/* * linux/arch/x86_64/kernel/ldt.c * * 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/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/proto.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, unsigned mincount, int reload) { void *oldldt; void *newldt; unsigned oldsize; if (mincount <= (unsigned)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); wmb(); pc->ldt = newldt; wmb(); pc->size = mincount; wmb(); if (reload) { #ifdef CONFIG_SMP cpumask_t mask; preempt_disable(); mask = cpumask_of_cpu(smp_processor_id()); load_LDT(pc); if (!cpus_equal(current->mm->cpu_vm_mask, mask)) smp_call_function(flush_ldt, NULL, 1, 1); preempt_enable(); #else load_LDT(pc); #endif } if (oldsize) { 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); 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; 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; } /* * * Don't touch the LDT register - we're already in the next thread. */ void destroy_context(struct mm_struct *mm) { if (mm->context.size) { if ((unsigned)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) { /* Arbitrary number */ /* x86-64 default LDT is all zeros */ if (bytecount > 128) bytecount = 128; if (clear_user(ptr, bytecount)) return -EFAULT; return bytecount; } static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode) { struct task_struct *me = current; struct mm_struct * mm = me->mm; __u32 entry_1, entry_2, *lp; 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, bytecount)) 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 >= (unsigned)mm->context.size) { error = alloc_ldt(¤t->mm->context, ldt_info.entry_number+1, 1); if (error < 0) goto out_unlock; } lp = (__u32 *) ((ldt_info.entry_number << 3) + (char *) mm->context.ldt); /* 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: *lp = entry_1; *(lp+1) = entry_2; error = 0; 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; }