1/*
  2 * Copyright 2012 Tilera Corporation. All Rights Reserved.
  3 *
  4 *   This program is free software; you can redistribute it and/or
  5 *   modify it under the terms of the GNU General Public License
  6 *   as published by the Free Software Foundation, version 2.
  7 *
  8 *   This program is distributed in the hope that it will be useful, but
  9 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 10 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 11 *   NON INFRINGEMENT.  See the GNU General Public License for
 12 *   more details.
 13 */
 14
 15#include <linux/binfmts.h>
 16#include <linux/compat.h>
 17#include <linux/elf.h>
 18#include <linux/mm.h>
 19#include <linux/pagemap.h>
 20
 21#include <asm/vdso.h>
 22#include <asm/mman.h>
 23#include <asm/sections.h>
 24
 25#include <arch/sim.h>
 26
 27/* The alignment of the vDSO. */
 28#define VDSO_ALIGNMENT  PAGE_SIZE
 29
 30
 31static unsigned int vdso_pages;
 32static struct page **vdso_pagelist;
 33
 34#ifdef CONFIG_COMPAT
 35static unsigned int vdso32_pages;
 36static struct page **vdso32_pagelist;
 37#endif
 38static int vdso_ready;
 39
 40/*
 41 * The vdso data page.
 42 */
 43static union {
 44	struct vdso_data	data;
 45	u8			page[PAGE_SIZE];
 46} vdso_data_store __page_aligned_data;
 47
 48struct vdso_data *vdso_data = &vdso_data_store.data;
 49
 50static unsigned int __read_mostly vdso_enabled = 1;
 51
 52static struct page **vdso_setup(void *vdso_kbase, unsigned int pages)
 53{
 54	int i;
 55	struct page **pagelist;
 56
 57	pagelist = kzalloc(sizeof(struct page *) * (pages + 1), GFP_KERNEL);
 58	BUG_ON(pagelist == NULL);
 59	for (i = 0; i < pages - 1; i++) {
 60		struct page *pg = virt_to_page(vdso_kbase + i*PAGE_SIZE);
 61		ClearPageReserved(pg);
 62		pagelist[i] = pg;
 63	}
 64	pagelist[pages - 1] = virt_to_page(vdso_data);
 65	pagelist[pages] = NULL;
 66
 67	return pagelist;
 68}
 69
 70static int __init vdso_init(void)
 71{
 72	int data_pages = sizeof(vdso_data_store) >> PAGE_SHIFT;
 73
 74	/*
 75	 * We can disable vDSO support generally, but we need to retain
 76	 * one page to support the two-bundle (16-byte) rt_sigreturn path.
 77	 */
 78	if (!vdso_enabled) {
 79		size_t offset = (unsigned long)&__vdso_rt_sigreturn;
 80		static struct page *sigret_page;
 81		sigret_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 82		BUG_ON(sigret_page == NULL);
 83		vdso_pagelist = &sigret_page;
 84		vdso_pages = 1;
 85		BUG_ON(offset >= PAGE_SIZE);
 86		memcpy(page_address(sigret_page) + offset,
 87		       vdso_start + offset, 16);
 88#ifdef CONFIG_COMPAT
 89		vdso32_pages = vdso_pages;
 90		vdso32_pagelist = vdso_pagelist;
 91#endif
 92		vdso_ready = 1;
 93		return 0;
 94	}
 95
 96	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
 97	vdso_pages += data_pages;
 98	vdso_pagelist = vdso_setup(vdso_start, vdso_pages);
 99
100#ifdef CONFIG_COMPAT
101	vdso32_pages = (vdso32_end - vdso32_start) >> PAGE_SHIFT;
102	vdso32_pages += data_pages;
103	vdso32_pagelist = vdso_setup(vdso32_start, vdso32_pages);
104#endif
105
106	smp_wmb();
107	vdso_ready = 1;
108
109	return 0;
110}
111arch_initcall(vdso_init);
112
113const char *arch_vma_name(struct vm_area_struct *vma)
114{
115	if (vma->vm_mm && vma->vm_start == VDSO_BASE)
116		return "[vdso]";
117#ifndef __tilegx__
118	if (vma->vm_start == MEM_USER_INTRPT)
119		return "[intrpt]";
120#endif
121	return NULL;
122}
123
124struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
125{
126	return NULL;
127}
128
129int in_gate_area(struct mm_struct *mm, unsigned long address)
130{
131	return 0;
132}
133
134int in_gate_area_no_mm(unsigned long address)
135{
136	return 0;
137}
138
139int setup_vdso_pages(void)
140{
141	struct page **pagelist;
142	unsigned long pages;
143	struct mm_struct *mm = current->mm;
144	unsigned long vdso_base = 0;
145	int retval = 0;
146
147	if (!vdso_ready)
148		return 0;
149
150	mm->context.vdso_base = 0;
151
152	pagelist = vdso_pagelist;
153	pages = vdso_pages;
154#ifdef CONFIG_COMPAT
155	if (is_compat_task()) {
156		pagelist = vdso32_pagelist;
157		pages = vdso32_pages;
158	}
159#endif
160
161	/*
162	 * vDSO has a problem and was disabled, just don't "enable" it for the
163	 * process.
164	 */
165	if (pages == 0)
166		return 0;
167
168	vdso_base = get_unmapped_area(NULL, vdso_base,
169				      (pages << PAGE_SHIFT) +
170				      ((VDSO_ALIGNMENT - 1) & PAGE_MASK),
171				      0, 0);
172	if (IS_ERR_VALUE(vdso_base)) {
173		retval = vdso_base;
174		return retval;
175	}
176
177	/* Add required alignment. */
178	vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
179
180	/*
181	 * Put vDSO base into mm struct. We need to do this before calling
182	 * install_special_mapping or the perf counter mmap tracking code
183	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
184	 */
185	mm->context.vdso_base = vdso_base;
186
187	/*
188	 * our vma flags don't have VM_WRITE so by default, the process isn't
189	 * allowed to write those pages.
190	 * gdb can break that with ptrace interface, and thus trigger COW on
191	 * those pages but it's then your responsibility to never do that on
192	 * the "data" page of the vDSO or you'll stop getting kernel updates
193	 * and your nice userland gettimeofday will be totally dead.
194	 * It's fine to use that for setting breakpoints in the vDSO code
195	 * pages though
196	 */
197	retval = install_special_mapping(mm, vdso_base,
198					 pages << PAGE_SHIFT,
199					 VM_READ|VM_EXEC |
200					 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
201					 pagelist);
202	if (retval)
203		mm->context.vdso_base = 0;
204
205	return retval;
206}
207
208static __init int vdso_func(char *s)
209{
210	return kstrtouint(s, 0, &vdso_enabled);
211}
212__setup("vdso=", vdso_func);