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(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
 58static 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
 75char *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
 87const 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
106void 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. */
117char *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
131static 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
143void 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
163static 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
179int 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
190int 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}