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 <clocksource/arm_arch_timer.h>
 25#include <vdso/helpers.h>
 26#include <vdso/vsyscall.h>
 27
 28#define MAX_SYMNAME	64
 29
 30static struct page **vdso_text_pagelist;
 31
 32extern char vdso_start[], vdso_end[];
 33
 34/* Total number of pages needed for the data and text portions of the VDSO. */
 35unsigned int vdso_total_pages __ro_after_init;
 36
 37static union vdso_data_store vdso_data_store __page_aligned_data;
 38struct vdso_data *vdso_data = vdso_data_store.data;
 39
 40static struct page *vdso_data_page __ro_after_init;
 41static const struct vm_special_mapping vdso_data_mapping = {
 42	.name = "[vvar]",
 43	.pages = &vdso_data_page,
 44};
 45
 46static int vdso_mremap(const struct vm_special_mapping *sm,
 47		struct vm_area_struct *new_vma)
 48{
 49	current->mm->context.vdso = new_vma->vm_start;
 50
 51	return 0;
 52}
 53
 54static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
 55	.name = "[vdso]",
 56	.mremap = vdso_mremap,
 57};
 58
 59struct elfinfo {
 60	Elf32_Ehdr	*hdr;		/* ptr to ELF */
 61	Elf32_Sym	*dynsym;	/* ptr to .dynsym section */
 62	unsigned long	dynsymsize;	/* size of .dynsym section */
 63	char		*dynstr;	/* ptr to .dynstr section */
 64};
 65
 66/* Cached result of boot-time check for whether the arch timer exists,
 67 * and if so, whether the virtual counter is useable.
 68 */
 69bool cntvct_ok __ro_after_init;
 70
 71static bool __init cntvct_functional(void)
 72{
 73	struct device_node *np;
 74	bool ret = false;
 75
 76	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
 77		goto out;
 78
 79	/* The arm_arch_timer core should export
 80	 * arch_timer_use_virtual or similar so we don't have to do
 81	 * this.
 82	 */
 83	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
 84	if (!np)
 85		np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
 86	if (!np)
 87		goto out_put;
 88
 89	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
 90		goto out_put;
 91
 92	ret = true;
 93
 94out_put:
 95	of_node_put(np);
 96out:
 97	return ret;
 98}
 99
100static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
101				  unsigned long *size)
102{
103	Elf32_Shdr *sechdrs;
104	unsigned int i;
105	char *secnames;
106
107	/* Grab section headers and strings so we can tell who is who */
108	sechdrs = (void *)ehdr + ehdr->e_shoff;
109	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
110
111	/* Find the section they want */
112	for (i = 1; i < ehdr->e_shnum; i++) {
113		if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
114			if (size)
115				*size = sechdrs[i].sh_size;
116			return (void *)ehdr + sechdrs[i].sh_offset;
117		}
118	}
119
120	if (size)
121		*size = 0;
122	return NULL;
123}
124
125static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
126{
127	unsigned int i;
128
129	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
130		char name[MAX_SYMNAME], *c;
131
132		if (lib->dynsym[i].st_name == 0)
133			continue;
134		strscpy(name, lib->dynstr + lib->dynsym[i].st_name,
135			MAX_SYMNAME);
136		c = strchr(name, '@');
137		if (c)
138			*c = 0;
139		if (strcmp(symname, name) == 0)
140			return &lib->dynsym[i];
141	}
142	return NULL;
143}
144
145static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
146{
147	Elf32_Sym *sym;
148
149	sym = find_symbol(lib, symname);
150	if (!sym)
151		return;
152
153	sym->st_name = 0;
154}
155
156static void __init patch_vdso(void *ehdr)
157{
158	struct elfinfo einfo;
159
160	einfo = (struct elfinfo) {
161		.hdr = ehdr,
162	};
163
164	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
165	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
166
167	/* If the virtual counter is absent or non-functional we don't
168	 * want programs to incur the slight additional overhead of
169	 * dispatching through the VDSO only to fall back to syscalls.
170	 */
171	if (!cntvct_ok) {
172		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
173		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
174		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
175	}
176}
177
178static int __init vdso_init(void)
179{
180	unsigned int text_pages;
181	int i;
182
183	if (memcmp(vdso_start, "\177ELF", 4)) {
184		pr_err("VDSO is not a valid ELF object!\n");
185		return -ENOEXEC;
186	}
187
188	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
189
190	/* Allocate the VDSO text pagelist */
191	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
192				     GFP_KERNEL);
193	if (vdso_text_pagelist == NULL)
194		return -ENOMEM;
195
196	/* Grab the VDSO data page. */
197	vdso_data_page = virt_to_page(vdso_data);
198
199	/* Grab the VDSO text pages. */
200	for (i = 0; i < text_pages; i++) {
201		struct page *page;
202
203		page = virt_to_page(vdso_start + i * PAGE_SIZE);
204		vdso_text_pagelist[i] = page;
205	}
206
207	vdso_text_mapping.pages = vdso_text_pagelist;
208
209	vdso_total_pages = 1; /* for the data/vvar page */
210	vdso_total_pages += text_pages;
211
212	cntvct_ok = cntvct_functional();
213
214	patch_vdso(vdso_start);
215
216	return 0;
217}
218arch_initcall(vdso_init);
219
220static int install_vvar(struct mm_struct *mm, unsigned long addr)
221{
222	struct vm_area_struct *vma;
223
224	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
225				       VM_READ | VM_MAYREAD,
226				       &vdso_data_mapping);
227
228	return PTR_ERR_OR_ZERO(vma);
229}
230
231/* assumes mmap_lock is write-locked */
232void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
233{
234	struct vm_area_struct *vma;
235	unsigned long len;
236
237	mm->context.vdso = 0;
238
239	if (vdso_text_pagelist == NULL)
240		return;
241
242	if (install_vvar(mm, addr))
243		return;
244
245	/* Account for vvar page. */
246	addr += PAGE_SIZE;
247	len = (vdso_total_pages - 1) << PAGE_SHIFT;
248
249	vma = _install_special_mapping(mm, addr, len,
250		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
251		&vdso_text_mapping);
252
253	if (!IS_ERR(vma))
254		mm->context.vdso = addr;
255}
256