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 <linux/binfmts.h> 24 #include <vdso/datapage.h> 25 #include <asm/asm-offsets.h> 26 #include <asm/processor.h> 27 #include <asm/mmu.h> 28 #include <asm/mmu_context.h> 29 #include <asm/sections.h> 30 #include <asm/vdso.h> 31 #include <asm/facility.h> 32 33 extern char vdso64_start, vdso64_end; 34 static void *vdso64_kbase = &vdso64_start; 35 static unsigned int vdso64_pages; 36 static struct page **vdso64_pagelist; 37 38 /* 39 * Should the kernel map a VDSO page into processes and pass its 40 * address down to glibc upon exec()? 41 */ 42 unsigned int __read_mostly vdso_enabled = 1; 43 44 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, 45 struct vm_area_struct *vma, struct vm_fault *vmf) 46 { 47 struct page **vdso_pagelist; 48 unsigned long vdso_pages; 49 50 vdso_pagelist = vdso64_pagelist; 51 vdso_pages = vdso64_pages; 52 53 if (vmf->pgoff >= vdso_pages) 54 return VM_FAULT_SIGBUS; 55 56 vmf->page = vdso_pagelist[vmf->pgoff]; 57 get_page(vmf->page); 58 return 0; 59 } 60 61 static int vdso_mremap(const struct vm_special_mapping *sm, 62 struct vm_area_struct *vma) 63 { 64 unsigned long vdso_pages; 65 66 vdso_pages = vdso64_pages; 67 68 if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start) 69 return -EINVAL; 70 71 if (WARN_ON_ONCE(current->mm != vma->vm_mm)) 72 return -EFAULT; 73 74 current->mm->context.vdso_base = vma->vm_start; 75 return 0; 76 } 77 78 static const struct vm_special_mapping vdso_mapping = { 79 .name = "[vdso]", 80 .fault = vdso_fault, 81 .mremap = vdso_mremap, 82 }; 83 84 static int __init vdso_setup(char *str) 85 { 86 bool enabled; 87 88 if (!kstrtobool(str, &enabled)) 89 vdso_enabled = enabled; 90 return 1; 91 } 92 __setup("vdso=", vdso_setup); 93 94 /* 95 * The vdso data page 96 */ 97 static union { 98 struct vdso_data data; 99 u8 page[PAGE_SIZE]; 100 } vdso_data_store __page_aligned_data; 101 struct vdso_data *vdso_data = (struct vdso_data *)&vdso_data_store.data; 102 /* 103 * Allocate/free per cpu vdso data. 104 */ 105 #define SEGMENT_ORDER 2 106 107 int vdso_alloc_per_cpu(struct lowcore *lowcore) 108 { 109 unsigned long segment_table, page_table, page_frame; 110 struct vdso_per_cpu_data *vd; 111 112 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER); 113 page_table = get_zeroed_page(GFP_KERNEL); 114 page_frame = get_zeroed_page(GFP_KERNEL); 115 if (!segment_table || !page_table || !page_frame) 116 goto out; 117 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER); 118 arch_set_page_dat(virt_to_page(page_table), 0); 119 120 /* Initialize per-cpu vdso data page */ 121 vd = (struct vdso_per_cpu_data *) page_frame; 122 vd->cpu_nr = lowcore->cpu_nr; 123 vd->node_id = cpu_to_node(vd->cpu_nr); 124 125 /* Set up page table for the vdso address space */ 126 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES); 127 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE); 128 129 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table; 130 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame; 131 132 lowcore->vdso_asce = segment_table + 133 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT; 134 lowcore->vdso_per_cpu_data = page_frame; 135 136 return 0; 137 138 out: 139 free_page(page_frame); 140 free_page(page_table); 141 free_pages(segment_table, SEGMENT_ORDER); 142 return -ENOMEM; 143 } 144 145 void vdso_free_per_cpu(struct lowcore *lowcore) 146 { 147 unsigned long segment_table, page_table, page_frame; 148 149 segment_table = lowcore->vdso_asce & PAGE_MASK; 150 page_table = *(unsigned long *) segment_table; 151 page_frame = *(unsigned long *) page_table; 152 153 free_page(page_frame); 154 free_page(page_table); 155 free_pages(segment_table, SEGMENT_ORDER); 156 } 157 158 /* 159 * This is called from binfmt_elf, we create the special vma for the 160 * vDSO and insert it into the mm struct tree 161 */ 162 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 163 { 164 struct mm_struct *mm = current->mm; 165 struct vm_area_struct *vma; 166 unsigned long vdso_pages; 167 unsigned long vdso_base; 168 int rc; 169 170 if (!vdso_enabled) 171 return 0; 172 173 if (is_compat_task()) 174 return 0; 175 176 vdso_pages = vdso64_pages; 177 /* 178 * vDSO has a problem and was disabled, just don't "enable" it for 179 * the process 180 */ 181 if (vdso_pages == 0) 182 return 0; 183 184 /* 185 * pick a base address for the vDSO in process space. We try to put 186 * it at vdso_base which is the "natural" base for it, but we might 187 * fail and end up putting it elsewhere. 188 */ 189 if (mmap_write_lock_killable(mm)) 190 return -EINTR; 191 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0); 192 if (IS_ERR_VALUE(vdso_base)) { 193 rc = vdso_base; 194 goto out_up; 195 } 196 197 /* 198 * our vma flags don't have VM_WRITE so by default, the process 199 * isn't allowed to write those pages. 200 * gdb can break that with ptrace interface, and thus trigger COW 201 * on those pages but it's then your responsibility to never do that 202 * on the "data" page of the vDSO or you'll stop getting kernel 203 * updates and your nice userland gettimeofday will be totally dead. 204 * It's fine to use that for setting breakpoints in the vDSO code 205 * pages though. 206 */ 207 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, 208 VM_READ|VM_EXEC| 209 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 210 &vdso_mapping); 211 if (IS_ERR(vma)) { 212 rc = PTR_ERR(vma); 213 goto out_up; 214 } 215 216 current->mm->context.vdso_base = vdso_base; 217 rc = 0; 218 219 out_up: 220 mmap_write_unlock(mm); 221 return rc; 222 } 223 224 static int __init vdso_init(void) 225 { 226 int i; 227 228 /* Calculate the size of the 64 bit vDSO */ 229 vdso64_pages = ((&vdso64_end - &vdso64_start 230 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1; 231 232 /* Make sure pages are in the correct state */ 233 vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *), 234 GFP_KERNEL); 235 BUG_ON(vdso64_pagelist == NULL); 236 for (i = 0; i < vdso64_pages - 1; i++) { 237 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE); 238 get_page(pg); 239 vdso64_pagelist[i] = pg; 240 } 241 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data); 242 vdso64_pagelist[vdso64_pages] = NULL; 243 if (vdso_alloc_per_cpu(&S390_lowcore)) 244 BUG(); 245 246 get_page(virt_to_page(vdso_data)); 247 248 return 0; 249 } 250 early_initcall(vdso_init); 251