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e5e3a04289
This patch removes the default_ldt[] array, as it has been unused since iBCS stopped being supported. This means it is now possible to actually set an empty LDT segment. In order to deal with this, the set_ldt_desc/load_LDT pair has been replaced with a single set_ldt() operation which is responsible for both setting up the LDT descriptor in the GDT, and reloading the LDT register. If there are no LDT entries, the LDT register is loaded with a NULL descriptor. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Andi Kleen <ak@suse.de> Acked-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andrew Morton <akpm@osdl.org>
252 lines
5.1 KiB
C
252 lines
5.1 KiB
C
/*
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* linux/arch/i386/kernel/ldt.c
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*
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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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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/smp_lock.h>
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <asm/ldt.h>
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#include <asm/desc.h>
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#include <asm/mmu_context.h>
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#ifdef CONFIG_SMP /* avoids "defined but not used" warnig */
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static void flush_ldt(void *null)
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{
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if (current->active_mm)
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load_LDT(¤t->active_mm->context);
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}
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#endif
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static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
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{
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void *oldldt;
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void *newldt;
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int oldsize;
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if (mincount <= pc->size)
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return 0;
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oldsize = pc->size;
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mincount = (mincount+511)&(~511);
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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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else
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newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
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if (!newldt)
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return -ENOMEM;
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if (oldsize)
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memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
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oldldt = pc->ldt;
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memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
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pc->ldt = newldt;
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wmb();
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pc->size = mincount;
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wmb();
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if (reload) {
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#ifdef CONFIG_SMP
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cpumask_t mask;
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preempt_disable();
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load_LDT(pc);
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mask = cpumask_of_cpu(smp_processor_id());
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if (!cpus_equal(current->mm->cpu_vm_mask, mask))
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smp_call_function(flush_ldt, NULL, 1, 1);
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preempt_enable();
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#else
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load_LDT(pc);
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#endif
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}
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if (oldsize) {
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if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
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vfree(oldldt);
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else
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kfree(oldldt);
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}
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return 0;
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}
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static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
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{
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int err = alloc_ldt(new, old->size, 0);
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if (err < 0)
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return err;
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memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
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return 0;
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}
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/*
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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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*/
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int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
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{
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struct mm_struct * old_mm;
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int retval = 0;
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init_MUTEX(&mm->context.sem);
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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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down(&old_mm->context.sem);
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retval = copy_ldt(&mm->context, &old_mm->context);
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up(&old_mm->context.sem);
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}
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return retval;
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}
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/*
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* No need to lock the MM as we are the last user
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*/
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void destroy_context(struct mm_struct *mm)
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{
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if (mm->context.size) {
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if (mm == current->active_mm)
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clear_LDT();
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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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else
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kfree(mm->context.ldt);
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mm->context.size = 0;
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}
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}
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static int read_ldt(void __user * ptr, unsigned long bytecount)
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{
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int err;
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unsigned long size;
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struct mm_struct * mm = current->mm;
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if (!mm->context.size)
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return 0;
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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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down(&mm->context.sem);
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size = mm->context.size*LDT_ENTRY_SIZE;
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if (size > bytecount)
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size = bytecount;
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err = 0;
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if (copy_to_user(ptr, mm->context.ldt, size))
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err = -EFAULT;
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up(&mm->context.sem);
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if (err < 0)
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goto error_return;
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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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err = -EFAULT;
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goto error_return;
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}
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}
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return bytecount;
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error_return:
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return err;
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}
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static int read_default_ldt(void __user * ptr, unsigned long bytecount)
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{
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int err;
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unsigned long size;
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err = 0;
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size = 5*sizeof(struct desc_struct);
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if (size > bytecount)
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size = bytecount;
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err = size;
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if (clear_user(ptr, size))
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err = -EFAULT;
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return err;
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}
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static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
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{
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struct mm_struct * mm = current->mm;
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__u32 entry_1, entry_2;
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int error;
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struct user_desc ldt_info;
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error = -EINVAL;
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if (bytecount != sizeof(ldt_info))
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goto out;
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error = -EFAULT;
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if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
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goto out;
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error = -EINVAL;
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if (ldt_info.entry_number >= LDT_ENTRIES)
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goto out;
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if (ldt_info.contents == 3) {
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if (oldmode)
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goto out;
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if (ldt_info.seg_not_present == 0)
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goto out;
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}
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down(&mm->context.sem);
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if (ldt_info.entry_number >= mm->context.size) {
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error = alloc_ldt(¤t->mm->context, ldt_info.entry_number+1, 1);
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if (error < 0)
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goto out_unlock;
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}
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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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entry_1 = 0;
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entry_2 = 0;
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goto install;
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}
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}
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entry_1 = LDT_entry_a(&ldt_info);
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entry_2 = LDT_entry_b(&ldt_info);
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if (oldmode)
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entry_2 &= ~(1 << 20);
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/* Install the new entry ... */
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install:
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write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1, entry_2);
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error = 0;
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out_unlock:
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up(&mm->context.sem);
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out:
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return error;
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}
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asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
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{
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int ret = -ENOSYS;
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switch (func) {
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case 0:
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ret = read_ldt(ptr, bytecount);
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break;
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case 1:
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ret = write_ldt(ptr, bytecount, 1);
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break;
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case 2:
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ret = read_default_ldt(ptr, bytecount);
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break;
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case 0x11:
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ret = write_ldt(ptr, bytecount, 0);
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break;
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}
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return ret;
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}
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