/arch/um/kernel/skas/mmu.c

  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	p4d_t *p4d;
 23	pud_t *pud;
 24	pmd_t *pmd;
 25	pte_t *pte;
 26
 27	pgd = pgd_offset(mm, proc);
 28
 29	p4d = p4d_alloc(mm, pgd, proc);
 30	if (!p4d)
 31		goto out;
 32
 33	pud = pud_alloc(mm, p4d, proc);
 34	if (!pud)
 35		goto out_pud;
 36
 37	pmd = pmd_alloc(mm, pud, proc);
 38	if (!pmd)
 39		goto out_pmd;
 40
 41	pte = pte_alloc_map(mm, pmd, proc);
 42	if (!pte)
 43		goto out_pte;
 44
 45	*pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
 46	*pte = pte_mkread(*pte);
 47	return 0;
 48
 49 out_pte:
 50	pmd_free(mm, pmd);
 51 out_pmd:
 52	pud_free(mm, pud);
 53 out_pud:
 54	p4d_free(mm, p4d);
 55 out:
 56	return -ENOMEM;
 57}
 58
 59int init_new_context(struct task_struct *task, struct mm_struct *mm)
 60{
 61 	struct mm_context *from_mm = NULL;
 62	struct mm_context *to_mm = &mm->context;
 63	unsigned long stack = 0;
 64	int ret = -ENOMEM;
 65
 66	stack = get_zeroed_page(GFP_KERNEL);
 67	if (stack == 0)
 68		goto out;
 69
 70	to_mm->id.stack = stack;
 71	if (current->mm != NULL && current->mm != &init_mm)
 72		from_mm = &current->mm->context;
 73
 74	block_signals_trace();
 75	if (from_mm)
 76		to_mm->id.u.pid = copy_context_skas0(stack,
 77						     from_mm->id.u.pid);
 78	else to_mm->id.u.pid = start_userspace(stack);
 79	unblock_signals_trace();
 80
 81	if (to_mm->id.u.pid < 0) {
 82		ret = to_mm->id.u.pid;
 83		goto out_free;
 84	}
 85
 86	ret = init_new_ldt(to_mm, from_mm);
 87	if (ret < 0) {
 88		printk(KERN_ERR "init_new_context_skas - init_ldt"
 89		       " failed, errno = %d\n", ret);
 90		goto out_free;
 91	}
 92
 93	return 0;
 94
 95 out_free:
 96	if (to_mm->id.stack != 0)
 97		free_page(to_mm->id.stack);
 98 out:
 99	return ret;
100}
101
102void uml_setup_stubs(struct mm_struct *mm)
103{
104	int err, ret;
105
106	ret = init_stub_pte(mm, STUB_CODE,
107			    (unsigned long) __syscall_stub_start);
108	if (ret)
109		goto out;
110
111	ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
112	if (ret)
113		goto out;
114
115	mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
116	mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
117
118	/* dup_mmap already holds mmap_sem */
119	err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
120				      VM_READ | VM_MAYREAD | VM_EXEC |
121				      VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
122				      mm->context.stub_pages);
123	if (err) {
124		printk(KERN_ERR "install_special_mapping returned %d\n", err);
125		goto out;
126	}
127	return;
128
129out:
130	force_sigsegv(SIGSEGV);
131}
132
133void arch_exit_mmap(struct mm_struct *mm)
134{
135	pte_t *pte;
136
137	pte = virt_to_pte(mm, STUB_CODE);
138	if (pte != NULL)
139		pte_clear(mm, STUB_CODE, pte);
140
141	pte = virt_to_pte(mm, STUB_DATA);
142	if (pte == NULL)
143		return;
144
145	pte_clear(mm, STUB_DATA, pte);
146}
147
148void destroy_context(struct mm_struct *mm)
149{
150	struct mm_context *mmu = &mm->context;
151
152	/*
153	 * If init_new_context wasn't called, this will be
154	 * zero, resulting in a kill(0), which will result in the
155	 * whole UML suddenly dying.  Also, cover negative and
156	 * 1 cases, since they shouldn't happen either.
157	 */
158	if (mmu->id.u.pid < 2) {
159		printk(KERN_ERR "corrupt mm_context - pid = %d\n",
160		       mmu->id.u.pid);
161		return;
162	}
163	os_kill_ptraced_process(mmu->id.u.pid, 1);
164
165	free_page(mmu->id.stack);
166	free_ldt(mmu);
167}