xref: /illumos-gate/usr/src/cmd/ast/ksh/builtins/alias.c (revision b30d1939)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  *
26  * Copyright 2021 OmniOS Community Edition (OmniOSce) Association.
27  */
28 
29 /*
30  * alias.c is a C version of the alias.sh wrapper (which links ksh
31  * builtins to commands in /usr/bin/, e.g. calling this wrapper as
32  * /usr/bin/alias will call the ksh "alias" builtin, running it as
33  * /usr/bin/cut will call the ksh "cut" builtin etc.
34  */
35 
36 #include <defs.h>
37 #include <shell.h>
38 #include <nval.h>
39 #include <cmdext.h>
40 #include <stdio.h>
41 #include <setjmp.h>
42 
43 #undef calloc
44 #undef free
45 
46 typedef struct {
47 	const char *name;
48 	int (* func)(int, char **, Shbltin_t *);
49 } bfastpathrec;
50 
51 /*
52  * We've disabled the "fastpath" codepath for some commands below
53  * because it causes a paradoxon for large input files (as used by
54  * ON PerfPIT for testing). For /usr/bin/rev (where the issue was
55  * first discovered) it looks like this:
56  * - for small files like /etc/profile the fastpath is faster in a loop
57  *   with 1000 iterations (8 seconds with fastpath, 14 seconds without
58  *   fastpath)
59  * - for large files (/usr/pub/UTF-8 replicated until the test file
60  *   reaches 24884706 bytes) the benchmark reverses: The fastpath now
61  *   needs 40 seconds and without fastpath it needs 30 seconds (for 100
62  *   iterations).
63  */
64 #if 0
65 #define	ENABLE_PERFORMANCE_PARADOXON 1
66 #endif
67 
68 /*
69  * List of libcmd builtins which do not require a |Shell_t| context.
70  * This list was automatically generated from <ast/cmdext.h>
71  */
72 static const
73 bfastpathrec fastpath_builtins[] =
74 {
75 	/* This list must be alphabetically sorted for |strcmp()| usage */
76 	{ "basename",	b_basename	},
77 	{ "cat",	b_cat		},
78 	{ "chgrp",	b_chgrp		},
79 	{ "chmod",	b_chmod		},
80 	{ "chown",	b_chown		},
81 #ifdef ENABLE_PERFORMANCE_PARADOXON
82 	{ "cksum",	b_cksum		},
83 #endif /* ENABLE_PERFORMANCE_PARADOXON */
84 	{ "cmp",	b_cmp		},
85 	{ "comm",	b_comm		},
86 	{ "cp",		b_cp		},
87 	{ "cut",	b_cut		},
88 	{ "date",	b_date		},
89 	{ "dirname",	b_dirname	},
90 	{ "expr",	b_expr		},
91 	{ "fds",	b_fds		},
92 	{ "fmt",	b_fmt		},
93 	{ "fold",	b_fold		},
94 	{ "getconf",	b_getconf	},
95 	{ "head",	b_head		},
96 	{ "id",		b_id		},
97 	{ "join",	b_join		},
98 	{ "ln",		b_ln		},
99 	{ "logname",	b_logname	},
100 	{ "md5sum",	b_md5sum	},
101 	{ "mkdir",	b_mkdir		},
102 	{ "mkfifo",	b_mkfifo	},
103 	{ "mktemp",	b_mktemp	},
104 	{ "mv",		b_mv		},
105 	{ "paste",	b_paste		},
106 	{ "pathchk",	b_pathchk	},
107 	{ "pids",	b_pids		},
108 #ifdef ENABLE_PERFORMANCE_PARADOXON
109 	{ "rev",	b_rev		},
110 #endif /* ENABLE_PERFORMANCE_PARADOXON */
111 	{ "rm",		b_rm		},
112 	{ "rmdir",	b_rmdir		},
113 	{ "stty",	b_stty		},
114 #ifdef ENABLE_PERFORMANCE_PARADOXON
115 	{ "sum",	b_sum		},
116 #endif /* ENABLE_PERFORMANCE_PARADOXON */
117 	{ "sync",	b_sync		},
118 	{ "tail",	b_tail		},
119 	{ "tee",	b_tee		},
120 	{ "tty",	b_tty		},
121 	{ "uname",	b_uname		},
122 	{ "uniq",	b_uniq		},
123 	{ "vmstate",	b_vmstate	},
124 	{ "wc",		b_wc		},
125 	{ NULL,		NULL		}
126 };
127 
128 static inline const bfastpathrec *
129 find_bfastpathrec(const char *name)
130 {
131 	unsigned int i;
132 	signed int cmpres;
133 	for (i = 0; fastpath_builtins[i].name != NULL; i++) {
134 		cmpres = strcmp(fastpath_builtins[i].name, name);
