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