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/processor.h> 25 #include <asm/mmu.h> 26 #include <asm/mmu_context.h> 27 #include <asm/sections.h> 28 #include <asm/vdso.h> 29 #include <asm/facility.h> 30 31 extern char vdso64_start, vdso64_end; 32 static void *vdso64_kbase = &vdso64_start; 33 static unsigned int vdso64_pages; 34 static struct page **vdso64_pagelist; 35 36 /* 37 * Should the kernel map a VDSO page into processes and pass its 38 * address down to glibc upon exec()? 39 */ 40 unsigned int __read_mostly vdso_enabled = 1; 41 42 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, 43 struct vm_area_struct *vma, struct vm_fault *vmf) 44 { 45 struct page **vdso_pagelist; 46 unsigned long vdso_pages; 47 48 vdso_pagelist = vdso64_pagelist; 49 vdso_pages = vdso64_pages; 50 51 if (vmf->pgoff >= vdso_pages) 52 return VM_FAULT_SIGBUS; 53 54 vmf->page = vdso_pagelist[vmf->pgoff]; 55 get_page(vmf->page); 56 return 0; 57 } 58 59 static int vdso_mremap(const struct vm_special_mapping *sm, 60 struct vm_area_struct *vma) 61 { 62 unsigned long vdso_pages; 63 64 vdso_pages = vdso64_pages; 65 66 if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start) 67 return -EINVAL; 68 69 if (WARN_ON_ONCE(current->mm != vma->vm_mm)) 70 return -EFAULT; 71 72 current->mm->context.vdso_base = vma->vm_start; 73 return 0; 74 } 75 76 static const struct vm_special_mapping vdso_mapping = { 77 .name = "[vdso]", 78 .fault = vdso_fault, 79 .mremap = vdso_mremap, 80 }; 81 82 static int __init vdso_setup(char *str) 83 { 84 bool enabled; 85 86 if (!kstrtobool(str, &enabled)) 87 vdso_enabled = enabled; 88 return 1; 89 } 90 __setup("vdso=", vdso_setup); 91 92 /* 93 * The vdso data page 94 */ 95 static union { 96 struct vdso_data data; 97 u8 page[PAGE_SIZE]; 98 } vdso_data_store __page_aligned_data; 99 struct vdso_data *vdso_data = &vdso_data_store.data; 100 101 /* 102 * Setup vdso data page. 103 */ 104 static void __init vdso_init_data(struct vdso_data *vd) 105 { 106 vd->ectg_available = test_facility(31); 107 } 108 109 /* 110 * Allocate/free per cpu vdso data. 111 */ 112 #define SEGMENT_ORDER 2 113 114 /* 115 * The initial vdso_data structure for the boot CPU. Eventually 116 * it is replaced with a properly allocated structure in vdso_init. 117 * This is necessary because a valid S390_lowcore.vdso_per_cpu_data 118 * pointer is required to be able to return from an interrupt or 119 * program check. See the exit paths in entry.S. 120 */ 121 struct vdso_data boot_vdso_data __initdata; 122 123 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore) 124 { 125 lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data; 126 } 127 128 int vdso_alloc_per_cpu(struct lowcore *lowcore) 129 { 130 unsigned long segment_table, page_table, page_frame; 131 struct vdso_per_cpu_data *vd; 132 133 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER); 134 page_table = get_zeroed_page(GFP_KERNEL); 135 page_frame = get_zeroed_page(GFP_KERNEL); 136 if (!segment_table || !page_table || !page_frame) 137 goto out; 138 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER); 139 arch_set_page_dat(virt_to_page(page_table), 0); 140 141 /* Initialize per-cpu vdso data page */ 142 vd = (struct vdso_per_cpu_data *) page_frame; 143 vd->cpu_nr = lowcore->cpu_nr; 144 vd->node_id = cpu_to_node(vd->cpu_nr); 145 146 /* Set up page table for the vdso address space */ 147 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES); 148 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE); 149 150 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table; 151 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame; 152 153 lowcore->vdso_asce = segment_table + 154 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT; 155 lowcore->vdso_per_cpu_data = page_frame; 156 157 return 0; 158 159 out: 160 free_page(page_frame); 161 free_page(page_table); 162 free_pages(segment_table, SEGMENT_ORDER); 163 return -ENOMEM; 164 } 165 166 void vdso_free_per_cpu(struct lowcore *lowcore) 167 { 168 unsigned long segment_table, page_table, page_frame; 169 170 segment_table = lowcore->vdso_asce & PAGE_MASK; 171 page_table = *(unsigned long *) segment_table; 172 page_frame = *(unsigned long *) page_table; 173 174 free_page(page_frame); 175 free_page(page_table); 176 free_pages(segment_table, SEGMENT_ORDER); 177 } 178 179 /* 180 * This is called from binfmt_elf, we create the special vma for the 181 * vDSO and insert it into the mm struct tree 182 */ 183 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 184 { 185 struct mm_struct *mm = current->mm; 186 struct vm_area_struct *vma; 187 unsigned long vdso_pages; 188 unsigned long vdso_base; 189 int rc; 190 191 if (!vdso_enabled) 192 return 0; 193 194 if (is_compat_task()) 195 return 0; 196 197 vdso_pages = vdso64_pages; 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 /* 206 * pick a base address for the vDSO in process space. We try to put 207 * it at vdso_base which is the "natural" base for it, but we might 208 * fail and end up putting it elsewhere. 209 */ 210 if (mmap_write_lock_killable(mm)) 211 return -EINTR; 212 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0); 213 if (IS_ERR_VALUE(vdso_base)) { 214 rc = vdso_base; 215 goto out_up; 216 } 217 218 /* 219 * our vma flags don't have VM_WRITE so by default, the process 220 * isn't allowed to write those pages. 221 * gdb can break that with ptrace interface, and thus trigger COW 222 * on those pages but it's then your responsibility to never do that 223 * on the "data" page of the vDSO or you'll stop getting kernel 224 * updates and your nice userland gettimeofday will be totally dead. 225 * It's fine to use that for setting breakpoints in the vDSO code 226 * pages though. 227 */ 228 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, 229 VM_READ|VM_EXEC| 230 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 231 &vdso_mapping); 232 if (IS_ERR(vma)) { 233 rc = PTR_ERR(vma); 234 goto out_up; 235 } 236 237 current->mm->context.vdso_base = vdso_base; 238 rc = 0; 239 240 out_up: 241 mmap_write_unlock(mm); 242 return rc; 243 } 244 245 static int __init vdso_init(void) 246 { 247 int i; 248 249 vdso_init_data(vdso_data); 250 251 /* Calculate the size of the 64 bit vDSO */ 252 vdso64_pages = ((&vdso64_end - &vdso64_start 253 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 254 255 /* Make sure pages are in the correct state */ 256 vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *), 257 GFP_KERNEL); 258 BUG_ON(vdso64_pagelist == NULL); 259 for (i = 0; i < vdso64_pages - 1; i++) { 260 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE); 261 get_page(pg); 262 vdso64_pagelist[i] = pg; 263 } 264 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data); 265 vdso64_pagelist[vdso64_pages] = NULL; 266 if (vdso_alloc_per_cpu(&S390_lowcore)) 267 BUG(); 268 269 get_page(virt_to_page(vdso_data)); 270 271 return 0; 272 } 273 early_initcall(vdso_init); 274