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_VDSO 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_VDSO 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_VDSO 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 *str) 101 { 102 bool enabled; 103 104 if (!kstrtobool(str, &enabled)) 105 vdso_enabled = enabled; 106 return 1; 107 } 108 __setup("vdso=", vdso_setup); 109 110 /* 111 * The vdso data page 112 */ 113 static union { 114 struct vdso_data data; 115 u8 page[PAGE_SIZE]; 116 } vdso_data_store __page_aligned_data; 117 struct vdso_data *vdso_data = &vdso_data_store.data; 118 119 /* 120 * Setup vdso data page. 121 */ 122 static void __init vdso_init_data(struct vdso_data *vd) 123 { 124 vd->ectg_available = test_facility(31); 125 } 126 127 /* 128 * Allocate/free per cpu vdso data. 129 */ 130 #define SEGMENT_ORDER 2 131 132 /* 133 * The initial vdso_data structure for the boot CPU. Eventually 134 * it is replaced with a properly allocated structure in vdso_init. 135 * This is necessary because a valid S390_lowcore.vdso_per_cpu_data 136 * pointer is required to be able to return from an interrupt or 137 * program check. See the exit paths in entry.S. 138 */ 139 struct vdso_data boot_vdso_data __initdata; 140 141 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore) 142 { 143 lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data; 144 } 145 146 int vdso_alloc_per_cpu(struct lowcore *lowcore) 147 { 148 unsigned long segment_table, page_table, page_frame; 149 struct vdso_per_cpu_data *vd; 150 151 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER); 152 page_table = get_zeroed_page(GFP_KERNEL); 153 page_frame = get_zeroed_page(GFP_KERNEL); 154 if (!segment_table || !page_table || !page_frame) 155 goto out; 156 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER); 157 arch_set_page_dat(virt_to_page(page_table), 0); 158 159 /* Initialize per-cpu vdso data page */ 160 vd = (struct vdso_per_cpu_data *) page_frame; 161 vd->cpu_nr = lowcore->cpu_nr; 162 vd->node_id = cpu_to_node(vd->cpu_nr); 163 164 /* Set up page table for the vdso address space */ 165 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES); 166 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE); 167 168 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table; 169 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame; 170 171 lowcore->vdso_asce = segment_table + 172 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT; 173 lowcore->vdso_per_cpu_data = page_frame; 174 175 return 0; 176 177 out: 178 free_page(page_frame); 179 free_page(page_table); 180 free_pages(segment_table, SEGMENT_ORDER); 181 return -ENOMEM; 182 } 183 184 void vdso_free_per_cpu(struct lowcore *lowcore) 185 { 186 unsigned long segment_table, page_table, page_frame; 187 188 segment_table = lowcore->vdso_asce & PAGE_MASK; 189 page_table = *(unsigned long *) segment_table; 190 page_frame = *(unsigned long *) page_table; 191 192 free_page(page_frame); 193 free_page(page_table); 194 free_pages(segment_table, SEGMENT_ORDER); 195 } 196 197 /* 198 * This is called from binfmt_elf, we create the special vma for the 199 * vDSO and insert it into the mm struct tree 200 */ 201 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 202 { 203 struct mm_struct *mm = current->mm; 204 struct vm_area_struct *vma; 205 unsigned long vdso_pages; 206 unsigned long vdso_base; 207 int rc; 208 209 if (!vdso_enabled) 210 return 0; 211 212 vdso_pages = vdso64_pages; 213 #ifdef CONFIG_COMPAT_VDSO 214 mm->context.compat_mm = is_compat_task(); 215 if (mm->context.compat_mm) 216 vdso_pages = vdso32_pages; 217 #endif 218 /* 219 * vDSO has a problem and was disabled, just don't "enable" it for 220 * the process 221 */ 222 if (vdso_pages == 0) 223 return 0; 224 225 /* 226 * pick a base address for the vDSO in process space. We try to put 227 * it at vdso_base which is the "natural" base for it, but we might 228 * fail and end up putting it elsewhere. 229 */ 230 if (down_write_killable(&mm->mmap_sem)) 231 return -EINTR; 232 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0); 233 if (IS_ERR_VALUE(vdso_base)) { 234 rc = vdso_base; 235 goto out_up; 236 } 237 238 /* 239 * our vma flags don't have VM_WRITE so by default, the process 240 * isn't allowed to write those pages. 241 * gdb can break that with ptrace interface, and thus trigger COW 242 * on those pages but it's then your responsibility to never do that 243 * on the "data" page of the vDSO or you'll stop getting kernel 244 * updates and your nice userland gettimeofday will be totally dead. 245 * It's fine to use that for setting breakpoints in the vDSO code 246 * pages though. 247 */ 248 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, 249 VM_READ|VM_EXEC| 250 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 251 &vdso_mapping); 252 if (IS_ERR(vma)) { 253 rc = PTR_ERR(vma); 254 goto out_up; 255 } 256 257 current->mm->context.vdso_base = vdso_base; 258 rc = 0; 259 260 out_up: 261 up_write(&mm->mmap_sem); 262 return rc; 263 } 264 265 static int __init vdso_init(void) 266 { 267 int i; 268 269 vdso_init_data(vdso_data); 270 #ifdef CONFIG_COMPAT_VDSO 271 /* Calculate the size of the 32 bit vDSO */ 272 vdso32_pages = ((&vdso32_end - &vdso32_start 273 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 274 275 /* Make sure pages are in the correct state */ 276 vdso32_pagelist = kcalloc(vdso32_pages + 1, sizeof(struct page *), 277 GFP_KERNEL); 278 BUG_ON(vdso32_pagelist == NULL); 279 for (i = 0; i < vdso32_pages - 1; i++) { 280 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE); 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 = kcalloc(vdso64_pages + 1, sizeof(struct page *), 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 get_page(pg); 299 vdso64_pagelist[i] = pg; 300 } 301 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data); 302 vdso64_pagelist[vdso64_pages] = NULL; 303 if (vdso_alloc_per_cpu(&S390_lowcore)) 304 BUG(); 305 306 get_page(virt_to_page(vdso_data)); 307 308 return 0; 309 } 310 early_initcall(vdso_init); 311