libbb: make warning go away

[oweals/busybox.git] / libbb / find_pid_by_name.c

diff --git a/libbb/find_pid_by_name.c b/libbb/find_pid_by_name.c
index e98616940c061ce28b9a62d74203ae7ac13fd590..db823d05b972323e2180e87f2a0892195787c01b 100644 (file)
--- a/libbb/find_pid_by_name.c
+++ b/libbb/find_pid_by_name.c
@@ -4,31 +4,96 @@
  *
  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
  *
- * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
 
 #include "libbb.h"
 
-/* find_pid_by_name()
+/*
+In Linux we have three ways to determine "process name":
+1. /proc/PID/stat has "...(name)...", among other things. It's so-called "comm" field.
+2. /proc/PID/cmdline's first NUL-terminated string. It's argv[0] from exec syscall.
+3. /proc/PID/exe symlink. Points to the running executable file.
+
+kernel threads:
+ comm: thread name
+ cmdline: empty
+ exe: <readlink fails>
+
+executable
+ comm: first 15 chars of base name
+ (if executable is a symlink, then first 15 chars of symlink name are used)
+ cmdline: argv[0] from exec syscall
+ exe: points to executable (resolves symlink, unlike comm)
+
+script (an executable with #!/path/to/interpreter):
+ comm: first 15 chars of script's base name (symlinks are not resolved)
+ cmdline: /path/to/interpreter (symlinks are not resolved)
+ (script name is in argv[1], args are pushed into argv[2] etc)
+ exe: points to interpreter's executable (symlinks are resolved)
+
+If FEATURE_PREFER_APPLETS=y (and more so if FEATURE_SH_STANDALONE=y),
+some commands started from busybox shell, xargs or find are started by
+execXXX("/proc/self/exe", applet_name, params....)
+and therefore comm field contains "exe".
+*/
+
+static int comm_match(procps_status_t *p, const char *procName)
+{
+       int argv1idx;
+       const char *argv1;
+
+       if (strncmp(p->comm, procName, 15) != 0)
+               return 0; /* comm does not match */
+
+       /* In Linux, if comm is 15 chars, it is truncated.
+        * (or maybe the name was exactly 15 chars, but there is
+        * no way to know that) */
+       if (p->comm[14] == '\0')
+               return 1; /* comm is not truncated - matches */
+
+       /* comm is truncated, but first 15 chars match.
+        * This can be crazily_long_script_name.sh!
+        * The telltale sign is basename(argv[1]) == procName */
+
+       if (!p->argv0)
+               return 0;
+
+       argv1idx = strlen(p->argv0) + 1;
+       if (argv1idx >= p->argv_len)
+               return 0;
+       argv1 = p->argv0 + argv1idx;
+
+       if (strcmp(bb_basename(argv1), procName) != 0)
+               return 0;
+
+       return 1;
+}
+
+/* This finds the pid of the specified process.
+ * Currently, it's implemented by rummaging through
+ * the proc filesystem.
  *
- *  Modified by Vladimir Oleynik for use with libbb/procps.c
- *  This finds the pid of the specified process.
- *  Currently, it's implemented by rummaging through
- *  the proc filesystem.
+ * Returns a list of all matching PIDs
+ * It is the caller's duty to free the returned pidlist.
  *
- *  Returns a list of all matching PIDs
- *  It is the caller's duty to free the returned pidlist.
+ * Modified by Vladimir Oleynik for use with libbb/procps.c
  */
-pid_t* find_pid_by_name(const char* procName)
+pid_t* FAST_FUNC find_pid_by_name(const char *procName)
 {
        pid_t* pidList;
        int i = 0;
        procps_status_t* p = NULL;
 
-       pidList = xmalloc(sizeof(*pidList));
-       while ((p = procps_scan(p, PSSCAN_PID|PSSCAN_COMM))) {
-               if (strncmp(p->comm, procName, sizeof(p->comm)-1) == 0) {
-                       pidList = xrealloc(pidList, sizeof(*pidList) * (i+2));
+       pidList = xzalloc(sizeof(*pidList));
+       while ((p = procps_scan(p, PSSCAN_PID|PSSCAN_COMM|PSSCAN_ARGVN|PSSCAN_EXE))) {
+               if (comm_match(p, procName)
+               /* or we require argv0 to match (essential for matching reexeced /proc/self/exe)*/
+                || (p->argv0 && strcmp(bb_basename(p->argv0), procName) == 0)
+               /* or we require /proc/PID/exe link to match */
+                || (p->exe && strcmp(bb_basename(p->exe), procName) == 0)
+               ) {
+                       pidList = xrealloc_vector(pidList, 2, i);
                        pidList[i++] = p->pid;
                }
        }
@@ -37,7 +102,7 @@ pid_t* find_pid_by_name(const char* procName)
        return pidList;
 }
 
-pid_t *pidlist_reverse(pid_t *pidList)
+pid_t* FAST_FUNC pidlist_reverse(pid_t *pidList)
 {
        int i = 0;
        while (pidList[i])