xref: /linux/tools/lib/subcmd/exec-cmd.c (revision cdd5b5a9761fd66d17586e4f4ba6588c70e640ea)
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(char * buf,size_t sz)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 
make_nonrelative_path(char * buf,size_t sz,const char * path)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 
system_path(const char * path)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 
extract_argv0_path(const char * argv0)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 
set_argv_exec_path(const char * exec_path)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. */
get_argv_exec_path(void)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 
add_path(char ** out,const char * path)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 
setup_path(void)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 
prepare_exec_cmd(const char ** argv)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 
execv_cmd(const char ** argv)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 
execl_cmd(const char * cmd,...)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