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