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 extern char vdso64_start, vdso64_end; 33 static void *vdso64_kbase = &vdso64_start; 34 static unsigned int vdso64_pages; 35 static struct page **vdso64_pagelist; 36 37 /* 38 * Should the kernel map a VDSO page into processes and pass its 39 * address down to glibc upon exec()? 40 */ 41 unsigned int __read_mostly vdso_enabled = 1; 42 43 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, 44 struct vm_area_struct *vma, struct vm_fault *vmf) 45 { 46 struct page **vdso_pagelist; 47 unsigned long vdso_pages; 48 49 vdso_pagelist = vdso64_pagelist; 50 vdso_pages = vdso64_pages; 51 52 if (vmf->pgoff >= vdso_pages) 53 return VM_FAULT_SIGBUS; 54 55 vmf->page = vdso_pagelist[vmf->pgoff]; 56 get_page(vmf->page); 57 return 0; 58 } 59 60 static int vdso_mremap(const struct vm_special_mapping *sm, 61 struct vm_area_struct *vma) 62 { 63 unsigned long vdso_pages; 64 65 vdso_pages = vdso64_pages; 66 67 if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start) 68 return -EINVAL; 69 70 if (WARN_ON_ONCE(current->mm != vma->vm_mm)) 71 return -EFAULT; 72 73 current->mm->context.vdso_base = vma->vm_start; 74 return 0; 75 } 76 77 static const struct vm_special_mapping vdso_mapping = { 78 .name = "[vdso]", 79 .fault = vdso_fault, 80 .mremap = vdso_mremap, 81 }; 82 83 static int __init vdso_setup(char *str) 84 { 85 bool enabled; 86 87 if (!kstrtobool(str, &enabled)) 88 vdso_enabled = enabled; 89 return 1; 90 } 91 __setup("vdso=", vdso_setup); 92 93 /* 94 * The vdso data page 95 */ 96 static union { 97 struct vdso_data data; 98 u8 page[PAGE_SIZE]; 99 } vdso_data_store __page_aligned_data; 100 struct vdso_data *vdso_data = &vdso_data_store.data; 101 102 /* 103 * Setup vdso data page. 104 */ 105 static void __init vdso_init_data(struct vdso_data *vd) 106 { 107 vd->ectg_available = test_facility(31); 108 } 109 110 /* 111 * Allocate/free per cpu vdso data. 112 */ 113 #define SEGMENT_ORDER 2 114 115 /* 116 * The initial vdso_data structure for the boot CPU. Eventually 117 * it is replaced with a properly allocated structure in vdso_init. 118 * This is necessary because a valid S390_lowcore.vdso_per_cpu_data 119 * pointer is required to be able to return from an interrupt or 120 * program check. See the exit paths in entry.S. 121 */ 122 struct vdso_data boot_vdso_data __initdata; 123 124 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore) 125 { 126 lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data; 127 } 128 129 int vdso_alloc_per_cpu(struct lowcore *lowcore) 130 { 131 unsigned long segment_table, page_table, page_frame; 132 struct vdso_per_cpu_data *vd; 133 134 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER); 135 page_table = get_zeroed_page(GFP_KERNEL); 136 page_frame = get_zeroed_page(GFP_KERNEL); 137 if (!segment_table || !page_table || !page_frame) 138 goto out; 139 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER); 140 arch_set_page_dat(virt_to_page(page_table), 0); 141 142 /* Initialize per-cpu vdso data page */ 143 vd = (struct vdso_per_cpu_data *) page_frame; 144 vd->cpu_nr = lowcore->cpu_nr; 145 vd->node_id = cpu_to_node(vd->cpu_nr); 146 147 /* Set up page table for the vdso address space */ 148 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES); 149 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE); 150 151 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table; 152 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame; 153 154 lowcore->vdso_asce = segment_table + 155 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT; 156 lowcore->vdso_per_cpu_data = page_frame; 157 158 return 0; 159 160 out: 161 free_page(page_frame); 162 free_page(page_table); 163 free_pages(segment_table, SEGMENT_ORDER); 164 return -ENOMEM; 165 } 166 167 void vdso_free_per_cpu(struct lowcore *lowcore) 168 { 169 unsigned long segment_table, page_table, page_frame; 170 171 segment_table = lowcore->vdso_asce & PAGE_MASK; 172 page_table = *(unsigned long *) segment_table; 173 page_frame = *(unsigned long *) page_table; 174 175 free_page(page_frame); 176 free_page(page_table); 177 free_pages(segment_table, SEGMENT_ORDER); 178 } 179 180 /* 181 * This is called from binfmt_elf, we create the special vma for the 182 * vDSO and insert it into the mm struct tree 183 */ 184 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 185 { 186 struct mm_struct *mm = current->mm; 187 struct vm_area_struct *vma; 188 unsigned long vdso_pages; 189 unsigned long vdso_base; 190 int rc; 191 192 if (!vdso_enabled) 193 return 0; 194 195 if (is_compat_task()) 196 return 0; 197 198 vdso_pages = vdso64_pages; 199 /* 200 * vDSO has a problem and was disabled, just don't "enable" it for 201 * the process 202 */ 203 if (vdso_pages == 0) 204 return 0; 205 206 /* 207 * pick a base address for the vDSO in process space. We try to put 208 * it at vdso_base which is the "natural" base for it, but we might 209 * fail and end up putting it elsewhere. 210 */ 211 if (down_write_killable(&mm->mmap_sem)) 212 return -EINTR; 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 * our vma flags don't have VM_WRITE so by default, the process 221 * isn't allowed to write those pages. 222 * gdb can break that with ptrace interface, and thus trigger COW 223 * on those pages but it's then your responsibility to never do that 224 * on the "data" page of the vDSO or you'll stop getting kernel 225 * updates and your nice userland gettimeofday will be totally dead. 226 * It's fine to use that for setting breakpoints in the vDSO code 227 * pages though. 228 */ 229 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, 230 VM_READ|VM_EXEC| 231 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 232 &vdso_mapping); 233 if (IS_ERR(vma)) { 234 rc = PTR_ERR(vma); 235 goto out_up; 236 } 237 238 current->mm->context.vdso_base = vdso_base; 239 rc = 0; 240 241 out_up: 242 up_write(&mm->mmap_sem); 243 return rc; 244 } 245 246 static int __init vdso_init(void) 247 { 248 int i; 249 250 vdso_init_data(vdso_data); 251 252 /* Calculate the size of the 64 bit vDSO */ 253 vdso64_pages = ((&vdso64_end - &vdso64_start 254 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 255 256 /* Make sure pages are in the correct state */ 257 vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *), 258 GFP_KERNEL); 259 BUG_ON(vdso64_pagelist == NULL); 260 for (i = 0; i < vdso64_pages - 1; i++) { 261 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE); 262 get_page(pg); 263 vdso64_pagelist[i] = pg; 264 } 265 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data); 266 vdso64_pagelist[vdso64_pages] = NULL; 267 if (vdso_alloc_per_cpu(&S390_lowcore)) 268 BUG(); 269 270 get_page(virt_to_page(vdso_data)); 271 272 return 0; 273 } 274 early_initcall(vdso_init); 275