135 		if (cmpres == 0)
136 			return (&fastpath_builtins[i]);
137 		else if (cmpres > 0)
138 			return (NULL);
139 	}
140 	return (NULL);
141 }
142 
143 static inline int
144 fastpath_builtin_main(const bfastpathrec *brec, int argc, char *argv[])
145 {
146 	setlocale(LC_ALL, ""); /* calls |_ast_setlocale()| */
147 
148 	return ((*brec->func)(argc, argv, NULL));
149 }
150 
151 
152 /* Builtin script, originally derived from alias.sh */
153 static const char *script = "\n"
154 /* Get name of builtin */
155 "typeset cmd=\"${0##*/}\"\n"
156 /*
157  * If the requested command is not an alias, load it explicitly
158  * to make sure it is not bound to a path (those built-ins which
159  * are mapped via shell aliases point to commands which are
160  * "special shell built-ins" which cannot be bound to a specific
161  * PATH element) - otherwise we may execute the wrong command
162  * if an executable with the same name sits in a PATH element
163  * before /usr/bin (e.g. /usr/xpg4/bin/ls would be executed
164  * before /usr/bin/ls if the path was something like
165  * PATH=/usr/xpg4/bin:/usr/bin).
166  */
167 "if [[ \"${cmd}\" != ~(Elr)(alias|unalias|command) ]] && "
168 	"! alias \"${cmd}\" >/dev/null 2>&1 ; then\n"
169 	"PATH='' builtin \"${cmd}\"\n"
170 "fi\n"
171 /* command is a keyword and needs to be handled separately */
172 "if [[ \"${cmd}\" == \"command\" ]] ; then\n"
173 	"command \"$@\"\n"
174 "else\n"
175 	"\"${cmd}\" \"$@\"\n"
176 "fi\n"
177 "exitval=$?";
178 
179 static inline int
180 script_builtin_main(int argc, char **argv)
181 {
182 	int i;
183 	Shell_t *shp;
184 	Namval_t *np;
185 	int exitval;
186 	char **xargv;
187 
188 	/*
189 	 * Create copy of |argv| array shifted by one position to
190 	 * emulate $ /usr/bin/sh <scriptname> <args1> <arg2> ... #.
191 	 * First position is set to "/usr/bin/sh" since other
192 	 * values may trigger special shell modes (e.g. *rsh* will
193 	 * trigger "restricted" shell mode etc.).
194 	 */
195 	xargv = calloc(argc + 2, sizeof (char *));
196 	if (xargv == NULL)
197 		return (1);
198 	xargv[0] = "/usr/bin/sh";
199 	for (i = 0; i < argc; i++)
200 		xargv[i + 1] = argv[i];
201 	xargv[i + 1] = NULL;
202 
203 	shp = sh_init(argc + 1, xargv, 0);
204 	if (!shp)
205 		error(ERROR_exit(1), "shell initialisation failed.");
206 	if (setjmp(*shp->jmplist) == 0)
207 		(void) sh_trap(script, 0);
208 
209 	np = nv_open("exitval", shp->var_tree, 0);
210 	if (!np)
211 		error(ERROR_exit(1), "variable %s not found.", "exitval");
212 	exitval = (int)nv_getnum(np);
213 	nv_close(np);
214 
215 	free(xargv);
216 
217 	return (exitval);
218 }
219 
220 int
221 main(int argc, char **argv)
222 {
223 	const char *progname;
224 	const bfastpathrec *brec;
225 	char execnamebuff[PATH_MAX + 1];
226 
227 	/* Get program name */
228 	if (pathprog(argv[0], execnamebuff, sizeof (execnamebuff)) <= 0)
229 		error(ERROR_exit(1), "could not determinate exec name.");
230 
231 	progname = (const char *)strrchr(execnamebuff, '/');
232 
233 	if (progname != NULL)
234 		progname++;
235 	else
236 		progname = execnamebuff;
237 
238 	/* Execute command... */
239 	if (brec = find_bfastpathrec(progname)) {
240 		/* ... either via a fast path (calling the code directly) ... */
241 		return (fastpath_builtin_main(brec, argc, argv));
242 	} else {
243 		/* ... or from within a full shell. */
244 		return (script_builtin_main(argc, argv));
245 	}
246 }
247