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