arch/x86/kernel/ldt_64.c

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