arch/x86/um/tls_32.c - linux - Git at Google

 /*
  * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
  * Licensed under the GPL
  */

 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include <asm/ptrace-abi.h>
 #include <os.h>
 #include <skas.h>
 #include <sysdep/tls.h>
 #include <asm/desc.h>

 /*
  * If needed we can detect when it's uninitialized.
  *
  * These are initialized in an initcall and unchanged thereafter.
  */
 static int host_supports_tls = -1;
 int host_gdt_entry_tls_min;

 static int do_set_thread_area(struct user_desc *info)
 {
 	int ret;
 	u32 cpu;

 	cpu = get_cpu();
 	ret = os_set_thread_area(info, userspace_pid[cpu]);
 	put_cpu();

 	if (ret)
 		printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
 		       "index = %d\n", ret, info->entry_number);

 	return ret;
 }

 /*
  * sys_get_thread_area: get a yet unused TLS descriptor index.
  * XXX: Consider leaving one free slot for glibc usage at first place. This must
  * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
  *
  * Also, this must be tested when compiling in SKAS mode with dynamic linking
  * and running against NPTL.
  */
 static int get_free_idx(struct task_struct* task)
 {
 	struct thread_struct *t = &task->thread;
 	int idx;

 	for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
 		if (!t->arch.tls_array[idx].present)
 			return idx + GDT_ENTRY_TLS_MIN;
 	return -ESRCH;
 }

 static inline void clear_user_desc(struct user_desc* info)
 {
 	/* Postcondition: LDT_empty(info) returns true. */
 	memset(info, 0, sizeof(*info));

 	/*
 	 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
 	 * indeed an empty user_desc.
 	 */
 	info->read_exec_only = 1;
 	info->seg_not_present = 1;
 }

 #define O_FORCE 1

 static int load_TLS(int flags, struct task_struct *to)
 {
 	int ret = 0;
 	int idx;

 	for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
 		struct uml_tls_struct* curr =
 			&to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];

 		/*
 		 * Actually, now if it wasn't flushed it gets cleared and
 		 * flushed to the host, which will clear it.
 		 */
 		if (!curr->present) {
 			if (!curr->flushed) {
 				clear_user_desc(&curr->tls);
 				curr->tls.entry_number = idx;
 			} else {
 				WARN_ON(!LDT_empty(&curr->tls));
 				continue;
 			}
 		}

 		if (!(flags & O_FORCE) && curr->flushed)
 			continue;

 		ret = do_set_thread_area(&curr->tls);
 		if (ret)
 			goto out;

 		curr->flushed = 1;
 	}
 out:
 	return ret;
 }

 /*
  * Verify if we need to do a flush for the new process, i.e. if there are any
  * present desc's, only if they haven't been flushed.
  */
 static inline int needs_TLS_update(struct task_struct *task)
 {
 	int i;
 	int ret = 0;

 	for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
 		struct uml_tls_struct* curr =
 			&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];

 		/*
 		 * Can't test curr->present, we may need to clear a descriptor
 		 * which had a value.
 		 */
 		if (curr->flushed)
 			continue;
 		ret = 1;
 		break;
 	}
 	return ret;
 }

 /*
  * On a newly forked process, the TLS descriptors haven't yet been flushed. So
  * we mark them as such and the first switch_to will do the job.
  */
 void clear_flushed_tls(struct task_struct *task)
 {
 	int i;

 	for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
 		struct uml_tls_struct* curr =
 			&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];

 		/*
 		 * Still correct to do this, if it wasn't present on the host it
 		 * will remain as flushed as it was.
 		 */
 		if (!curr->present)
 			continue;

 		curr->flushed = 0;
 	}
 }

 /*
  * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
  * common host process. So this is needed in SKAS0 too.
  *
  * However, if each thread had a different host process (and this was discussed
  * for SMP support) this won't be needed.
  *
  * And this will not need be used when (and if) we'll add support to the host
  * SKAS patch.
  */

 int arch_switch_tls(struct task_struct *to)
 {
 	if (!host_supports_tls)
 		return 0;

 	/*
 	 * We have no need whatsoever to switch TLS for kernel threads; beyond
 	 * that, that would also result in us calling os_set_thread_area with
 	 * userspace_pid[cpu] == 0, which gives an error.
 	 */
 	if (likely(to->mm))
 		return load_TLS(O_FORCE, to);

 	return 0;
 }

 static int set_tls_entry(struct task_struct* task, struct user_desc *info,
 			 int idx, int flushed)
 {
 	struct thread_struct *t = &task->thread;

 	if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 		return -EINVAL;

