lib/get_ppid_of.c

   1 /* Determine the parent process of a given process.
   2    Copyright (C) 2019-2024 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2019.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation, either version 3 of the
   8    License, or (at your option) any later version.
   9
  10    This file is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "get_ppid_of.h"
  22
  23 #include <stdio.h>
  24 #include <string.h>
  25
  26 #if defined __linux__ || defined __ANDROID__ || (defined __FreeBSD_kernel__ && !defined __FreeBSD__) || defined __GNU__ || defined __FreeBSD__ || defined __DragonFly__ || defined __NetBSD__ || defined __minix || defined __sun /* Linux, GNU/kFreeBSD, GNU/Hurd, FreeBSD, NetBSD, Minix, Solaris */
  27 # include <fcntl.h>
  28 # include <unistd.h>
  29 #endif
  30
  31 #if defined __OpenBSD__                                     /* OpenBSD */
  32 # include <sys/sysctl.h> /* sysctl, struct kinfo_proc */
  33 #endif
  34
  35 #if defined __APPLE__ && defined __MACH__                   /* Mac OS X */
  36 /* Get MAC_OS_X_VERSION_MIN_REQUIRED, MAC_OS_X_VERSION_MAX_ALLOWED.
  37    The version at runtime satisfies
  38    MAC_OS_X_VERSION_MIN_REQUIRED <= version <= MAC_OS_X_VERSION_MAX_ALLOWED.  */
  39 # include <AvailabilityMacros.h>
  40 # if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
  41 #  include <libproc.h>
  42 #  if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
  43 /* Mac OS X versions < 10.5 don't have this function.  Therefore declare it as
  44    weak, in order to avoid a runtime error when the binaries are run on these
  45    older versions.  */
  46 extern int proc_pidinfo (int, int, uint64_t, void *, int) WEAK_IMPORT_ATTRIBUTE;
  47 #  endif
  48 # endif
  49 #endif
  50
  51 #if defined _AIX                                            /* AIX */
  52 # include <procinfo.h>
  53 #endif
  54
  55 #if defined __hpux                                          /* HP-UX */
  56 # include <unistd.h>
  57 # include <sys/param.h>
  58 # include <sys/pstat.h>
  59 #endif
  60
  61 #if defined __sgi                                           /* IRIX */
  62 # include <unistd.h>
  63 # include <fcntl.h>
  64 # include <sys/procfs.h>
  65 #endif
  66
  67 #if defined __CYGWIN__                                      /* Cygwin */
  68 # define WIN32_LEAN_AND_MEAN
  69 # include <windows.h> /* needed to get 'struct external_pinfo' defined */
  70 # include <sys/cygwin.h>
  71 #endif
  72
  73 #if defined __BEOS__ || defined __HAIKU__                   /* BeOS, Haiku */
  74 # include <unistd.h>
  75 #endif
  76
  77 pid_t
  78 get_ppid_of (pid_t pid)
  79 {
  80 #if defined __linux__ || defined __ANDROID__ || (defined __FreeBSD_kernel__ && !defined __FreeBSD__) || defined __GNU__ /* Linux, GNU/kFreeBSD, GNU/Hurd */
  81 /* GNU/kFreeBSD mounts /proc as linprocfs, which looks like a Linux /proc
  82    file system.  */
  83
  84   /* Read the contents of /proc/<pid>/status into memory.  */
  85   char filename[6 + 10 + 7 + 1];
  86   int fd;
  87
  88   sprintf (filename, "/proc/%u/status", (unsigned int) pid);
  89   fd = open (filename, O_RDONLY | O_CLOEXEC);
  90   if (fd >= 0)
  91     {
  92       char buf[4096 + 1];
  93       ssize_t nread = read (fd, buf, sizeof (buf) - 1);
  94       close (fd);
  95       if (nread >= 0)
  96         {
  97           char *bufend = buf + nread;
  98           char *p;
  99
 100           /* NUL-terminate the buffer.  */
 101           *bufend = '\0';
 102
 103           /* Search for a line that starts with "PPid:".  */
 104           for (p = buf;;)
 105             {
 106               if (bufend - p >= 5 && memcmp (p, "PPid:", 5) == 0)
 107                 {
 108                   unsigned int ppid = 0;
 109                   if (sscanf (p + 5, "%u", &ppid) > 0)
 110                     return ppid;
 111                 }
 112               p = strchr (p, '\n');
 113               if (p != NULL)
 114                 p++;
 115               else
 116                 break;
 117             }
