1/*
2 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4 * Licensed under the GPL
5 */
6
7#include <linux/mm.h>
8#include <linux/sched.h>
9#include <linux/slab.h>
10#include <asm/pgalloc.h>
11#include <asm/pgtable.h>
12#include <asm/sections.h>
13#include <as-layout.h>
14#include <os.h>
15#include <skas.h>
16
17static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
18			 unsigned long kernel)
19{
20	pgd_t *pgd;
21	pud_t *pud;
22	pmd_t *pmd;
23	pte_t *pte;
24
25	pgd = pgd_offset(mm, proc);
26	pud = pud_alloc(mm, pgd, proc);
27	if (!pud)
28		goto out;
29
30	pmd = pmd_alloc(mm, pud, proc);
31	if (!pmd)
32		goto out_pmd;
33
34	pte = pte_alloc_map(mm, NULL, pmd, proc);
35	if (!pte)
36		goto out_pte;
37
38	*pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
39	*pte = pte_mkread(*pte);
40	return 0;
41
42 out_pte:
43	pmd_free(mm, pmd);
44 out_pmd:
45	pud_free(mm, pud);
46 out:
47	return -ENOMEM;
48}
49
50int init_new_context(struct task_struct *task, struct mm_struct *mm)
51{
52 	struct mm_context *from_mm = NULL;
53	struct mm_context *to_mm = &mm->context;
54	unsigned long stack = 0;
55	int ret = -ENOMEM;
56
57	stack = get_zeroed_page(GFP_KERNEL);
58	if (stack == 0)
59		goto out;
60
61	to_mm->id.stack = stack;
62	if (current->mm != NULL && current->mm != &init_mm)
63		from_mm = &current->mm->context;
64
65	block_signals();
66	if (from_mm)
67		to_mm->id.u.pid = copy_context_skas0(stack,
68						     from_mm->id.u.pid);
69	else to_mm->id.u.pid = start_userspace(stack);
70	unblock_signals();
71
72	if (to_mm->id.u.pid < 0) {
73		ret = to_mm->id.u.pid;
74		goto out_free;
75	}
76
77	ret = init_new_ldt(to_mm, from_mm);
78	if (ret < 0) {
79		printk(KERN_ERR "init_new_context_skas - init_ldt"
80		       " failed, errno = %d\n", ret);
81		goto out_free;
82	}
83
84	return 0;
85
86 out_free:
87	if (to_mm->id.stack != 0)
88		free_page(to_mm->id.stack);
89 out:
90	return ret;
91}
92
93void uml_setup_stubs(struct mm_struct *mm)
94{
95	int err, ret;
96
97	ret = init_stub_pte(mm, STUB_CODE,
98			    (unsigned long) __syscall_stub_start);
99	if (ret)
100		goto out;
101
102	ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
103	if (ret)
104		goto out;
105
106	mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
107	mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
108
109	/* dup_mmap already holds mmap_sem */
110	err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
111				      VM_READ | VM_MAYREAD | VM_EXEC |
112				      VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
113				      mm->context.stub_pages);
114	if (err) {
115		printk(KERN_ERR "install_special_mapping returned %d\n", err);
116		goto out;
117	}
118	return;
119
120out:
121	force_sigsegv(SIGSEGV, current);
122}
123
124void arch_exit_mmap(struct mm_struct *mm)
125{
126	pte_t *pte;
127
128	pte = virt_to_pte(mm, STUB_CODE);
129	if (pte != NULL)
130		pte_clear(mm, STUB_CODE, pte);
131
132	pte = virt_to_pte(mm, STUB_DATA);
133	if (pte == NULL)
134		return;
135
136	pte_clear(mm, STUB_DATA, pte);
137}
138
139void destroy_context(struct mm_struct *mm)
140{
141	struct mm_context *mmu = &mm->context;
142
143	/*
144	 * If init_new_context wasn't called, this will be
145	 * zero, resulting in a kill(0), which will result in the
146	 * whole UML suddenly dying.  Also, cover negative and
147	 * 1 cases, since they shouldn't happen either.
148	 */
149	if (mmu->id.u.pid < 2) {
150		printk(KERN_ERR "corrupt mm_context - pid = %d\n",
151		       mmu->id.u.pid);
152		return;
153	}
154	os_kill_ptraced_process(mmu->id.u.pid, 1);
155
156	free_page(mmu->id.stack);
157	free_ldt(mmu);
158}
159