2 * Adapted from arm64 version.
4 * Copyright (C) 2012 ARM Limited
5 * Copyright (C) 2015 Mentor Graphics Corporation.
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #include <linux/elf.h>
21 #include <linux/err.h>
22 #include <linux/kernel.h>
25 #include <linux/printk.h>
26 #include <linux/slab.h>
27 #include <linux/timekeeper_internal.h>
28 #include <linux/vmalloc.h>
29 #include <asm/arch_timer.h>
30 #include <asm/barrier.h>
31 #include <asm/cacheflush.h>
34 #include <asm/vdso_datapage.h>
35 #include <clocksource/arm_arch_timer.h>
37 #define MAX_SYMNAME 64
39 static struct page **vdso_text_pagelist;
41 extern char vdso_start[], vdso_end[];
43 /* Total number of pages needed for the data and text portions of the VDSO. */
44 unsigned int vdso_total_pages __read_mostly;
49 static union vdso_data_store vdso_data_store __page_aligned_data;
50 static struct vdso_data *vdso_data = &vdso_data_store.data;
52 static struct page *vdso_data_page;
53 static struct vm_special_mapping vdso_data_mapping = {
55 .pages = &vdso_data_page,
58 static struct vm_special_mapping vdso_text_mapping = {
63 Elf32_Ehdr *hdr; /* ptr to ELF */
64 Elf32_Sym *dynsym; /* ptr to .dynsym section */
65 unsigned long dynsymsize; /* size of .dynsym section */
66 char *dynstr; /* ptr to .dynstr section */
69 /* Cached result of boot-time check for whether the arch timer exists,
70 * and if so, whether the virtual counter is useable.
72 static bool cntvct_ok __read_mostly;
74 static bool __init cntvct_functional(void)
76 struct device_node *np;
79 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
82 /* The arm_arch_timer core should export
83 * arch_timer_use_virtual or similar so we don't have to do
86 np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
88 np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
92 if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
103 static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
110 /* Grab section headers and strings so we can tell who is who */
111 sechdrs = (void *)ehdr + ehdr->e_shoff;
112 secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;
114 /* Find the section they want */
115 for (i = 1; i < ehdr->e_shnum; i++) {
116 if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
118 *size = sechdrs[i].sh_size;
119 return (void *)ehdr + sechdrs[i].sh_offset;
128 static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
132 for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
133 char name[MAX_SYMNAME], *c;
135 if (lib->dynsym[i].st_name == 0)
137 strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
139 c = strchr(name, '@');
142 if (strcmp(symname, name) == 0)
143 return &lib->dynsym[i];
148 static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
152 sym = find_symbol(lib, symname);
159 static void __init patch_vdso(void *ehdr)
161 struct elfinfo einfo;
163 einfo = (struct elfinfo) {
167 einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
168 einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);
170 /* If the virtual counter is absent or non-functional we don't
171 * want programs to incur the slight additional overhead of
172 * dispatching through the VDSO only to fall back to syscalls.
175 vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
176 vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
180 static int __init vdso_init(void)
182 unsigned int text_pages;
185 if (memcmp(vdso_start, "\177ELF", 4)) {
186 pr_err("VDSO is not a valid ELF object!\n");
190 text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
191 pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start);
193 /* Allocate the VDSO text pagelist */
194 vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
196 if (vdso_text_pagelist == NULL)
199 /* Grab the VDSO data page. */
200 vdso_data_page = virt_to_page(vdso_data);
202 /* Grab the VDSO text pages. */
203 for (i = 0; i < text_pages; i++) {
206 page = virt_to_page(vdso_start + i * PAGE_SIZE);
207 vdso_text_pagelist[i] = page;
210 vdso_text_mapping.pages = vdso_text_pagelist;
212 vdso_total_pages = 1; /* for the data/vvar page */
213 vdso_total_pages += text_pages;
215 cntvct_ok = cntvct_functional();
217 patch_vdso(vdso_start);
221 arch_initcall(vdso_init);
223 static int install_vvar(struct mm_struct *mm, unsigned long addr)
225 struct vm_area_struct *vma;
227 vma = _install_special_mapping(mm, addr, PAGE_SIZE,
228 VM_READ | VM_MAYREAD,
231 return IS_ERR(vma) ? PTR_ERR(vma) : 0;
234 /* assumes mmap_sem is write-locked */
235 void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
237 struct vm_area_struct *vma;
240 mm->context.vdso = 0;
242 if (vdso_text_pagelist == NULL)
245 if (install_vvar(mm, addr))
248 /* Account for vvar page. */
250 len = (vdso_total_pages - 1) << PAGE_SHIFT;
252 vma = _install_special_mapping(mm, addr, len,
253 VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
257 mm->context.vdso = addr;
260 static void vdso_write_begin(struct vdso_data *vdata)
262 ++vdso_data->seq_count;
263 smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
266 static void vdso_write_end(struct vdso_data *vdata)
268 smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
269 ++vdso_data->seq_count;
272 static bool tk_is_cntvct(const struct timekeeper *tk)
274 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
277 if (strcmp(tk->tkr_mono.clock->name, "arch_sys_counter") != 0)
284 * update_vsyscall - update the vdso data page
286 * Increment the sequence counter, making it odd, indicating to
287 * userspace that an update is in progress. Update the fields used
288 * for coarse clocks and, if the architected system timer is in use,
289 * the fields used for high precision clocks. Increment the sequence
290 * counter again, making it even, indicating to userspace that the
291 * update is finished.
293 * Userspace is expected to sample seq_count before reading any other
294 * fields from the data page. If seq_count is odd, userspace is
295 * expected to wait until it becomes even. After copying data from
296 * the page, userspace must sample seq_count again; if it has changed
297 * from its previous value, userspace must retry the whole sequence.
299 * Calls to update_vsyscall are serialized by the timekeeping core.
301 void update_vsyscall(struct timekeeper *tk)
303 struct timespec64 *wtm = &tk->wall_to_monotonic;
306 /* The entry points have been zeroed, so there is no
307 * point in updating the data page.
312 vdso_write_begin(vdso_data);
314 vdso_data->tk_is_cntvct = tk_is_cntvct(tk);
315 vdso_data->xtime_coarse_sec = tk->xtime_sec;
316 vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >>
318 vdso_data->wtm_clock_sec = wtm->tv_sec;
319 vdso_data->wtm_clock_nsec = wtm->tv_nsec;
321 if (vdso_data->tk_is_cntvct) {
322 vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last;
323 vdso_data->xtime_clock_sec = tk->xtime_sec;
324 vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec;
325 vdso_data->cs_mult = tk->tkr_mono.mult;
326 vdso_data->cs_shift = tk->tkr_mono.shift;
327 vdso_data->cs_mask = tk->tkr_mono.mask;
330 vdso_write_end(vdso_data);
332 flush_dcache_page(virt_to_page(vdso_data));
335 void update_vsyscall_tz(void)
337 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
338 vdso_data->tz_dsttime = sys_tz.tz_dsttime;
339 flush_dcache_page(virt_to_page(vdso_data));