 118         }
 119     }
 120
 121 #endif
 122
 123 #if defined __FreeBSD__ || defined __DragonFly__ || defined __NetBSD__ /* FreeBSD, NetBSD */
 124
 125   /* Read the contents of /proc/<pid>/status into memory.  */
 126   char filename[6 + 10 + 7 + 1];
 127   int fd;
 128
 129   sprintf (filename, "/proc/%u/status", (unsigned int) pid);
 130   fd = open (filename, O_RDONLY | O_CLOEXEC);
 131   if (fd >= 0)
 132     {
 133       char buf[4096 + 1];
 134       ssize_t nread = read (fd, buf, sizeof (buf) - 1);
 135       close (fd);
 136       if (nread >= 0)
 137         {
 138           char *p;
 139
 140           /* NUL-terminate the buffer.  */
 141           buf[nread] = '\0';
 142
 143           /* Search for the third space-separated field.  */
 144           p = strchr (buf, ' ');
 145           if (p != NULL)
 146             {
 147               p = strchr (p + 1, ' ');
 148               if (p != NULL)
 149                 {
 150                   unsigned int ppid = 0;
 151                   if (sscanf (p + 1, "%u", &ppid) > 0)
 152                     return ppid;
 153                 }
 154             }
 155         }
 156     }
 157
 158 #endif
 159
 160 #if defined __minix                                         /* Minix */
 161
 162   /* Read the contents of /proc/<pid>/psinfo into memory.  */
 163   char filename[6 + 10 + 7 + 1];
 164   int fd;
 165
 166   sprintf (filename, "/proc/%u/psinfo", (unsigned int) pid);
 167   fd = open (filename, O_RDONLY | O_CLOEXEC);
 168   if (fd >= 0)
 169     {
 170       char buf[4096 + 1];
 171       ssize_t nread = read (fd, buf, sizeof (buf) - 1);
 172       close (fd);
 173       if (nread >= 0)
 174         {
 175           char *p;
 176           int count;
 177
 178           /* NUL-terminate the buffer.  */
 179           buf[nread] = '\0';
 180
 181           /* Search for the 16th space-separated field.  */
 182           p = strchr (buf, ' ');
 183           for (count = 1; p != NULL && count < 15; count++)
 184             p = strchr (p + 1, ' ');
 185           if (p != NULL)
 186             {
 187               unsigned int ppid = 0;
 188               if (sscanf (p + 1, "%u", &ppid) > 0)
 189                 return ppid;
 190             }
 191         }
 192     }
 193
 194 #endif
 195
 196 #if defined __sun                                           /* Solaris */
 197
 198   /* Read the contents of /proc/<pid>/psinfo into memory.
 199      Alternatively, we could read the contents of /proc/<pid>/status into
 200      memory.  But it contains a lot of information that we don't need.  */
 201   char filename[6 + 10 + 7 + 1];
 202   int fd;
 203
 204   sprintf (filename, "/proc/%u/psinfo", (unsigned int) pid);
 205   fd = open (filename, O_RDONLY | O_CLOEXEC);
 206   if (fd >= 0)
 207     {
 208       /* The contents is a 'struct psinfo'.  But since 'struct psinfo'
 209          has a different size in a 32-bit and a 64-bit environment, we
 210          avoid it.  Nevertheless, the size of this contents depends on
 211          whether the process that reads it is 32-bit or 64-bit!  */
 212       #if defined __LP64__
 213       # define PSINFO_SIZE 416
 214       #else
 215       # define PSINFO_SIZE 336
 216       #endif
 217       union { char all[PSINFO_SIZE]; unsigned int header[11]; } buf;
 218       ssize_t nread = read (fd, buf.all, sizeof (buf.all));
 219       close (fd);
 220       if (nread >= (ssize_t) sizeof (buf.header))
 221         return buf.header[3];
 222     }
 223
 224 #endif
 225
 226 #if defined __OpenBSD__                                     /* OpenBSD */
 227
 228   /* Documentation: https://man.openbsd.org/sysctl.2  */
 229   int info_path[] =
 230     { CTL_KERN, KERN_PROC, KERN_PROC_PID, pid, sizeof (struct kinfo_proc), 1 };
 231   struct kinfo_proc info;
 232   size_t len;
 233
 234   len = sizeof (info);
 235   if (sysctl (info_path, 6, &info, &len, NULL, 0) >= 0 && len == sizeof (info))
 236     return info.p_ppid;
 237
 238 #endif
 239
 240 #if defined __APPLE__ && defined __MACH__                   /* Mac OS X */
