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
 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
 36/*
 37 * The VDSO data page.
 38 */
 39static union vdso_data_store vdso_data_store __page_aligned_data;
 40static struct vdso_data *vdso_data = &vdso_data_store.data;
 41
 42static struct page *vdso_data_page __ro_after_init;
 43static const struct vm_special_mapping vdso_data_mapping = {
 44	.name = "[vvar]",
 45	.pages = &vdso_data_page,
 46};
 47
 48static int vdso_mremap(const struct vm_special_mapping *sm,
 49		struct vm_area_struct *new_vma)
 50{
 51	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
 52	unsigned long vdso_size;
 53
 54	/* without VVAR page */
 55	vdso_size = (vdso_total_pages - 1) << PAGE_SHIFT;
 56
 57	if (vdso_size != new_size)
 58		return -EINVAL;
 59
 60	current->mm->context.vdso = new_vma->vm_start;
 61
 62	return 0;
 63}
 64
 65static struct vm_special_mapping vdso_text_mapping __ro_after_init = {
 66	.name = "[vdso]",
 67	.mremap = vdso_mremap,
 68};
 69
 70struct elfinfo {
 71	Elf32_Ehdr	*hdr;		/* ptr to ELF */
 72	Elf32_Sym	*dynsym;	/* ptr to .dynsym section */
 73	unsigned long	dynsymsize;	/* size of .dynsym section */
 74	char		*dynstr;	/* ptr to .dynstr section */
 75};
 76
 77/* Cached result of boot-time check for whether the arch timer exists,
 78 * and if so, whether the virtual counter is useable.
 79 */
 80static bool cntvct_ok __ro_after_init;
 81
 82static bool __init cntvct_functional(void)
 83{
 84	struct device_node *np;
 85	bool ret = false;
 86
 87	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
 88		goto out;
 89
 90	/* The arm_arch_timer core should export
 91	 * arch_timer_use_virtual or similar so we don't have to do
 92	 * this.
 93	 */
 94	np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
 95	if (!np)
 96		goto out_put;
 97
 98	if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
 99		goto out_put;
100
101	ret = true;
102
103out_put:
104	of_node_put(np);
105out:
106	return ret;
107}
108
109static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
110				  unsigned long *size)
111{
112	Elf32_Shdr *sechdrs;
113	unsigned int i;
114	char *secnames;
115
116	/* Grab section headers and strings so we can tell who is who */
117	sechdrs = (void *)ehdr + ehdr->e_shoff;
118	secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
119
120	/* Find the section they want */
121	for (i = 1; i < ehdr->e_shnum; i++) {
122		if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
123			if (size)
124				*size = sechdrs[i].sh_size;
125			return (void *)ehdr + sechdrs[i].sh_offset;
126		}
127	}
128
129	if (size)
130		*size = 0;
131	return NULL;
132}
133
134static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
135{
136	unsigned int i;
137
138	for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
139		char name[MAX_SYMNAME], *c;
140
141		if (lib->dynsym[i].st_name == 0)
142			continue;
143		strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
144			MAX_SYMNAME);
145		c = strchr(name, '@');
146		if (c)
147			*c = 0;
148		if (strcmp(symname, name) == 0)
149			return &lib->dynsym[i];
150	}
151	return NULL;
152}
153
154static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
155{
156	Elf32_Sym *sym;
157
158	sym = find_symbol(lib, symname);
159	if (!sym)
160		return;
161
162	sym->st_name = 0;
163}
164
165static void __init patch_vdso(void *ehdr)
166{
167	struct elfinfo einfo;
168
169	einfo = (struct elfinfo) {
170		.hdr = ehdr,
171	};
172
173	einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
174	einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
175
176	/* If the virtual counter is absent or non-functional we don't
177	 * want programs to incur the slight additional overhead of
178	 * dispatching through the VDSO only to fall back to syscalls.
