ldt.c

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    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 }

Cache object: 3d4009dd21767c095d5fea62b6d6d834

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FreeBSD/Linux Kernel Cross Reference sys/arch/x86_64/kernel/ldt.c

FreeBSD/Linux Kernel Cross Reference
sys/arch/x86_64/kernel/ldt.c