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* Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
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* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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* Copyright (C) 2002 Andi Kleen
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* This handles calls from both 32bit and 64bit mode.
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#include <linux/errno.h>
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#include <linux/gfp.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/smp.h>
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#include <linux/vmalloc.h>
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#include <linux/uaccess.h>
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#include <asm/system.h>
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#include <asm/mmu_context.h>
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#include <asm/syscalls.h>
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static void flush_ldt(void *current_mm)
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if (current->active_mm == current_mm)
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load_LDT(¤t->active_mm->context);
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static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
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void *oldldt, *newldt;
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if (mincount <= pc->size)
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mincount = (mincount + (PAGE_SIZE / LDT_ENTRY_SIZE - 1)) &
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(~(PAGE_SIZE / LDT_ENTRY_SIZE - 1));
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if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE)
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newldt = vmalloc(mincount * LDT_ENTRY_SIZE);
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newldt = (void *)__get_free_page(GFP_KERNEL);
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memcpy(newldt, pc->ldt, oldsize * LDT_ENTRY_SIZE);
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memset(newldt + oldsize * LDT_ENTRY_SIZE, 0,
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(mincount - oldsize) * LDT_ENTRY_SIZE);
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paravirt_alloc_ldt(newldt, mincount);
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/* CHECKME: Do we really need this ? */
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if (!cpumask_equal(mm_cpumask(current->mm),
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cpumask_of(smp_processor_id())))
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smp_call_function(flush_ldt, current->mm, 1);
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paravirt_free_ldt(oldldt, oldsize);
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if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
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put_page(virt_to_page(oldldt));
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static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
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int err = alloc_ldt(new, old->size, 0);
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for (i = 0; i < old->size; i++)
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write_ldt_entry(new->ldt, i, old->ldt + i * LDT_ENTRY_SIZE);
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* we do not have to muck with descriptors here, that is
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* done in switch_mm() as needed.
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int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
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struct mm_struct *old_mm;
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mutex_init(&mm->context.lock);
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mm->context.size = 0;
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old_mm = current->mm;
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if (old_mm && old_mm->context.size > 0) {
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mutex_lock(&old_mm->context.lock);
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retval = copy_ldt(&mm->context, &old_mm->context);
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mutex_unlock(&old_mm->context.lock);
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* No need to lock the MM as we are the last user
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* 64bit: Don't touch the LDT register - we're already in the next thread.
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void destroy_context(struct mm_struct *mm)
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if (mm->context.size) {
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/* CHECKME: Can this ever happen ? */
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if (mm == current->active_mm)
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paravirt_free_ldt(mm->context.ldt, mm->context.size);
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if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE)
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vfree(mm->context.ldt);
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put_page(virt_to_page(mm->context.ldt));
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mm->context.size = 0;
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static int read_ldt(void __user *ptr, unsigned long bytecount)
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struct mm_struct *mm = current->mm;
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if (!mm->context.size)
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if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
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bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
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mutex_lock(&mm->context.lock);
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size = mm->context.size * LDT_ENTRY_SIZE;
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if (size > bytecount)
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if (copy_to_user(ptr, mm->context.ldt, size))
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mutex_unlock(&mm->context.lock);
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if (size != bytecount) {
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/* zero-fill the rest */
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if (clear_user(ptr + size, bytecount - size) != 0) {
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static int read_default_ldt(void __user *ptr, unsigned long bytecount)
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/* CHECKME: Can we use _one_ random number ? */
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unsigned long size = 5 * sizeof(struct desc_struct);
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unsigned long size = 128;
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if (bytecount > size)
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if (clear_user(ptr, bytecount))
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static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
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struct mm_struct *mm = current->mm;
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struct desc_struct ldt;
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struct user_desc ldt_info;
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if (bytecount != sizeof(ldt_info))
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if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
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if (ldt_info.entry_number >= LDT_ENTRIES)
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if (ldt_info.contents == 3) {
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if (ldt_info.seg_not_present == 0)
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mutex_lock(&mm->context.lock);
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if (ldt_info.entry_number >= mm->context.size) {
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error = alloc_ldt(¤t->mm->context,
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ldt_info.entry_number + 1, 1);
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/* Allow LDTs to be cleared by the user. */
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if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
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if (oldmode || LDT_empty(&ldt_info)) {
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memset(&ldt, 0, sizeof(ldt));
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fill_ldt(&ldt, &ldt_info);
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/* Install the new entry ... */
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write_ldt_entry(mm->context.ldt, ldt_info.entry_number, &ldt);
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mutex_unlock(&mm->context.lock);
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asmlinkage int sys_modify_ldt(int func, void __user *ptr,
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unsigned long bytecount)
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ret = read_ldt(ptr, bytecount);
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ret = write_ldt(ptr, bytecount, 1);
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ret = read_default_ldt(ptr, bytecount);
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ret = write_ldt(ptr, bytecount, 0);