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/cache.h>
21 #include <linux/elf.h>
22 #include <linux/err.h>
23 #include <linux/kernel.h>
26 #include <linux/printk.h>
27 #include <linux/slab.h>
28 #include <linux/timekeeper_internal.h>
29 #include <linux/vmalloc.h>
30 #include <asm/arch_timer.h>
31 #include <asm/barrier.h>
32 #include <asm/cacheflush.h>
35 #include <asm/vdso_datapage.h>
36 #include <clocksource/arm_arch_timer.h>
38 #define MAX_SYMNAME 64
40 static struct page
**vdso_text_pagelist
;
42 /* Total number of pages needed for the data and text portions of the VDSO. */
43 unsigned int vdso_total_pages __ro_after_init
;
48 static union vdso_data_store vdso_data_store __page_aligned_data
;
49 static struct vdso_data
*vdso_data
= &vdso_data_store
.data
;
51 static struct page
*vdso_data_page __ro_after_init
;
52 static const struct vm_special_mapping vdso_data_mapping
= {
54 .pages
= &vdso_data_page
,
57 static struct vm_special_mapping vdso_text_mapping __ro_after_init
= {
62 Elf32_Ehdr
*hdr
; /* ptr to ELF */
63 Elf32_Sym
*dynsym
; /* ptr to .dynsym section */
64 unsigned long dynsymsize
; /* size of .dynsym section */
65 char *dynstr
; /* ptr to .dynstr section */
68 /* Cached result of boot-time check for whether the arch timer exists,
69 * and if so, whether the virtual counter is useable.
71 static bool cntvct_ok __ro_after_init
;
73 static bool __init
cntvct_functional(void)
75 struct device_node
*np
;
78 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER
))
81 /* The arm_arch_timer core should export
82 * arch_timer_use_virtual or similar so we don't have to do
85 np
= of_find_compatible_node(NULL
, NULL
, "arm,armv7-timer");
89 if (of_property_read_bool(np
, "arm,cpu-registers-not-fw-configured"))
100 static void * __init
find_section(Elf32_Ehdr
*ehdr
, const char *name
,
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
;
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) {
115 *size
= sechdrs
[i
].sh_size
;
116 return (void *)ehdr
+ sechdrs
[i
].sh_offset
;
125 static Elf32_Sym
* __init
find_symbol(struct elfinfo
*lib
, const char *symname
)
129 for (i
= 0; i
< (lib
->dynsymsize
/ sizeof(Elf32_Sym
)); i
++) {
130 char name
[MAX_SYMNAME
], *c
;
132 if (lib
->dynsym
[i
].st_name
== 0)
134 strlcpy(name
, lib
->dynstr
+ lib
->dynsym
[i
].st_name
,
136 c
= strchr(name
, '@');
139 if (strcmp(symname
, name
) == 0)
140 return &lib
->dynsym
[i
];
145 static void __init
vdso_nullpatch_one(struct elfinfo
*lib
, const char *symname
)
149 sym
= find_symbol(lib
, symname
);
156 static void __init
patch_vdso(void *ehdr
)
158 struct elfinfo einfo
;
160 einfo
= (struct elfinfo
) {
164 einfo
.dynsym
= find_section(einfo
.hdr
, ".dynsym", &einfo
.dynsymsize
);
165 einfo
.dynstr
= find_section(einfo
.hdr
, ".dynstr", NULL
);
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.
