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 #if defined(CONFIG_32BIT) || defined(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 #ifdef CONFIG_64BIT 43 extern char vdso64_start, vdso64_end; 44 static void *vdso64_kbase = &vdso64_start; 45 static unsigned int vdso64_pages; 46 static struct page **vdso64_pagelist; 47 #endif /* CONFIG_64BIT */ 48 49 /* 50 * Should the kernel map a VDSO page into processes and pass its 51 * address down to glibc upon exec()? 52 */ 53 unsigned int __read_mostly vdso_enabled = 1; 54 55 static int __init vdso_setup(char *s) 56 { 57 unsigned long val; 58 int rc; 59 60 rc = 0; 61 if (strncmp(s, "on", 3) == 0) 62 vdso_enabled = 1; 63 else if (strncmp(s, "off", 4) == 0) 64 vdso_enabled = 0; 65 else { 66 rc = kstrtoul(s, 0, &val); 67 vdso_enabled = rc ? 0 : !!val; 68 } 69 return !rc; 70 } 71 __setup("vdso=", vdso_setup); 72 73 /* 74 * The vdso data page 75 */ 76 static union { 77 struct vdso_data data; 78 u8 page[PAGE_SIZE]; 79 } vdso_data_store __page_aligned_data; 80 struct vdso_data *vdso_data = &vdso_data_store.data; 81 82 /* 83 * Setup vdso data page. 84 */ 85 static void vdso_init_data(struct vdso_data *vd) 86 { 87 vd->ectg_available = test_facility(31); 88 } 89 90 #ifdef CONFIG_64BIT 91 /* 92 * Allocate/free per cpu vdso data. 93 */ 94 #define SEGMENT_ORDER 2 95 96 int vdso_alloc_per_cpu(struct _lowcore *lowcore) 97 { 98 unsigned long segment_table, page_table, page_frame; 99 u32 *psal, *aste; 100 int i; 101 102 lowcore->vdso_per_cpu_data = __LC_PASTE; 103 104 if (!vdso_enabled) 105 return 0; 106 107 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER); 108 page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA); 109 page_frame = get_zeroed_page(GFP_KERNEL); 110 if (!segment_table || !page_table || !page_frame) 111 goto out; 112 113 clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY, 114 PAGE_SIZE << SEGMENT_ORDER); 115 clear_table((unsigned long *) page_table, _PAGE_INVALID, 116 256*sizeof(unsigned long)); 117 118 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table; 119 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame; 120 121 psal = (u32 *) (page_table + 256*sizeof(unsigned long)); 122 aste = psal + 32; 123 124 for (i = 4; i < 32; i += 4) 125 psal[i] = 0x80000000; 126 127 lowcore->paste[4] = (u32)(addr_t) psal; 128 psal[0] = 0x02000000; 129 psal[2] = (u32)(addr_t) aste; 130 *(unsigned long *) (aste + 2) = segment_table + 131 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT; 132 aste[4] = (u32)(addr_t) psal; 133 lowcore->vdso_per_cpu_data = page_frame; 134 135 return 0; 136 137 out: 138 free_page(page_frame); 139 free_page(page_table); 140 free_pages(segment_table, SEGMENT_ORDER); 141 return -ENOMEM; 142 } 143 144 void vdso_free_per_cpu(struct _lowcore *lowcore) 145 { 146 unsigned long segment_table, page_table, page_frame; 147 u32 *psal, *aste; 148 149 if (!vdso_enabled) 150 return; 151 152 psal = (u32 *)(addr_t) lowcore->paste[4]; 153 aste = (u32 *)(addr_t) psal[2]; 154 segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK; 155 page_table = *(unsigned long *) segment_table; 156 page_frame = *(unsigned long *) page_table; 157 158 free_page(page_frame); 159 free_page(page_table); 160 free_pages(segment_table, SEGMENT_ORDER); 161 } 162 163 static void vdso_init_cr5(void) 164 { 165 unsigned long cr5; 166 167 if (!vdso_enabled) 168 return; 169 cr5 = offsetof(struct _lowcore, paste); 170 __ctl_load(cr5, 5, 5); 171 } 172 #endif /* CONFIG_64BIT */ 173 174 /* 175 * This is called from binfmt_elf, we create the special vma for the 176 * vDSO and insert it into the mm struct tree 177 */ 178 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 179 { 180 struct mm_struct *mm = current->mm; 181 struct page **vdso_pagelist; 182 unsigned long vdso_pages; 183 unsigned long vdso_base; 184 int rc; 185 186 if (!vdso_enabled) 187 return 0; 188 /* 189 * Only map the vdso for dynamically linked elf binaries. 