+
+static int read_ldt(void __user * ptr, unsigned long bytecount)
+{
+ int i, err = 0;
+ unsigned long size;
+ uml_ldt_t * ldt = ¤t->mm->context.skas.ldt;
+
+ if(!ldt->entry_count)
+ goto out;
+ if(bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
+ bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
+ err = bytecount;
+
+ if(ptrace_ldt){
+ return read_ldt_from_host(ptr, bytecount);
+ }
+
+ down(&ldt->semaphore);
+ if(ldt->entry_count <= LDT_DIRECT_ENTRIES){
+ size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
+ if(size > bytecount)
+ size = bytecount;
+ if(copy_to_user(ptr, ldt->u.entries, size))
+ err = -EFAULT;
+ bytecount -= size;
+ ptr += size;
+ }
+ else {
+ for(i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
+ i++){
+ size = PAGE_SIZE;
+ if(size > bytecount)
+ size = bytecount;
+ if(copy_to_user(ptr, ldt->u.pages[i], size)){
+ err = -EFAULT;
+ break;
+ }
+ bytecount -= size;
+ ptr += size;
+ }
+ }
+ up(&ldt->semaphore);
+
+ if(bytecount == 0 || err == -EFAULT)
+ goto out;
+
+ if(clear_user(ptr, bytecount))
+ err = -EFAULT;
+
+out:
+ return err;
+}
+
+static int read_default_ldt(void __user * ptr, unsigned long bytecount)
+{
+ int err;
+
+ if(bytecount > 5*LDT_ENTRY_SIZE)
+ bytecount = 5*LDT_ENTRY_SIZE;
+
+ err = bytecount;
+ /* UML doesn't support lcall7 and lcall27.
+ * So, we don't really have a default ldt, but emulate
+ * an empty ldt of common host default ldt size.
+ */
+ if(clear_user(ptr, bytecount))
+ err = -EFAULT;
+
+ return err;
+}
+
+static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
+{
+ uml_ldt_t * ldt = ¤t->mm->context.skas.ldt;
+ struct mm_id * mm_idp = ¤t->mm->context.skas.id;
+ int i, err;
+ struct user_desc ldt_info;
+ struct ldt_entry entry0, *ldt_p;
+ void *addr = NULL;
+
+ err = -EINVAL;
+ if(bytecount != sizeof(ldt_info))
+ goto out;
+ err = -EFAULT;
+ if(copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
+ goto out;
+
+ err = -EINVAL;
+ if(ldt_info.entry_number >= LDT_ENTRIES)
+ goto out;
+ if(ldt_info.contents == 3){
+ if (func == 1)
+ goto out;
+ if (ldt_info.seg_not_present == 0)
+ goto out;
+ }
+
+ if(!ptrace_ldt)
+ down(&ldt->semaphore);
+
+ err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
+ if(err)
+ goto out_unlock;
+ else if(ptrace_ldt) {
+ /* With PTRACE_LDT available, this is used as a flag only */
+ ldt->entry_count = 1;
+ goto out;
+ }
+
+ if(ldt_info.entry_number >= ldt->entry_count &&
+ ldt_info.entry_number >= LDT_DIRECT_ENTRIES){
+ for(i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
+ i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
+ i++){
+ if(i == 0)
+ memcpy(&entry0, ldt->u.entries,
+ sizeof(entry0));
+ ldt->u.pages[i] = (struct ldt_entry *)
+ __get_free_page(GFP_KERNEL|__GFP_ZERO);
+ if(!ldt->u.pages[i]){
+ err = -ENOMEM;
+ /* Undo the change in host */
+ memset(&ldt_info, 0, sizeof(ldt_info));
+ write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
+ goto out_unlock;
+ }
+ if(i == 0) {
+ memcpy(ldt->u.pages[0], &entry0,
+ sizeof(entry0));
+ memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
+ sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
+ }
+ ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
+ }
+ }
+ if(ldt->entry_count <= ldt_info.entry_number)
+ ldt->entry_count = ldt_info.entry_number + 1;
+
+ if(ldt->entry_count <= LDT_DIRECT_ENTRIES)
+ ldt_p = ldt->u.entries + ldt_info.entry_number;
+ else
+ ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
+ ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
+
+ if(ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
+ (func == 1 || LDT_empty(&ldt_info))){
+ ldt_p->a = 0;
+ ldt_p->b = 0;
+ }
+ else{
+ if (func == 1)
+ ldt_info.useable = 0;
+ ldt_p->a = LDT_entry_a(&ldt_info);
+ ldt_p->b = LDT_entry_b(&ldt_info);
+ }
+ err = 0;
+
+out_unlock:
+ up(&ldt->semaphore);
+out:
+ return err;
+}
+
+static long do_modify_ldt_skas(int func, void __user *ptr,
+ unsigned long bytecount)
+{
+ int ret = -ENOSYS;
+
+ switch (func) {
+ case 0:
+ ret = read_ldt(ptr, bytecount);
+ break;
+ case 1:
+ case 0x11:
+ ret = write_ldt(ptr, bytecount, func);
+ break;
+ case 2:
+ ret = read_default_ldt(ptr, bytecount);
+ break;
+ }
+ return ret;
+}
+
+short dummy_list[9] = {0, -1};
+short * host_ldt_entries = NULL;
+
