1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2015 Thomas Meyer ([email protected])
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 */
20 static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE);
21
init_new_context(struct task_struct * task,struct mm_struct * mm)22 int 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
destroy_context(struct mm_struct * mm)54 void 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 }
73