release/src-rt-6.x/linux/linux-2.6/arch/x86_64/kernel/ldt.c

   1 /*
   2  * linux/arch/x86_64/kernel/ldt.c
   3  *
   4  * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
   5  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
   6  * Copyright (C) 2002 Andi Kleen
   7  *
   8  * This handles calls from both 32bit and 64bit mode.
   9  */
  10
  11 #include <linux/errno.h>
  12 #include <linux/sched.h>
  13 #include <linux/string.h>
  14 #include <linux/mm.h>
  15 #include <linux/smp.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/slab.h>
  18
  19 #include <asm/uaccess.h>
  20 #include <asm/system.h>
  21 #include <asm/ldt.h>
  22 #include <asm/desc.h>
  23 #include <asm/proto.h>
  24
  25 #ifdef CONFIG_SMP /* avoids "defined but not used" warnig */
  26 static void flush_ldt(void *null)
  27 {
  28         if (current->active_mm)
  29                load_LDT(&current->active_mm->context);
  30 }
  31 #endif
  32
  33 static int alloc_ldt(mm_context_t *pc, unsigned mincount, int reload)
  34 {
  35         void *oldldt;
  36         void *newldt;
  37         unsigned oldsize;
  38
  39         if (mincount <= (unsigned)pc->size)
  40                 return 0;
  41         oldsize = pc->size;
  42         mincount = (mincount+511)&(~511);
  43         if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
  44                 newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
  45         else
  46                 newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
  47
  48         if (!newldt)
  49                 return -ENOMEM;
  50
  51         if (oldsize)
  52                 memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
  53         oldldt = pc->ldt;
  54         memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
  55         wmb();
  56         pc->ldt = newldt;
  57         wmb();
  58         pc->size = mincount;
  59         wmb();
  60         if (reload) {
  61 #ifdef CONFIG_SMP
  62                 cpumask_t mask;
  63
  64                 preempt_disable();
  65                 mask = cpumask_of_cpu(smp_processor_id());
  66                 load_LDT(pc);
  67                 if (!cpus_equal(current->mm->cpu_vm_mask, mask))
  68                         smp_call_function(flush_ldt, NULL, 1, 1);
  69                 preempt_enable();
  70 #else
  71                 load_LDT(pc);
  72 #endif
  73         }
  74         if (oldsize) {
  75                 if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
  76                         vfree(oldldt);
  77                 else
  78                         kfree(oldldt);
  79         }
  80         return 0;
  81 }
  82
  83 static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
  84 {
  85         int err = alloc_ldt(new, old->size, 0);
  86         if (err < 0)
  87                 return err;
  88         memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
  89         return 0;
  90 }
  91
  92 /*
  93  * we do not have to muck with descriptors here, that is
  94  * done in switch_mm() as needed.
  95  */
  96 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  97 {
  98         struct mm_struct * old_mm;
  99         int retval = 0;
 100
 101         init_MUTEX(&mm->context.sem);
 102         mm->context.size = 0;
 103         old_mm = current->mm;
 104         if (old_mm && old_mm->context.size > 0) {
 105                 down(&old_mm->context.sem);
 106                 retval = copy_ldt(&mm->context, &old_mm->context);
 107                 up(&old_mm->context.sem);
 108         }
 109         return retval;
 110 }
 111
 112 /*
 113  *
 114  * Don't touch the LDT register - we're already in the next thread.
 115  */
 116 void destroy_context(struct mm_struct *mm)
 117 {
 118         if (mm->context.size) {
 119                 if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
 120                         vfree(mm->context.ldt);
 121                 else
 122                         kfree(mm->context.ldt);
 123                 mm->context.size = 0;
 124         }
 125 }
 126
 127 static int read_ldt(void __user * ptr, unsigned long bytecount)
 128 {
 129         int err;
 130         unsigned long size;
 131         struct mm_struct * mm = current->mm;
 132
 133         if (!mm->context.size)
 134                 return 0;
 135         if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 136                 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
 137
 138         down(&mm->context.sem);
 139         size = mm->context.size*LDT_ENTRY_SIZE;
 140         if (size > bytecount)
 141                 size = bytecount;
 142
 143         err = 0;
 144         if (copy_to_user(ptr, mm->context.ldt, size))
 145                 err = -EFAULT;
 146         up(&mm->context.sem);
 147         if (err < 0)
 148                 goto error_return;
 149         if (size != bytecount) {
 150                 /* zero-fill the rest */
 151                 if (clear_user(ptr+size, bytecount-size) != 0) {
 152                         err = -EFAULT;
 153                         goto error_return;
 154                 }
 155         }
 156         return bytecount;
 157 error_return:
 158         return err;
 159 }
 160
 161 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 162 {
 163         /* Arbitrary number */
 164         /* x86-64 default LDT is all zeros */
 165         if (bytecount > 128)
 166                 bytecount = 128;
 167         if (clear_user(ptr, bytecount))
 168                 return -EFAULT;
 169         return bytecount;
 170 }
 171
 172 static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
 173 {
 174         struct task_struct *me = current;
 175         struct mm_struct * mm = me->mm;
 176         __u32 entry_1, entry_2, *lp;
 177         int error;
 178         struct user_desc ldt_info;
 179
 180         error = -EINVAL;
 181
 182         if (bytecount != sizeof(ldt_info))
 183                 goto out;
 184         error = -EFAULT;
 185         if (copy_from_user(&ldt_info, ptr, bytecount))
 186                 goto out;
 187
 188         error = -EINVAL;
 189         if (ldt_info.entry_number >= LDT_ENTRIES)
 190                 goto out;
 191         if (ldt_info.contents == 3) {
 192                 if (oldmode)
 193                         goto out;
 194                 if (ldt_info.seg_not_present == 0)
 195                         goto out;
 196         }
 197
 198         down(&mm->context.sem);
 199         if (ldt_info.entry_number >= (unsigned)mm->context.size) {
 200                 error = alloc_ldt(&current->mm->context, ldt_info.entry_number+1, 1);
 201                 if (error < 0)
 202                         goto out_unlock;
 203         }
 204
 205         lp = (__u32 *) ((ldt_info.entry_number << 3) + (char *) mm->context.ldt);
 206
 207         /* Allow LDTs to be cleared by the user. */
 208         if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
 209                 if (oldmode || LDT_empty(&ldt_info)) {
 210                         entry_1 = 0;
 211                         entry_2 = 0;
 212                         goto install;
 213                 }
 214         }
 215
 216         entry_1 = LDT_entry_a(&ldt_info);
 217         entry_2 = LDT_entry_b(&ldt_info);
 218         if (oldmode)
 219                 entry_2 &= ~(1 << 20);
 220
 221         /* Install the new entry ...  */
 222 install:
 223         *lp     = entry_1;
 224         *(lp+1) = entry_2;
 225         error = 0;
 226
 227 out_unlock:
 228         up(&mm->context.sem);
 229 out:
 230         return error;
 231 }
 232
 233 asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
 234 {
 235         int ret = -ENOSYS;
 236
 237         switch (func) {
 238         case 0:
 239                 ret = read_ldt(ptr, bytecount);
 240                 break;
 241         case 1:
 242                 ret = write_ldt(ptr, bytecount, 1);
 243                 break;
 244         case 2:
 245                 ret = read_default_ldt(ptr, bytecount);
 246                 break;
 247         case 0x11:
 248                 ret = write_ldt(ptr, bytecount, 0);
 249                 break;
 250         }
 251         return ret;
 252 }