xref: /openbmc/linux/arch/s390/kernel/vdso.c (revision be709d48)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * vdso setup for s390
4  *
5  *  Copyright IBM Corp. 2008
6  *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
7  */
8 
9 #include <linux/init.h>
10 #include <linux/errno.h>
11 #include <linux/sched.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/smp.h>
15 #include <linux/stddef.h>
16 #include <linux/unistd.h>
17 #include <linux/slab.h>
18 #include <linux/user.h>
19 #include <linux/elf.h>
20 #include <linux/security.h>
21 #include <linux/memblock.h>
22 #include <linux/compat.h>
23 #include <asm/asm-offsets.h>
24 #include <asm/pgtable.h>
25 #include <asm/processor.h>
26 #include <asm/mmu.h>
27 #include <asm/mmu_context.h>
28 #include <asm/sections.h>
29 #include <asm/vdso.h>
30 #include <asm/facility.h>
31 
32 #ifdef CONFIG_COMPAT
33 extern char vdso32_start, vdso32_end;
34 static void *vdso32_kbase = &vdso32_start;
35 static unsigned int vdso32_pages;
36 static struct page **vdso32_pagelist;
37 #endif
38 
39 extern char vdso64_start, vdso64_end;
40 static void *vdso64_kbase = &vdso64_start;
41 static unsigned int vdso64_pages;
42 static struct page **vdso64_pagelist;
43 
44 /*
45  * Should the kernel map a VDSO page into processes and pass its
46  * address down to glibc upon exec()?
47  */
48 unsigned int __read_mostly vdso_enabled = 1;
49 
50 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
51 		      struct vm_area_struct *vma, struct vm_fault *vmf)
52 {
53 	struct page **vdso_pagelist;
54 	unsigned long vdso_pages;
55 
56 	vdso_pagelist = vdso64_pagelist;
57 	vdso_pages = vdso64_pages;
58 #ifdef CONFIG_COMPAT
59 	if (vma->vm_mm->context.compat_mm) {
60 		vdso_pagelist = vdso32_pagelist;
61 		vdso_pages = vdso32_pages;
62 	}
63 #endif
64 
65 	if (vmf->pgoff >= vdso_pages)
66 		return VM_FAULT_SIGBUS;
67 
68 	vmf->page = vdso_pagelist[vmf->pgoff];
69 	get_page(vmf->page);
70 	return 0;
71 }
72 
73 static int vdso_mremap(const struct vm_special_mapping *sm,
74 		       struct vm_area_struct *vma)
75 {
76 	unsigned long vdso_pages;
77 
78 	vdso_pages = vdso64_pages;
79 #ifdef CONFIG_COMPAT
80 	if (vma->vm_mm->context.compat_mm)
81 		vdso_pages = vdso32_pages;
82 #endif
83 
84 	if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
85 		return -EINVAL;
86 
87 	if (WARN_ON_ONCE(current->mm != vma->vm_mm))
88 		return -EFAULT;
89 
90 	current->mm->context.vdso_base = vma->vm_start;
91 	return 0;
92 }
93 
94 static const struct vm_special_mapping vdso_mapping = {
95 	.name = "[vdso]",
96 	.fault = vdso_fault,
97 	.mremap = vdso_mremap,
98 };
99 
100 static int __init vdso_setup(char *s)
101 {
102 	unsigned long val;
103 	int rc;
104 
105 	rc = 0;
106 	if (strncmp(s, "on", 3) == 0)
107 		vdso_enabled = 1;
108 	else if (strncmp(s, "off", 4) == 0)
109 		vdso_enabled = 0;
110 	else {
111 		rc = kstrtoul(s, 0, &val);
112 		vdso_enabled = rc ? 0 : !!val;
113 	}
114 	return !rc;
115 }
116 __setup("vdso=", vdso_setup);
117 
118 /*
119  * The vdso data page
120  */
121 static union {
122 	struct vdso_data	data;
123 	u8			page[PAGE_SIZE];
124 } vdso_data_store __page_aligned_data;
125 struct vdso_data *vdso_data = &vdso_data_store.data;
126 
127 /*
128  * Setup vdso data page.
129  */
130 static void __init vdso_init_data(struct vdso_data *vd)
131 {
132 	vd->ectg_available = test_facility(31);
133 }
134 
135 /*
136  * Allocate/free per cpu vdso data.
137  */
138 #define SEGMENT_ORDER	2
139 
140 /*
141  * The initial vdso_data structure for the boot CPU. Eventually
142  * it is replaced with a properly allocated structure in vdso_init.
143  * This is necessary because a valid S390_lowcore.vdso_per_cpu_data
144  * pointer is required to be able to return from an interrupt or
145  * program check. See the exit paths in entry.S.
