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
 29#define is_dir_sep(c) ((c) == '/')
 30
 31static int is_absolute_path(const char *path)
 32{
 33	return path[0] == '/';
 34}
 35
 36static 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
 55static 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
 72char *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
 84const 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
103void 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. */
114char *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
128static 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
140void 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
160static 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
176int 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
187int 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}