release/src/router/busybox/libbb/find_pid_by_name.c

   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 GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9
  10 #include "libbb.h"
  11
  12 /*
  13 In Linux we have three ways to determine "process name":
  14 1. /proc/PID/stat has "...(name)...", among other things. It's so-called "comm" field.
  15 2. /proc/PID/cmdline's first NUL-terminated string. It's argv[0] from exec syscall.
  16 3. /proc/PID/exe symlink. Points to the running executable file.
  17
  18 kernel threads:
  19  comm: thread name
  20  cmdline: empty
  21  exe: <readlink fails>
  22
  23 executable
  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
  29 script (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
  35 If FEATURE_PREFER_APPLETS=y (and more so if FEATURE_SH_STANDALONE=y),
  36 some commands started from busybox shell, xargs or find are started by
  37 execXXX("/proc/self/exe", applet_name, params....)
  38 and therefore comm field contains "exe".
  39 */
  40
  41 static 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  */
  82 pid_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
 105 pid_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 }