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