 241 # if MAC_OS_X_VERSION_MAX_ALLOWED >= 1050
 242
 243   /* Mac OS X >= 10.7 has PROC_PIDT_SHORTBSDINFO.  */
 244 #  if defined PROC_PIDT_SHORTBSDINFO
 245 #   if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
 246   if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
 247 #   endif
 248     {
 249       struct proc_bsdshortinfo info;
 250
 251       if (proc_pidinfo (pid, PROC_PIDT_SHORTBSDINFO, 0, &info, sizeof (info))
 252           == sizeof (info))
 253         return info.pbsi_ppid;
 254     }
 255 #  endif
 256
 257 #  if MAC_OS_X_VERSION_MIN_REQUIRED < 1070
 258   /* For older versions, use PROC_PIDTBSDINFO instead.  */
 259   /* Note: The second part of 'struct proc_bsdinfo' differs in size between
 260      32-bit and 64-bit environments, and the kernel of Mac OS X 10.5 knows
 261      only about the 32-bit 'struct proc_bsdinfo'.  Fortunately all the info
 262      we need is in the first part, which is the same in 32-bit and 64-bit.  */
 263 #   if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
 264   if (proc_pidinfo != NULL) /* at runtime Mac OS X >= 10.5 ? */
 265 #   endif
 266     {
 267       struct proc_bsdinfo info;
 268
 269       if (proc_pidinfo (pid, PROC_PIDTBSDINFO, 0, &info, 128) == 128)
 270         return info.pbi_ppid;
 271     }
 272 #  endif
 273
 274 # endif
 275 #endif
 276
 277 #if defined _AIX                                            /* AIX */
 278
 279   /* Reference: https://www.ibm.com/support/knowledgecenter/en/ssw_aix_61/com.ibm.aix.basetrf1/getprocs.htm
 280   */
 281   struct procentry64 procs;
 282   if (getprocs64 (&procs, sizeof procs, NULL, 0, &pid, 1) > 0)
 283     return procs.pi_ppid;
 284
 285 #endif
 286
 287 #if defined __hpux                                          /* HP-UX */
 288
 289   struct pst_status status;
 290   if (pstat_getproc (&status, sizeof status, 0, pid) > 0)
 291     return status.pst_ppid;
 292   else
 293     {
 294 # if !defined __LP64__
 295       /* Support for 32-bit programs running in 64-bit HP-UX.
 296          The documented way to do this is to use the same source code
 297          as above, but in a compilation unit where '#define _PSTAT64 1'
 298          is in effect.  I prefer a single compilation unit; the struct
 299          size and the offsets are not going to change.  */
 300       char status64[1216];
 301       if (__pstat_getproc64 (status64, sizeof status64, 0, pid) > 0)
 302         return *(unsigned long long *)(status64 + 24);
 303 # endif
 304     }
 305
 306 #endif
 307
 308 #if defined __sgi                                           /* IRIX */
 309
 310   char filename[12 + 10 + 1];
 311   int fd;
 312
 313   sprintf (filename, "/proc/pinfo/%u", pid);
 314   fd = open (filename, O_RDONLY | O_CLOEXEC);
 315   if (0 <= fd)
 316     {
 317       prpsinfo_t buf;
 318       int ioctl_ok = 0 <= ioctl (fd, PIOCPSINFO, &buf);
 319       close (fd);
 320       if (ioctl_ok)
 321         return buf.pr_ppid;
 322     }
 323
 324 #endif
 325
 326 #if defined __CYGWIN__                                      /* Cygwin */
 327
 328   struct external_pinfo *info =
 329     (struct external_pinfo *) cygwin_internal (CW_GETPINFO, pid);
 330   if (info != NULL)
 331     return info->ppid;
 332
 333 #endif
 334
 335 #if defined __BEOS__ || defined __HAIKU__                   /* BeOS, Haiku */
 336
 337   if (pid == getpid ())
 338     return getppid ();
 339
 340 #endif
 341
 342   return 0;
 343 }
 344
 345 #ifdef TEST
 346
 347 #include <stdlib.h>
 348 #include <unistd.h>
 349
 350 /* Usage: ./a.out
 351    or:    ./a.out PID
 352  */
 353 int
 354 main (int argc, char *argv[])
 355 {
 356   char *arg = argv[1];
 357   pid_t pid = (arg != NULL ? atoi (arg) : getpid ());
 358   pid_t parent = get_ppid_of (pid);
 359   printf ("PID=%lu PPID=%lu\n", (unsigned long) pid, (unsigned long) parent);
 360   return 0;
 361 }
 362
 363 /*
 364  * Local Variables:
 365  * compile-command: "gcc -ggdb -DTEST -Wall -I.. get_ppid_of.c"
 366  * End:
 367  */
 368
 369 #endif