arch/x86/kernel/tls.c

   1 #include <linux/kernel.h>
   2 #include <linux/errno.h>
   3 #include <linux/sched.h>
   4 #include <linux/user.h>
   5
   6 #include <asm/uaccess.h>
   7 #include <asm/desc.h>
   8 #include <asm/system.h>
   9 #include <asm/ldt.h>
  10 #include <asm/processor.h>
  11 #include <asm/proto.h>
  12
  13 /*
  14  * sys_alloc_thread_area: get a yet unused TLS descriptor index.
  15  */
  16 static int get_free_idx(void)
  17 {
  18         struct thread_struct *t = &current->thread;
  19         int idx;
  20
  21         for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
  22                 if (desc_empty(&t->tls_array[idx]))
  23                         return idx + GDT_ENTRY_TLS_MIN;
  24         return -ESRCH;
  25 }
  26
  27 /*
  28  * Set a given TLS descriptor:
  29  */
  30 int do_set_thread_area(struct task_struct *p, int idx,
  31                        struct user_desc __user *u_info,
  32                        int can_allocate)
  33 {
  34         struct thread_struct *t = &p->thread;
  35         struct user_desc info;
  36         u32 *desc;
  37         int cpu;
  38
  39         if (copy_from_user(&info, u_info, sizeof(info)))
  40                 return -EFAULT;
  41
  42         if (idx == -1)
  43                 idx = info.entry_number;
  44
  45         /*
  46          * index -1 means the kernel should try to find and
  47          * allocate an empty descriptor:
  48          */
  49         if (idx == -1 && can_allocate) {
  50                 idx = get_free_idx();
  51                 if (idx < 0)
  52                         return idx;
  53                 if (put_user(idx, &u_info->entry_number))
  54                         return -EFAULT;
  55         }
  56
  57         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
  58                 return -EINVAL;
  59
  60         desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
  61
  62         /*
  63          * We must not get preempted while modifying the TLS.
  64          */
  65         cpu = get_cpu();
  66
  67         if (LDT_empty(&info)) {
  68                 desc[0] = 0;
  69                 desc[1] = 0;
  70         } else
  71                 fill_ldt((struct desc_struct *)desc, &info);
  72
  73         if (t == &current->thread)
  74                 load_TLS(t, cpu);
  75
  76         put_cpu();
  77         return 0;
  78 }
  79
  80 asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
  81 {
  82         return do_set_thread_area(current, -1, u_info, 1);
  83 }
  84
  85
  86 /*
  87  * Get the current Thread-Local Storage area:
  88  */
  89
  90 #define GET_LIMIT(desc)         (((desc)[0] & 0x0ffff) | ((desc)[1] & 0xf0000))
  91 #define GET_32BIT(desc)         (((desc)[1] >> 22) & 1)
  92 #define GET_CONTENTS(desc)      (((desc)[1] >> 10) & 3)
  93 #define GET_WRITABLE(desc)      (((desc)[1] >>  9) & 1)
  94 #define GET_LIMIT_PAGES(desc)   (((desc)[1] >> 23) & 1)
  95 #define GET_PRESENT(desc)       (((desc)[1] >> 15) & 1)
  96 #define GET_USEABLE(desc)       (((desc)[1] >> 20) & 1)
  97 #define GET_LONGMODE(desc)      (((desc)[1] >> 21) & 1)
  98
  99 int do_get_thread_area(struct task_struct *p, int idx,
 100                        struct user_desc __user *u_info)
 101 {
 102         struct thread_struct *t = &p->thread;
 103         struct user_desc info;
 104         u32 *desc;
 105
 106         if (idx == -1 && get_user(idx, &u_info->entry_number))
 107                 return -EFAULT;
 108         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 109                 return -EINVAL;
 110
 111         desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
 112
 113         memset(&info, 0, sizeof(struct user_desc));
 114         info.entry_number = idx;
 115         info.base_addr = get_desc_base((void *)desc);
 116         info.limit = GET_LIMIT(desc);
 117         info.seg_32bit = GET_32BIT(desc);
 118         info.contents = GET_CONTENTS(desc);
 119         info.read_exec_only = !GET_WRITABLE(desc);
 120         info.limit_in_pages = GET_LIMIT_PAGES(desc);
 121         info.seg_not_present = !GET_PRESENT(desc);
 122         info.useable = GET_USEABLE(desc);
 123 #ifdef CONFIG_X86_64
 124         info.lm = GET_LONGMODE(desc);
 125 #endif
 126
 127         if (copy_to_user(u_info, &info, sizeof(info)))
 128                 return -EFAULT;
 129         return 0;
 130 }
 131
 132 asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
 133 {
 134         return do_get_thread_area(current, -1, u_info);
 135 }