+void ldt_get_host_info(void)
+{
+ long ret;
+ struct ldt_entry * ldt;
+ int i, size, k, order;
+
+ host_ldt_entries = dummy_list+1;
+
+ for(i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++);
+
+ ldt = (struct ldt_entry *)
+ __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
+ if(ldt == NULL) {
+ printk("ldt_get_host_info: couldn't allocate buffer for host ldt\n");
+ return;
+ }
+
+ ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
+ if(ret < 0) {
+ printk("ldt_get_host_info: couldn't read host ldt\n");
+ goto out_free;
+ }
+ if(ret == 0) {
+ /* default_ldt is active, simply write an empty entry 0 */
+ host_ldt_entries = dummy_list;
+ goto out_free;
+ }
+
+ for(i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++){
+ if(ldt[i].a != 0 || ldt[i].b != 0)
+ size++;
+ }
+
+ if(size < ARRAY_SIZE(dummy_list))
+ host_ldt_entries = dummy_list;
+ else {
+ size = (size + 1) * sizeof(dummy_list[0]);
+ host_ldt_entries = kmalloc(size, GFP_KERNEL);
+ if(host_ldt_entries == NULL) {
+ printk("ldt_get_host_info: couldn't allocate host ldt list\n");
+ goto out_free;
+ }
+ }
+
+ for(i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++){
+ if(ldt[i].a != 0 || ldt[i].b != 0) {
+ host_ldt_entries[k++] = i;
+ }
+ }
+ host_ldt_entries[k] = -1;
+
+out_free:
+ free_pages((unsigned long)ldt, order);
+}
+
+long init_new_ldt(struct mmu_context_skas * new_mm,
+ struct mmu_context_skas * from_mm)
+{
+ struct user_desc desc;
+ short * num_p;
+ int i;
+ long page, err=0;
+ void *addr = NULL;
+ struct proc_mm_op copy;
+
+
+ if(!ptrace_ldt)
+ init_MUTEX(&new_mm->ldt.semaphore);
+
+ if(!from_mm){
+ memset(&desc, 0, sizeof(desc));
+ /*
+ * We have to initialize a clean ldt.
+ */
+ if(proc_mm) {
+ /*
+ * If the new mm was created using proc_mm, host's
+ * default-ldt currently is assigned, which normally
+ * contains the call-gates for lcall7 and lcall27.
+ * To remove these gates, we simply write an empty
+ * entry as number 0 to the host.
+ */
+ err = write_ldt_entry(&new_mm->id, 1, &desc,
+ &addr, 1);
+ }
+ else{
+ /*
+ * Now we try to retrieve info about the ldt, we
+ * inherited from the host. All ldt-entries found
+ * will be reset in the following loop
+ */
+ if(host_ldt_entries == NULL)
+ ldt_get_host_info();
+ for(num_p=host_ldt_entries; *num_p != -1; num_p++){
+ desc.entry_number = *num_p;
+ err = write_ldt_entry(&new_mm->id, 1, &desc,
+ &addr, *(num_p + 1) == -1);
+ if(err)
+ break;
+ }
+ }
+ new_mm->ldt.entry_count = 0;
+
+ goto out;
+ }
+
+ if(proc_mm){
+ /* We have a valid from_mm, so we now have to copy the LDT of
+ * from_mm to new_mm, because using proc_mm an new mm with
+ * an empty/default LDT was created in new_mm()
+ */
+ copy = ((struct proc_mm_op) { .op = MM_COPY_SEGMENTS,
+ .u =
+ { .copy_segments =
+ from_mm->id.u.mm_fd } } );
+ i = os_write_file(new_mm->id.u.mm_fd, ©, sizeof(copy));
+ if(i != sizeof(copy))
+ printk("new_mm : /proc/mm copy_segments failed, "
+ "err = %d\n", -i);
+ }
+
+ if(!ptrace_ldt) {
+ /* Our local LDT is used to supply the data for
+ * modify_ldt(READLDT), if PTRACE_LDT isn't available,
+ * i.e., we have to use the stub for modify_ldt, which
+ * can't handle the big read buffer of up to 64kB.
+ */
+ down(&from_mm->ldt.semaphore);
+ if(from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES){
+ memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
+ sizeof(new_mm->ldt.u.entries));
+ }
+ else{
+ i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
+ while(i-->0){
+ page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
+ if (!page){
+ err = -ENOMEM;
+ break;
+ }
+ new_mm->ldt.u.pages[i] =
+ (struct ldt_entry *) page;
+ memcpy(new_mm->ldt.u.pages[i],
+ from_mm->ldt.u.pages[i], PAGE_SIZE);
+ }
+ }
+ new_mm->ldt.entry_count = from_mm->ldt.entry_count;
+ up(&from_mm->ldt.semaphore);
+ }
+
+ out:
+ return err;
+}
+
+
+void free_ldt(struct mmu_context_skas * mm)
+{
+ int i;
+
+ if(!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES){
+ i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
+ while(i-- > 0){
+ free_page((long )mm->ldt.u.pages[i]);
+ }
+ }
+ mm->ldt.entry_count = 0;
+}
+#endif
+
+int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
+{
+ return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
+ ptr, bytecount));
+}