summaryrefslogtreecommitdiff
path: root/arch/riscv/kernel/vdso.c
blob: 69b05b6c181b6d252c6d95d11605b76154619c0c (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
 *                    <benh@kernel.crashing.org>
 * Copyright (C) 2012 ARM Limited
 * Copyright (C) 2015 Regents of the University of California
 */

#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/binfmts.h>
#include <linux/err.h>
#include <asm/page.h>
#include <asm/vdso.h>
#include <linux/time_namespace.h>

#ifdef CONFIG_GENERIC_TIME_VSYSCALL
#include <vdso/datapage.h>
#else
struct vdso_data {
};
#endif

extern char vdso_start[], vdso_end[];
#ifdef CONFIG_COMPAT
extern char compat_vdso_start[], compat_vdso_end[];
#endif

enum vvar_pages {
	VVAR_DATA_PAGE_OFFSET,
	VVAR_TIMENS_PAGE_OFFSET,
	VVAR_NR_PAGES,
};

enum rv_vdso_map {
	RV_VDSO_MAP_VVAR,
	RV_VDSO_MAP_VDSO,
};

#define VVAR_SIZE  (VVAR_NR_PAGES << PAGE_SHIFT)

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

struct __vdso_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 int vdso_mremap(const struct vm_special_mapping *sm,
		       struct vm_area_struct *new_vma)
{
	current->mm->context.vdso = (void *)new_vma->vm_start;

	return 0;
}

static void __init __vdso_init(struct __vdso_info *vdso_info)
{
	unsigned int i;
	struct page **vdso_pagelist;
	unsigned long pfn;

	if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4))
		panic("vDSO is not a valid ELF object!\n");

	vdso_info->vdso_pages = (
		vdso_info->vdso_code_end -
		vdso_info->vdso_code_start) >>
		PAGE_SHIFT;

	vdso_pagelist = kcalloc(vdso_info->vdso_pages,
				sizeof(struct page *),
				GFP_KERNEL);
	if (vdso_pagelist == NULL)
		panic("vDSO kcalloc failed!\n");

	/* Grab the vDSO code pages. */
	pfn = sym_to_pfn(vdso_info->vdso_code_start);

	for (i = 0; i < vdso_info->vdso_pages; i++)
		vdso_pagelist[i] = pfn_to_page(pfn + i);

	vdso_info->cm->pages = vdso_pagelist;
}

#ifdef CONFIG_TIME_NS
struct vdso_data *arch_get_vdso_data(void *vvar_page)
{
	return (struct vdso_data *)(vvar_page);
}

/*
 * The vvar mapping contains data for a specific time namespace, so when a task
 * changes namespace we must unmap its vvar data for the old namespace.
 * Subsequent faults will map in data for the new namespace.
 *
 * For more details see timens_setup_vdso_data().
 */
int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
{
	struct mm_struct *mm = task->mm;
	struct vm_area_struct *vma;
	struct __vdso_info *vdso_info = mm->context.vdso_info;

	mmap_read_lock(mm);

	for (vma = mm->mmap; vma; vma = vma->vm_next) {
		unsigned long size = vma->vm_end - vma->vm_start;

		if (vma_is_special_mapping(vma, vdso_info->dm))
			zap_page_range(vma, vma->vm_start, size);
	}

	mmap_read_unlock(mm);
	return 0;
}

static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
	if (likely(vma->vm_mm == current->mm))
		return current->nsproxy->time_ns->vvar_page;

	/*
	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
	 * through interfaces like /proc/$pid/mem or
	 * process_vm_{readv,writev}() as long as there's no .access()
	 * in special_mapping_vmops.
	 * For more details check_vma_flags() and __access_remote_vm()
	 */
	WARN(1, "vvar_page accessed remotely");

	return NULL;
}
#else
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
	return NULL;
}
#endif

static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
			     struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct page *timens_page = find_timens_vvar_page(vma);
	unsigned long pfn;

	switch (vmf->pgoff) {
	case VVAR_DATA_PAGE_OFFSET:
		if (timens_page)
			pfn = page_to_pfn(timens_page);
		else
			pfn = sym_to_pfn(vdso_data);
		break;
#ifdef CONFIG_TIME_NS
	case VVAR_TIMENS_PAGE_OFFSET:
		/*
		 * If a task belongs to a time namespace then a namespace
		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
		 * offset.
		 * See also the comment near timens_setup_vdso_data().
		 */
		if (!timens_page)
			return VM_FAULT_SIGBUS;
		pfn = sym_to_pfn(vdso_data);
		break;
#endif /* CONFIG_TIME_NS */
	default:
		return VM_FAULT_SIGBUS;
	}

	return vmf_insert_pfn(vma, vmf->address, pfn);
}

static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
	[RV_VDSO_MAP_VVAR] = {
		.name   = "[vvar]",
		.fault = vvar_fault,
	},
	[RV_VDSO_MAP_VDSO] = {
		.name   = "[vdso]",
		.mremap = vdso_mremap,
	},
};

static struct __vdso_info vdso_info __ro_after_init = {
	.name = "vdso",
	.vdso_code_start = vdso_start,
	.vdso_code_end = vdso_end,
	.dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
	.cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
};

#ifdef CONFIG_COMPAT
static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = {
	[RV_VDSO_MAP_VVAR] = {
		.name   = "[vvar]",
		.fault = vvar_fault,
	},
	[RV_VDSO_MAP_VDSO] = {
		.name   = "[vdso]",
		.mremap = vdso_mremap,
	},
};

static struct __vdso_info compat_vdso_info __ro_after_init = {
	.name = "compat_vdso",
	.vdso_code_start = compat_vdso_start,
	.vdso_code_end = compat_vdso_end,
	.dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR],
	.cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO],
};
#endif

static int __init vdso_init(void)
{
	__vdso_init(&vdso_info);
#ifdef CONFIG_COMPAT
	__vdso_init(&compat_vdso_info);
#endif

	return 0;
}
arch_initcall(vdso_init);

static int __setup_additional_pages(struct mm_struct *mm,
				    struct linux_binprm *bprm,
				    int uses_interp,
				    struct __vdso_info *vdso_info)
{
	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
	void *ret;

	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);

	vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
	/* Be sure to map the data page */
	vdso_mapping_len = vdso_text_len + VVAR_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, VVAR_SIZE,
		(VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm);
	if (IS_ERR(ret))
		goto up_fail;

	vdso_base += VVAR_SIZE;
	mm->context.vdso = (void *)vdso_base;
	mm->context.vdso_info = (void *)vdso_info;

	ret =
	   _install_special_mapping(mm, vdso_base, vdso_text_len,
		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
		vdso_info->cm);

	if (IS_ERR(ret))
		goto up_fail;

	return 0;

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

#ifdef CONFIG_COMPAT
int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
				       int uses_interp)
{
	struct mm_struct *mm = current->mm;
	int ret;

	if (mmap_write_lock_killable(mm))
		return -EINTR;

	ret = __setup_additional_pages(mm, bprm, uses_interp,
							&compat_vdso_info);
	mmap_write_unlock(mm);

	return ret;
}
#endif

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

	if (mmap_write_lock_killable(mm))
		return -EINTR;

	ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
	mmap_write_unlock(mm);

	return ret;
}