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exec.c

/*    $NetBSD: exec.c,v 1.35 2003/01/22 20:36:04 dsl Exp $  */

/*-
 * Copyright (c) 1991, 1993
 *    The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)exec.c  8.4 (Berkeley) 6/8/95";
#else
__RCSID("$NetBSD: exec.c,v 1.35 2003/01/22 20:36:04 dsl Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sysexits.h>
#include <paths.h>

/*
 * When commands are first encountered, they are entered in a hash table.
 * This ensures that a full path search will not have to be done for them
 * on each invocation.
 *
 * We should investigate converting to a linear search, even though that
 * would make the command name "hash" a misnomer.
 */

#include "shell.h"
#include "main.h"
#include "nodes.h"
#include "parser.h"
#include "redir.h"
#include "eval.h"
#include "exec.h"
#include "builtins.h"
#include "var.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "syntax.h"
#include "memalloc.h"
#include "error.h"
#include "init.h"
#include "mystring.h"
#include "show.h"
#include "jobs.h"
#include "alias.h"


#define CMDTABLESIZE 31       /* should be prime */
#define ARB 1                 /* actual size determined at run time */



struct tblentry {
      struct tblentry *next;  /* next entry in hash chain */
      union param param;      /* definition of builtin function */
      short cmdtype;          /* index identifying command */
      char rehash;            /* if set, cd done since entry created */
      char cmdname[ARB];      /* name of command */
};


STATIC struct tblentry *cmdtable[CMDTABLESIZE];
STATIC int builtinloc = -1;         /* index in path of %builtin, or -1 */
int exerrno;                        /* Last exec error */


STATIC void tryexec(char *, char **, char **);
STATIC void printentry(struct tblentry *);
STATIC void clearcmdentry(int);
STATIC struct tblentry *cmdlookup(const char *, int);
STATIC void delete_cmd_entry(void);
STATIC void addcmdentry(char *, struct cmdentry *);
STATIC int describe_command(struct output *, char *, int);


/*
 * Exec a program.  Never returns.  If you change this routine, you may
 * have to change the find_command routine as well.
 */

void
shellexec(char **argv, const char *path, int idx)
{
      char *cmdname;
      int e;
      char **envp;

      clearredir(1);
      envp = environment();
      if (strchr(argv[0], '/') != NULL) {
            tryexec(argv[0], argv, envp);
            e = errno;
      } else {
            e = ENOENT;
            while ((cmdname = padvance(&path, argv[0])) != NULL) {
                  if (--idx < 0 && pathopt == NULL) {
                        tryexec(cmdname, argv, envp);
                        if (errno != ENOENT && errno != ENOTDIR)
                              e = errno;
                  }
                  stunalloc(cmdname);
            }
      }

      /* Map to POSIX errors */
      switch (e) {
      case EACCES:
            exerrno = 126;
            break;
      case ENOENT:
            exerrno = 127;
            break;
      default:
            exerrno = 2;
            break;
      }
      TRACE(("shellexec failed for %s, errno %d, suppressint %d\n",
            argv[0], e, suppressint ));
      exerror(EXEXEC, "%s: %s", argv[0], errmsg(e, E_EXEC));
      /* NOTREACHED */
}


STATIC void
tryexec(char *cmd, char **argv, char **envp)
{
      int repeated = 0;
#if !defined(BSD) && !defined(linux)
      char *p;
#endif

repeat:
#ifdef SYSV
      do {
            execve(cmd, argv, envp);
      } while (errno == EINTR);
#else
      execve(cmd, argv, envp);
#endif
      if (repeated++) {
            ckfree(argv);
      } else if (errno == ENOEXEC) {
            char **ap;
            char **new;

            for (ap = argv; *ap; ap++)
                  ;
            ap = new = ckmalloc((ap - argv + 2) * sizeof(char *));
            *ap++ = cmd = _PATH_BSHELL;
            while ((*ap++ = *argv++))
                  ;
            argv = new;
            goto repeat;
      }
}



