v4.19.13 snapshot.
diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
new file mode 100644
index 0000000..998fbb4
--- /dev/null
+++ b/arch/um/os-Linux/umid.c
@@ -0,0 +1,397 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <init.h>
+#include <os.h>
+
+#define UML_DIR "~/.uml/"
+
+#define UMID_LEN 64
+
+/* Changed by set_umid, which is run early in boot */
+static char umid[UMID_LEN] = { 0 };
+
+/* Changed by set_uml_dir and make_uml_dir, which are run early in boot */
+static char *uml_dir = UML_DIR;
+
+static int __init make_uml_dir(void)
+{
+ char dir[512] = { '\0' };
+ int len, err;
+
+ if (*uml_dir == '~') {
+ char *home = getenv("HOME");
+
+ err = -ENOENT;
+ if (home == NULL) {
+ printk(UM_KERN_ERR
+ "%s: no value in environment for $HOME\n",
+ __func__);
+ goto err;
+ }
+ strlcpy(dir, home, sizeof(dir));
+ uml_dir++;
+ }
+ strlcat(dir, uml_dir, sizeof(dir));
+ len = strlen(dir);
+ if (len > 0 && dir[len - 1] != '/')
+ strlcat(dir, "/", sizeof(dir));
+
+ err = -ENOMEM;
+ uml_dir = malloc(strlen(dir) + 1);
+ if (uml_dir == NULL) {
+ printk(UM_KERN_ERR "%s : malloc failed, errno = %d\n",
+ __func__, errno);
+ goto err;
+ }
+ strcpy(uml_dir, dir);
+
+ if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) {
+ printk(UM_KERN_ERR "Failed to mkdir '%s': %s\n",
+ uml_dir, strerror(errno));
+ err = -errno;
+ goto err_free;
+ }
+ return 0;
+
+err_free:
+ free(uml_dir);
+err:
+ uml_dir = NULL;
+ return err;
+}
+
+/*
+ * Unlinks the files contained in @dir and then removes @dir.
+ * Doesn't handle directory trees, so it's not like rm -rf, but almost such. We
+ * ignore ENOENT errors for anything (they happen, strangely enough - possibly
+ * due to races between multiple dying UML threads).
+ */
+static int remove_files_and_dir(char *dir)
+{
+ DIR *directory;
+ struct dirent *ent;
+ int len;
+ char file[256];
+ int ret;
+
+ directory = opendir(dir);
+ if (directory == NULL) {
+ if (errno != ENOENT)
+ return -errno;
+ else
+ return 0;
+ }
+
+ while ((ent = readdir(directory)) != NULL) {
+ if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
+ continue;
+ len = strlen(dir) + sizeof("/") + strlen(ent->d_name) + 1;
+ if (len > sizeof(file)) {
+ ret = -E2BIG;
+ goto out;
+ }
+
+ sprintf(file, "%s/%s", dir, ent->d_name);
+ if (unlink(file) < 0 && errno != ENOENT) {
+ ret = -errno;
+ goto out;
+ }
+ }
+
+ if (rmdir(dir) < 0 && errno != ENOENT) {
+ ret = -errno;
+ goto out;
+ }
+
+ ret = 0;
+out:
+ closedir(directory);
+ return ret;
+}
+
+/*
+ * This says that there isn't already a user of the specified directory even if
+ * there are errors during the checking. This is because if these errors
+ * happen, the directory is unusable by the pre-existing UML, so we might as
+ * well take it over. This could happen either by
+ * the existing UML somehow corrupting its umid directory
+ * something other than UML sticking stuff in the directory
+ * this boot racing with a shutdown of the other UML
+ * In any of these cases, the directory isn't useful for anything else.
+ *
+ * Boolean return: 1 if in use, 0 otherwise.
+ */
+static inline int is_umdir_used(char *dir)
+{
+ char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
+ char pid[sizeof("nnnnn\0")], *end;
+ int dead, fd, p, n, err;
+
+ n = snprintf(file, sizeof(file), "%s/pid", dir);
+ if (n >= sizeof(file)) {
+ printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n");
+ err = -E2BIG;
+ goto out;
+ }
+
+ dead = 0;
+ fd = open(file, O_RDONLY);
+ if (fd < 0) {
+ fd = -errno;
+ if (fd != -ENOENT) {
+ printk(UM_KERN_ERR "is_umdir_used : couldn't open pid "
+ "file '%s', err = %d\n", file, -fd);
+ }
+ goto out;
+ }
+
+ err = 0;
+ n = read(fd, pid, sizeof(pid));
+ if (n < 0) {
+ printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
+ "'%s', err = %d\n", file, errno);
+ goto out_close;
+ } else if (n == 0) {
+ printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
+ "'%s', 0-byte read\n", file);
+ goto out_close;
+ }
+
+ p = strtoul(pid, &end, 0);
+ if (end == pid) {
+ printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file "
+ "'%s', errno = %d\n", file, errno);
+ goto out_close;
+ }
+
+ if ((kill(p, 0) == 0) || (errno != ESRCH)) {
+ printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n",
+ umid, p);
+ return 1;
+ }
+
+out_close:
+ close(fd);
+out:
+ return 0;
+}
+
+/*
+ * Try to remove the directory @dir unless it's in use.
