summaryrefslogtreecommitdiff
path: root/arch/arm64/kernel/vdso.c
blob: d51a898fd60f2bb634b7c9baeedc2b6010945a50 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
// SPDX-License-Identifier: GPL-2.0-only
/*
 * VDSO implementations.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#include <linux/cache.h>
#include <linux/clocksource.h>
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <vdso/datapage.h>
#include <vdso/helpers.h>
#include <vdso/vsyscall.h>

#include <asm/cacheflush.h>
#include <asm/signal32.h>
#include <asm/vdso.h>

extern char vdso_start[], vdso_end[];
#ifdef CONFIG_COMPAT_VDSO
extern char vdso32_start[], vdso32_end[];
#endif /* CONFIG_COMPAT_VDSO */

enum vdso_abi {
	VDSO_ABI_AA64,
#ifdef CONFIG_COMPAT_VDSO
	VDSO_ABI_AA32,
#endif /* CONFIG_COMPAT_VDSO */
};

struct vdso_abi_info {
	const char *name;
	const char *vdso_code_start;
	const char *vdso_code_end;
	unsigned long vdso_pages;
	/* Data Mapping */
	struct vm_special_mapping *dm;
	/* Code Mapping */
	struct vm_special_mapping *cm;
};

static struct vdso_abi_info vdso_info[] __ro_after_init = {
	[VDSO_ABI_AA64] = {
		.name = "vdso",
		.vdso_code_start = vdso_start,
		.vdso_code_end = vdso_end,
	},
#ifdef CONFIG_COMPAT_VDSO
	[VDSO_ABI_AA32] = {
		.name = "vdso32",
		.vdso_code_start = vdso32_start,
		.vdso_code_end = vdso32_end,
	},
#endif /* CONFIG_COMPAT_VDSO */
};

/*
 * The vDSO data page.
 */
static union {
	struct vdso_data	data[CS_BASES];
	u8			page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = vdso_data_store.data;

static int __vdso_remap(enum vdso_abi abi,
			const struct vm_special_mapping *sm,
			struct vm_area_struct *new_vma)
{
	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
	unsigned long vdso_size = vdso_info[abi].vdso_code_end -
				  vdso_info[abi].vdso_code_start;

	if (vdso_size != new_size)
		return -EINVAL;

	current->mm->context.vdso = (void *)new_vma->vm_start;

	return 0;
}

static int __vdso_init(enum vdso_abi abi)
{
	int i;
	struct page **vdso_pagelist;
	unsigned long pfn;

	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
		pr_err("vDSO is not a valid ELF object!\n");
		return -EINVAL;
	}

	vdso_info[abi].vdso_pages = (
			vdso_info[abi].vdso_code_end -
			vdso_info[abi].vdso_code_start) >>
			PAGE_SHIFT;

	/* Allocate the vDSO pagelist, plus a page for the data. */
	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages + 1,
				sizeof(struct page *),
				GFP_KERNEL);
	if (vdso_pagelist == NULL)
		return -ENOMEM;

	/* Grab the vDSO data page. */
	vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));


	/* Grab the vDSO code pages. */
	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);

	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);

	vdso_info[abi].dm->pages = &vdso_pagelist[0];
	vdso_info[abi].cm->pages = &vdso_pagelist[1];

	return 0;
}

static int __setup_additional_pages(enum vdso_abi abi,
				    struct mm_struct *mm,
				    struct linux_binprm *bprm,
				    int uses_interp)
{
	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
	unsigned long gp_flags = 0;
	void *ret;

	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
	/* Be sure to map the data page */
	vdso_mapping_len = vdso_text_len + PAGE_SIZE;

	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
	if (IS_ERR_VALUE(vdso_base)) {
		ret = ERR_PTR(vdso_base);
		goto up_fail;
	}

	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
				       VM_READ|VM_MAYREAD,
				       vdso_info[abi].dm);
	if (IS_ERR(ret))
		goto up_fail;

	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
		gp_flags = VM_ARM64_BTI;

	vdso_base += PAGE_SIZE;
	mm->context.vdso = (void *)vdso_base;
	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
				       VM_READ|VM_EXEC|gp_flags|
				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
				       vdso_info[abi].cm);
	if (IS_ERR(ret))
		goto up_fail;

	return 0;

up_fail:
	mm->context.vdso = NULL;
	return PTR_ERR(ret);
}

#ifdef CONFIG_COMPAT
/*
 * Create and map the vectors page for AArch32 tasks.
 */
#ifdef CONFIG_COMPAT_VDSO
static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
		struct vm_area_struct *new_vma)
{
	return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
}
#endif /* CONFIG_COMPAT_VDSO */

enum aarch32_map {
	AA32_MAP_VECTORS, /* kuser helpers */
#ifdef CONFIG_COMPAT_VDSO
	AA32_MAP_VVAR,
	AA32_MAP_VDSO,
#else
	AA32_MAP_SIGPAGE
#endif
};

static struct page *aarch32_vectors_page __ro_after_init;
#ifndef CONFIG_COMPAT_VDSO
static struct page *aarch32_sig_page __ro_after_init;
#endif

