--- /dev/null
+/*
+ * linux/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/smp_lock.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();
+#endif
+ make_pages_readonly(
+ pc->ldt,
+ (pc->size * LDT_ENTRY_SIZE) / PAGE_SIZE,
+ XENFEAT_writable_descriptor_tables);
+ load_LDT(pc);
+#ifdef CONFIG_SMP
+ 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();
+#endif
+ }
+ if (oldsize) {
+ make_pages_writable(
+ oldldt,
+ (oldsize * LDT_ENTRY_SIZE) / PAGE_SIZE,
+ XENFEAT_writable_descriptor_tables);
+ 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);
+ make_pages_readonly(
+ new->ldt,
+ (new->size * LDT_ENTRY_SIZE) / PAGE_SIZE,
+ XENFEAT_writable_descriptor_tables);
+ 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;
+ mm->context.has_foreign_mappings = 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();
+ make_pages_writable(
+ mm->context.ldt,
+ (mm->context.size * LDT_ENTRY_SIZE) / PAGE_SIZE,
+ XENFEAT_writable_descriptor_tables);
+ 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;
+ void *address;
+
+ err = 0;
+ address = &default_ldt[0];
+ size = 5*sizeof(struct desc_struct);
+ if (size > bytecount)
+ size = bytecount;
+
+ err = size;
+ if (copy_to_user(ptr, address, 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:
+ error = write_ldt_entry(mm->context.ldt, ldt_info.entry_number,
+ entry_1, entry_2);
+
+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;
+}
git://git.onelab.eu / linux-2.6.git / blobdiff