/*
 * Do a path search.  The variable path (passed by reference) should be
 * set to the start of the path before the first call; padvance will update
 * this value as it proceeds.  Successive calls to padvance will return
 * the possible path expansions in sequence.  If an option (indicated by
 * a percent sign) appears in the path entry then the global variable
 * pathopt will be set to point to it; otherwise pathopt will be set to
 * NULL.
 */

const char *pathopt;

char *
padvance(const char **path, const char *name)
{
      const char *p;
      char *q;
      const char *start;
      size_t len;

      if (*path == NULL)
            return NULL;
      start = *path;
      for (p = start ; *p && *p != ':' && *p != '%' ; p++);
      len = p - start + strlen(name) + 2; /* "2" is for '/' and '\0' */
      while (stackblocksize() < len)
            growstackblock();
      q = stackblock();
      if (p != start) {
            memcpy(q, start, p - start);
            q += p - start;
            *q++ = '/';
      }
      strcpy(q, name);
      pathopt = NULL;
      if (*p == '%') {
            pathopt = ++p;
            while (*p && *p != ':')  p++;
      }
      if (*p == ':')
            *path = p + 1;
      else
            *path = NULL;
      return stalloc(len);
}



/*** Command hashing code ***/


int
hashcmd(int argc, char **argv)
{
      struct tblentry **pp;
      struct tblentry *cmdp;
      int c;
      struct cmdentry entry;
      char *name;

      while ((c = nextopt("r")) != '\0') {
            clearcmdentry(0);
            return 0;
      }
      if (*argptr == NULL) {
            for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                  for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                        if (cmdp->cmdtype == CMDNORMAL)
                              printentry(cmdp);
                  }
            }
            return 0;
      }
      c = 0;
      while ((name = *argptr) != NULL) {
            if ((cmdp = cmdlookup(name, 0)) != NULL
             && (cmdp->cmdtype == CMDNORMAL
                 || (cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0)))
                  delete_cmd_entry();
            find_command(name, &entry, DO_ERR, pathval());
            if (entry.cmdtype == CMDUNKNOWN)
                  c = 1;
            argptr++;
      }
      return c;
}


STATIC void
printentry(struct tblentry *cmdp)
{
      int idx;
      const char *path;
      char *name;

      idx = cmdp->param.index;
      path = pathval();
      do {
            name = padvance(&path, cmdp->cmdname);
            stunalloc(name);
      } while (--idx >= 0);
      out1str(name);
      out1fmt(snlfmt, cmdp->rehash ? "*" : nullstr);
}



/*
 * Resolve a command name.  If you change this routine, you may have to
 * change the shellexec routine as well.
 */

void
find_command(char *name, struct cmdentry *entry, int act, const char *path)
{
      struct tblentry *cmdp;
      int idx;
      int prev;
      char *fullname;
      struct stat64 statb;
      int e;
      int updatetbl;
      struct builtincmd *bcmd;

      /* If name contains a slash, don't use PATH or hash table */
      if (strchr(name, '/') != NULL) {
            entry->u.index = -1;
            if (act & DO_ABS) {
                  while (stat64(name, &statb) < 0) {
#ifdef SYSV
                        if (errno == EINTR)
                              continue;
#endif
                        entry->cmdtype = CMDUNKNOWN;
                        return;
                  }
            }
            entry->cmdtype = CMDNORMAL;
            return;
      }

      updatetbl = (path == pathval());
      if (!updatetbl) {
            act |= DO_ALTPATH;
            if (strstr(path, "%builtin") != NULL)
                  act |= DO_ALTBLTIN;
      }

      /* If name is in the table, check answer will be ok */
      if ((cmdp = cmdlookup(name, 0)) != NULL) {
            int bit;

            switch (cmdp->cmdtype) {
            default:
#if DEBUG
                  abort();
#endif
            case CMDNORMAL:
                  bit = DO_ALTPATH;
                  break;
            case CMDFUNCTION:
                  bit = DO_NOFUNC;
                  break;
            case CMDBUILTIN:
                  bit = DO_ALTBLTIN;
                  break;
            }
            if (act & bit) {
                  updatetbl = 0;
                  cmdp = NULL;
            } else if (cmdp->rehash == 0)
                  /* if not invalidated by cd, we're done */
                  goto success;
      }

      /* If %builtin not in path, check for builtin next */
      bcmd = find_builtin(name);
      if (bcmd && (bcmd->flags & BUILTIN_REGULAR || (
            act & DO_ALTPATH ? !(act & DO_ALTBLTIN) : builtinloc <= 0
      )))
            goto builtin_success;

