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tls32.c

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

/*
 * 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((struct n_desc_struct *)(t->tls_array) + idx))
                  return idx + GDT_ENTRY_TLS_MIN;
      return -ESRCH;
}

/*
 * Set a given TLS descriptor:
 * When you want addresses > 32bit use arch_prctl() 
 */
int do_set_thread_area(struct thread_struct *t, struct user_desc __user *u_info)
{
      struct user_desc info;
      struct n_desc_struct *desc;
      int cpu, idx;

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

      idx = info.entry_number;

      /*
       * index -1 means the kernel should try to find and
       * allocate an empty descriptor:
       */
      if (idx == -1) {
            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;

      desc = ((struct n_desc_struct *)t->tls_array) + idx - GDT_ENTRY_TLS_MIN;

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

      if (LDT_empty(&info)) {
            desc->a = 0;
            desc->b = 0;
      } else {
            desc->a = LDT_entry_a(&info);
            desc->b = LDT_entry_b(&info);
      }
      if (t == &current->thread)
            load_TLS(t, cpu);

      put_cpu();
      return 0;
}

asmlinkage long sys32_set_thread_area(struct user_desc __user *u_info)
{ 
      return do_set_thread_area(&current->thread, u_info); 
} 


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

#define GET_BASE(desc) ( \
      (((desc)->a >> 16) & 0x0000ffff) | \
      (((desc)->b << 16) & 0x00ff0000) | \
      ( (desc)->b        & 0xff000000)   )

#define GET_LIMIT(desc) ( \
      ((desc)->a & 0x0ffff) | \
       ((desc)->b & 0xf0000) )
      
#define GET_32BIT(desc)       (((desc)->b >> 22) & 1)
#define GET_CONTENTS(desc)    (((desc)->b >> 10) & 3)
#define GET_WRITABLE(desc)    (((desc)->b >>  9) & 1)
#define GET_LIMIT_PAGES(desc) (((desc)->b >> 23) & 1)
#define GET_PRESENT(desc)     (((desc)->b >> 15) & 1)
#define GET_USEABLE(desc)     (((desc)->b >> 20) & 1)
#define GET_LONGMODE(desc)    (((desc)->b >> 21) & 1)

int do_get_thread_area(struct thread_struct *t, struct user_desc __user *u_info)
{
      struct user_desc info;
      struct n_desc_struct *desc;
      int idx;

      if (get_user(idx, &u_info->entry_number))
            return -EFAULT;
      if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
            return -EINVAL;

      desc = ((struct n_desc_struct *)t->tls_array) + idx - GDT_ENTRY_TLS_MIN;

      memset(&info, 0, sizeof(struct user_desc));
      info.entry_number = idx;
      info.base_addr = GET_BASE(desc);
      info.limit = GET_LIMIT(desc);
      info.seg_32bit = GET_32BIT(desc);
      info.contents = GET_CONTENTS(desc);
      info.read_exec_only = !GET_WRITABLE(desc);
      info.limit_in_pages = GET_LIMIT_PAGES(desc);
      info.seg_not_present = !GET_PRESENT(desc);
      info.useable = GET_USEABLE(desc);
      info.lm = GET_LONGMODE(desc);

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

asmlinkage long sys32_get_thread_area(struct user_desc __user *u_info)
{
      return do_get_thread_area(&current->thread, u_info);
} 


int ia32_child_tls(struct task_struct *p, struct pt_regs *childregs)
{
      struct n_desc_struct *desc;
      struct user_desc info;
      struct user_desc __user *cp;
      int idx;
      
      cp = (void __user *)childregs->rsi;
      if (copy_from_user(&info, cp, sizeof(info)))
            return -EFAULT;
      if (LDT_empty(&info))
            return -EINVAL;
      
      idx = info.entry_number;
      if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
            return -EINVAL;
      
      desc = (struct n_desc_struct *)(p->thread.tls_array) + idx - GDT_ENTRY_TLS_MIN;
      desc->a = LDT_entry_a(&info);
      desc->b = LDT_entry_b(&info);

      return 0;
}

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