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	current->mm->context.vdso = new_vma->vm_start;
 54
 55	return 0;
 56}
 57
 58static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
 59	.name = "[vdso]",
 60	.mremap = vdso_mremap,
 61};
 62
 63struct elfinfo {
 64	Elf32_Ehdr	*hdr;		/* ptr to ELF */
 65	Elf32_Sym	*dynsym;	/* ptr to .dynsym section */
 66	unsigned long	dynsymsize;	/* size of .dynsym section */
 67	char		*dynstr;	/* ptr to .dynstr section */
 68};
 69
 70/* Cached result of boot-time check for whether the arch timer exists,
 71 * and if so, whether the virtual counter is useable.
 72 */
 73bool cntvct_ok __ro_after_init;
 74
 75static bool __init cntvct_functional(void)
 76{
 77	struct device_node *np;
 78	bool ret = false;
 79
 80	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
 81		goto out;
 82
 83	/* The arm_arch_timer core should export
 84	 * arch_timer_use_virtual or similar so we don't have to do
 85	 * this.
 86	 */
 87	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
 88	if (!np)
 89		np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
 90	if (!np)
 91		goto out_put;
 92
 93	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
 94		goto out_put;
 95
 96	ret = true;
 97
 98out_put:
 99	of_node_put(np);
100out:
101	return ret;
102}
103
104static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
105				  unsigned long *size)
106{
107	Elf32_Shdr *sechdrs;
108	unsigned int i;
109	char *secnames;
110
111	/* Grab section headers and strings so we can tell who is who */
112	sechdrs = (void *)ehdr + ehdr->e_shoff;
113	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
114
115	/* Find the section they want */
116	for (i = 1; i < ehdr->e_shnum; i++) {
117		if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
118			if (size)
119				*size = sechdrs[i].sh_size;
120			return (void *)ehdr + sechdrs[i].sh_offset;
121		}
122	}
123
124	if (size)
125		*size = 0;
126	return NULL;
127}
128
129static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
130{
131	unsigned int i;
132
133	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
134		char name[MAX_SYMNAME], *c;
135
136		if (lib->dynsym[i].st_name == 0)
137			continue;
138		strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
139			MAX_SYMNAME);
140		c = strchr(name, '@');
141		if (c)
142			*c = 0;
143		if (strcmp(symname, name) == 0)
144			return &lib->dynsym[i];
145	}
146	return NULL;
147}
148
149static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
150{
151	Elf32_Sym *sym;
152
153	sym = find_symbol(lib, symname);
154	if (!sym)
155		return;
156
157	sym->st_name = 0;
158}
159
160static void __init patch_vdso(void *ehdr)
161{
162	struct elfinfo einfo;
163
164	einfo = (struct elfinfo) {
165		.hdr = ehdr,
166	};
167
168	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
169	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
170
171	/* If the virtual counter is absent or non-functional we don't
172	 * want programs to incur the slight additional overhead of
173	 * dispatching through the VDSO only to fall back to syscalls.
174	 */
175	if (!cntvct_ok) {
176		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
177		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
178		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
179	}
180}
181
182static int __init vdso_init(void)
183{
184	unsigned int text_pages;
185	int i;
186
187	if (memcmp(vdso_start, "\177ELF", 4)) {
188		pr_err("VDSO is not a valid ELF object!\n");
189		return -ENOEXEC;
190	}
191
192	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
193
194	/* Allocate the VDSO text pagelist */
195	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
196				     GFP_KERNEL);
197	if (vdso_text_pagelist == NULL)
198		return -ENOMEM;
199
200	/* Grab the VDSO data page. */
201	vdso_data_page = virt_to_page(vdso_data);
202
203	/* Grab the VDSO text pages. */
204	for (i = 0; i < text_pages; i++) {
205		struct page *page;
206
207		page = virt_to_page(vdso_start + i * PAGE_SIZE);
208		vdso_text_pagelist[i] = page;
209	}
210
211	vdso_text_mapping.pages = vdso_text_pagelist;
212
213	vdso_total_pages = 1; /* for the data/vvar page */
214	vdso_total_pages += text_pages;
215
216	cntvct_ok = cntvct_functional();
217
218	patch_vdso(vdso_start);
219
220	return 0;
221}
222arch_initcall(vdso_init);
223
224static int install_vvar(struct mm_struct *mm, unsigned long addr)
225{
226	struct vm_area_struct *vma;
227
228	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
229				       VM_READ | VM_MAYREAD,
230				       &vdso_data_mapping);
231
232	return PTR_ERR_OR_ZERO(vma);
233}
234
235/* assumes mmap_lock is write-locked */
236void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
237{
238	struct vm_area_struct *vma;
239	unsigned long len;
240
241	mm->context.vdso = 0;
242
243	if (vdso_text_pagelist == NULL)
244		return;
245
246	if (install_vvar(mm, addr))
247		return;
248
249	/* Account for vvar page. */
250	addr += PAGE_SIZE;
251	len = (vdso_total_pages - 1) << PAGE_SHIFT;
252
253	vma = _install_special_mapping(mm, addr, len,
254		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
255		&vdso_text_mapping);
256
257	if (!IS_ERR(vma))
258		mm->context.vdso = addr;
259}
260