      /* We have to search path. */
      prev = -1;        /* where to start */
      if (cmdp && cmdp->rehash) {   /* doing a rehash */
            if (cmdp->cmdtype == CMDBUILTIN)
                  prev = builtinloc;
            else
                  prev = cmdp->param.index;
      }

      e = ENOENT;
      idx = -1;
loop:
      while ((fullname = padvance(&path, name)) != NULL) {
            stunalloc(fullname);
            idx++;
            if (pathopt) {
                  if (prefix(pathopt, "builtin")) {
                        if (bcmd)
                              goto builtin_success;
                        continue;
                  } else if (!(act & DO_NOFUNC) &&
                           prefix(pathopt, "func")) {
                        /* handled below */
                  } else {
                        /* ignore unimplemented options */
                        continue;
                  }
            }
            /* if rehash, don't redo absolute path names */
            if (fullname[0] == '/' && idx <= prev) {
                  if (idx < prev)
                        continue;
                  TRACE(("searchexec \"%s\": no change\n", name));
                  goto success;
            }
            while (stat64(fullname, &statb) < 0) {
#ifdef SYSV
                  if (errno == EINTR)
                        continue;
#endif
                  if (errno != ENOENT && errno != ENOTDIR)
                        e = errno;
                  goto loop;
            }
            e = EACCES; /* if we fail, this will be the error */
            if (!S_ISREG(statb.st_mode))
                  continue;
            if (pathopt) {          /* this is a %func directory */
                  stalloc(strlen(fullname) + 1);
                  readcmdfile(fullname);
                  if ((cmdp = cmdlookup(name, 0)) == NULL ||
                      cmdp->cmdtype != CMDFUNCTION)
                        error("%s not defined in %s", name, fullname);
                  stunalloc(fullname);
                  goto success;
            }
#ifdef notdef
            /* XXX this code stops root executing stuff, and is buggy
               if you need a group from the group list. */
            if (statb.st_uid == geteuid()) {
                  if ((statb.st_mode & 0100) == 0)
                        goto loop;
            } else if (statb.st_gid == getegid()) {
                  if ((statb.st_mode & 010) == 0)
                        goto loop;
            } else {
                  if ((statb.st_mode & 01) == 0)
                        goto loop;
            }
#endif
            TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
            if (!updatetbl) {
                  entry->cmdtype = CMDNORMAL;
                  entry->u.index = idx;
                  return;
            }
            INTOFF;
            cmdp = cmdlookup(name, 1);
            cmdp->cmdtype = CMDNORMAL;
            cmdp->param.index = idx;
            INTON;
            goto success;
      }

      /* We failed.  If there was an entry for this command, delete it */
      if (cmdp && updatetbl)
            delete_cmd_entry();
      if (act & DO_ERR)
            sh_warnx("%s: %s", name, errmsg(e, E_EXEC));
      entry->cmdtype = CMDUNKNOWN;
      return;

builtin_success:
      if (!updatetbl) {
            entry->cmdtype = CMDBUILTIN;
            entry->u.cmd = bcmd;
            return;
      }
      INTOFF;
      cmdp = cmdlookup(name, 1);
      cmdp->cmdtype = CMDBUILTIN;
      cmdp->param.cmd = bcmd;
      INTON;
success:
      cmdp->rehash = 0;
      entry->cmdtype = cmdp->cmdtype;
      entry->u = cmdp->param;
}



/*
 * Search the table of builtin commands.
 */

struct builtincmd *
find_builtin(const char *name)
{
      struct builtincmd *bp;

      bp = bsearch(
            &name, builtincmd, NUMBUILTINS, sizeof(struct builtincmd),
            pstrcmp
      );
      return bp;
}



/*
 * Called when a cd is done.  Marks all commands so the next time they
 * are executed they will be rehashed.
 */

void
hashcd(void)
{
      struct tblentry **pp;
      struct tblentry *cmdp;

      for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
            for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                  if (cmdp->cmdtype == CMDNORMAL || (
                        cmdp->cmdtype == CMDBUILTIN &&
                        !(cmdp->param.cmd->flags & BUILTIN_REGULAR) &&
                        builtinloc > 0
                  ))
                        cmdp->rehash = 1;
            }
      }
}



