empty
  21 exe: <readlink fails>
  22
  23executable
  24 comm: first 15 chars of base name
  25 (if executable is a symlink, then first 15 chars of symlink name are used)
  26 cmdline: argv[0] from exec syscall
  27 exe: points to executable (resolves symlink, unlike comm)
  28
  29script (an executable with #!/path/to/interpreter):
  30 comm: first 15 chars of script's base name (symlinks are not resolved)
  31 cmdline: /path/to/interpreter (symlinks are not resolved)
  32 (script name is in argv[1], args are pushed into argv[2] etc)
  33 exe: points to interpreter's executable (symlinks are resolved)
  34
  35If FEATURE_PREFER_APPLETS=y (and more so if FEATURE_SH_STANDALONE=y),
  36some commands started from busybox shell, xargs or find are started by
  37execXXX("/proc/self/exe", applet_name, params....)
  38and therefore comm field contains "exe".
  39*/
  40
  41static int comm_match(procps_status_t *p, const char *procName)
  42{
  43        int argv1idx;
  44        const char *argv1;
  45
  46        if (strncmp(p->comm, procName, 15) != 0)
  47                return 0; /* comm does not match */
  48
  49        /* In Linux, if comm is 15 chars, it is truncated.
  50         * (or maybe the name was exactly 15 chars, but there is
  51         * no way to know that) */
  52        if (p->comm[14] == '\0')
  53                return 1; /* comm is not truncated - matches */
  54
  55        /* comm is truncated, but first 15 chars match.
  56         * This can be crazily_long_script_name.sh!
  57         * The telltale sign is basename(argv[1]) == procName */
  58
  59        if (!p->argv0)
  60                return 0;
  61
  62        argv1idx = strlen(p->argv0) + 1;
  63        if (argv1idx >= p->argv_len)
  64                return 0;
  65        argv1 = p->argv0 + argv1idx;
  66
  67        if (strcmp(bb_basename(argv1), procName) != 0)
  68                return 0;
  69
  70        return 1;
  71}
  72
  73/* This finds the pid of the specified process.
  74 * Currently, it's implemented by rummaging through
  75 * the proc filesystem.
  76 *
  77 * Returns a list of all matching PIDs
  78 * It is the caller's duty to free the returned pidlist.
  79 *
  80 * Modified by Vladimir Oleynik for use with libbb/procps.c
  81 */
  82pid_t* FAST_FUNC find_pid_by_name(const char *procName)
  83{
  84        pid_t* pidList;
  85        int i = 0;
  86        procps_status_t* p = NULL;
  87
  88        pidList = xzalloc(sizeof(*pidList));
  89        while ((p = procps_scan(p, PSSCAN_PID|PSSCAN_COMM|PSSCAN_ARGVN|PSSCAN_EXE))) {
  90                if (comm_match(p, procName)
  91                /* or we require argv0 to match (essential for matching reexeced /proc/self/exe)*/
  92                 || (p->argv0 && strcmp(bb_basename(p->argv0), procName) == 0)
  93                /* or we require /proc/PID/exe link to match */
  94                 || (p->exe && strcmp(bb_basename(p->exe), procName) == 0)
  95                ) {
  96                        pidList = xrealloc_vector(pidList, 2, i);
  97                        pidList[i++] = p->pid;
  98                }
  99        }
 100
 101        pidList[i] = 0;
 102        return pidList;
 103}
 104
 105pid_t* FAST_FUNC pidlist_reverse(pid_t *pidList)
 106{
 107        int i = 0;
 108        while (pidList[i])
 109                i++;
 110        if (--i >= 0) {
 111                pid_t k;
 112                int j;
 113                for (j = 0; i > j; i--, j++) {
 114                        k = pidList[i];
 115                        pidList[i] = pidList[j];
 116                        pidList[j] = k;
 117                }
 118        }
 119        return pidList;
 120}
 121