freebsd-skq/bin/sh/exec.c
Jilles Tjoelker 4b45b49a70 sh: Remove special %builtin PATH entry.
All builtins are now always found before a PATH search.

Most ash derivatives have an undocumented feature where the presence of an
entry "%builtin" in $PATH will cause builtins to be checked at that point of
the PATH search, rather than before looking at any directories as documented
in the man page (very old versions do document this feature).

I am removing this feature from sh, as it complicates the code, may violate
expectations (for example, /usr/bin/alias is very close to a forkbomb with
PATH=/usr/bin:%builtin, only /usr/bin/builtin not being another link saves
it) and appears to be unused (all the %builtin google code search finds is
in some sort of ash source code).

Note that aliases and functions took and take precedence above builtins.
Because aliases work on a lexical level they can only ever be overridden on
a lexical level (quoting or preceding 'builtin' or 'command'). Allowing
override of functions via PATH does not really fit in the model of sh and it
would work differently from %builtin if implemented.

Note: POSIX says special builtins are found before functions. We comply to
this because we do not allow functions with the same name as a special
builtin.

Silence from:	freebsd-hackers@ (message sent 20101225)
Discussed with:	dougb
2011-01-09 21:07:30 +00:00

826 lines
17 KiB
C

/*-
* 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.
* 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
#if 0
static char sccsid[] = "@(#)exec.c 8.4 (Berkeley) 6/8/95";
#endif
#endif /* not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.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 */
int special; /* flag for special builtin commands */
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];
int exerrno = 0; /* Last exec error */
static void tryexec(char *, char **, char **);
static void printentry(struct tblentry *, int);
static struct tblentry *cmdlookup(const char *, int);
static void delete_cmd_entry(void);
/*
* 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, char **envp, const char *path, int idx)
{
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 (--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;
}
if (e == ENOENT || e == ENOTDIR)
exerror(EXEXEC, "%s: not found", argv[0]);
exerror(EXEXEC, "%s: %s", argv[0], strerror(e));
}
static void
tryexec(char *cmd, char **argv, char **envp)
{
int e;
execve(cmd, argv, envp);
e = errno;
if (e == ENOEXEC) {
initshellproc();
setinputfile(cmd, 0);
commandname = arg0 = savestr(argv[0]);
setparam(argv + 1);
exraise(EXSHELLPROC);
/*NOTREACHED*/
}
errno = e;
}
/*
* 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, *start;
char *q;
int len;
if (*path == NULL)
return NULL;
start = *path;
for (p = start; *p && *p != ':' && *p != '%'; p++)
; /* nothing */
len = p - start + strlen(name) + 2; /* "2" is for '/' and '\0' */
STARTSTACKSTR(q);
CHECKSTRSPACE(len, q);
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 __unused, char **argv __unused)
{
struct tblentry **pp;
struct tblentry *cmdp;
int c;
int verbose;
struct cmdentry entry;
char *name;
verbose = 0;
while ((c = nextopt("rv")) != '\0') {
if (c == 'r') {
clearcmdentry(0);
} else if (c == 'v') {
verbose++;
}
}
if (*argptr == NULL) {
for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
if (cmdp->cmdtype == CMDNORMAL)
printentry(cmdp, verbose);
}
}
return 0;
}
while ((name = *argptr) != NULL) {
if ((cmdp = cmdlookup(name, 0)) != NULL
&& cmdp->cmdtype == CMDNORMAL)
delete_cmd_entry();
find_command(name, &entry, DO_ERR, pathval());
if (verbose) {
