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