2 * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
3 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
6 #include <linux/errno.h>
7 #include <linux/sched.h>
8 #include <linux/string.h>
10 #include <linux/smp.h>
11 #include <linux/vmalloc.h>
12 #include <linux/slab.h>
14 #include <asm/uaccess.h>
15 #include <asm/system.h>
18 #include <asm/mmu_context.h>
21 static void flush_ldt(void *null)
23 if (current->active_mm)
24 load_LDT(¤t->active_mm->context);
28 static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
30 void *oldldt, *newldt;
33 if (mincount <= pc->size)
36 mincount = (mincount + 511) & (~511);
37 if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE)
38 newldt = vmalloc(mincount * LDT_ENTRY_SIZE);
40 newldt = kmalloc(mincount * LDT_ENTRY_SIZE, GFP_KERNEL);
46 memcpy(newldt, pc->ldt, oldsize * LDT_ENTRY_SIZE);
48 memset(newldt + oldsize * LDT_ENTRY_SIZE, 0,
49 (mincount - oldsize) * LDT_ENTRY_SIZE);
61 mask = cpumask_of_cpu(smp_processor_id());
62 if (!cpus_equal(current->mm->cpu_vm_mask, mask))
63 smp_call_function(flush_ldt, NULL, 1, 1);
70 if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
78 static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
80 int err = alloc_ldt(new, old->size, 0);
84 memcpy(new->ldt, old->ldt, old->size * LDT_ENTRY_SIZE);
89 * we do not have to muck with descriptors here, that is
90 * done in switch_mm() as needed.
92 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
94 struct mm_struct *old_mm;
97 mutex_init(&mm->context.lock);
100 if (old_mm && old_mm->context.size > 0) {
101 mutex_lock(&old_mm->context.lock);
102 retval = copy_ldt(&mm->context, &old_mm->context);
103 mutex_unlock(&old_mm->context.lock);
109 * No need to lock the MM as we are the last user
111 void destroy_context(struct mm_struct *mm)
113 if (mm->context.size) {
114 if (mm == current->active_mm)
116 if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE)
117 vfree(mm->context.ldt);
119 kfree(mm->context.ldt);
120 mm->context.size = 0;
124 static int read_ldt(void __user *ptr, unsigned long bytecount)
128 struct mm_struct *mm = current->mm;
130 if (!mm->context.size)
132 if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
133 bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
135 mutex_lock(&mm->context.lock);
136 size = mm->context.size * LDT_ENTRY_SIZE;
137 if (size > bytecount)
141 if (copy_to_user(ptr, mm->context.ldt, size))
143 mutex_unlock(&mm->context.lock);
146 if (size != bytecount) {
147 /* zero-fill the rest */
148 if (clear_user(ptr + size, bytecount - size) != 0) {
158 static int read_default_ldt(void __user *ptr, unsigned long bytecount)
164 size = 5 * sizeof(struct desc_struct);
165 if (size > bytecount)
169 if (clear_user(ptr, size))
175 static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
177 struct mm_struct *mm = current->mm;
178 __u32 entry_1, entry_2;
180 struct user_desc ldt_info;
183 if (bytecount != sizeof(ldt_info))
186 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
190 if (ldt_info.entry_number >= LDT_ENTRIES)
192 if (ldt_info.contents == 3) {
195 if (ldt_info.seg_not_present == 0)
199 mutex_lock(&mm->context.lock);
200 if (ldt_info.entry_number >= mm->context.size) {
201 error = alloc_ldt(¤t->mm->context,
202 ldt_info.entry_number + 1, 1);
207 /* Allow LDTs to be cleared by the user. */
208 if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
209 if (oldmode || LDT_empty(&ldt_info)) {
216 entry_1 = LDT_entry_a(&ldt_info);
217 entry_2 = LDT_entry_b(&ldt_info);
219 entry_2 &= ~(1 << 20);
221 /* Install the new entry ... */
223 write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1,
228 mutex_unlock(&mm->context.lock);
233 asmlinkage int sys_modify_ldt(int func, void __user *ptr,
234 unsigned long bytecount)
240 ret = read_ldt(ptr, bytecount);
243 ret = write_ldt(ptr, bytecount, 1);
246 ret = read_default_ldt(ptr, bytecount);
249 ret = write_ldt(ptr, bytecount, 0);