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/binfmts.h> 10 #include <linux/compat.h> 11 #include <linux/elf.h> 12 #include <linux/errno.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/mm.h> 17 #include <linux/slab.h> 18 #include <linux/smp.h> 19 #include <linux/random.h> 20 #include <linux/vdso_datastore.h> 21 #include <vdso/datapage.h> 22 #include <asm/vdso/vsyscall.h> 23 #include <asm/alternative.h> 24 #include <asm/vdso.h> 25 26 extern char vdso64_start[], vdso64_end[]; 27 extern char vdso32_start[], vdso32_end[]; 28 29 static int vdso_mremap(const struct vm_special_mapping *sm, 30 struct vm_area_struct *vma) 31 { 32 current->mm->context.vdso_base = vma->vm_start; 33 return 0; 34 } 35 36 static struct vm_special_mapping vdso64_mapping = { 37 .name = "[vdso]", 38 .mremap = vdso_mremap, 39 }; 40 41 static struct vm_special_mapping vdso32_mapping = { 42 .name = "[vdso]", 43 .mremap = vdso_mremap, 44 }; 45 46 int vdso_getcpu_init(void) 47 { 48 set_tod_programmable_field(smp_processor_id()); 49 return 0; 50 } 51 early_initcall(vdso_getcpu_init); /* Must be called before SMP init */ 52 53 static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len) 54 { 55 unsigned long vvar_start, vdso_text_start, vdso_text_len; 56 struct vm_special_mapping *vdso_mapping; 57 struct mm_struct *mm = current->mm; 58 struct vm_area_struct *vma; 59 int rc; 60 61 BUILD_BUG_ON(VDSO_NR_PAGES != __VDSO_PAGES); 62 if (mmap_write_lock_killable(mm)) 63 return -EINTR; 64 65 if (is_compat_task()) { 66 vdso_text_len = vdso32_end - vdso32_start; 67 vdso_mapping = &vdso32_mapping; 68 } else { 69 vdso_text_len = vdso64_end - vdso64_start; 70 vdso_mapping = &vdso64_mapping; 71 } 72 vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0); 73 rc = vvar_start; 74 if (IS_ERR_VALUE(vvar_start)) 75 goto out; 76 vma = vdso_install_vvar_mapping(mm, vvar_start); 77 rc = PTR_ERR(vma); 78 if (IS_ERR(vma)) 79 goto out; 80 vdso_text_start = vvar_start + VDSO_NR_PAGES * PAGE_SIZE; 81 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 82 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 83 VM_READ|VM_EXEC|VM_SEALED_SYSMAP| 84 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 85 vdso_mapping); 86 if (IS_ERR(vma)) { 87 do_munmap(mm, vvar_start, PAGE_SIZE, NULL); 88 rc = PTR_ERR(vma); 89 } else { 90 current->mm->context.vdso_base = vdso_text_start; 91 rc = 0; 92 } 93 out: 94 mmap_write_unlock(mm); 95 return rc; 96 } 97 98 static unsigned long vdso_addr(unsigned long start, unsigned long len) 99 { 100 unsigned long addr, end, offset; 101 102 /* 103 * Round up the start address. It can start out unaligned as a result 104 * of stack start randomization. 105 */ 106 start = PAGE_ALIGN(start); 107 108 /* Round the lowest possible end address up to a PMD boundary. */ 109 end = (start + len + PMD_SIZE - 1) & PMD_MASK; 110 if (end >= VDSO_BASE) 111 end = VDSO_BASE; 112 end -= len; 113 114 if (end > start) { 115 offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1); 116 addr = start + (offset << PAGE_SHIFT); 117 } else { 118 addr = start; 119 } 120 return addr; 121 } 122 123 unsigned long vdso_text_size(void) 124 { 125 unsigned long size; 126 127 if (is_compat_task()) 128 size = vdso32_end - vdso32_start; 129 else 130 size = vdso64_end - vdso64_start; 131 return PAGE_ALIGN(size); 132 } 133 134 unsigned long vdso_size(void) 135 { 136 return vdso_text_size() + VDSO_NR_PAGES * PAGE_SIZE; 137 } 138 139 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 140 { 141 unsigned long addr = VDSO_BASE; 142 unsigned long size = vdso_size(); 143 144 if (current->flags & PF_RANDOMIZE) 145 addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size); 146 return map_vdso(addr, size); 147 } 148 149 static struct page ** __init vdso_setup_pages(void *start, void *end) 150 { 151 int pages = (end - start) >> PAGE_SHIFT; 152 struct page **pagelist; 153 int i; 154 155 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 156 if (!pagelist) 157 panic("%s: Cannot allocate page list for VDSO", __func__); 158 for (i = 0; i < pages; i++) 159 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 160 return pagelist; 161 } 162 163 static void vdso_apply_alternatives(void) 164 { 165 const struct elf64_shdr *alt, *shdr; 166 struct alt_instr *start, *end; 167 const struct elf64_hdr *hdr; 168 169 hdr = (struct elf64_hdr *)vdso64_start; 170 shdr = (void *)hdr + hdr->e_shoff; 171 alt = find_section(hdr, shdr, ".altinstructions"); 172 if (!alt) 173 return; 174 start = (void *)hdr + alt->sh_offset; 175 end = (void *)hdr + alt->sh_offset + alt->sh_size; 176 apply_alternatives(start, end); 177 } 178 179 static int __init vdso_init(void) 180 { 181 vdso_apply_alternatives(); 182 vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end); 183 if (IS_ENABLED(CONFIG_COMPAT)) 184 vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end); 185 return 0; 186 } 187 arch_initcall(vdso_init); 188