root/arch/x86/kernel/tls.c

DEFINITIONS

1. get_free_idx
2. set_tls_desc
3. do_set_thread_area
4. sys_set_thread_area
5. fill_user_desc
6. do_get_thread_area
7. sys_get_thread_area
8. regset_tls_active
9. regset_tls_get
10. regset_tls_set

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/user.h>
#include <linux/regset.h>

#include <asm/uaccess.h>
#include <asm/desc.h>
#include <asm/system.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/proto.h>
#include <asm/syscalls.h>

#include "tls.h"

/*
 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
 */
static int get_free_idx(void)
{
        struct thread_struct *t = &current->thread;
        int idx;

        for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
                if (desc_empty(&t->tls_array[idx]))
                        return idx + GDT_ENTRY_TLS_MIN;
        return -ESRCH;
}

static void set_tls_desc(struct task_struct *p, int idx,
                         const struct user_desc *info, int n)
{
        struct thread_struct *t = &p->thread;
        struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
        int cpu;

        /*
         * We must not get preempted while modifying the TLS.
         */
        cpu = get_cpu();

        while (n-- > 0) {
                if (LDT_empty(info))
                        desc->a = desc->b = 0;
                else
                        fill_ldt(desc, info);
                ++info;
                ++desc;
        }

        if (t == &current->thread)
                load_TLS(t, cpu);

        put_cpu();
}

/*
 * Set a given TLS descriptor:
 */
int do_set_thread_area(struct task_struct *p, int idx,
                       struct user_desc __user *u_info,
                       int can_allocate)
{
        struct user_desc info;

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

        if (idx == -1)
                idx = info.entry_number;

        /*
         * index -1 means the kernel should try to find and
         * allocate an empty descriptor:
         */
        if (idx == -1 && can_allocate) {
                idx = get_free_idx();
                if (idx < 0)
                        return idx;
                if (put_user(idx, &u_info->entry_number))
                        return -EFAULT;
        }

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

        set_tls_desc(p, idx, &info, 1);

        return 0;
}

asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
{
        int ret = do_set_thread_area(current, -1, u_info, 1);
        asmlinkage_protect(1, ret, u_info);
        return ret;
}


/*
 * Get the current Thread-Local Storage area:
 */

static void fill_user_desc(struct user_desc *info, int idx,
                           const struct desc_struct *desc)

{
        memset(info, 0, sizeof(*info));
        info->entry_number = idx;
        info->base_addr = get_desc_base(desc);
        info->limit = get_desc_limit(desc);
        info->seg_32bit = desc->d;
        info->contents = desc->type >> 2;
        info->read_exec_only = !(desc->type & 2);
        info->limit_in_pages = desc->g;
        info->seg_not_present = !desc->p;
        info->useable = desc->avl;
#ifdef CONFIG_X86_64
        info->lm = desc->l;
#endif
}

int do_get_thread_area(struct task_struct *p, int idx,
                       struct user_desc __user *u_info)
{
        struct user_desc info;

        if (idx == -1 && get_user(idx, &u_info->entry_number))
                return -EFAULT;

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

        fill_user_desc(&info, idx,
                       &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);

        if (copy_to_user(u_info, &info, sizeof(info)))
                return -EFAULT;
        return 0;
}

asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
{
        int ret = do_get_thread_area(current, -1, u_info);
        asmlinkage_protect(1, ret, u_info);
        return ret;
}

int regset_tls_active(struct task_struct *target,
                      const struct user_regset *regset)
{
        struct thread_struct *t = &target->thread;
        int n = GDT_ENTRY_TLS_ENTRIES;
        while (n > 0 && desc_empty(&t->tls_array[n - 1]))
                --n;
        return n;
}

int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
                   unsigned int pos, unsigned int count,
                   void *kbuf, void __user *ubuf)
{
        const struct desc_struct *tls;

        if (pos > GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
            (pos % sizeof(struct user_desc)) != 0 ||
            (count % sizeof(struct user_desc)) != 0)
                return -EINVAL;

        pos /= sizeof(struct user_desc);
        count /= sizeof(struct user_desc);

        tls = &target->thread.tls_array[pos];

        if (kbuf) {
                struct user_desc *info = kbuf;
                while (count-- > 0)
                        fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
                                       tls++);
        } else {
                struct user_desc __user *u_info = ubuf;
                while (count-- > 0) {
                        struct user_desc info;
                        fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
                        if (__copy_to_user(u_info++, &info, sizeof(info)))
                                return -EFAULT;
                }
        }

        return 0;
}

int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
                   unsigned int pos, unsigned int count,
                   const void *kbuf, const void __user *ubuf)
{
        struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
        const struct user_desc *info;

        if (pos > GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
            (pos % sizeof(struct user_desc)) != 0 ||
            (count % sizeof(struct user_desc)) != 0)
                return -EINVAL;

        if (kbuf)
                info = kbuf;
        else if (__copy_from_user(infobuf, ubuf, count))
                return -EFAULT;
        else
                info = infobuf;

        set_tls_desc(target,
                     GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
                     info, count / sizeof(struct user_desc));

        return 0;
}