146  */
147 struct vdso_data boot_vdso_data __initdata;
148 
149 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore)
150 {
151 	lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data;
152 }
153 
154 int vdso_alloc_per_cpu(struct lowcore *lowcore)
155 {
156 	unsigned long segment_table, page_table, page_frame;
157 	struct vdso_per_cpu_data *vd;
158 
159 	segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
160 	page_table = get_zeroed_page(GFP_KERNEL);
161 	page_frame = get_zeroed_page(GFP_KERNEL);
162 	if (!segment_table || !page_table || !page_frame)
163 		goto out;
164 	arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
165 	arch_set_page_dat(virt_to_page(page_table), 0);
166 
167 	/* Initialize per-cpu vdso data page */
168 	vd = (struct vdso_per_cpu_data *) page_frame;
169 	vd->cpu_nr = lowcore->cpu_nr;
170 	vd->node_id = cpu_to_node(vd->cpu_nr);
171 
172 	/* Set up page table for the vdso address space */
173 	memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
174 	memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
175 
176 	*(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
177 	*(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
178 
179 	lowcore->vdso_asce = segment_table +
180 		_ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
181 	lowcore->vdso_per_cpu_data = page_frame;
182 
183 	return 0;
184 
185 out:
186 	free_page(page_frame);
187 	free_page(page_table);
188 	free_pages(segment_table, SEGMENT_ORDER);
189 	return -ENOMEM;
190 }
191 
192 void vdso_free_per_cpu(struct lowcore *lowcore)
193 {
194 	unsigned long segment_table, page_table, page_frame;
195 
196 	segment_table = lowcore->vdso_asce & PAGE_MASK;
197 	page_table = *(unsigned long *) segment_table;
198 	page_frame = *(unsigned long *) page_table;
199 
200 	free_page(page_frame);
201 	free_page(page_table);
202 	free_pages(segment_table, SEGMENT_ORDER);
203 }
204 
205 /*
206  * This is called from binfmt_elf, we create the special vma for the
207  * vDSO and insert it into the mm struct tree
208  */
209 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
210 {
211 	struct mm_struct *mm = current->mm;
212 	struct vm_area_struct *vma;
213 	unsigned long vdso_pages;
214 	unsigned long vdso_base;
215 	int rc;
216 
217 	if (!vdso_enabled)
218 		return 0;
219 	/*
220 	 * Only map the vdso for dynamically linked elf binaries.
221 	 */
222 	if (!uses_interp)
223 		return 0;
224 
225 	vdso_pages = vdso64_pages;
226 #ifdef CONFIG_COMPAT
227 	mm->context.compat_mm = is_compat_task();
228 	if (mm->context.compat_mm)
229 		vdso_pages = vdso32_pages;
230 #endif
231 	/*
232 	 * vDSO has a problem and was disabled, just don't "enable" it for
233 	 * the process
234 	 */
235 	if (vdso_pages == 0)
236 		return 0;
237 
238 	/*
239 	 * pick a base address for the vDSO in process space. We try to put
240 	 * it at vdso_base which is the "natural" base for it, but we might
241 	 * fail and end up putting it elsewhere.
242 	 */
243 	if (down_write_killable(&mm->mmap_sem))
244 		return -EINTR;
245 	vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
246 	if (IS_ERR_VALUE(vdso_base)) {
247 		rc = vdso_base;
248 		goto out_up;
249 	}
250 
251 	/*
252 	 * our vma flags don't have VM_WRITE so by default, the process
253 	 * isn't allowed to write those pages.
254 	 * gdb can break that with ptrace interface, and thus trigger COW
255 	 * on those pages but it's then your responsibility to never do that
256 	 * on the "data" page of the vDSO or you'll stop getting kernel
257 	 * updates and your nice userland gettimeofday will be totally dead.
258 	 * It's fine to use that for setting breakpoints in the vDSO code
259 	 * pages though.
260 	 */
261 	vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
262 				       VM_READ|VM_EXEC|
263 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
264 				       &vdso_mapping);
265 	if (IS_ERR(vma)) {
266 		rc = PTR_ERR(vma);
267 		goto out_up;
268 	}
269 
270 	current->mm->context.vdso_base = vdso_base;
271 	rc = 0;
272 
273 out_up:
274 	up_write(&mm->mmap_sem);
275 	return rc;
276 }
277 
278 static int __init vdso_init(void)
279 {
280 	int i;
281 
282 	vdso_init_data(vdso_data);
283 #ifdef CONFIG_COMPAT
284 	/* Calculate the size of the 32 bit vDSO */
285 	vdso32_pages = ((&vdso32_end - &vdso32_start
286 			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
287 
288 	/* Make sure pages are in the correct state */
289 	vdso32_pagelist = kcalloc(vdso32_pages + 1, sizeof(struct page *),
290 				  GFP_KERNEL);
291 	BUG_ON(vdso32_pagelist == NULL);
292 	for (i = 0; i < vdso32_pages - 1; i++) {
293 		struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
294 		get_page(pg);
295 		vdso32_pagelist[i] = pg;
296 	}
297 	vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
298 	vdso32_pagelist[vdso32_pages] = NULL;
299 #endif
300 
301 	/* Calculate the size of the 64 bit vDSO */
302 	vdso64_pages = ((&vdso64_end - &vdso64_start
303 			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
304 
305 	/* Make sure pages are in the correct state */
306 	vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
307 				  GFP_KERNEL);
308 	BUG_ON(vdso64_pagelist == NULL);
309 	for (i = 0; i < vdso64_pages - 1; i++) {
310 		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
311 		get_page(pg);
312 		vdso64_pagelist[i] = pg;
313 	}
314 	vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
315 	vdso64_pagelist[vdso64_pages] = NULL;
316 	if (vdso_alloc_per_cpu(&S390_lowcore))
317 		BUG();
318 
319 	get_page(virt_to_page(vdso_data));
320 
321 	return 0;
322 }
323 early_initcall(vdso_init);
324