if (entry.cmdtype != CMDUNKNOWN) { /* if no error msg */
cmdp = cmdlookup(name, 0);
if (cmdp != NULL)
printentry(cmdp, verbose);
else
outfmt(out2, "%s: not found\n", name);
}
flushall();
}
argptr++;
}
return 0;
}
static void
printentry(struct tblentry *cmdp, int verbose)
{
int idx;
const char *path;
char *name;
if (cmdp->cmdtype == CMDNORMAL) {
idx = cmdp->param.index;
path = pathval();
do {
name = padvance(&path, cmdp->cmdname);
stunalloc(name);
} while (--idx >= 0);
out1str(name);
} else if (cmdp->cmdtype == CMDBUILTIN) {
out1fmt("builtin %s", cmdp->cmdname);
} else if (cmdp->cmdtype == CMDFUNCTION) {
out1fmt("function %s", cmdp->cmdname);
if (verbose) {
INTOFF;
name = commandtext(getfuncnode(cmdp->param.func));
out1c(' ');
out1str(name);
ckfree(name);
INTON;
}
#ifdef 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(const char *name, struct cmdentry *entry, int act,
const char *path)
{
struct tblentry *cmdp, loc_cmd;
int idx;
int prev;
char *fullname;
struct stat statb;
int e;
int i;
int spec;
/* 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) {
if (cmdp->cmdtype == CMDFUNCTION && act & DO_NOFUNC)
cmdp = NULL;
else
goto success;
}
/* Check for builtin next */
if ((i = find_builtin(name, &spec)) >= 0) {
INTOFF;
cmdp = cmdlookup(name, 1);
if (cmdp->cmdtype == CMDFUNCTION)
cmdp = &loc_cmd;
cmdp->cmdtype = CMDBUILTIN;
cmdp->param.index = i;
cmdp->special = spec;
INTON;
goto success;
}
/* We have to search path. */
prev = -1; /* where to start */
if (cmdp) { /* doing a rehash */
if (cmdp->cmdtype == CMDBUILTIN)
prev = -1;
else
prev = cmdp->param.index;
}
e = ENOENT;
idx = -1;
loop:
while ((fullname = padvance(&path, name)) != NULL) {
stunalloc(fullname);
idx++;
if (pathopt) {
if (prefix("func", pathopt)) {
/* handled below */
} else {
goto loop; /* ignore unimplemented options */
}
}
/* if rehash, don't redo absolute path names */
if (fullname[0] == '/' && idx <= prev) {
if (idx < prev)
goto loop;
TRACE(("searchexec \"%s\": no change\n", name));
goto success;
}
if (stat(fullname, &statb) < 0) {
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))
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;
}
#ifdef notdef
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));
INTOFF;
cmdp = cmdlookup(name, 1);
if (cmdp->cmdtype == CMDFUNCTION)
cmdp = &loc_cmd;
cmdp->cmdtype = CMDNORMAL;
cmdp->param.index = idx;
INTON;
goto success;
}
/* We failed. If there was an entry for this command, delete it */
if (cmdp && cmdp->cmdtype != CMDFUNCTION)
delete_cmd_entry();
if (act & DO_ERR) {
if (e == ENOENT || e == ENOTDIR)
outfmt(out2, "%s: not found\n", name);
else
outfmt(out2, "%s: %s\n", name, strerror(e));
}
entry->cmdtype = CMDUNKNOWN;
entry->u.index = 0;
return;
success:
cmdp->rehash = 0;
entry->cmdtype = cmdp->cmdtype;
entry->u = cmdp->param;
entry->special = cmdp->special;
}
/*
* Search the table of builtin commands.
*/
int
find_builtin(const char *name, int *special)
{
const struct builtincmd *bp;
for (bp = builtincmd ; bp->name ; bp++) {
if (*bp->name == *name && equal(bp->name, name)) {
*special = bp->special;
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(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->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(const char *newval)
{
const char *old, *new;
int idx;
int firstchange;
old = pathval();
new = newval;
firstchange = 9999; /* assume no change */
idx = 0;
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 == ':') {
idx++;
}
new++, old++;
}
clearcmdentry(firstchange);
}
/*
* Clear out command entries. The argument specifies the first entry in
* PATH which has changed.
*/
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)) {
