lib/portability.c

/* portability.c - code to workaround the deficiencies of various platforms.
 *
 * Copyright 2012 Rob Landley <rob@landley.net>
 * Copyright 2012 Georgi Chorbadzhiyski <gf@unixsol.org>
 */

#include "toys.h"

// We can't fork() on nommu systems, and vfork() requires an exec() or exit()
// before resuming the parent (because they share a heap until then). And no,
// we can't implement our own clone() call that does the equivalent of fork()
// because nommu heaps use physical addresses so if we copy the heap all our
// pointers are wrong. (You need an mmu in order to map two heaps to the same
// address range without interfering with each other.) In the absence of
// a portable way to tell malloc() to start a new heap without freeing the old
// one, you pretty much need the exec().)

// So we exec ourselves (via /proc/self/exe, if anybody knows a way to
// re-exec self without depending on the filesystem, I'm all ears),
// and use the arguments to signal reentry.

#if CFG_TOYBOX_FORK
pid_t xfork(void)
{
  pid_t pid = fork();

  if (pid < 0) perror_exit("fork");

  return pid;
}
#endif

int xgetrandom(void *buf, unsigned buflen, unsigned flags)
{
  int fd;

#if CFG_TOYBOX_GETRANDOM
  if (buflen == getrandom(buf, buflen, flags&~WARN_ONLY)) return 1;
  if (errno!=ENOSYS && !(flags&WARN_ONLY)) perror_exit("getrandom");
#endif
  fd = xopen(flags ? "/dev/random" : "/dev/urandom",O_RDONLY|(flags&WARN_ONLY));
  if (fd == -1) return 0;
  xreadall(fd, buf, buflen);
  close(fd);

  return 1;
}

// Get list of mounted filesystems, including stat and statvfs info.
// Returns a reversed list, which is good for finding overmounts and such.

#if defined(__APPLE__) || defined(__FreeBSD__)

#include <sys/mount.h>

struct mtab_list *xgetmountlist(char *path)
{
  struct mtab_list *mtlist = 0, *mt;
  struct statfs *entries;
  int i, count;

  if (path) error_exit("xgetmountlist");
  if ((count = getmntinfo(&entries, 0)) == 0) perror_exit("getmntinfo");

  // The "test" part of the loop is done before the first time through and
  // again after each "increment", so putting the actual load there avoids
  // duplicating it. If the load was NULL, the loop stops.

  for (i = 0; i < count; ++i) {
    struct statfs *me = &entries[i];

    mt = xzalloc(sizeof(struct mtab_list) + strlen(me->f_fstypename) +
      strlen(me->f_mntonname) + strlen(me->f_mntfromname) + strlen("") + 4);
    dlist_add_nomalloc((void *)&mtlist, (void *)mt);

    // Collect details about mounted filesystem.
    // Don't report errors, just leave data zeroed.
    stat(me->f_mntonname, &(mt->stat));
    statvfs(me->f_mntonname, &(mt->statvfs));

    // Remember information from struct statfs.
    mt->dir = stpcpy(mt->type, me->f_fstypename)+1;
    mt->device = stpcpy(mt->dir, me->f_mntonname)+1;
    mt->opts = stpcpy(mt->device, me->f_mntfromname)+1;
    strcpy(mt->opts, ""); /* TODO: reverse from f_flags? */
  }

  return mtlist;
}

#else

#include <mntent.h>

static void octal_deslash(char *s)
{
  char *o = s;

  while (*s) {
    if (*s == '\\') {
      int i, oct = 0;

      for (i = 1; i < 4; i++) {
        if (!isdigit(s[i])) break;
        oct = (oct<<3)+s[i]-'0';
      }
      if (i == 4) {
        *o++ = oct;
        s += i;
        continue;
      }
    }
    *o++ = *s++;
  }

  *o = 0;
}

// Check if this type matches list.
// Odd syntax: typelist all yes = if any, typelist all no = if none.

