tls.c

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#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/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;
}