arch/x86/kernel/ldt_32.c

   1 /*
   2  * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
   3  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
   4  */
   5
   6 #include <linux/errno.h>
   7 #include <linux/sched.h>
   8 #include <linux/string.h>
   9 #include <linux/mm.h>
  10 #include <linux/smp.h>
  11 #include <linux/vmalloc.h>
  12 #include <linux/slab.h>
  13
  14 #include <asm/uaccess.h>
  15 #include <asm/system.h>
  16 #include <asm/ldt.h>
  17 #include <asm/desc.h>
  18 #include <asm/mmu_context.h>
  19
  20 #ifdef CONFIG_SMP /* avoids "defined but not used" warnig */
  21 static void flush_ldt(void *null)
  22 {
  23         if (current->active_mm)
  24                 load_LDT(&current->active_mm->context);
  25 }
  26 #endif
  27
  28 static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
  29 {
  30         void *oldldt;
  31         void *newldt;
  32         int oldsize;
  33
  34         if (mincount <= pc->size)
  35                 return 0;
  36         oldsize = pc->size;
  37         mincount = (mincount+511)&(~511);
  38         if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
  39                 newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
  40         else
  41                 newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
  42
  43         if (!newldt)
  44                 return -ENOMEM;
  45
  46         if (oldsize)
  47                 memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
  48         oldldt = pc->ldt;
  49         memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
  50         pc->ldt = newldt;
  51         wmb();
  52         pc->size = mincount;
  53         wmb();
  54
  55         if (reload) {
  56 #ifdef CONFIG_SMP
  57                 cpumask_t mask;
  58                 preempt_disable();
  59                 load_LDT(pc);
  60                 mask = cpumask_of_cpu(smp_processor_id());
  61                 if (!cpus_equal(current->mm->cpu_vm_mask, mask))
  62                         smp_call_function(flush_ldt, NULL, 1, 1);
  63                 preempt_enable();
  64 #else
  65                 load_LDT(pc);
  66 #endif
  67         }
  68         if (oldsize) {
  69                 if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
  70                         vfree(oldldt);
  71                 else
  72                         kfree(oldldt);
  73         }
  74         return 0;
  75 }
  76
  77 static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
  78 {
  79         int err = alloc_ldt(new, old->size, 0);
  80         if (err < 0)
  81                 return err;
  82         memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
  83         return 0;
  84 }
  85
  86 /*
  87  * we do not have to muck with descriptors here, that is
  88  * done in switch_mm() as needed.
  89  */
  90 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  91 {
  92         struct mm_struct * old_mm;
  93         int retval = 0;
  94
  95         mutex_init(&mm->context.lock);
  96         mm->context.size = 0;
  97         old_mm = current->mm;
  98         if (old_mm && old_mm->context.size > 0) {
  99                 mutex_lock(&old_mm->context.lock);
 100                 retval = copy_ldt(&mm->context, &old_mm->context);
 101                 mutex_unlock(&old_mm->context.lock);
 102         }
 103         return retval;
 104 }
 105
 106 /*
 107  * No need to lock the MM as we are the last user
 108  */
 109 void destroy_context(struct mm_struct *mm)
 110 {
 111         if (mm->context.size) {
 112                 if (mm == current->active_mm)
 113                         clear_LDT();
 114                 if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
 115                         vfree(mm->context.ldt);
 116                 else
 117                         kfree(mm->context.ldt);
 118                 mm->context.size = 0;
 119         }
 120 }
 121
 122 static int read_ldt(void __user * ptr, unsigned long bytecount)
 123 {
 124         int err;
 125         unsigned long size;
 126         struct mm_struct * mm = current->mm;
 127
 128         if (!mm->context.size)
 129                 return 0;
 130         if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 131                 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
 132
 133         mutex_lock(&mm->context.lock);
 134         size = mm->context.size*LDT_ENTRY_SIZE;
 135         if (size > bytecount)
 136                 size = bytecount;
 137
 138         err = 0;
 139         if (copy_to_user(ptr, mm->context.ldt, size))
 140                 err = -EFAULT;
 141         mutex_unlock(&mm->context.lock);
 142         if (err < 0)
 143                 goto error_return;
 144         if (size != bytecount) {
 145                 /* zero-fill the rest */
 146                 if (clear_user(ptr+size, bytecount-size) != 0) {
 147                         err = -EFAULT;
 148                         goto error_return;
 149                 }
 150         }
 151         return bytecount;
 152 error_return:
 153         return err;
 154 }
 155
 156 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 157 {
 158         int err;
 159         unsigned long size;
 160
 161         err = 0;
 162         size = 5*sizeof(struct desc_struct);
 163         if (size > bytecount)
 164                 size = bytecount;
 165
 166         err = size;
 167         if (clear_user(ptr, size))
 168                 err = -EFAULT;
 169
 170         return err;
 171 }
 172
 173 static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
 174 {
 175         struct mm_struct * mm = current->mm;
 176         __u32 entry_1, entry_2;
 177         int error;
 178         struct user_desc ldt_info;
 179
 180         error = -EINVAL;
 181         if (bytecount != sizeof(ldt_info))
 182                 goto out;
 183         error = -EFAULT;
 184         if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
 185                 goto out;
 186
 187         error = -EINVAL;
 188         if (ldt_info.entry_number >= LDT_ENTRIES)
 189                 goto out;
 190         if (ldt_info.contents == 3) {
 191                 if (oldmode)
 192                         goto out;
 193                 if (ldt_info.seg_not_present == 0)
 194                         goto out;
 195         }
 196
 197         mutex_lock(&mm->context.lock);
 198         if (ldt_info.entry_number >= mm->context.size) {
 199                 error = alloc_ldt(&current->mm->context, ldt_info.entry_number+1, 1);
 200                 if (error < 0)
 201                         goto out_unlock;
 202         }
 203
 204         /* Allow LDTs to be cleared by the user. */
 205         if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
 206                 if (oldmode || LDT_empty(&ldt_info)) {
 207                         entry_1 = 0;
 208                         entry_2 = 0;
 209                         goto install;
 210                 }
 211         }
 212
 213         entry_1 = LDT_entry_a(&ldt_info);
 214         entry_2 = LDT_entry_b(&ldt_info);
 215         if (oldmode)
 216                 entry_2 &= ~(1 << 20);
 217
 218         /* Install the new entry ...  */
 219 install:
 220         write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1, entry_2);
 221         error = 0;
 222
 223 out_unlock:
 224         mutex_unlock(&mm->context.lock);
 225 out:
 226         return error;
 227 }
 228
 229 asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
 230 {
 231         int ret = -ENOSYS;
 232
 233         switch (func) {
 234         case 0:
 235                 ret = read_ldt(ptr, bytecount);
 236                 break;
 237         case 1:
 238                 ret = write_ldt(ptr, bytecount, 1);
 239                 break;
 240         case 2:
 241                 ret = read_default_ldt(ptr, bytecount);
 242                 break;
 243         case 0x11:
 244                 ret = write_ldt(ptr, bytecount, 0);
 245                 break;
 246         }
 247         return ret;
 248 }