int mountlist_istype(struct mtab_list *ml, char *typelist)
{
  int len, skip;
  char *t;

  if (!typelist) return 1;

  skip = strncmp(typelist, "no", 2);

  for (;;) {
    if (!(t = comma_iterate(&typelist, &len))) break;
    if (!skip) {
      // If one -t starts with "no", the rest must too
      if (strncmp(t, "no", 2)) error_exit("bad typelist");
      if (!strncmp(t+2, ml->type, len-2)) {
        skip = 1;
        break;
      }
    } else if (!strncmp(t, ml->type, len) && !ml->type[len]) {
      skip = 0;
      break;
    }
  }

  return !skip;
}

struct mtab_list *xgetmountlist(char *path)
{
  struct mtab_list *mtlist = 0, *mt;
  struct mntent *me;
  FILE *fp;
  char *p = path ? path : "/proc/mounts";

  if (!(fp = setmntent(p, "r"))) perror_exit("bad %s", p);

  // The "test" part of the loop is done before the first time through and
  // again after each "increment", so putting the actual load there avoids
  // duplicating it. If the load was NULL, the loop stops.

  while ((me = getmntent(fp))) {
    mt = xzalloc(sizeof(struct mtab_list) + strlen(me->mnt_fsname) +
      strlen(me->mnt_dir) + strlen(me->mnt_type) + strlen(me->mnt_opts) + 4);
    dlist_add_nomalloc((void *)&mtlist, (void *)mt);

    // Collect details about mounted filesystem
    // Don't report errors, just leave data zeroed
    if (!path) {
      stat(me->mnt_dir, &(mt->stat));
      statvfs(me->mnt_dir, &(mt->statvfs));
    }

    // Remember information from /proc/mounts
    mt->dir = stpcpy(mt->type, me->mnt_type)+1;
    mt->device = stpcpy(mt->dir, me->mnt_dir)+1;
    mt->opts = stpcpy(mt->device, me->mnt_fsname)+1;
    strcpy(mt->opts, me->mnt_opts);

    octal_deslash(mt->dir);
    octal_deslash(mt->device);
  }
  endmntent(fp);

  return mtlist;
}

#endif

#ifdef __APPLE__

#include <sys/event.h>

struct xnotify *xnotify_init(int max)
{
  struct xnotify *not = xzalloc(sizeof(struct xnotify));

  not->max = max;
  if ((not->kq = kqueue()) == -1) perror_exit("kqueue");
  not->paths = xmalloc(max * sizeof(char *));
  not->fds = xmalloc(max * sizeof(int));

  return not;
}

int xnotify_add(struct xnotify *not, int fd, char *path)
{
  struct kevent event;

  if (not->count == not->max) error_exit("xnotify_add overflow");
  EV_SET(&event, fd, EVFILT_VNODE, EV_ADD|EV_CLEAR, NOTE_WRITE, 0, NULL);
  if (kevent(not->kq, &event, 1, NULL, 0, NULL) == -1 || event.flags & EV_ERROR)
    return -1;
  not->paths[not->count] = path;
  not->fds[not->count++] = fd;

  return 0;
}

int xnotify_wait(struct xnotify *not, char **path)
{
  struct kevent event;
  int i;

  for (;;) {
    if (kevent(not->kq, NULL, 0, &event, 1, NULL) != -1) {
      // We get the fd for free, but still have to search for the path.
      for (i = 0; i<not->count; i++) if (not->fds[i]==event.ident) {
        *path = not->paths[i];

        return event.ident;
      }
    }
  }
}

#else

#include <sys/inotify.h>

struct xnotify *xnotify_init(int max)
{
  struct xnotify *not = xzalloc(sizeof(struct xnotify));

  not->max = max;
  if ((not->kq = inotify_init()) < 0) perror_exit("inotify_init");
  not->paths = xmalloc(max * sizeof(char *));
  not->fds = xmalloc(max * 2 * sizeof(int));