static struct vm_special_mapping aarch32_vdso_maps[] = {
	[AA32_MAP_VECTORS] = {
		.name	= "[vectors]", /* ABI */
		.pages	= &aarch32_vectors_page,
	},
#ifdef CONFIG_COMPAT_VDSO
	[AA32_MAP_VVAR] = {
		.name = "[vvar]",
	},
	[AA32_MAP_VDSO] = {
		.name = "[vdso]",
		.mremap = aarch32_vdso_mremap,
	},
#else
	[AA32_MAP_SIGPAGE] = {
		.name	= "[sigpage]", /* ABI */
		.pages	= &aarch32_sig_page,
	},
#endif /* CONFIG_COMPAT_VDSO */
};

static int aarch32_alloc_kuser_vdso_page(void)
{
	extern char __kuser_helper_start[], __kuser_helper_end[];
	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
	unsigned long vdso_page;

	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
		return 0;

	vdso_page = get_zeroed_page(GFP_ATOMIC);
	if (!vdso_page)
		return -ENOMEM;

	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
	       kuser_sz);
	aarch32_vectors_page = virt_to_page(vdso_page);
	flush_dcache_page(aarch32_vectors_page);
	return 0;
}

#ifdef CONFIG_COMPAT_VDSO
static int __aarch32_alloc_vdso_pages(void)
{
	int ret;

	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];

	ret = __vdso_init(VDSO_ABI_AA32);
	if (ret)
		return ret;

	return aarch32_alloc_kuser_vdso_page();
}
#else
static int __aarch32_alloc_vdso_pages(void)
{
	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
	unsigned long sigpage;
	int ret;

	sigpage = get_zeroed_page(GFP_ATOMIC);
	if (!sigpage)
		return -ENOMEM;

	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
	aarch32_sig_page = virt_to_page(sigpage);
	flush_dcache_page(aarch32_sig_page);

	ret = aarch32_alloc_kuser_vdso_page();
	if (ret)
		free_page(sigpage);

	return ret;
}
#endif /* CONFIG_COMPAT_VDSO */

static int __init aarch32_alloc_vdso_pages(void)
{
	return __aarch32_alloc_vdso_pages();
}
arch_initcall(aarch32_alloc_vdso_pages);

static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
{
	void *ret;

	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
		return 0;

	/*
	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
	 * not safe to CoW the page containing the CPU exception vectors.
	 */
	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
				       VM_READ | VM_EXEC |
				       VM_MAYREAD | VM_MAYEXEC,
				       &aarch32_vdso_maps[AA32_MAP_VECTORS]);

	return PTR_ERR_OR_ZERO(ret);
}

#ifndef CONFIG_COMPAT_VDSO
static int aarch32_sigreturn_setup(struct mm_struct *mm)
{
	unsigned long addr;
	void *ret;

	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
	if (IS_ERR_VALUE(addr)) {
		ret = ERR_PTR(addr);
		goto out;
	}

	/*
	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
	 * set breakpoints.
	 */
	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
				       VM_READ | VM_EXEC | VM_MAYREAD |
				       VM_MAYWRITE | VM_MAYEXEC,
				       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
	if (IS_ERR(ret))
		goto out;

	mm->context.vdso = (void *)addr;

out:
	return PTR_ERR_OR_ZERO(ret);
}
#endif /* !CONFIG_COMPAT_VDSO */

int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
	struct mm_struct *mm = current->mm;
	int ret;

	if (down_write_killable(&mm->mmap_sem))
		return -EINTR;

	ret = aarch32_kuser_helpers_setup(mm);
	if (ret)
		goto out;

#ifdef CONFIG_COMPAT_VDSO
	ret = __setup_additional_pages(VDSO_ABI_AA32,
				       mm,
				       bprm,
				       uses_interp);
#else
	ret = aarch32_sigreturn_setup(mm);
#endif /* CONFIG_COMPAT_VDSO */

out:
	up_write(&mm->mmap_sem);
	return ret;
}
#endif /* CONFIG_COMPAT */

static int vdso_mremap(const struct vm_special_mapping *sm,
		struct vm_area_struct *new_vma)
{
	return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
}

enum aarch64_map {
	AA64_MAP_VVAR,
	AA64_MAP_VDSO,
};

static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
	[AA64_MAP_VVAR] = {
		.name	= "[vvar]",
	},
	[AA64_MAP_VDSO] = {
		.name	= "[vdso]",
		.mremap = vdso_mremap,
	},
};

static int __init vdso_init(void)
{
	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];

	return __vdso_init(VDSO_ABI_AA64);
}
arch_initcall(vdso_init);

int arch_setup_additional_pages(struct linux_binprm *bprm,
				int uses_interp)
{
	struct mm_struct *mm = current->mm;
	int ret;

	if (down_write_killable(&mm->mmap_sem))
		return -EINTR;

	ret = __setup_additional_pages(VDSO_ABI_AA64,
				       mm,
				       bprm,
				       uses_interp);

	up_write(&mm->mmap_sem);

	return ret;
}