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 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 */ 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 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 } 140 141 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 } 159 160 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 */ 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 } 246 247 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 } 253 254 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_wmb(); 303 304 return 0; 305 } 306 early_initcall(vdso_init); 307