  return not;
}

int xnotify_add(struct xnotify *not, int fd, char *path)
{
  int i = 2*not->count;

  if (not->max == not->count) error_exit("xnotify_add overflow");
  if ((not->fds[i] = inotify_add_watch(not->kq, path, IN_MODIFY))==-1)
    return -1;
  not->fds[i+1] = fd;
  not->paths[not->count++] = path;

  return 0;
}

int xnotify_wait(struct xnotify *not, char **path)
{
  struct inotify_event ev;
  int i;

  for (;;) {
    if (sizeof(ev)!=read(not->kq, &ev, sizeof(ev))) perror_exit("inotify");

    for (i = 0; i<not->count; i++) if (ev.wd==not->fds[2*i]) {
      *path = not->paths[i];

      return not->fds[2*i+1];
    }
  }
}

#endif

#ifdef __APPLE__

ssize_t xattr_get(const char *path, const char *name, void *value, size_t size)
{
  return getxattr(path, name, value, size, 0, 0);
}

ssize_t xattr_lget(const char *path, const char *name, void *value, size_t size)
{
  return getxattr(path, name, value, size, 0, XATTR_NOFOLLOW);
}

ssize_t xattr_fget(int fd, const char *name, void *value, size_t size)
{
  return fgetxattr(fd, name, value, size, 0, 0);
}

ssize_t xattr_list(const char *path, char *list, size_t size)
{
  return listxattr(path, list, size, 0);
}

ssize_t xattr_llist(const char *path, char *list, size_t size)
{
  return listxattr(path, list, size, XATTR_NOFOLLOW);
}

ssize_t xattr_flist(int fd, char *list, size_t size)
{
  return flistxattr(fd, list, size, 0);
}

ssize_t xattr_set(const char* path, const char* name,
                  const void* value, size_t size, int flags)
{
  return setxattr(path, name, value, size, 0, flags);
}

ssize_t xattr_lset(const char* path, const char* name,
                   const void* value, size_t size, int flags)
{
  return setxattr(path, name, value, size, 0, flags | XATTR_NOFOLLOW);
}

ssize_t xattr_fset(int fd, const char* name,
                   const void* value, size_t size, int flags)
{
  return fsetxattr(fd, name, value, size, 0, flags);
}

#else

ssize_t xattr_get(const char *path, const char *name, void *value, size_t size)
{
  return getxattr(path, name, value, size);
}

ssize_t xattr_lget(const char *path, const char *name, void *value, size_t size)
{
  return lgetxattr(path, name, value, size);
}

ssize_t xattr_fget(int fd, const char *name, void *value, size_t size)
{
  return fgetxattr(fd, name, value, size);
}

ssize_t xattr_list(const char *path, char *list, size_t size)
{
  return listxattr(path, list, size);
}

ssize_t xattr_llist(const char *path, char *list, size_t size)
{
  return llistxattr(path, list, size);
}

ssize_t xattr_flist(int fd, char *list, size_t size)
{
  return flistxattr(fd, list, size);
}

ssize_t xattr_set(const char* path, const char* name,
                  const void* value, size_t size, int flags)
{
  return setxattr(path, name, value, size, flags);
}

ssize_t xattr_lset(const char* path, const char* name,
                   const void* value, size_t size, int flags)
{
  return lsetxattr(path, name, value, size, flags);
}

ssize_t xattr_fset(int fd, const char* name,
                   const void* value, size_t size, int flags)
{
  return fsetxattr(fd, name, value, size, flags);
}


#endif

#ifdef __APPLE__
// In the absence of a mknodat system call, fchdir to dirfd and back
// around a regular mknod call...
int mknodat(int dirfd, const char *path, mode_t mode, dev_t dev)
{
  int old_dirfd = open(".", O_RDONLY), result;

  if (old_dirfd == -1 || fchdir(dirfd) == -1) return -1;
  result = mknod(path, mode, dev);
  if (fchdir(old_dirfd) == -1) perror_exit("mknodat couldn't return");
  return result;
}
#endif