190 */ 191 if (!uses_interp) 192 return 0; 193 194 #ifdef CONFIG_64BIT 195 vdso_pagelist = vdso64_pagelist; 196 vdso_pages = vdso64_pages; 197 #ifdef CONFIG_COMPAT 198 if (is_compat_task()) { 199 vdso_pagelist = vdso32_pagelist; 200 vdso_pages = vdso32_pages; 201 } 202 #endif 203 #else 204 vdso_pagelist = vdso32_pagelist; 205 vdso_pages = vdso32_pages; 206 #endif 207 208 /* 209 * vDSO has a problem and was disabled, just don't "enable" it for 210 * the process 211 */ 212 if (vdso_pages == 0) 213 return 0; 214 215 current->mm->context.vdso_base = 0; 216 217 /* 218 * pick a base address for the vDSO in process space. We try to put 219 * it at vdso_base which is the "natural" base for it, but we might 220 * fail and end up putting it elsewhere. 221 */ 222 down_write(&mm->mmap_sem); 223 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0); 224 if (IS_ERR_VALUE(vdso_base)) { 225 rc = vdso_base; 226 goto out_up; 227 } 228 229 /* 230 * Put vDSO base into mm struct. We need to do this before calling 231 * install_special_mapping or the perf counter mmap tracking code 232 * will fail to recognise it as a vDSO (since arch_vma_name fails). 233 */ 234 current->mm->context.vdso_base = vdso_base; 235 236 /* 237 * our vma flags don't have VM_WRITE so by default, the process 238 * isn't allowed to write those pages. 239 * gdb can break that with ptrace interface, and thus trigger COW 240 * on those pages but it's then your responsibility to never do that 241 * on the "data" page of the vDSO or you'll stop getting kernel 242 * updates and your nice userland gettimeofday will be totally dead. 243 * It's fine to use that for setting breakpoints in the vDSO code 244 * pages though. 245 */ 246 rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, 247 VM_READ|VM_EXEC| 248 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 249 vdso_pagelist); 250 if (rc) 251 current->mm->context.vdso_base = 0; 252 out_up: 253 up_write(&mm->mmap_sem); 254 return rc; 255 } 256 257 const char *arch_vma_name(struct vm_area_struct *vma) 258 { 259 if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base) 260 return "[vdso]"; 261 return NULL; 262 } 263 264 static int __init vdso_init(void) 265 { 266 int i; 267 268 if (!vdso_enabled) 269 return 0; 270 vdso_init_data(vdso_data); 271 #if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT) 272 /* Calculate the size of the 32 bit vDSO */ 273 vdso32_pages = ((&vdso32_end - &vdso32_start 274 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 275 276 /* Make sure pages are in the correct state */ 277 vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1), 278 GFP_KERNEL); 279 BUG_ON(vdso32_pagelist == NULL); 280 for (i = 0; i < vdso32_pages - 1; i++) { 281 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE); 282 ClearPageReserved(pg); 283 get_page(pg); 284 vdso32_pagelist[i] = pg; 285 } 286 vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data); 287 vdso32_pagelist[vdso32_pages] = NULL; 288 #endif 289 290 #ifdef CONFIG_64BIT 291 /* Calculate the size of the 64 bit vDSO */ 292 vdso64_pages = ((&vdso64_end - &vdso64_start 293 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 294 295 /* Make sure pages are in the correct state */ 296 vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1), 297 GFP_KERNEL); 298 BUG_ON(vdso64_pagelist == NULL); 299 for (i = 0; i < vdso64_pages - 1; i++) { 300 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE); 301 ClearPageReserved(pg); 302 get_page(pg); 303 vdso64_pagelist[i] = pg; 304 } 305 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data); 306 vdso64_pagelist[vdso64_pages] = NULL; 307 if (vdso_alloc_per_cpu(&S390_lowcore)) 308 BUG(); 309 vdso_init_cr5(); 310 #endif /* CONFIG_64BIT */ 311 312 get_page(virt_to_page(vdso_data)); 313 314 smp_wmb(); 315 316 return 0; 317 } 318 early_initcall(vdso_init); 319