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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
4 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
5 */
6
7#include <linux/mm.h>
8#include <linux/sched/signal.h>
9#include <linux/slab.h>
10
11#include <asm/pgalloc.h>
12#include <asm/sections.h>
13#include <asm/mmu_context.h>
14#include <as-layout.h>
15#include <os.h>
16#include <skas.h>
17#include <stub-data.h>
18
19/* Ensure the stub_data struct covers the allocated area */
20static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
21
22int init_new_context(struct task_struct *task, struct mm_struct *mm)
23{
24 struct mm_id *new_id = &mm->context.id;
25 unsigned long stack = 0;
26 int ret = -ENOMEM;
27
28 stack = __get_free_pages(GFP_KERNEL | __GFP_ZERO, ilog2(STUB_DATA_PAGES));
29 if (stack == 0)
30 goto out;
31
32 new_id->stack = stack;
33
34 block_signals_trace();
35 new_id->pid = start_userspace(stack);
36 unblock_signals_trace();
37
38 if (new_id->pid < 0) {
39 ret = new_id->pid;
40 goto out_free;
41 }
42
43 /* Ensure the new MM is clean and nothing unwanted is mapped */
44 unmap(new_id, 0, STUB_START);
45
46 return 0;
47
48 out_free:
49 free_pages(new_id->stack, ilog2(STUB_DATA_PAGES));
50 out:
51 return ret;
52}
53
54void destroy_context(struct mm_struct *mm)
55{
56 struct mm_context *mmu = &mm->context;
57
58 /*
59 * If init_new_context wasn't called, this will be
60 * zero, resulting in a kill(0), which will result in the
61 * whole UML suddenly dying. Also, cover negative and
62 * 1 cases, since they shouldn't happen either.
63 */
64 if (mmu->id.pid < 2) {
65 printk(KERN_ERR "corrupt mm_context - pid = %d\n",
66 mmu->id.pid);
67 return;
68 }
69 os_kill_ptraced_process(mmu->id.pid, 1);
70
71 free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES));
72}
1/*
2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <linux/mm.h>
7#include <linux/sched.h>
8#include <linux/slab.h>
9#include <asm/pgalloc.h>
10#include <asm/pgtable.h>
11#include <as-layout.h>
12#include <os.h>
13#include <skas.h>
14
15extern int __syscall_stub_start;
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 if (skas_needs_stub) {
58 stack = get_zeroed_page(GFP_KERNEL);
59 if (stack == 0)
60 goto out;
61 }
62
63 to_mm->id.stack = stack;
64 if (current->mm != NULL && current->mm != &init_mm)
65 from_mm = ¤t->mm->context;
66
67 if (proc_mm) {
68 ret = new_mm(stack);
69 if (ret < 0) {
70 printk(KERN_ERR "init_new_context_skas - "
71 "new_mm failed, errno = %d\n", ret);
72 goto out_free;
73 }
74 to_mm->id.u.mm_fd = ret;
75 }
76 else {
77 if (from_mm)
78 to_mm->id.u.pid = copy_context_skas0(stack,
79 from_mm->id.u.pid);
80 else to_mm->id.u.pid = start_userspace(stack);
81
82 if (to_mm->id.u.pid < 0) {
83 ret = to_mm->id.u.pid;
84 goto out_free;
85 }
86 }
87
88 ret = init_new_ldt(to_mm, from_mm);
89 if (ret < 0) {
90 printk(KERN_ERR "init_new_context_skas - init_ldt"
91 " failed, errno = %d\n", ret);
92 goto out_free;
93 }
94
95 return 0;
96
97 out_free:
98 if (to_mm->id.stack != 0)
99 free_page(to_mm->id.stack);
100 out:
101 return ret;
102}
103
104void uml_setup_stubs(struct mm_struct *mm)
105{
106 int err, ret;
107
108 if (!skas_needs_stub)
109 return;
110
111 ret = init_stub_pte(mm, STUB_CODE,
112 (unsigned long) &__syscall_stub_start);
113 if (ret)
114 goto out;
115
116 ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
117 if (ret)
118 goto out;
119
120 mm->context.stub_pages[0] = virt_to_page(&__syscall_stub_start);
121 mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
122
123 /* dup_mmap already holds mmap_sem */
124 err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
125 VM_READ | VM_MAYREAD | VM_EXEC |
126 VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
127 mm->context.stub_pages);
128 if (err) {
129 printk(KERN_ERR "install_special_mapping returned %d\n", err);
130 goto out;
131 }
132 return;
133
134out:
135 force_sigsegv(SIGSEGV, current);
136}
137
138void arch_exit_mmap(struct mm_struct *mm)
139{
140 pte_t *pte;
141
142 pte = virt_to_pte(mm, STUB_CODE);
143 if (pte != NULL)
144 pte_clear(mm, STUB_CODE, pte);
145
146 pte = virt_to_pte(mm, STUB_DATA);
147 if (pte == NULL)
148 return;
149
150 pte_clear(mm, STUB_DATA, pte);
151}
152
153void destroy_context(struct mm_struct *mm)
154{
155 struct mm_context *mmu = &mm->context;
156
157 if (proc_mm)
158 os_close_file(mmu->id.u.mm_fd);
159 else {
160 /*
161 * If init_new_context wasn't called, this will be
162 * zero, resulting in a kill(0), which will result in the
163 * whole UML suddenly dying. Also, cover negative and
164 * 1 cases, since they shouldn't happen either.
165 */
166 if (mmu->id.u.pid < 2) {
167 printk(KERN_ERR "corrupt mm_context - pid = %d\n",
168 mmu->id.u.pid);
169 return;
170 }
171 os_kill_ptraced_process(mmu->id.u.pid, 1);
172 }
173
174 if (skas_needs_stub)
175 free_page(mmu->id.stack);
176
177 free_ldt(mmu);
178}