swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Tip revision: 02f8c6aee8df3cdc935e9bdd4f2d020306035dbe authored by Linus Torvalds on 22 July 2011, 02:17:23 UTC
Linux 3.0
Linux 3.0
Tip revision: 02f8c6a
umid.c
/*
* 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 "kern_constants.h"
#include "os.h"
#include "user.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 "make_uml_dir : no value in "
"environment for $HOME\n");
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) {
printf("make_uml_dir : malloc failed, errno = %d\n", errno);
goto err;
}
strcpy(uml_dir, dir);
if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) {
printf("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') {
printf("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) {
printf("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)
printf("remove_umid_dir - remove_files_and_dir failed with "
"err = %d\n", err);
}
__uml_exitcall(remove_umid_dir);