 	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
 	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
 	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;

 	return 0;
 }

 int arch_set_tls(struct task_struct *new, unsigned long tls)
 {
 	struct user_desc info;
 	int idx, ret = -EFAULT;

 	if (copy_from_user(&info, (void __user *) tls, sizeof(info)))
 		goto out;

 	ret = -EINVAL;
 	if (LDT_empty(&info))
 		goto out;

 	idx = info.entry_number;

 	ret = set_tls_entry(new, &info, idx, 0);
 out:
 	return ret;
 }

 static int get_tls_entry(struct task_struct *task, struct user_desc *info,
 			 int idx)
 {
 	struct thread_struct *t = &task->thread;

 	if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 		return -EINVAL;

 	if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
 		goto clear;

 	*info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;

 out:
 	/*
 	 * Temporary debugging check, to make sure that things have been
 	 * flushed. This could be triggered if load_TLS() failed.
 	 */
 	if (unlikely(task == current &&
 		     !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
 		printk(KERN_ERR "get_tls_entry: task with pid %d got here "
 				"without flushed TLS.", current->pid);
 	}

 	return 0;
 clear:
 	/*
 	 * When the TLS entry has not been set, the values read to user in the
 	 * tls_array are 0 (because it's cleared at boot, see
 	 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
 	 */
 	clear_user_desc(info);
 	info->entry_number = idx;
 	goto out;
 }

 SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
 {
 	struct user_desc info;
 	int idx, ret;

 	if (!host_supports_tls)
 		return -ENOSYS;

 	if (copy_from_user(&info, user_desc, sizeof(info)))
 		return -EFAULT;

 	idx = info.entry_number;

 	if (idx == -1) {
 		idx = get_free_idx(current);
 		if (idx < 0)
 			return idx;
 		info.entry_number = idx;
 		/* Tell the user which slot we chose for him.*/
 		if (put_user(idx, &user_desc->entry_number))
 			return -EFAULT;
 	}

 	ret = do_set_thread_area(&info);
 	if (ret)
 		return ret;
 	return set_tls_entry(current, &info, idx, 1);
 }

 /*
  * Perform set_thread_area on behalf of the traced child.
  * Note: error handling is not done on the deferred load, and this differ from
  * i386. However the only possible error are caused by bugs.
  */
 int ptrace_set_thread_area(struct task_struct *child, int idx,
 			   struct user_desc __user *user_desc)
 {
 	struct user_desc info;

 	if (!host_supports_tls)
 		return -EIO;

 	if (copy_from_user(&info, user_desc, sizeof(info)))
 		return -EFAULT;

 	return set_tls_entry(child, &info, idx, 0);
 }

 SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
 {
 	struct user_desc info;
 	int idx, ret;

 	if (!host_supports_tls)
 		return -ENOSYS;

 	if (get_user(idx, &user_desc->entry_number))
 		return -EFAULT;

 	ret = get_tls_entry(current, &info, idx);
 	if (ret < 0)
 		goto out;

 	if (copy_to_user(user_desc, &info, sizeof(info)))
 		ret = -EFAULT;

 out:
 	return ret;
 }

 /*
  * Perform get_thread_area on behalf of the traced child.
  */
 int ptrace_get_thread_area(struct task_struct *child, int idx,
 		struct user_desc __user *user_desc)
 {
 	struct user_desc info;
 	int ret;

 	if (!host_supports_tls)
 		return -EIO;

 	ret = get_tls_entry(child, &info, idx);
 	if (ret < 0)
 		goto out;

 	if (copy_to_user(user_desc, &info, sizeof(info)))
 		ret = -EFAULT;
 out:
 	return ret;
 }

 /*
  * This code is really i386-only, but it detects and logs x86_64 GDT indexes
  * if a 32-bit UML is running on a 64-bit host.
  */
 static int __init __setup_host_supports_tls(void)
 {
 	check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
 	if (host_supports_tls) {
 		printk(KERN_INFO "Host TLS support detected\n");
 		printk(KERN_INFO "Detected host type: ");
 		switch (host_gdt_entry_tls_min) {
 		case GDT_ENTRY_TLS_MIN_I386:
 			printk(KERN_CONT "i386");
 			break;
 		case GDT_ENTRY_TLS_MIN_X86_64:
 			printk(KERN_CONT "x86_64");
 			break;
 		}
 		printk(KERN_CONT " (GDT indexes %d to %d)\n",
 		       host_gdt_entry_tls_min,
 		       host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
 	} else
 		printk(KERN_ERR "  Host TLS support NOT detected! "
 				"TLS support inside UML will not work\n");
 	return 0;
 }