/*
 * Fix command hash table when PATH changed.
 * Called before PATH is changed.  The argument is the new value of PATH;
 * pathval() still returns the old value at this point.
 * Called with interrupts off.
 */

void
changepath(const char *newval)
{
      const char *old, *new;
      int idx;
      int firstchange;
      int bltin;

      old = pathval();
      new = newval;
      firstchange = 9999;     /* assume no change */
      idx = 0;
      bltin = -1;
      for (;;) {
            if (*old != *new) {
                  firstchange = idx;
                  if ((*old == '\0' && *new == ':')
                   || (*old == ':' && *new == '\0'))
                        firstchange++;
                  old = new;  /* ignore subsequent differences */
            }
            if (*new == '\0')
                  break;
            if (*new == '%' && bltin < 0 && prefix(new + 1, "builtin"))
                  bltin = idx;
            if (*new == ':') {
                  idx++;
            }
            new++, old++;
      }
      if (builtinloc < 0 && bltin >= 0)
            builtinloc = bltin;           /* zap builtins */
      if (builtinloc >= 0 && bltin < 0)
            firstchange = 0;
      clearcmdentry(firstchange);
      builtinloc = bltin;
}


/*
 * Clear out command entries.  The argument specifies the first entry in
 * PATH which has changed.
 */

STATIC void
clearcmdentry(int firstchange)
{
      struct tblentry **tblp;
      struct tblentry **pp;
      struct tblentry *cmdp;

      INTOFF;
      for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
            pp = tblp;
            while ((cmdp = *pp) != NULL) {
                  if ((cmdp->cmdtype == CMDNORMAL &&
                       cmdp->param.index >= firstchange)
                   || (cmdp->cmdtype == CMDBUILTIN &&
                       builtinloc >= firstchange)) {
                        *pp = cmdp->next;
                        ckfree(cmdp);
                  } else {
                        pp = &cmdp->next;
                  }
            }
      }
      INTON;
}



/*
 * Locate a command in the command hash table.  If "add" is nonzero,
 * add the command to the table if it is not already present.  The
 * variable "lastcmdentry" is set to point to the address of the link
 * pointing to the entry, so that delete_cmd_entry can delete the
 * entry.
 *
 * Interrupts must be off if called with add != 0.
 */

struct tblentry **lastcmdentry;


STATIC struct tblentry *
cmdlookup(const char *name, int add)
{
      unsigned int hashval;
      const char *p;
      struct tblentry *cmdp;
      struct tblentry **pp;

      p = name;
      hashval = (unsigned char)*p << 4;
      while (*p)
            hashval += (unsigned char)*p++;
      hashval &= 0x7FFF;
      pp = &cmdtable[hashval % CMDTABLESIZE];
      for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
            if (equal(cmdp->cmdname, name))
                  break;
            pp = &cmdp->next;
      }
      if (add && cmdp == NULL) {
            cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
                              + strlen(name) + 1);
            cmdp->next = NULL;
            cmdp->cmdtype = CMDUNKNOWN;
            strcpy(cmdp->cmdname, name);
      }
      lastcmdentry = pp;
      return cmdp;
}

/*
 * Delete the command entry returned on the last lookup.
 */

STATIC void
delete_cmd_entry(void)
{
      struct tblentry *cmdp;

      INTOFF;
      cmdp = *lastcmdentry;
      *lastcmdentry = cmdp->next;
      if (cmdp->cmdtype == CMDFUNCTION)
            freefunc(cmdp->param.func);
      ckfree(cmdp);
      INTON;
}



#ifdef notdef
void
getcmdentry(char *name, struct cmdentry *entry)
{
      struct tblentry *cmdp = cmdlookup(name, 0);

      if (cmdp) {
            entry->u = cmdp->param;
            entry->cmdtype = cmdp->cmdtype;
      } else {
            entry->cmdtype = CMDUNKNOWN;
            entry->u.index = 0;
      }
}
#endif


/*
 * Add a new command entry, replacing any existing command entry for
 * the same name - except special builtins.
 */

