1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Adapted from arm64 version.
  4 *
  5 * Copyright (C) 2012 ARM Limited
  6 * Copyright (C) 2015 Mentor Graphics Corporation.
  7 */
  8
  9#include <linux/cache.h>
 10#include <linux/elf.h>
 11#include <linux/err.h>
 12#include <linux/kernel.h>
 13#include <linux/mm.h>
 14#include <linux/of.h>
 15#include <linux/printk.h>
 16#include <linux/slab.h>
 17#include <linux/timekeeper_internal.h>
 18#include <linux/vmalloc.h>
 19#include <asm/arch_timer.h>
 20#include <asm/barrier.h>
 21#include <asm/cacheflush.h>
 22#include <asm/page.h>
 23#include <asm/vdso.h>
 24#include <asm/vdso_datapage.h>
 25#include <clocksource/arm_arch_timer.h>
 26#include <vdso/helpers.h>
 27#include <vdso/vsyscall.h>
 28
 29#define MAX_SYMNAME	64
 30
 31static struct page **vdso_text_pagelist;
 32
 33extern char vdso_start[], vdso_end[];
 34
 35/* Total number of pages needed for the data and text portions of the VDSO. */
 36unsigned int vdso_total_pages __ro_after_init;
 37
 38/*
 39 * The VDSO data page.
 40 */
 41static union vdso_data_store vdso_data_store __page_aligned_data;
 42struct vdso_data *vdso_data = vdso_data_store.data;
 43
 44static struct page *vdso_data_page __ro_after_init;
 45static const struct vm_special_mapping vdso_data_mapping = {
 46	.name = "[vvar]",
 47	.pages = &vdso_data_page,
 48};
 49
 50static int vdso_mremap(const struct vm_special_mapping *sm,
 51		struct vm_area_struct *new_vma)
 52{
 53	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
 54	unsigned long vdso_size;
 55
 56	/* without VVAR page */
 57	vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT;
 58
 59	if (vdso_size != new_size)
 60		return -EINVAL;
 61
 62	current->mm->context.vdso = new_vma->vm_start;
 63
 64	return 0;
 65}
 66
 67static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
 68	.name = "[vdso]",
 69	.mremap = vdso_mremap,
 70};
 71
 72struct elfinfo {
 73	Elf32_Ehdr	*hdr;		/* ptr to ELF */
 74	Elf32_Sym	*dynsym;	/* ptr to .dynsym section */
 75	unsigned long	dynsymsize;	/* size of .dynsym section */
 76	char		*dynstr;	/* ptr to .dynstr section */
 77};
 78
 79/* Cached result of boot-time check for whether the arch timer exists,
 80 * and if so, whether the virtual counter is useable.
 81 */
 82bool cntvct_ok __ro_after_init;
 83
 84static bool __init cntvct_functional(void)
 85{
 86	struct device_node *np;
 87	bool ret = false;
 88
 89	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
 90		goto out;
 91
 92	/* The arm_arch_timer core should export
 93	 * arch_timer_use_virtual or similar so we don't have to do
 94	 * this.
 95	 */
 96	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
 97	if (!np)
 98		np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
 99	if (!np)
100		goto out_put;
101
102	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
103		goto out_put;
104
105	ret = true;
106
107out_put:
108	of_node_put(np);
109out:
110	return ret;
111}
112
113static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
114				  unsigned long *size)
115{
116	Elf32_Shdr *sechdrs;
117	unsigned int i;
118	char *secnames;
119
120	/* Grab section headers and strings so we can tell who is who */
121	sechdrs = (void *)ehdr + ehdr->e_shoff;
122	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
123
124	/* Find the section they want */
125	for (i = 1; i < ehdr->e_shnum; i++) {
126		if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
127			if (size)
128				*size = sechdrs[i].sh_size;
129			return (void *)ehdr + sechdrs[i].sh_offset;
130		}
131	}
132
133	if (size)
134		*size = 0;
135	return NULL;
136}
137
138static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
139{
140	unsigned int i;
141
142	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
143		char name[MAX_SYMNAME], *c;
144
145		if (lib->dynsym[i].st_name == 0)
146			continue;
147		strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
148			MAX_SYMNAME);
149		c = strchr(name, '@');
150		if (c)
151			*c = 0;
152		if (strcmp(symname, name) == 0)
153			return &lib->dynsym[i];
154	}
155	return NULL;
156}
157
158static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
159{
160	Elf32_Sym *sym;
161
162	sym = find_symbol(lib, symname);
163	if (!sym)
164		return;
165
166	sym->st_name = 0;
167}
168
169static void __init patch_vdso(void *ehdr)
170{
171	struct elfinfo einfo;
172
173	einfo = (struct elfinfo) {
174		.hdr = ehdr,
175	};
176
177	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
178	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
179
180	/* If the virtual counter is absent or non-functional we don't
181	 * want programs to incur the slight additional overhead of
182	 * dispatching through the VDSO only to fall back to syscalls.
183	 */
184	if (!cntvct_ok) {
185		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
186		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
187		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
188	}
189}
190
191static int __init vdso_init(void)
192{
193	unsigned int text_pages;
194	int i;
195
196	if (memcmp(vdso_start, "\177ELF", 4)) {
197		pr_err("VDSO is not a valid ELF object!\n");
198		return -ENOEXEC;
199	}
200
201	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
202
203	/* Allocate the VDSO text pagelist */
204	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
205				     GFP_KERNEL);
206	if (vdso_text_pagelist == NULL)
207		return -ENOMEM;
208
209	/* Grab the VDSO data page. */
210	vdso_data_page = virt_to_page(vdso_data);
211
212	/* Grab the VDSO text pages. */
213	for (i = 0; i < text_pages; i++) {
214		struct page *page;
215
216		page = virt_to_page(vdso_start + i * PAGE_SIZE);
217		vdso_text_pagelist[i] = page;
218	}
219
220	vdso_text_mapping.pages = vdso_text_pagelist;
221
222	vdso_total_pages = 1; /* for the data/vvar page */
223	vdso_total_pages += text_pages;
224
225	cntvct_ok = cntvct_functional();
226
227	patch_vdso(vdso_start);
228
229	return 0;
230}
231arch_initcall(vdso_init);
232
233static int install_vvar(struct mm_struct *mm, unsigned long addr)
234{
235	struct vm_area_struct *vma;
236
237	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
238				       VM_READ | VM_MAYREAD,
239				       &vdso_data_mapping);
240
241	return PTR_ERR_OR_ZERO(vma);
242}
243
244/* assumes mmap_lock is write-locked */
245void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
246{
247	struct vm_area_struct *vma;
248	unsigned long len;
249
250	mm->context.vdso = 0;
251
252	if (vdso_text_pagelist == NULL)
253		return;
254
255	if (install_vvar(mm, addr))
256		return;
257
258	/* Account for vvar page. */
259	addr += PAGE_SIZE;
260	len = (vdso_total_pages - 1) << PAGE_SHIFT;
261
262	vma = _install_special_mapping(mm, addr, len,
263		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
264		&vdso_text_mapping);
265
266	if (!IS_ERR(vma))
267		mm->context.vdso = addr;
268}
269