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1 /*
2  * vdso setup for s390
3  *
4  *  Copyright IBM Corp. 2008
5  *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
6  *
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 only)
9  * as published by the Free Software Foundation.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/errno.h>
14 #include <linux/sched.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/smp.h>
18 #include <linux/stddef.h>
19 #include <linux/unistd.h>
20 #include <linux/slab.h>
21 #include <linux/user.h>
22 #include <linux/elf.h>
23 #include <linux/security.h>
24 #include <linux/bootmem.h>
25 #include <linux/compat.h>
26 #include <asm/asm-offsets.h>
27 #include <asm/pgtable.h>
28 #include <asm/processor.h>
29 #include <asm/mmu.h>
30 #include <asm/mmu_context.h>
31 #include <asm/sections.h>
32 #include <asm/vdso.h>
33 #include <asm/facility.h>
34 
35 #ifdef CONFIG_COMPAT
36 extern char vdso32_start, vdso32_end;
37 static void *vdso32_kbase = &vdso32_start;
38 static unsigned int vdso32_pages;
39 static struct page **vdso32_pagelist;
40 #endif
41 
42 extern char vdso64_start, vdso64_end;
43 static void *vdso64_kbase = &vdso64_start;
44 static unsigned int vdso64_pages;
45 static struct page **vdso64_pagelist;
46 
47 /*
48  * Should the kernel map a VDSO page into processes and pass its
49  * address down to glibc upon exec()?
50  */
51 unsigned int __read_mostly vdso_enabled = 1;
52 
vdso_setup(char * s)53 static int __init vdso_setup(char *s)
54 {
55 	unsigned long val;
56 	int rc;
57 
58 	rc = 0;
59 	if (strncmp(s, "on", 3) == 0)
60 		vdso_enabled = 1;
61 	else if (strncmp(s, "off", 4) == 0)
62 		vdso_enabled = 0;
63 	else {
64 		rc = kstrtoul(s, 0, &val);
65 		vdso_enabled = rc ? 0 : !!val;
66 	}
67 	return !rc;
68 }
69 __setup("vdso=", vdso_setup);
70 
71 /*
72  * The vdso data page
73  */
74 static union {
75 	struct vdso_data	data;
76 	u8			page[PAGE_SIZE];
77 } vdso_data_store __page_aligned_data;
78 struct vdso_data *vdso_data = &vdso_data_store.data;
79 
80 /*
81  * Setup vdso data page.
82  */
vdso_init_data(struct vdso_data * vd)83 static void vdso_init_data(struct vdso_data *vd)
84 {
85 	vd->ectg_available = test_facility(31);
86 }
87 
88 /*
89  * Allocate/free per cpu vdso data.
90  */
91 #define SEGMENT_ORDER	2
92 
vdso_alloc_per_cpu(struct _lowcore * lowcore)93 int vdso_alloc_per_cpu(struct _lowcore *lowcore)
94 {
95 	unsigned long segment_table, page_table, page_frame;
96 	u32 *psal, *aste;
97 	int i;
98 
99 	lowcore->vdso_per_cpu_data = __LC_PASTE;
100 
101 	if (!vdso_enabled)
102 		return 0;
103 
104 	segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
105 	page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
106 	page_frame = get_zeroed_page(GFP_KERNEL);
107 	if (!segment_table || !page_table || !page_frame)
108 		goto out;
109 
110 	clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
111 		    PAGE_SIZE << SEGMENT_ORDER);
112 	clear_table((unsigned long *) page_table, _PAGE_INVALID,
113 		    256*sizeof(unsigned long));
114 
115 	*(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
116 	*(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
117 
118 	psal = (u32 *) (page_table + 256*sizeof(unsigned long));
119 	aste = psal + 32;
120 
121 	for (i = 4; i < 32; i += 4)
122 		psal[i] = 0x80000000;
123 
124 	lowcore->paste[4] = (u32)(addr_t) psal;
125 	psal[0] = 0x02000000;
126 	psal[2] = (u32)(addr_t) aste;
127 	*(unsigned long *) (aste + 2) = segment_table +
128 		_ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
129 	aste[4] = (u32)(addr_t) psal;
130 	lowcore->vdso_per_cpu_data = page_frame;
131 
132 	return 0;
133 
134 out:
135 	free_page(page_frame);
136 	free_page(page_table);
137 	free_pages(segment_table, SEGMENT_ORDER);
138 	return -ENOMEM;
139 }
140 
vdso_free_per_cpu(struct _lowcore * lowcore)141 void vdso_free_per_cpu(struct _lowcore *lowcore)
142 {
143 	unsigned long segment_table, page_table, page_frame;
144 	u32 *psal, *aste;
145 
146 	if (!vdso_enabled)
147 		return;
148 
149 	psal = (u32 *)(addr_t) lowcore->paste[4];
150 	aste = (u32 *)(addr_t) psal[2];
151 	segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
152 	page_table = *(unsigned long *) segment_table;
153 	page_frame = *(unsigned long *) page_table;
154 
155 	free_page(page_frame);
156 	free_page(page_table);
157 	free_pages(segment_table, SEGMENT_ORDER);
158 }
159 
vdso_init_cr5(void)160 static void vdso_init_cr5(void)
161 {
162 	unsigned long cr5;
163 
164 	if (!vdso_enabled)
165 		return;
166 	cr5 = offsetof(struct _lowcore, paste);
167 	__ctl_load(cr5, 5, 5);
168 }
169 
170 /*
171  * This is called from binfmt_elf, we create the special vma for the
172  * vDSO and insert it into the mm struct tree
173  */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)174 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
175 {
176 	struct mm_struct *mm = current->mm;
177 	struct page **vdso_pagelist;
178 	unsigned long vdso_pages;
179 	unsigned long vdso_base;
180 	int rc;
181 
182 	if (!vdso_enabled)
183 		return 0;
184 	/*
185 	 * Only map the vdso for dynamically linked elf binaries.
