Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/configh
[linux-2.6] / arch / um / kernel / skas / mmu.c
1 /* 
2  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
3  * Licensed under the GPL
4  */
5
6 #include "linux/sched.h"
7 #include "linux/list.h"
8 #include "linux/spinlock.h"
9 #include "linux/slab.h"
10 #include "linux/errno.h"
11 #include "linux/mm.h"
12 #include "asm/current.h"
13 #include "asm/segment.h"
14 #include "asm/mmu.h"
15 #include "asm/pgalloc.h"
16 #include "asm/pgtable.h"
17 #include "asm/ldt.h"
18 #include "os.h"
19 #include "skas.h"
20
21 extern int __syscall_stub_start;
22
23 static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
24                          unsigned long kernel)
25 {
26         pgd_t *pgd;
27         pud_t *pud;
28         pmd_t *pmd;
29         pte_t *pte;
30
31         pgd = pgd_offset(mm, proc);
32         pud = pud_alloc(mm, pgd, proc);
33         if (!pud)
34                 goto out;
35
36         pmd = pmd_alloc(mm, pud, proc);
37         if (!pmd)
38                 goto out_pmd;
39
40         pte = pte_alloc_map(mm, pmd, proc);
41         if (!pte)
42                 goto out_pte;
43
44         /* There's an interaction between the skas0 stub pages, stack
45          * randomization, and the BUG at the end of exit_mmap.  exit_mmap
46          * checks that the number of page tables freed is the same as had
47          * been allocated.  If the stack is on the last page table page,
48          * then the stack pte page will be freed, and if not, it won't.  To
49          * avoid having to know where the stack is, or if the process mapped
50          * something at the top of its address space for some other reason,
51          * we set TASK_SIZE to end at the start of the last page table.
52          * This keeps exit_mmap off the last page, but introduces a leak
53          * of that page.  So, we hang onto it here and free it in
54          * destroy_context_skas.
55          */
56
57         mm->context.skas.last_page_table = pmd_page_vaddr(*pmd);
58 #ifdef CONFIG_3_LEVEL_PGTABLES
59         mm->context.skas.last_pmd = (unsigned long) __va(pud_val(*pud));
60 #endif
61
62         *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
63         /* This is wrong for the code page, but it doesn't matter since the
64          * stub is mapped by hand with the correct permissions.
65          */
66         *pte = pte_mkwrite(*pte);
67         return(0);
68
69  out_pmd:
70         pud_free(pud);
71  out_pte:
72         pmd_free(pmd);
73  out:
74         return(-ENOMEM);
75 }
76
77 int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
78 {
79         struct mmu_context_skas *from_mm = NULL;
80         struct mmu_context_skas *to_mm = &mm->context.skas;
81         unsigned long stack = 0;
82         int ret = -ENOMEM;
83
84         if(skas_needs_stub){
85                 stack = get_zeroed_page(GFP_KERNEL);
86                 if(stack == 0)
87                         goto out;
88
89                 /* This zeros the entry that pgd_alloc didn't, needed since
90                  * we are about to reinitialize it, and want mm.nr_ptes to
91                  * be accurate.
92                  */
93                 mm->pgd[USER_PTRS_PER_PGD] = __pgd(0);
94
95                 ret = init_stub_pte(mm, CONFIG_STUB_CODE,
96                                     (unsigned long) &__syscall_stub_start);
97                 if(ret)
98                         goto out_free;
99
100                 ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack);
101                 if(ret)
102                         goto out_free;
103
104                 mm->nr_ptes--;
105         }
106
107         to_mm->id.stack = stack;
108         if(current->mm != NULL && current->mm != &init_mm)
109                 from_mm = &current->mm->context.skas;
110
111         if(proc_mm){
112                 ret = new_mm(stack);
113                 if(ret < 0){
114                         printk("init_new_context_skas - new_mm failed, "
115                                "errno = %d\n", ret);
116                         goto out_free;
117                 }
118                 to_mm->id.u.mm_fd = ret;
119         }
120         else {
121                 if(from_mm)
122                         to_mm->id.u.pid = copy_context_skas0(stack,
123                                                              from_mm->id.u.pid);
124                 else to_mm->id.u.pid = start_userspace(stack);
125         }
126
127         ret = init_new_ldt(to_mm, from_mm);
128         if(ret < 0){
129                 printk("init_new_context_skas - init_ldt"
130                        " failed, errno = %d\n", ret);
131                 goto out_free;
132         }
133
134         return 0;
135
136  out_free:
137         if(to_mm->id.stack != 0)
138                 free_page(to_mm->id.stack);
139  out:
140         return ret;
141 }
142
143 void destroy_context_skas(struct mm_struct *mm)
144 {
145         struct mmu_context_skas *mmu = &mm->context.skas;
146
147         if(proc_mm)
148                 os_close_file(mmu->id.u.mm_fd);
149         else
150                 os_kill_ptraced_process(mmu->id.u.pid, 1);
151
152         if(!proc_mm || !ptrace_faultinfo){
153                 free_page(mmu->id.stack);
154                 pte_lock_deinit(virt_to_page(mmu->last_page_table));
155                 pte_free_kernel((pte_t *) mmu->last_page_table);
156                 dec_zone_page_state(virt_to_page(mmu->last_page_table), NR_PAGETABLE);
157 #ifdef CONFIG_3_LEVEL_PGTABLES
158                 pmd_free((pmd_t *) mmu->last_pmd);
159 #endif
160         }
161 }