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
17 static const char *argv_exec_path;
18 static const char *argv0_path;
19
20 void 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
34 static int is_absolute_path(const char *path)
35 {
36 return path[0] == '/';
37 }
38
39 static 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
57 static 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
77 char *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
89 const 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
108 void 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. */
119 char *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
133 static 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
148 void 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
168 static 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
184 int 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
195 int 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
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