*pp = cmdp->next;
ckfree(cmdp);
} else {
pp = &cmdp->next;
}
}
}
INTON;
}
/*
* Delete all functions.
*/
#ifdef mkinit
MKINIT void deletefuncs(void);
SHELLPROC {
deletefuncs();
}
#endif
void
deletefuncs(void)
{
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;
unreffunc(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.
*/
static struct tblentry **lastcmdentry;
static struct tblentry *
cmdlookup(const char *name, int add)
{
int hashval;
const 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(void)
{
struct tblentry *cmdp;
INTOFF;
cmdp = *lastcmdentry;
*lastcmdentry = cmdp->next;
ckfree(cmdp);
INTON;
}
/*
* Add a new command entry, replacing any existing command entry for
* the same name.
*/
void
addcmdentry(const char *name, struct cmdentry *entry)
{
struct tblentry *cmdp;
INTOFF;
cmdp = cmdlookup(name, 1);
if (cmdp->cmdtype == CMDFUNCTION) {
unreffunc(cmdp->param.func);
}
cmdp->cmdtype = entry->cmdtype;
cmdp->param = entry->u;
INTON;
}
/*
* Define a shell function.
*/
void
defun(const 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.
*/
int
unsetfunc(const char *name)
{
struct tblentry *cmdp;
if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->cmdtype == CMDFUNCTION) {
unreffunc(cmdp->param.func);
delete_cmd_entry();
return (0);
}
return (0);
}
/*
* Shared code for the following builtin commands:
* type, command -v, command -V
*/
int
typecmd_impl(int argc, char **argv, int cmd, const char *path)
{
struct cmdentry entry;
struct tblentry *cmdp;
const char *const *pp;
struct alias *ap;
int i;
int error1 = 0;
if (path != pathval())
clearcmdentry(0);
for (i = 1; i < argc; i++) {
/* First look at the keywords */
for (pp = parsekwd; *pp; pp++)
if (**pp == *argv[i] && equal(*pp, argv[i]))
break;
if (*pp) {
if (cmd == TYPECMD_SMALLV)
out1fmt("%s\n", argv[i]);
else
out1fmt("%s is a shell keyword\n", argv[i]);
continue;
}
/* Then look at the aliases */
if ((ap = lookupalias(argv[i], 1)) != NULL) {
if (cmd == TYPECMD_SMALLV)
out1fmt("alias %s='%s'\n", argv[i], ap->val);
else
out1fmt("%s is an alias for %s\n", argv[i],
ap->val);
continue;
}
/* Then check if it is a tracked alias */
if ((cmdp = cmdlookup(argv[i], 0)) != NULL) {
entry.cmdtype = cmdp->cmdtype;
entry.u = cmdp->param;
entry.special = cmdp->special;
}
else {
/* Finally use brute force */
find_command(argv[i], &entry, 0, path);
}
switch (entry.cmdtype) {
case CMDNORMAL: {
if (strchr(argv[i], '/') == NULL) {
const char *path2 = path;
char *name;
int j = entry.u.index;
do {
name = padvance(&path2, argv[i]);
stunalloc(name);
} while (--j >= 0);
if (cmd == TYPECMD_SMALLV)
out1fmt("%s\n", name);
else
out1fmt("%s is%s %s\n", argv[i],
(cmdp && cmd == TYPECMD_TYPE) ?
" a tracked alias for" : "",
name);
} else {
if (eaccess(argv[i], X_OK) == 0) {
if (cmd == TYPECMD_SMALLV)
out1fmt("%s\n", argv[i]);
else
out1fmt("%s is %s\n", argv[i],
argv[i]);
} else {
if (cmd != TYPECMD_SMALLV)
outfmt(out2, "%s: %s\n",
argv[i], strerror(errno));
error1 |= 127;
}
}
break;
}
case CMDFUNCTION:
if (cmd == TYPECMD_SMALLV)
out1fmt("%s\n", argv[i]);
else
out1fmt("%s is a shell function\n", argv[i]);
break;
case CMDBUILTIN:
if (cmd == TYPECMD_SMALLV)
out1fmt("%s\n", argv[i]);
else if (entry.special)
out1fmt("%s is a special shell builtin\n",
argv[i]);
else
out1fmt("%s is a shell builtin\n", argv[i]);
break;
default:
if (cmd != TYPECMD_SMALLV)
outfmt(out2, "%s: not found\n", argv[i]);
error1 |= 127;
break;
}
}
if (path != pathval())
clearcmdentry(0);
return error1;
}
/*
* Locate and print what a word is...
*/
int
typecmd(int argc, char **argv)
{
return typecmd_impl(argc, argv, TYPECMD_TYPE, bltinlookup("PATH", 1));
}