exec.c

操作系统源代码

	/* 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();
	}
}