186 	 */
187 	if (!uses_interp)
188 		return 0;
189 
190 	vdso_pagelist = vdso64_pagelist;
191 	vdso_pages = vdso64_pages;
192 #ifdef CONFIG_COMPAT
193 	if (is_compat_task()) {
194 		vdso_pagelist = vdso32_pagelist;
195 		vdso_pages = vdso32_pages;
196 	}
197 #endif
198 	/*
199 	 * vDSO has a problem and was disabled, just don't "enable" it for
200 	 * the process
201 	 */
202 	if (vdso_pages == 0)
203 		return 0;
204 
205 	current->mm->context.vdso_base = 0;
206 
207 	/*
208 	 * pick a base address for the vDSO in process space. We try to put
209 	 * it at vdso_base which is the "natural" base for it, but we might
210 	 * fail and end up putting it elsewhere.
211 	 */
212 	down_write(&mm->mmap_sem);
213 	vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
214 	if (IS_ERR_VALUE(vdso_base)) {
215 		rc = vdso_base;
216 		goto out_up;
217 	}
218 
219 	/*
220 	 * Put vDSO base into mm struct. We need to do this before calling
221 	 * install_special_mapping or the perf counter mmap tracking code
222 	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
223 	 */
224 	current->mm->context.vdso_base = vdso_base;
225 
226 	/*
227 	 * our vma flags don't have VM_WRITE so by default, the process
228 	 * isn't allowed to write those pages.
229 	 * gdb can break that with ptrace interface, and thus trigger COW
230 	 * on those pages but it's then your responsibility to never do that
231 	 * on the "data" page of the vDSO or you'll stop getting kernel
232 	 * updates and your nice userland gettimeofday will be totally dead.
233 	 * It's fine to use that for setting breakpoints in the vDSO code
234 	 * pages though.
235 	 */
236 	rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
237 				     VM_READ|VM_EXEC|
238 				     VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
239 				     vdso_pagelist);
240 	if (rc)
241 		current->mm->context.vdso_base = 0;
242 out_up:
243 	up_write(&mm->mmap_sem);
244 	return rc;
245 }
246 
arch_vma_name(struct vm_area_struct * vma)247 const char *arch_vma_name(struct vm_area_struct *vma)
248 {
249 	if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
250 		return "[vdso]";
251 	return NULL;
252 }
253 
vdso_init(void)254 static int __init vdso_init(void)
255 {
256 	int i;
257 
258 	if (!vdso_enabled)
259 		return 0;
260 	vdso_init_data(vdso_data);
261 #ifdef CONFIG_COMPAT
262 	/* Calculate the size of the 32 bit vDSO */
263 	vdso32_pages = ((&vdso32_end - &vdso32_start
264 			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
265 
266 	/* Make sure pages are in the correct state */
267 	vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
268 				  GFP_KERNEL);
269 	BUG_ON(vdso32_pagelist == NULL);
270 	for (i = 0; i < vdso32_pages - 1; i++) {
271 		struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
272 		ClearPageReserved(pg);
273 		get_page(pg);
274 		vdso32_pagelist[i] = pg;
275 	}
276 	vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
277 	vdso32_pagelist[vdso32_pages] = NULL;
278 #endif
279 
280 	/* Calculate the size of the 64 bit vDSO */
281 	vdso64_pages = ((&vdso64_end - &vdso64_start
282 			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
283 
284 	/* Make sure pages are in the correct state */
285 	vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
286 				  GFP_KERNEL);
287 	BUG_ON(vdso64_pagelist == NULL);
288 	for (i = 0; i < vdso64_pages - 1; i++) {
289 		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
290 		ClearPageReserved(pg);
291 		get_page(pg);
292 		vdso64_pagelist[i] = pg;
293 	}
294 	vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
295 	vdso64_pagelist[vdso64_pages] = NULL;
296 	if (vdso_alloc_per_cpu(&S390_lowcore))
297 		BUG();
298 	vdso_init_cr5();
299 
300 	get_page(virt_to_page(vdso_data));
301 
302 	smp_mb();
303 
304 	return 0;
305 }
306 early_initcall(vdso_init);
307