arch/um/os-Linux/umid.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  */

 #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) + strlen("/") + 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 pid[sizeof("nnnnnnnnn")], *end, *file;
 	int dead, fd, p, n, err;
 	size_t filelen = strlen(dir) + sizeof("/pid") + 1;

 	file = malloc(filelen);
 	if (!file)
 		return -ENOMEM;

 	snprintf(file, filelen, "%s/pid", dir);

 	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:
 	free(file);
 	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 pid[sizeof("nnnnnnnnn")], *file;
 	int fd, n;

 	n = strlen(uml_dir) + UMID_LEN + sizeof("/pid");
 	file = malloc(n);
 	if (!file)
 		return;

 	if (umid_file_name("pid", file, n))
 		goto out;

 	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));
 		goto out;
 	}

 	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);
 out:
 	free(file);
 }

 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, err;

 	dir = malloc(strlen(uml_dir) + UMID_LEN + 1);
 	if (!dir)
 		return;

 	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);

 	free(dir);
 }

 __uml_exitcall(remove_umid_dir);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
	*/

	#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) + strlen("/") + 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 pid[sizeof("nnnnnnnnn")], end, file;
	int dead, fd, p, n, err;
	size_t filelen = strlen(dir) + sizeof("/pid") + 1;

	file = malloc(filelen);
	if (!file)
	return -ENOMEM;

	snprintf(file, filelen, "%s/pid", dir);

	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:
	free(file);
	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 pid[sizeof("nnnnnnnnn")], *file;
	int fd, n;

	n = strlen(uml_dir) + UMID_LEN + sizeof("/pid");
	file = malloc(n);
	if (!file)
	return;

	if (umid_file_name("pid", file, n))
	goto out;

	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));
	goto out;
	}

	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);
	out:
	free(file);
	}

	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, err;

	dir = malloc(strlen(uml_dir) + UMID_LEN + 1);
	if (!dir)
	return;

	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);

	free(dir);
	}

	__uml_exitcall(remove_umid_dir);