 __initcall(__setup_host_supports_tls);
	/*
	* Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
	* Licensed under the GPL
	*/

	#include <linux/percpu.h>
	#include <linux/sched.h>
	#include <linux/syscalls.h>
	#include <linux/uaccess.h>
	#include <asm/ptrace-abi.h>
	#include <os.h>
	#include <skas.h>
	#include <sysdep/tls.h>
	#include <asm/desc.h>

	/*
	* If needed we can detect when it's uninitialized.
	*
	* These are initialized in an initcall and unchanged thereafter.
	*/
	static int host_supports_tls = -1;
	int host_gdt_entry_tls_min;

	static int do_set_thread_area(struct user_desc *info)
	{
	int ret;
	u32 cpu;

	cpu = get_cpu();
	ret = os_set_thread_area(info, userspace_pid[cpu]);
	put_cpu();

	if (ret)
	printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
	"index = %d\n", ret, info->entry_number);

	return ret;
	}

	/*
	* sys_get_thread_area: get a yet unused TLS descriptor index.
	* XXX: Consider leaving one free slot for glibc usage at first place. This must
	* be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
	*
	* Also, this must be tested when compiling in SKAS mode with dynamic linking
	* and running against NPTL.
	*/
	static int get_free_idx(struct task_struct* task)
	{
	struct thread_struct *t = &task->thread;
	int idx;

	for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
	if (!t->arch.tls_array[idx].present)
	return idx + GDT_ENTRY_TLS_MIN;
	return -ESRCH;
	}

	static inline void clear_user_desc(struct user_desc* info)
	{
	/* Postcondition: LDT_empty(info) returns true. */
	memset(info, 0, sizeof(*info));

	/*
	* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
	* indeed an empty user_desc.
	*/
	info->read_exec_only = 1;
	info->seg_not_present = 1;
	}

	#define O_FORCE 1

	static int load_TLS(int flags, struct task_struct *to)
	{
	int ret = 0;
	int idx;

	for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
	struct uml_tls_struct* curr =
	&to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];

	/*
	* Actually, now if it wasn't flushed it gets cleared and
	* flushed to the host, which will clear it.
	*/
	if (!curr->present) {
	if (!curr->flushed) {
	clear_user_desc(&curr->tls);
	curr->tls.entry_number = idx;
	} else {
	WARN_ON(!LDT_empty(&curr->tls));
	continue;
	}
	}

	if (!(flags & O_FORCE) && curr->flushed)
	continue;

	ret = do_set_thread_area(&curr->tls);
	if (ret)
	goto out;

	curr->flushed = 1;
	}
	out:
	return ret;
	}

	/*
	* Verify if we need to do a flush for the new process, i.e. if there are any
	* present desc's, only if they haven't been flushed.
	*/
	static inline int needs_TLS_update(struct task_struct *task)
	{
	int i;
	int ret = 0;

	for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
	struct uml_tls_struct* curr =
	&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];

	/*
	* Can't test curr->present, we may need to clear a descriptor
	* which had a value.
	*/
	if (curr->flushed)
	continue;
	ret = 1;
	break;
	}
	return ret;
	}

	/*
	* On a newly forked process, the TLS descriptors haven't yet been flushed. So
	* we mark them as such and the first switch_to will do the job.
	*/
	void clear_flushed_tls(struct task_struct *task)
	{
	int i;

	for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
	struct uml_tls_struct* curr =
	&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];

	/*
	* Still correct to do this, if it wasn't present on the host it
	* will remain as flushed as it was.
	*/
	if (!curr->present)
	continue;

	curr->flushed = 0;
	}
	}

	/*
	* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
	* common host process. So this is needed in SKAS0 too.
	*
	* However, if each thread had a different host process (and this was discussed
	* for SMP support) this won't be needed.
	*
	* And this will not need be used when (and if) we'll add support to the host
	* SKAS patch.
	*/

	int arch_switch_tls(struct task_struct *to)
	{
	if (!host_supports_tls)
	return 0;

	/*
	* We have no need whatsoever to switch TLS for kernel threads; beyond
	* that, that would also result in us calling os_set_thread_area with
	* userspace_pid[cpu] == 0, which gives an error.
	*/
	if (likely(to->mm))
	return load_TLS(O_FORCE, to);

	return 0;
	}

	static int set_tls_entry(struct task_struct* task, struct user_desc *info,
	int idx, int flushed)
	{
	struct thread_struct *t = &task->thread;

	if (idx < GDT_ENTRY_TLS_MIN \|\| idx > GDT_ENTRY_TLS_MAX)
	return -EINVAL;