// Signals required by POSIX 2008:
// http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html

#define SIGNIFY(x) {SIG##x, #x}

static const struct signame signames[] = {
  // POSIX
  SIGNIFY(ABRT), SIGNIFY(ALRM), SIGNIFY(BUS),
  SIGNIFY(FPE), SIGNIFY(HUP), SIGNIFY(ILL), SIGNIFY(INT), SIGNIFY(KILL),
  SIGNIFY(PIPE), SIGNIFY(QUIT), SIGNIFY(SEGV), SIGNIFY(TERM),
  SIGNIFY(USR1), SIGNIFY(USR2), SIGNIFY(SYS), SIGNIFY(TRAP),
  SIGNIFY(VTALRM), SIGNIFY(XCPU), SIGNIFY(XFSZ),
  // Non-POSIX signals that cause termination
  SIGNIFY(PROF), SIGNIFY(IO),
#ifdef __linux__
  SIGNIFY(STKFLT), SIGNIFY(POLL), SIGNIFY(PWR),
#elif defined(__APPLE__)
  SIGNIFY(EMT), SIGNIFY(INFO),
#endif

  // Note: sigatexit relies on all the signals with a default disposition that
  // terminates the process coming *before* SIGCHLD.

  // POSIX signals that don't cause termination
  SIGNIFY(CHLD), SIGNIFY(CONT), SIGNIFY(STOP), SIGNIFY(TSTP),
  SIGNIFY(TTIN), SIGNIFY(TTOU), SIGNIFY(URG),
  // Non-POSIX signals that don't cause termination
  SIGNIFY(WINCH),
};
int signames_len = ARRAY_LEN(signames);

#undef SIGNIFY

void xsignal_all_killers(void *handler)
{
  int i;

  for (i=0; signames[i].num != SIGCHLD; i++)
    if (signames[i].num != SIGKILL)
      xsignal(signames[i].num, handler ? exit_signal : SIG_DFL);
}

// Convert a string like "9", "KILL", "SIGHUP", or "SIGRTMIN+2" to a number.
int sig_to_num(char *sigstr)
{
  int i, offset;
  char *s;

  // Numeric?
  i = estrtol(sigstr, &s, 10);
  if (!errno && !*s) return i;

  // Skip leading "SIG".
  strcasestart(&sigstr, "sig");

  // Named signal?
  for (i=0; i<ARRAY_LEN(signames); i++)
    if (!strcasecmp(sigstr, signames[i].name)) return signames[i].num;

  // Real-time signal?
#ifdef SIGRTMIN
  if (strcasestart(&sigstr, "rtmin")) i = SIGRTMIN;
  else if (strcasestart(&sigstr, "rtmax")) i = SIGRTMAX;
  else return -1;

  // No offset?
  if (!*sigstr) return i;

  // We allow any offset that's still a real-time signal: SIGRTMIN+20 is fine.
  // Others are more restrictive, only accepting what they show with -l.
  offset = estrtol(sigstr, &s, 10);
  if (errno || *s) return -1;
  i += offset;
  if (i >= SIGRTMIN && i <= SIGRTMAX) return i;
#endif

  return -1;
}

char *num_to_sig(int sig)
{
  int i;

  // A named signal?
  for (i=0; i<signames_len; i++)
    if (signames[i].num == sig) return signames[i].name;

  // A real-time signal?
#ifdef SIGRTMIN
  if (sig == SIGRTMIN) return "RTMIN";
  if (sig == SIGRTMAX) return "RTMAX";
  if (sig > SIGRTMIN && sig < SIGRTMAX) {
    if (sig-SIGRTMIN <= SIGRTMAX-sig) sprintf(libbuf, "RTMIN+%d", sig-SIGRTMIN);
    else sprintf(libbuf, "RTMAX-%d", SIGRTMAX-sig);
    return libbuf;
  }
#endif

  return NULL;
}