v4.19.13 snapshot.
diff --git a/tools/lib/subcmd/exec-cmd.c b/tools/lib/subcmd/exec-cmd.c
new file mode 100644
index 0000000..33e94fb
--- /dev/null
+++ b/tools/lib/subcmd/exec-cmd.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <linux/string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "subcmd-util.h"
+#include "exec-cmd.h"
+#include "subcmd-config.h"
+
+#define MAX_ARGS 32
+#define PATH_MAX 4096
+
+static const char *argv_exec_path;
+static const char *argv0_path;
+
+void exec_cmd_init(const char *exec_name, const char *prefix,
+ const char *exec_path, const char *exec_path_env)
+{
+ subcmd_config.exec_name = exec_name;
+ subcmd_config.prefix = prefix;
+ subcmd_config.exec_path = exec_path;
+ subcmd_config.exec_path_env = exec_path_env;
+}
+
+#define is_dir_sep(c) ((c) == '/')
+
+static int is_absolute_path(const char *path)
+{
+ return path[0] == '/';
+}
+
+static const char *get_pwd_cwd(void)
+{
+ static char cwd[PATH_MAX + 1];
+ char *pwd;
+ struct stat cwd_stat, pwd_stat;
+ if (getcwd(cwd, PATH_MAX) == NULL)
+ return NULL;
+ pwd = getenv("PWD");
+ if (pwd && strcmp(pwd, cwd)) {
+ stat(cwd, &cwd_stat);
+ if (!stat(pwd, &pwd_stat) &&
+ pwd_stat.st_dev == cwd_stat.st_dev &&
+ pwd_stat.st_ino == cwd_stat.st_ino) {
+ strlcpy(cwd, pwd, PATH_MAX);
+ }
+ }
+ return cwd;
+}
+
+static const char *make_nonrelative_path(const char *path)
+{
+ static char buf[PATH_MAX + 1];
+
+ if (is_absolute_path(path)) {
+ if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
+ die("Too long path: %.*s", 60, path);
+ } else {
+ const char *cwd = get_pwd_cwd();
+ if (!cwd)
+ die("Cannot determine the current working directory");
+ if (snprintf(buf, PATH_MAX, "%s/%s", cwd, path) >= PATH_MAX)
+ die("Too long path: %.*s", 60, path);
+ }
+ return buf;
+}
+
+char *system_path(const char *path)
+{
+ char *buf = NULL;
+
+ if (is_absolute_path(path))
+ return strdup(path);
+
+ astrcatf(&buf, "%s/%s", subcmd_config.prefix, path);
+
+ return buf;
+}
+
+const char *extract_argv0_path(const char *argv0)
+{
+ const char *slash;
+
+ if (!argv0 || !*argv0)
+ return NULL;
+ slash = argv0 + strlen(argv0);
+
+ while (argv0 <= slash && !is_dir_sep(*slash))
+ slash--;
+
+ if (slash >= argv0) {
+ argv0_path = strndup(argv0, slash - argv0);
+ return argv0_path ? slash + 1 : NULL;
+ }
+
+ return argv0;
+}
+
+void set_argv_exec_path(const char *exec_path)
+{
+ argv_exec_path = exec_path;
+ /*
+ * Propagate this setting to external programs.
+ */
+ setenv(subcmd_config.exec_path_env, exec_path, 1);
+}
+
+
+/* Returns the highest-priority location to look for subprograms. */
+char *get_argv_exec_path(void)
+{
+ char *env;
+
+ if (argv_exec_path)
+ return strdup(argv_exec_path);
+
+ env = getenv(subcmd_config.exec_path_env);
+ if (env && *env)
+ return strdup(env);
+
+ return system_path(subcmd_config.exec_path);
+}
+
+static void add_path(char **out, const char *path)
+{
+ if (path && *path) {
+ if (is_absolute_path(path))
+ astrcat(out, path);
+ else
+ astrcat(out, make_nonrelative_path(path));
+
+ astrcat(out, ":");
+ }
+}
+
+void setup_path(void)
+{
+ const char *old_path = getenv("PATH");
+ char *new_path = NULL;
+ char *tmp = get_argv_exec_path();
+
+ add_path(&new_path, tmp);
+ add_path(&new_path, argv0_path);
+ free(tmp);
+
+ if (old_path)
+ astrcat(&new_path, old_path);
+ else
+ astrcat(&new_path, "/usr/local/bin:/usr/bin:/bin");
+
+ setenv("PATH", new_path, 1);
+
+ free(new_path);
+}
+
+static const char **prepare_exec_cmd(const char **argv)
+{
+ int argc;
+ const char **nargv;
+
+ for (argc = 0; argv[argc]; argc++)
+ ; /* just counting */
+ nargv = malloc(sizeof(*nargv) * (argc + 2));
+
+ nargv[0] = subcmd_config.exec_name;
+ for (argc = 0; argv[argc]; argc++)
+ nargv[argc + 1] = argv[argc];
+ nargv[argc + 1] = NULL;
+ return nargv;
+}
+
+int execv_cmd(const char **argv) {
+ const char **nargv = prepare_exec_cmd(argv);
+
+ /* execvp() can only ever return if it fails */
+ execvp(subcmd_config.exec_name, (char **)nargv);
+
+ free(nargv);
+ return -1;
+}
+
+
+int execl_cmd(const char *cmd,...)
+{
+ int argc;
+ const char *argv[MAX_ARGS + 1];
+ const char *arg;
+ va_list param;
+
+ va_start(param, cmd);
+ argv[0] = cmd;
+ argc = 1;
+ while (argc < MAX_ARGS) {
+ arg = argv[argc++] = va_arg(param, char *);
+ if (!arg)
+ break;
+ }
+ va_end(param);
+ if (MAX_ARGS <= argc) {
+ fprintf(stderr, " Error: too many args to run %s\n", cmd);
+ return -1;
+ }
+
+ argv[argc] = NULL;
+ return execv_cmd(argv);
+}