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
21extern int __syscall_stub_start;
22
23static 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	*pte = pte_mkread(*pte);
64	return(0);
65
66 out_pmd:
67	pud_free(pud);
68 out_pte:
69	pmd_free(pmd);
70 out:
71	return(-ENOMEM);
72}
73
74int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
75{
76 	struct mmu_context_skas *from_mm = NULL;
77	struct mmu_context_skas *to_mm = &mm->context.skas;
78	unsigned long stack = 0;
79	int ret = -ENOMEM;
80
81	if(skas_needs_stub){
82		stack = get_zeroed_page(GFP_KERNEL);
83		if(stack == 0)
84			goto out;
85
86		/* This zeros the entry that pgd_alloc didn't, needed since
87		 * we are about to reinitialize it, and want mm.nr_ptes to
88		 * be accurate.
89		 */
90		mm->pgd[USER_PTRS_PER_PGD] = __pgd(0);
91
92		ret = init_stub_pte(mm, CONFIG_STUB_CODE,
93				    (unsigned long) &__syscall_stub_start);
94		if(ret)
95			goto out_free;
96
97		ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack);
98		if(ret)
99			goto out_free;
100
101		mm->nr_ptes--;
102	}
103
104	to_mm->id.stack = stack;
105	if(current->mm != NULL && current->mm != &init_mm)
106		from_mm = &current->mm->context.skas;
107
108	if(proc_mm){
109		ret = new_mm(stack);
110		if(ret < 0){
111			printk("init_new_context_skas - new_mm failed, "
112			       "errno = %d\n", ret);
113			goto out_free;
114		}
115		to_mm->id.u.mm_fd = ret;
116	}
117	else {
118		if(from_mm)
119			to_mm->id.u.pid = copy_context_skas0(stack,
120							     from_mm->id.u.pid);
121		else to_mm->id.u.pid = start_userspace(stack);
122	}
123
124	ret = init_new_ldt(to_mm, from_mm);
125	if(ret < 0){
126		printk("init_new_context_skas - init_ldt"
127		       " failed, errno = %d\n", ret);
128		goto out_free;
129	}
130
131	return 0;
132
133 out_free:
134	if(to_mm->id.stack != 0)
135		free_page(to_mm->id.stack);
136 out:
137	return ret;
138}
139
140void destroy_context_skas(struct mm_struct *mm)
141{
142	struct mmu_context_skas *mmu = &mm->context.skas;
143
144	if(proc_mm)
145		os_close_file(mmu->id.u.mm_fd);
146	else
147		os_kill_ptraced_process(mmu->id.u.pid, 1);
148
149	if(!proc_mm || !ptrace_faultinfo){
150		free_page(mmu->id.stack);
151		pte_lock_deinit(virt_to_page(mmu->last_page_table));
152		pte_free_kernel((pte_t *) mmu->last_page_table);
153		dec_zone_page_state(virt_to_page(mmu->last_page_table), NR_PAGETABLE);
154#ifdef CONFIG_3_LEVEL_PGTABLES
155		pmd_free((pmd_t *) mmu->last_pmd);
156#endif
157	}
158}
159