exec.c

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/*-
 * Copyright (c) 1991 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.
 */

#ifndef lint
static char sccsid[] = "@(#)exec.c      5.2 (Berkeley) 3/13/91";
#endif /* not lint */

/*
 * 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 <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.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 */


#ifdef __STDC__
STATIC void tryexec(char *, char **, char **);
STATIC void execinterp(char **, char **);
STATIC void printentry(struct tblentry *);
STATIC void clearcmdentry(int);
STATIC struct tblentry *cmdlookup(char *, int);
STATIC void delete_cmd_entry(void);
#else
STATIC void tryexec();
STATIC void execinterp();
STATIC void printentry();
STATIC void clearcmdentry();
STATIC struct tblentry *cmdlookup();
STATIC void delete_cmd_entry();
#endif



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

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

        if (strchr(argv[0], '/') != NULL) {
                tryexec(argv[0], argv, envp);
                e = errno;
        } else {
                e = ENOENT;
                while ((cmdname = padvance(&path, argv[0])) != NULL) {
                        if (--index < 0 && pathopt == NULL) {
                                tryexec(cmdname, argv, envp);
                                if (errno != ENOENT && errno != ENOTDIR)
                                        e = errno;
                        }
                        stunalloc(cmdname);
                }
        }
        error2(argv[0], errmsg(e, E_EXEC));
}


STATIC void
tryexec(cmd, argv, envp)
        char *cmd;
        char **argv;
        char **envp;
        {
        int e;
        char *p;

#ifdef SYSV
        do {
                execve(cmd, argv, envp);
        } while (errno == EINTR);
#else
        execve(cmd, argv, envp);
#endif
#if HASHBANG
        e = errno;
        if (e == ENOEXEC) {
                initshellproc();
                setinputfile(cmd, 0);
                commandname = arg0 = savestr(argv[0]);
#ifndef BSD
                pgetc(); pungetc();             /* fill up input buffer */
                p = parsenextc;
                if (parsenleft > 2 && p[0] == '#' && p[1] == '!') {
                        argv[0] = cmd;
                        execinterp(argv, envp);
                }
#endif
                setparam(argv + 1);
                exraise(EXSHELLPROC);
                /*NOTREACHED*/
        }
        errno = e;
#endif
}


#if !defined(BSD) && HASHBANG
/*
 * Execute an interpreter introduced by "#!", for systems where this
 * feature has not been built into the kernel.  If the interpreter is
 * the shell, return (effectively ignoring the "#!").  If the execution
 * of the interpreter fails, exit.
 *
 * This code peeks inside the input buffer in order to avoid actually
 * reading any input.  It would benefit from a rewrite.
 */

#define NEWARGS 5

STATIC void
execinterp(argv, envp)
        char **argv, **envp;
        {
        int n;
        char *inp;
        char *outp;
        char c;
        char *p;
        char **ap;
        char *newargs[NEWARGS];
        int i;
        char **ap2;
        char **new;

        n = parsenleft - 2;
        inp = parsenextc + 2;
        ap = newargs;
        for (;;) {
                while (--n >= 0 && (*inp == ' ' || *inp == '\t'))
                        inp++;
                if (n < 0)
                        goto bad;
                if ((c = *inp++) == '\n')
                        break;
                if (ap == &newargs[NEWARGS])
bad:              error("Bad #! line");
                STARTSTACKSTR(outp);
                do {
                        STPUTC(c, outp);
                } while (--n >= 0 && (c = *inp++) != ' ' && c != '\t' && c != '\n');
                STPUTC('\0', outp);
                n++, inp--;
                *ap++ = grabstackstr(outp);
        }
#if !__minix
        if (ap == newargs + 1) {        /* if no args, maybe no exec is needed */
                p = newargs[0];
                for (;;) {
                        if (equal(p, "sh") || equal(p, "ash")) {
                                return;
                        }
                        while (*p != '/') {
                                if (*p == '\0')
                                        goto break2;
                                p++;
                        }
                        p++;
                }
break2:;
        }
#endif
        i = (char *)ap - (char *)newargs;               /* size in bytes */
        if (i == 0)
                error("Bad #! line");
        for (ap2 = argv ; *ap2++ != NULL ; );
        new = ckmalloc(i + ((char *)ap2 - (char *)argv));
        ap = newargs, ap2 = new;
        while ((i -= sizeof (char **)) >= 0)
                *ap2++ = *ap++;
        ap = argv;
        while (*ap2++ = *ap++);
        shellexec(new, envp, pathval(), 0);
}
#endif



/*
 * 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.
 */

char *pathopt;

char *
padvance(path, name)
        char **path;
        char *name;
        {
        register char *p, *q;
        char *start;
        int 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) {
                bcopy(start, q, 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 ***/


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

        if (argc <= 1) {
                for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
                        for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
                                printentry(cmdp);
                        }
                }
                return 0;
        }
        verbose = 0;
        while ((c = nextopt("rv")) != '\0') {
                if (c == 'r') {
                        clearcmdentry(0);
                } else if (c == 'v') {
                        verbose++;
                }
        }
        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, 1);
                if (verbose) {
                        if (entry.cmdtype != CMDUNKNOWN) {      /* if no error msg */
                                cmdp = cmdlookup(name, 0);
                                printentry(cmdp);
                        }
                        flushall();
                }
                argptr++;
        }
        return 0;
}