172 vdso_nullpatch_one(&einfo
, "__vdso_gettimeofday");
173 vdso_nullpatch_one(&einfo
, "__vdso_clock_gettime");
177 static int __init
vdso_init(void)
179 unsigned int text_pages
;
182 if (memcmp(&vdso_start
, "\177ELF", 4)) {
183 pr_err("VDSO is not a valid ELF object!\n");
187 text_pages
= (&vdso_end
- &vdso_start
) >> PAGE_SHIFT
;
188 pr_debug("vdso: %i text pages at base %p\n", text_pages
, &vdso_start
);
190 /* Allocate the VDSO text pagelist */
191 vdso_text_pagelist
= kcalloc(text_pages
, sizeof(struct page
*),
193 if (vdso_text_pagelist
== NULL
)
196 /* Grab the VDSO data page. */
197 vdso_data_page
= virt_to_page(vdso_data
);
199 /* Grab the VDSO text pages. */
200 for (i
= 0; i
< text_pages
; i
++) {
203 page
= virt_to_page(&vdso_start
+ i
* PAGE_SIZE
);
204 vdso_text_pagelist
[i
] = page
;
207 vdso_text_mapping
.pages
= vdso_text_pagelist
;
209 vdso_total_pages
= 1; /* for the data/vvar page */
210 vdso_total_pages
+= text_pages
;
212 cntvct_ok
= cntvct_functional();
214 patch_vdso(&vdso_start
);
218 arch_initcall(vdso_init
);
220 static int install_vvar(struct mm_struct
*mm
, unsigned long addr
)
222 struct vm_area_struct
*vma
;
224 vma
= _install_special_mapping(mm
, addr
, PAGE_SIZE
,
225 VM_READ
| VM_MAYREAD
,
228 return PTR_ERR_OR_ZERO(vma
);
231 /* assumes mmap_sem is write-locked */
232 void arm_install_vdso(struct mm_struct
*mm
, unsigned long addr
)
234 struct vm_area_struct
*vma
;
237 mm
->context
.vdso
= 0;
239 if (vdso_text_pagelist
== NULL
)
242 if (install_vvar(mm
, addr
))
245 /* Account for vvar page. */
247 len
= (vdso_total_pages
- 1) << PAGE_SHIFT
;
249 vma
= _install_special_mapping(mm
, addr
, len
,
250 VM_READ
| VM_EXEC
| VM_MAYREAD
| VM_MAYWRITE
| VM_MAYEXEC
,
254 mm
->context
.vdso
= addr
;
257 static void vdso_write_begin(struct vdso_data
*vdata
)
259 ++vdso_data
->seq_count
;
260 smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */
263 static void vdso_write_end(struct vdso_data
*vdata
)
265 smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */
266 ++vdso_data
->seq_count
;
269 static bool tk_is_cntvct(const struct timekeeper
*tk
)
271 if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER
))
274 if (!tk
->tkr_mono
.clock
->archdata
.vdso_direct
)
281 * update_vsyscall - update the vdso data page
283 * Increment the sequence counter, making it odd, indicating to
284 * userspace that an update is in progress. Update the fields used
285 * for coarse clocks and, if the architected system timer is in use,
286 * the fields used for high precision clocks. Increment the sequence
287 * counter again, making it even, indicating to userspace that the
288 * update is finished.
290 * Userspace is expected to sample seq_count before reading any other
291 * fields from the data page. If seq_count is odd, userspace is
292 * expected to wait until it becomes even. After copying data from
293 * the page, userspace must sample seq_count again; if it has changed
294 * from its previous value, userspace must retry the whole sequence.
296 * Calls to update_vsyscall are serialized by the timekeeping core.
298 void update_vsyscall(struct timekeeper
*tk
)
300 struct timespec64
*wtm
= &tk
->wall_to_monotonic
;
303 /* The entry points have been zeroed, so there is no
304 * point in updating the data page.
309 vdso_write_begin(vdso_data
);
311 vdso_data
->tk_is_cntvct
= tk_is_cntvct(tk
);
312 vdso_data
->xtime_coarse_sec
= tk
->xtime_sec
;
313 vdso_data
->xtime_coarse_nsec
= (u32
)(tk
->tkr_mono
.xtime_nsec
>>
315 vdso_data
->wtm_clock_sec
= wtm
->tv_sec
;
316 vdso_data
->wtm_clock_nsec
= wtm
->tv_nsec
;
318 if (vdso_data
->tk_is_cntvct
) {
319 vdso_data
->cs_cycle_last
= tk
->tkr_mono
.cycle_last
;
320 vdso_data
->xtime_clock_sec
= tk
->xtime_sec
;
321 vdso_data
->xtime_clock_snsec
= tk
->tkr_mono
.xtime_nsec
;
322 vdso_data
->cs_mult
= tk
->tkr_mono
.mult
;
323 vdso_data
->cs_shift
= tk
->tkr_mono
.shift
;
324 vdso_data
->cs_mask
= tk
->tkr_mono
.mask
;
327 vdso_write_end(vdso_data
);
329 flush_dcache_page(virt_to_page(vdso_data
));
332 void update_vsyscall_tz(void)
334 vdso_data
->tz_minuteswest
= sys_tz
.tz_minuteswest
;
335 vdso_data
->tz_dsttime
= sys_tz
.tz_dsttime
;
336 flush_dcache_page(virt_to_page(vdso_data
));