diff options
Diffstat (limited to 'arch/x86/kernel/ldt.c')
| -rw-r--r-- | arch/x86/kernel/ldt.c | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c new file mode 100644 index 00000000000..8a7660c8394 --- /dev/null +++ b/arch/x86/kernel/ldt.c @@ -0,0 +1,260 @@ +/* + * 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 <asm/uaccess.h> +#include <asm/system.h> +#include <asm/ldt.h> +#include <asm/desc.h> +#include <asm/mmu_context.h> + +#ifdef CONFIG_SMP +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, *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 = (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); + +#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 + cpumask_t mask; + + preempt_disable(); + load_LDT(pc); + 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(); +#else + load_LDT(pc); +#endif + } + if (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); + + 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; + + 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 + 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; +} |