| | 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 */ |
| | 20 | static_assert(sizeof(struct stub_data) == STUB_DATA_PAGES * UM_KERN_PAGE_SIZE); |
| | 21 | |
| | 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->u.pid = start_userspace(stack); |
| | 36 | unblock_signals_trace(); |
| | 37 | |
| | 38 | if (new_id->u.pid < 0) { |
| | 39 | ret = new_id->u.pid; |
| | 40 | goto out_free; |
| | 41 | } |
| | 42 | |
| | 43 | /* |
| | 44 | * Ensure the new MM is clean and nothing unwanted is mapped. |
| | 45 | * |
| | 46 | * TODO: We should clear the memory up to STUB_START to ensure there is |
| | 47 | * nothing mapped there, i.e. we (currently) have: |
| | 48 | * |
| | 49 | * |- user memory -|- unused -|- stub -|- unused -| |
| | 50 | * ^ TASK_SIZE ^ STUB_START |
| | 51 | * |
| | 52 | * Meaning we have two unused areas where we may still have valid |
| | 53 | * mappings from our internal clone(). That isn't really a problem as |
| | 54 | * userspace is not going to access them, but it is definitely not |
| | 55 | * correct. |
| | 56 | * |
| | 57 | * However, we are "lucky" and if rseq is configured, then on 32 bit |
| | 58 | * it will fall into the first empty range while on 64 bit it is going |
| | 59 | * to use an anonymous mapping in the second range. As such, things |
| | 60 | * continue to work for now as long as we don't start unmapping these |
| | 61 | * areas. |
| | 62 | * |
| | 63 | * Change this to STUB_START once we have a clean userspace. |
| | 64 | */ |
| | 65 | unmap(new_id, 0, TASK_SIZE); |
| | 66 | |
| | 67 | return 0; |
| | 68 | |
| | 69 | out_free: |
| | 70 | if (new_id->stack != 0) |
| | 71 | free_pages(new_id->stack, ilog2(STUB_DATA_PAGES)); |
| | 72 | out: |
| | 73 | return ret; |
| | 74 | } |
| | 75 | |
| | 76 | void destroy_context(struct mm_struct *mm) |
| | 77 | { |
| | 78 | struct mm_context *mmu = &mm->context; |
| | 79 | |
| | 80 | /* |
| | 81 | * If init_new_context wasn't called, this will be |
| | 82 | * zero, resulting in a kill(0), which will result in the |
| | 83 | * whole UML suddenly dying. Also, cover negative and |
| | 84 | * 1 cases, since they shouldn't happen either. |
| | 85 | */ |
| | 86 | if (mmu->id.u.pid < 2) { |
| | 87 | printk(KERN_ERR "corrupt mm_context - pid = %d\n", |
| | 88 | mmu->id.u.pid); |
| | 89 | return; |
| | 90 | } |
| | 91 | os_kill_ptraced_process(mmu->id.u.pid, 1); |
| | 92 | |
| | 93 | free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES)); |
| | 94 | } |
projects / linux-2.6-block.git / blame_incremental