179	 */
180	if (!cntvct_ok) {
181		vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
182		vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
183	}
184}
185
186static int __init vdso_init(void)
187{
188	unsigned int text_pages;
189	int i;
190
191	if (memcmp(vdso_start, "\177ELF", 4)) {
192		pr_err("VDSO is not a valid ELF object!\n");
193		return -ENOEXEC;
194	}
195
196	text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
197
198	/* Allocate the VDSO text pagelist */
199	vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
200				     GFP_KERNEL);
201	if (vdso_text_pagelist == NULL)
202		return -ENOMEM;
203
204	/* Grab the VDSO data page. */
205	vdso_data_page = virt_to_page(vdso_data);
206
207	/* Grab the VDSO text pages. */
208	for (i = 0; i < text_pages; i++) {
209		struct page *page;
210
211		page = virt_to_page(vdso_start + i * PAGE_SIZE);
212		vdso_text_pagelist[i] = page;
213	}
214
215	vdso_text_mapping.pages = vdso_text_pagelist;
216
217	vdso_total_pages = 1; /* for the data/vvar page */
218	vdso_total_pages += text_pages;
219
220	cntvct_ok = cntvct_functional();
221
222	patch_vdso(vdso_start);
223
224	return 0;
225}
226arch_initcall(vdso_init);
227
228static int install_vvar(struct mm_struct *mm, unsigned long addr)
229{
230	struct vm_area_struct *vma;
231
232	vma = _install_special_mapping(mm, addr, PAGE_SIZE,
233				       VM_READ | VM_MAYREAD,
234				       &vdso_data_mapping);
235
236	return PTR_ERR_OR_ZERO(vma);
237}
238
239/* assumes mmap_sem is write-locked */
240void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
241{
242	struct vm_area_struct *vma;
243	unsigned long len;
244
245	mm->context.vdso = 0;
246
247	if (vdso_text_pagelist == NULL)
248		return;
249
250	if (install_vvar(mm, addr))
251		return;
252
253	/* Account for vvar page. */
254	addr += PAGE_SIZE;
255	len = (vdso_total_pages - 1) << PAGE_SHIFT;
256
257	vma = _install_special_mapping(mm, addr, len,
258		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
259		&vdso_text_mapping);
260
261	if (!IS_ERR(vma))
262		mm->context.vdso = addr;
263}
264
265static void vdso_write_begin(struct vdso_data *vdata)
266{
267	++vdso_data->seq_count;
268	smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
269}
270
271static void vdso_write_end(struct vdso_data *vdata)
272{
273	smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
274	++vdso_data->seq_count;
275}
276
277static bool tk_is_cntvct(const struct timekeeper *tk)
278{
279	if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
280		return false;
281
282	if (!tk->tkr_mono.clock->archdata.vdso_direct)
283		return false;
284
285	return true;
286}
287
288/**
289 * update_vsyscall - update the vdso data page
290 *
291 * Increment the sequence counter, making it odd, indicating to
292 * userspace that an update is in progress.  Update the fields used
293 * for coarse clocks and, if the architected system timer is in use,
294 * the fields used for high precision clocks.  Increment the sequence
295 * counter again, making it even, indicating to userspace that the
296 * update is finished.
297 *
298 * Userspace is expected to sample seq_count before reading any other
299 * fields from the data page.  If seq_count is odd, userspace is
300 * expected to wait until it becomes even.  After copying data from
301 * the page, userspace must sample seq_count again; if it has changed
302 * from its previous value, userspace must retry the whole sequence.
303 *
304 * Calls to update_vsyscall are serialized by the timekeeping core.
305 */
306void update_vsyscall(struct timekeeper *tk)
307{
308	struct timespec64 *wtm = &tk->wall_to_monotonic;
309
310	if (!cntvct_ok) {
311		/* The entry points have been zeroed, so there is no
312		 * point in updating the data page.
313		 */
314		return;
315	}
316
317	vdso_write_begin(vdso_data);
318
319	vdso_data->tk_is_cntvct			= tk_is_cntvct(tk);
320	vdso_data->xtime_coarse_sec		= tk->xtime_sec;
321	vdso_data->xtime_coarse_nsec		= (u32)(tk->tkr_mono.xtime_nsec >>
322							tk->tkr_mono.shift);
323	vdso_data->wtm_clock_sec		= wtm->tv_sec;
324	vdso_data->wtm_clock_nsec		= wtm->tv_nsec;
325
326	if (vdso_data->tk_is_cntvct) {
327		vdso_data->cs_cycle_last	= tk->tkr_mono.cycle_last;
328		vdso_data->xtime_clock_sec	= tk->xtime_sec;
329		vdso_data->xtime_clock_snsec	= tk->tkr_mono.xtime_nsec;
330		vdso_data->cs_mult		= tk->tkr_mono.mult;
331		vdso_data->cs_shift		= tk->tkr_mono.shift;
332		vdso_data->cs_mask		= tk->tkr_mono.mask;
333	}
334
335	vdso_write_end(vdso_data);
336
337	flush_dcache_page(virt_to_page(vdso_data));
338}
339
340void update_vsyscall_tz(void)
341{
342	vdso_data->tz_minuteswest	= sys_tz.tz_minuteswest;
343	vdso_data->tz_dsttime		= sys_tz.tz_dsttime;
344	flush_dcache_page(virt_to_page(vdso_data));
345}