/* * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> * Copyright (C) 2002 Andi Kleen * * This handles calls from both 32bit and 64bit mode. */ #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/uaccess.h> #include <asm/system.h> #include <asm/ldt.h> #include <asm/desc.h> #include <asm/mmu_context.h> #include <asm/syscalls.h> #ifdef CONFIG_SMP static void flush_ldt(void *current_mm) { if (current->active_mm == current_mm) load_LDT(¤t->active_mm->context); } #endif static int alloc_ldt(mm_context_t *pc, int mincount, int reload) { void *oldldt, *newldt; int oldsize; if (mincount <= pc->size) return 0; oldsize = pc->size; mincount = (mincount + (PAGE_SIZE / LDT_ENTRY_SIZE - 1)) & (~(PAGE_SIZE / LDT_ENTRY_SIZE - 1)); if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE) newldt = vmalloc(mincount * LDT_ENTRY_SIZE); else newldt = (void *)__get_free_page(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); paravirt_alloc_ldt(newldt, mincount); #ifdef CONFIG_X86_64 /* CHECKME: Do we really need this ? */ wmb(); #endif pc->ldt = newldt; wmb(); pc->size = mincount; wmb(); if (reload) { #ifdef CONFIG_SMP preempt_disable(); load_LDT(pc); if (!cpumask_equal(mm_cpumask(current->mm), cpumask_of(smp_processor_id()))) smp_call_function(flush_ldt, current->mm, 1); preempt_enable(); #else load_LDT(pc); #endif } if (oldsize) { paravirt_free_ldt(oldldt, oldsize); if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE) vfree(oldldt); else put_page(virt_to_page(oldldt)); } return 0; } static inline int copy_ldt(mm_context_t *new, mm_context_t *old) { int err = alloc_ldt(new, old->size, 0); int i; if (err < 0) return err; for (i = 0; i < old->size; i++) write_ldt_entry(new->ldt, i, old->ldt + i * 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; mutex_init(&mm->context.lock); mm->context.size = 0; old_mm = current->mm; if (old_mm && old_mm->context.size > 0) { mutex_lock(&old_mm->context.lock); retval = copy_ldt(&mm->context, &old_mm->context); mutex_unlock(&old_mm->context.lock); } return retval; } /* * No need to lock the MM as we are the last user * * 64bit: Don't touch the LDT register - we're already in the next thread. */ void destroy_context(struct mm_struct *mm) { if (mm->context.size) { #ifdef CONFIG_X86_32 /* CHECKME: Can this ever happen ? */ if (mm == current->active_mm) clear_LDT(); #endif paravirt_free_ldt(mm->context.ldt, mm->context.size); if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE) vfree(mm->context.ldt); else put_page(virt_to_page(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; mutex_lock(&mm->context.lock); 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; mutex_unlock(&mm->context.lock); 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) { /* CHECKME: Can we use _one_ random number ? */ #ifdef CONFIG_X86_32 unsigned long size = 5 * sizeof(struct desc_struct); #else unsigned long size = 128; #endif if (bytecount > size) bytecount = size; if (clear_user(ptr, bytecount)) return -EFAULT; return bytecount; } static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) { struct mm_struct *mm = current->mm; struct desc_struct ldt; 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; } mutex_lock(&mm->context.lock); 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)) { memset(&ldt, 0, sizeof(ldt)); goto install; } } fill_ldt(&ldt, &ldt_info); if (oldmode) ldt.avl = 0; /* Install the new entry ... */ install: write_ldt_entry(mm->context.ldt, ldt_info.entry_number, &ldt); error = 0; out_unlock: mutex_unlock(&mm->context.lock); 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; }