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

        if (cmdp->cmdtype == CMDNORMAL) {
                index = cmdp->param.index;
                path = pathval();
                do {
                        name = padvance(&path, cmdp->cmdname);
                        stunalloc(name);
                } while (--index >= 0);
                out1str(name);
        } else if (cmdp->cmdtype == CMDBUILTIN) {
                out1fmt("builtin %s", cmdp->cmdname);
        } else if (cmdp->cmdtype == CMDFUNCTION) {
                out1fmt("function %s", cmdp->cmdname);
#if DEBUG
        } else {
                error("internal error: cmdtype %d", cmdp->cmdtype);
#endif
        }
        if (cmdp->rehash)
                out1c('*');
        out1c('\n');
}



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

void
find_command(name, entry, printerr)
        char *name;
        struct cmdentry *entry;
        {
        struct tblentry *cmdp;
        int index;
        int prev;
        char *path;
        char *fullname;
        struct stat statb;
        int e;
        int i;

        /* If name contains a slash, don't use the hash table */
        if (strchr(name, '/') != NULL) {
                entry->cmdtype = CMDNORMAL;
                entry->u.index = 0;
                return;
        }

        /* If name is in the table, and not invalidated by cd, we're done */
        if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->rehash == 0)
                goto success;

        /* If %builtin not in path, check for builtin next */
        if (builtinloc < 0 && (i = find_builtin(name)) >= 0) {
                INTOFF;
                cmdp = cmdlookup(name, 1);
                cmdp->cmdtype = CMDBUILTIN;
                cmdp->param.index = i;
                INTON;
                goto success;
        }

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

        path = pathval();
        e = ENOENT;
        index = -1;
loop:
        while ((fullname = padvance(&path, name)) != NULL) {
                stunalloc(fullname);
                index++;
                if (pathopt) {
                        if (prefix("builtin", pathopt)) {
                                if ((i = find_builtin(name)) < 0)
                                        goto loop;
                                INTOFF;
                                cmdp = cmdlookup(name, 1);
                                cmdp->cmdtype = CMDBUILTIN;
                                cmdp->param.index = i;
                                INTON;
                                goto success;
                        } else if (prefix("func", pathopt)) {
                                /* handled below */
                        } else {
                                goto loop;      /* ignore unimplemented options */
                        }
                }
                /* if rehash, don't redo absolute path names */
                if (fullname[0] == '/' && index <= prev) {
                        if (index < prev)
                                goto loop;
                        TRACE(("searchexec \"%s\": no change\n", name));
                        goto success;
                }
                while (stat(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 ((statb.st_mode & S_IFMT) != S_IFREG)
                        goto loop;
                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;
                }
                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 __minix_vmd || defined(BSD)
                        gid_t group_list[NGROUPS_MAX];
                        int ngroups, i;

                        ngroups = getgroups(NGROUPS_MAX, group_list);

                        for (i = 0; i < ngroups; i++) {
                                if (statb.st_gid == group_list[i]) break;
                        }
                        if (i < ngroups) {
                                if ((statb.st_mode & 010) == 0)
                                        goto loop;
                        } else
#endif
                        if ((statb.st_mode & 01) == 0)
                                goto loop;
                }
                TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
                INTOFF;
                cmdp = cmdlookup(name, 1);
                cmdp->cmdtype = CMDNORMAL;
                cmdp->param.index = index;
                INTON;
                goto success;
        }

        /* We failed.  If there was an entry for this command, delete it */
        if (cmdp)
                delete_cmd_entry();
        if (printerr)
                outfmt(out2, "%s: %s\n", name, errmsg(e, E_EXEC));
        entry->cmdtype = CMDUNKNOWN;
        return;

success:
        cmdp->rehash = 0;
        entry->cmdtype = cmdp->cmdtype;
        entry->u = cmdp->param;
}



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

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

        for (bp = builtincmd ; bp->name ; bp++) {
                if (*bp->name == *name && equal(bp->name, name))
                        return bp->code;
        }
        return -1;
}



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

void
hashcd() {
        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 && builtinloc >= 0)
                                cmdp->rehash = 1;
                }
        }
}



/*
 * 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(newval)
        char *newval;
        {
        char *old, *new;
        int index;
        int firstchange;
        int bltin;

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


/*
 * Delete all functions.
 */

#ifdef mkinit
MKINIT void deletefuncs();

SHELLPROC {
        deletefuncs();
}
#endif

void
deletefuncs() {
        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 == CMDFUNCTION) {
                                *pp = cmdp->next;
                                freefunc(cmdp->param.func);
                                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.
 */

struct tblentry **lastcmdentry;


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

        p = name;
        hashval = *p << 4;
        while (*p)
                hashval += *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) {
                INTOFF;
                cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
                                        + strlen(name) + 1);
                cmdp->next = NULL;
                cmdp->cmdtype = CMDUNKNOWN;
                cmdp->rehash = 0;
                strcpy(cmdp->cmdname, name);
                INTON;
        }
        lastcmdentry = pp;
        return cmdp;
}


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

STATIC void
delete_cmd_entry() {
        struct tblentry *cmdp;

        INTOFF;
        cmdp = *lastcmdentry;
        *lastcmdentry = cmdp->next;
        ckfree(cmdp);
        INTON;
}



#ifdef notdef
void
getcmdentry(name, entry)
        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.
 */

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

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


/*
 * Define a shell function.
 */

void
defun(name, func)
        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(name)
        char *name;
        {
        struct tblentry *cmdp;

        if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->cmdtype == CMDFUNCTION) {
                freefunc(cmdp->param.func);
                delete_cmd_entry();
        }
}

---