+ * Precondition: @dir exists.
+ * Returns 0 for success, < 0 for failure in removal or if the directory is in
+ * use.
+ */
+static int umdir_take_if_dead(char *dir)
+{
+ int ret;
+ if (is_umdir_used(dir))
+ return -EEXIST;
+
+ ret = remove_files_and_dir(dir);
+ if (ret) {
+ printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir "
+ "failed with err = %d\n", ret);
+ }
+ return ret;
+}
+
+static void __init create_pid_file(void)
+{
+ char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
+ char pid[sizeof("nnnnn\0")];
+ int fd, n;
+
+ if (umid_file_name("pid", file, sizeof(file)))
+ return;
+
+ fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
+ if (fd < 0) {
+ printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: "
+ "%s\n", file, strerror(errno));
+ return;
+ }
+
+ snprintf(pid, sizeof(pid), "%d\n", getpid());
+ n = write(fd, pid, strlen(pid));
+ if (n != strlen(pid))
+ printk(UM_KERN_ERR "Write of pid file failed - err = %d\n",
+ errno);
+
+ close(fd);
+}
+
+int __init set_umid(char *name)
+{
+ if (strlen(name) > UMID_LEN - 1)
+ return -E2BIG;
+
+ strlcpy(umid, name, sizeof(umid));
+
+ return 0;
+}
+
+/* Changed in make_umid, which is called during early boot */
+static int umid_setup = 0;
+
+static int __init make_umid(void)
+{
+ int fd, err;
+ char tmp[256];
+
+ if (umid_setup)
+ return 0;
+
+ make_uml_dir();
+
+ if (*umid == '\0') {
+ strlcpy(tmp, uml_dir, sizeof(tmp));
+ strlcat(tmp, "XXXXXX", sizeof(tmp));
+ fd = mkstemp(tmp);
+ if (fd < 0) {
+ printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: "
+ "%s\n", tmp, strerror(errno));
+ err = -errno;
+ goto err;
+ }
+
+ close(fd);
+
+ set_umid(&tmp[strlen(uml_dir)]);
+
+ /*
+ * There's a nice tiny little race between this unlink and
+ * the mkdir below. It'd be nice if there were a mkstemp
+ * for directories.
+ */
+ if (unlink(tmp)) {
+ err = -errno;
+ goto err;
+ }
+ }
+
+ snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid);
+ err = mkdir(tmp, 0777);
+ if (err < 0) {
+ err = -errno;
+ if (err != -EEXIST)
+ goto err;
+
+ if (umdir_take_if_dead(tmp) < 0)
+ goto err;
+
+ err = mkdir(tmp, 0777);
+ }
+ if (err) {
+ err = -errno;
+ printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid,
+ errno);
+ goto err;
+ }
+
+ umid_setup = 1;
+
+ create_pid_file();
+
+ err = 0;
+ err:
+ return err;
+}
+
+static int __init make_umid_init(void)
+{
+ if (!make_umid())
+ return 0;
+
+ /*
+ * If initializing with the given umid failed, then try again with
+ * a random one.
+ */
+ printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a "
+ "random umid\n", umid);
+ *umid = '\0';
+ make_umid();
+
+ return 0;
+}
+
+__initcall(make_umid_init);
+
+int __init umid_file_name(char *name, char *buf, int len)
+{
+ int n, err;
+
+ err = make_umid();
+ if (err)
+ return err;
+
+ n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name);
+ if (n >= len) {
+ printk(UM_KERN_ERR "umid_file_name : buffer too short\n");
+ return -E2BIG;
+ }
+
+ return 0;
+}
+
+char *get_umid(void)
+{
+ return umid;
+}
+
+static int __init set_uml_dir(char *name, int *add)
+{
+ if (*name == '\0') {
+ os_warn("uml_dir can't be an empty string\n");
+ return 0;
+ }
+
+ if (name[strlen(name) - 1] == '/') {
+ uml_dir = name;
+ return 0;
+ }
+
+ uml_dir = malloc(strlen(name) + 2);
+ if (uml_dir == NULL) {
+ os_warn("Failed to malloc uml_dir - error = %d\n", errno);
+
+ /*
+ * Return 0 here because do_initcalls doesn't look at
+ * the return value.
+ */
+ return 0;
+ }
+ sprintf(uml_dir, "%s/", name);
+
+ return 0;
+}
+
+__uml_setup("uml_dir=", set_uml_dir,
+"uml_dir=<directory>\n"
+" The location to place the pid and umid files.\n\n"
+);
+
+static void remove_umid_dir(void)
+{
+ char dir[strlen(uml_dir) + UMID_LEN + 1], err;
+
+ sprintf(dir, "%s%s", uml_dir, umid);
+ err = remove_files_and_dir(dir);
+ if (err)
+ os_warn("%s - remove_files_and_dir failed with err = %d\n",
+ __func__, err);
+}
+
+__uml_exitcall(remove_umid_dir);