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/*
* linux/arch/i386/kernel/ldt.c
*
* Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
*/
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/ldt.h>
#include <asm/desc.h>
#include <asm/mmu_context.h>
#ifdef CONFIG_SMP /* avoids "defined but not used" warnig */
static void flush_ldt(void *null)
{
if (current->active_mm)
load_LDT(¤t->active_mm->context);
}
#endif
static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
{
void *oldldt;
void *newldt;
int oldsize;
if (mincount <= pc->size)
return 0;
oldsize = pc->size;
mincount = (mincount+511)&(~511);
if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
else
newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
if (!newldt)
return -ENOMEM;
if (oldsize)
memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
oldldt = pc->ldt;
memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
pc->ldt = newldt;
wmb();
pc->size = mincount;
wmb();
if (reload) {
#ifdef CONFIG_SMP
cpumask_t mask;
preempt_disable();
load_LDT(pc);
mask = cpumask_of_cpu(smp_processor_id());
if (!cpus_equal(current->mm->cpu_vm_mask, mask))
smp_call_function(flush_ldt, NULL, 1, 1);
preempt_enable();
#else
load_LDT(pc);
#endif
}
if (oldsize) {
if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(oldldt);
else
kfree(oldldt);
}
return 0;
}
static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
{
int err = alloc_ldt(new, old->size, 0);
if (err < 0)
return err;
memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
return 0;
}
/*
* we do not have to muck with descriptors here, that is
* done in switch_mm() as needed.
*/
int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
struct mm_struct * old_mm;
int retval = 0;
init_MUTEX(&mm->context.sem);
mm->context.size = 0;
old_mm = current->mm;
if (old_mm && old_mm->context.size > 0) {
down(&old_mm->context.sem);
retval = copy_ldt(&mm->context, &old_mm->context);
up(&old_mm->context.sem);
}
return retval;
}
/*
* No need to lock the MM as we are the last user
*/
void destroy_context(struct mm_struct *mm)
{
if (mm->context.size) {
if (mm == current->active_mm)
clear_LDT();
if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(mm->context.ldt);
else
kfree(mm->context.ldt);
mm->context.size = 0;
}
}
static int read_ldt(void __user * ptr, unsigned long bytecount)
{
int err;
unsigned long size;
struct mm_struct * mm = current->mm;
if (!mm->context.size)
return 0;
if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
down(&mm->context.sem);
size = mm->context.size*LDT_ENTRY_SIZE;
if (size > bytecount)
size = bytecount;
err = 0;
if (copy_to_user(ptr, mm->context.ldt, size))
err = -EFAULT;
up(&mm->context.sem);
if (err < 0)
goto error_return;
if (size != bytecount) {
/* zero-fill the rest */
if (clear_user(ptr+size, bytecount-size) != 0) {
err = -EFAULT;
goto error_return;
}
}
return bytecount;
error_return:
return err;
}
static int read_default_ldt(void __user * ptr, unsigned long bytecount)
{
int err;
unsigned long size;
err = 0;
size = 5*sizeof(struct desc_struct);
if (size > bytecount)
size = bytecount;
err = size;
if (clear_user(ptr, size))
err = -EFAULT;
return err;
}
static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
{
struct mm_struct * mm = current->mm;
__u32 entry_1, entry_2;
int error;
struct user_desc ldt_info;
error = -EINVAL;
if (bytecount != sizeof(ldt_info))
goto out;
error = -EFAULT;
if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
goto out;
error = -EINVAL;
if (ldt_info.entry_number >= LDT_ENTRIES)
goto out;
if (ldt_info.contents == 3) {
if (oldmode)
goto out;
if (ldt_info.seg_not_present == 0)
goto out;
}
down(&mm->context.sem);
if (ldt_info.entry_number >= mm->context.size) {
error = alloc_ldt(¤t->mm->context, ldt_info.entry_number+1, 1);
if (error < 0)
goto out_unlock;
}
/* Allow LDTs to be cleared by the user. */
if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
if (oldmode || LDT_empty(&ldt_info)) {
entry_1 = 0;
entry_2 = 0;
goto install;
}
}
entry_1 = LDT_entry_a(&ldt_info);
entry_2 = LDT_entry_b(&ldt_info);
if (oldmode)
entry_2 &= ~(1 << 20);
/* Install the new entry ... */
install:
write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1, entry_2);
error = 0;
out_unlock:
up(&mm->context.sem);
out:
return error;
}
asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
{
int ret = -ENOSYS;
switch (func) {
case 0:
ret = read_ldt(ptr, bytecount);
break;
case 1:
ret = write_ldt(ptr, bytecount, 1);
break;
case 2:
ret = read_default_ldt(ptr, bytecount);
break;
case 0x11:
ret = write_ldt(ptr, bytecount, 0);
break;
}
return ret;
}
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