STATIC void
addcmdentry(char *name, struct cmdentry *entry)
{
      struct tblentry *cmdp;

      cmdp = cmdlookup(name, 1);
      if (cmdp->cmdtype == CMDFUNCTION) {
            freefunc(cmdp->param.func);
      }
      cmdp->cmdtype = entry->cmdtype;
      cmdp->param = entry->u;
      cmdp->rehash = 0;
}


/*
 * Define a shell function.
 */

void
defun(char *name, union node *func)
{
      struct cmdentry entry;

      INTOFF;
      entry.cmdtype = CMDFUNCTION;
      entry.u.func = copyfunc(func);
      addcmdentry(name, &entry);
      INTON;
}


/*
 * Delete a function if it exists.
 */

void
unsetfunc(const char *name)
{
      struct tblentry *cmdp;

      if ((cmdp = cmdlookup(name, 0)) != NULL &&
          cmdp->cmdtype == CMDFUNCTION)
            delete_cmd_entry();
}

/*
 * Locate and print what a word is...
 */

int
typecmd(int argc, char **argv)
{
      int i;
      int err = 0;

      for (i = 1; i < argc; i++) {
            err |= describe_command(out1, argv[i], 1);
      }
      return err;
}

STATIC int
describe_command(out, command, verbose)
      struct output *out;
      char *command;
      int verbose;
{
      struct cmdentry entry;
      struct tblentry *cmdp;
      const struct alias *ap;
      const char *path = pathval();

      if (verbose) {
            outstr(command, out);
      }

      /* First look at the keywords */
      if (findkwd(command)) {
            outstr(verbose ? " is a shell keyword" : command, out);
            goto out;
      }

      /* Then look at the aliases */
      if ((ap = lookupalias(command, 0)) != NULL) {
            if (verbose) {
                  outfmt(out, " is an alias for %s", ap->val);
            } else {
                  outstr("alias ", out);
                  printalias(ap);
                  return 0;
            }
            goto out;
      }

      /* Then check if it is a tracked alias */
      if ((cmdp = cmdlookup(command, 0)) != NULL) {
            entry.cmdtype = cmdp->cmdtype;
            entry.u = cmdp->param;
      } else {
            /* Finally use brute force */
            find_command(command, &entry, DO_ABS, path);
      }

      switch (entry.cmdtype) {
      case CMDNORMAL: {
            int j = entry.u.index;
            char *p;
            if (j == -1) {
                  p = command;
            } else {
                  do {
                        p = padvance(&path, command);
                        stunalloc(p);
                  } while (--j >= 0);
            }
            if (verbose) {
                  outfmt(
                        out, " is%s %s",
                        cmdp ? " a tracked alias for" : nullstr, p
                  );
            } else {
                  outstr(p, out);
            }
            break;
      }

      case CMDFUNCTION:
            if (verbose) {
                  outstr(" is a shell function", out);
            } else {
                  outstr(command, out);
            }
            break;

      case CMDBUILTIN:
            if (verbose) {
                  outfmt(
                        out, " is a %sshell builtin",
                        entry.u.cmd->flags & BUILTIN_SPECIAL ?
                              "special " : nullstr
                  );
            } else {
                  outstr(command, out);
            }
            break;

      default:
            if (verbose) {
                  outstr(": not found\n", out);
            }
            return 127;
      }

out:
      outc('\n', out);
      return 0;
}

int
commandcmd(argc, argv)
      int argc;
      char **argv;
{
      int c;
      int default_path = 0;
      int verify_only = 0;
      int verbose_verify_only = 0;

      while ((c = nextopt("pvV")) != '\0')
            switch (c) {
            default:
#ifdef DEBUG
                  outfmt(out2,
"command: nextopt returned character code 0%o\n", c);
                  return EX_SOFTWARE;
#endif
            case 'p':
                  default_path = 1;
                  break;
            case 'v':
                  verify_only = 1;
                  break;
            case 'V':
                  verbose_verify_only = 1;
                  break;
            }

      if (default_path + verify_only + verbose_verify_only > 1 ||
          !*argptr) {
                  outfmt(out2,
"command [-p] command [arg ...]\n");
                  outfmt(out2,
"command {-v|-V} command\n");
                  return EX_USAGE;
      }

      if (verify_only || verbose_verify_only) {
            return describe_command(out1, *argptr, verbose_verify_only);
      }

      return 0;
}

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