1// SPDX-License-Identifier: GPL-2.0
2#include <linux/compiler.h>
3#include <linux/string.h>
4#include <sys/types.h>
5#include <sys/stat.h>
6#include <unistd.h>
7#include <string.h>
8#include <stdlib.h>
9#include <stdio.h>
10#include "subcmd-util.h"
11#include "exec-cmd.h"
12#include "subcmd-config.h"
13
14#define MAX_ARGS	32
15#define PATH_MAX	4096
16
17static const char *argv_exec_path;
18static const char *argv0_path;
19
20void exec_cmd_init(const char *exec_name, const char *prefix,
21		   const char *exec_path, const char *exec_path_env)
22{
23	subcmd_config.exec_name		= exec_name;
24	subcmd_config.prefix		= prefix;
25	subcmd_config.exec_path		= exec_path;
26	subcmd_config.exec_path_env	= exec_path_env;
27
28	/* Setup environment variable for invoked shell script. */
29	setenv("PREFIX", prefix, 1);
30}
31
32#define is_dir_sep(c) ((c) == '/')
33
34static int is_absolute_path(const char *path)
35{
36	return path[0] == '/';
37}
38
39static const char *get_pwd_cwd(char *buf, size_t sz)
40{
41	char *pwd;
42	struct stat cwd_stat, pwd_stat;
43	if (getcwd(buf, sz) == NULL)
44		return NULL;
45	pwd = getenv("PWD");
46	if (pwd && strcmp(pwd, buf)) {
47		stat(buf, &cwd_stat);
48		if (!stat(pwd, &pwd_stat) &&
49		    pwd_stat.st_dev == cwd_stat.st_dev &&
50		    pwd_stat.st_ino == cwd_stat.st_ino) {
51			strlcpy(buf, pwd, sz);
52		}
53	}
54	return buf;
55}
56
57static const char *make_nonrelative_path(char *buf, size_t sz, const char *path)
58{
59	if (is_absolute_path(path)) {
60		if (strlcpy(buf, path, sz) >= sz)
61			die("Too long path: %.*s", 60, path);
62	} else {
63		const char *cwd = get_pwd_cwd(buf, sz);
64
65		if (!cwd)
66			die("Cannot determine the current working directory");
67
68		if (strlen(cwd) + strlen(path) + 2 >= sz)
69			die("Too long path: %.*s", 60, path);
70
71		strcat(buf, "/");
72		strcat(buf, path);
73	}
74	return buf;
75}
76
77char *system_path(const char *path)
78{
79	char *buf = NULL;
80
81	if (is_absolute_path(path))
82		return strdup(path);
83
84	astrcatf(&buf, "%s/%s", subcmd_config.prefix, path);
85
86	return buf;
87}
88
89const char *extract_argv0_path(const char *argv0)
90{
91	const char *slash;
92
93	if (!argv0 || !*argv0)
94		return NULL;
95	slash = argv0 + strlen(argv0);
96
97	while (argv0 <= slash && !is_dir_sep(*slash))
98		slash--;
99
100	if (slash >= argv0) {
101		argv0_path = strndup(argv0, slash - argv0);
102		return argv0_path ? slash + 1 : NULL;
103	}
104
105	return argv0;
106}
107
108void set_argv_exec_path(const char *exec_path)
109{
110	argv_exec_path = exec_path;
111	/*
112	 * Propagate this setting to external programs.
113	 */
114	setenv(subcmd_config.exec_path_env, exec_path, 1);
115}
116
117
118/* Returns the highest-priority location to look for subprograms. */
119char *get_argv_exec_path(void)
120{
121	char *env;
122
123	if (argv_exec_path)
124		return strdup(argv_exec_path);
125
126	env = getenv(subcmd_config.exec_path_env);
127	if (env && *env)
128		return strdup(env);
129
130	return system_path(subcmd_config.exec_path);
131}
132
133static void add_path(char **out, const char *path)
134{
135	if (path && *path) {
136		if (is_absolute_path(path))
137			astrcat(out, path);
138		else {
139			char buf[PATH_MAX];
140
141			astrcat(out, make_nonrelative_path(buf, sizeof(buf), path));
142		}
143
144		astrcat(out, ":");
145	}
146}
147
148void setup_path(void)
149{
150	const char *old_path = getenv("PATH");
151	char *new_path = NULL;
152	char *tmp = get_argv_exec_path();
153
154	add_path(&new_path, tmp);
155	add_path(&new_path, argv0_path);
156	free(tmp);
157
158	if (old_path)
159		astrcat(&new_path, old_path);
160	else
161		astrcat(&new_path, "/usr/local/bin:/usr/bin:/bin");
162
163	setenv("PATH", new_path, 1);
164
165	free(new_path);
166}
167
168static const char **prepare_exec_cmd(const char **argv)
169{
170	int argc;
171	const char **nargv;
172
173	for (argc = 0; argv[argc]; argc++)
174		; /* just counting */
175	nargv = malloc(sizeof(*nargv) * (argc + 2));
176
177	nargv[0] = subcmd_config.exec_name;
178	for (argc = 0; argv[argc]; argc++)
179		nargv[argc + 1] = argv[argc];
180	nargv[argc + 1] = NULL;
181	return nargv;
182}
183
184int execv_cmd(const char **argv) {
185	const char **nargv = prepare_exec_cmd(argv);
186
187	/* execvp() can only ever return if it fails */
188	execvp(subcmd_config.exec_name, (char **)nargv);
189
190	free(nargv);
191	return -1;
192}
193
194
195int execl_cmd(const char *cmd,...)
196{
197	int argc;
198	const char *argv[MAX_ARGS + 1];
199	const char *arg;
200	va_list param;
201
202	va_start(param, cmd);
203	argv[0] = cmd;
204	argc = 1;
205	while (argc < MAX_ARGS) {
206		arg = argv[argc++] = va_arg(param, char *);
207		if (!arg)
208			break;
209	}
210	va_end(param);
211	if (MAX_ARGS <= argc) {
212		fprintf(stderr, " Error: too many args to run %s\n", cmd);
213		return -1;
214	}
215
216	argv[argc] = NULL;
217	return execv_cmd(argv);
218}
219