	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
	t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;

	return 0;
	}

	int arch_set_tls(struct task_struct *new, unsigned long tls)
	{
	struct user_desc info;
	int idx, ret = -EFAULT;

	if (copy_from_user(&info, (void __user *) tls, sizeof(info)))
	goto out;

	ret = -EINVAL;
	if (LDT_empty(&info))
	goto out;

	idx = info.entry_number;

	ret = set_tls_entry(new, &info, idx, 0);
	out:
	return ret;
	}

	static int get_tls_entry(struct task_struct task, struct user_desc info,
	int idx)
	{
	struct thread_struct *t = &task->thread;

	if (idx < GDT_ENTRY_TLS_MIN \|\| idx > GDT_ENTRY_TLS_MAX)
	return -EINVAL;

	if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
	goto clear;

	*info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;

	out:
	/*
	* Temporary debugging check, to make sure that things have been
	* flushed. This could be triggered if load_TLS() failed.
	*/
	if (unlikely(task == current &&
	!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
	printk(KERN_ERR "get_tls_entry: task with pid %d got here "
	"without flushed TLS.", current->pid);
	}

	return 0;
	clear:
	/*
	* When the TLS entry has not been set, the values read to user in the
	* tls_array are 0 (because it's cleared at boot, see
	* arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
	*/
	clear_user_desc(info);
	info->entry_number = idx;
	goto out;
	}

	SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
	{
	struct user_desc info;
	int idx, ret;

	if (!host_supports_tls)
	return -ENOSYS;

	if (copy_from_user(&info, user_desc, sizeof(info)))
	return -EFAULT;

	idx = info.entry_number;

	if (idx == -1) {
	idx = get_free_idx(current);
	if (idx < 0)
	return idx;
	info.entry_number = idx;
	/* Tell the user which slot we chose for him.*/
	if (put_user(idx, &user_desc->entry_number))
	return -EFAULT;
	}

	ret = do_set_thread_area(&info);
	if (ret)
	return ret;
	return set_tls_entry(current, &info, idx, 1);
	}

	/*
	* Perform set_thread_area on behalf of the traced child.
	* Note: error handling is not done on the deferred load, and this differ from
	* i386. However the only possible error are caused by bugs.
	*/
	int ptrace_set_thread_area(struct task_struct *child, int idx,
	struct user_desc __user *user_desc)
	{
	struct user_desc info;

	if (!host_supports_tls)
	return -EIO;

	if (copy_from_user(&info, user_desc, sizeof(info)))
	return -EFAULT;

	return set_tls_entry(child, &info, idx, 0);
	}

	SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
	{
	struct user_desc info;
	int idx, ret;

	if (!host_supports_tls)
	return -ENOSYS;

	if (get_user(idx, &user_desc->entry_number))
	return -EFAULT;

	ret = get_tls_entry(current, &info, idx);
	if (ret < 0)
	goto out;

	if (copy_to_user(user_desc, &info, sizeof(info)))
	ret = -EFAULT;

	out:
	return ret;
	}

	/*
	* Perform get_thread_area on behalf of the traced child.
	*/
	int ptrace_get_thread_area(struct task_struct *child, int idx,
	struct user_desc __user *user_desc)
	{
	struct user_desc info;
	int ret;

	if (!host_supports_tls)
	return -EIO;

	ret = get_tls_entry(child, &info, idx);
	if (ret < 0)
	goto out;

	if (copy_to_user(user_desc, &info, sizeof(info)))
	ret = -EFAULT;
	out:
	return ret;
	}

	/*
	* This code is really i386-only, but it detects and logs x86_64 GDT indexes
	* if a 32-bit UML is running on a 64-bit host.
	*/
	static int __init __setup_host_supports_tls(void)
	{
	check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
	if (host_supports_tls) {
	printk(KERN_INFO "Host TLS support detected\n");
	printk(KERN_INFO "Detected host type: ");
	switch (host_gdt_entry_tls_min) {
	case GDT_ENTRY_TLS_MIN_I386:
	printk(KERN_CONT "i386");
	break;
	case GDT_ENTRY_TLS_MIN_X86_64:
	printk(KERN_CONT "x86_64");
	break;
	}
	printk(KERN_CONT " (GDT indexes %d to %d)\n",
	host_gdt_entry_tls_min,
	host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
	} else
	printk(KERN_ERR " Host TLS support NOT detected! "
	"TLS support inside UML will not work\n");
	return 0;
	}

	__initcall(__setup_host_supports_tls);