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