1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2022 Helge Deller <deller@gmx.de> 4 * 5 * based on arch/s390/kernel/vdso.c which is 6 * Copyright IBM Corp. 2008 7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) 8 */ 9 10 #include <linux/kernel.h> 11 #include <linux/mm.h> 12 #include <linux/slab.h> 13 #include <linux/elf.h> 14 #include <linux/timekeeper_internal.h> 15 #include <linux/compat.h> 16 #include <linux/nsproxy.h> 17 #include <linux/time_namespace.h> 18 #include <linux/random.h> 19 20 #include <asm/pgtable.h> 21 #include <asm/page.h> 22 #include <asm/sections.h> 23 #include <asm/vdso.h> 24 #include <asm/cacheflush.h> 25 26 extern char vdso32_start, vdso32_end; 27 extern char vdso64_start, vdso64_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 #ifdef CONFIG_64BIT 37 static struct vm_special_mapping vdso64_mapping = { 38 .name = "[vdso]", 39 .mremap = vdso_mremap, 40 }; 41 #endif 42 43 static struct vm_special_mapping vdso32_mapping = { 44 .name = "[vdso]", 45 .mremap = vdso_mremap, 46 }; 47 48 /* 49 * This is called from binfmt_elf, we create the special vma for the 50 * vDSO and insert it into the mm struct tree 51 */ 52 int arch_setup_additional_pages(struct linux_binprm *bprm, 53 int executable_stack) 54 { 55 56 unsigned long vdso_text_start, vdso_text_len, map_base; 57 struct vm_special_mapping *vdso_mapping; 58 struct mm_struct *mm = current->mm; 59 struct vm_area_struct *vma; 60 int rc; 61 62 if (mmap_write_lock_killable(mm)) 63 return -EINTR; 64 65 #ifdef CONFIG_64BIT 66 if (!is_compat_task()) { 67 vdso_text_len = &vdso64_end - &vdso64_start; 68 vdso_mapping = &vdso64_mapping; 69 } else 70 #endif 71 { 72 vdso_text_len = &vdso32_end - &vdso32_start; 73 vdso_mapping = &vdso32_mapping; 74 } 75 76 map_base = mm->mmap_base; 77 if (current->flags & PF_RANDOMIZE) 78 map_base -= prandom_u32_max(0x20) * PAGE_SIZE; 79 80 vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0); 81 82 /* VM_MAYWRITE for COW so gdb can set breakpoints */ 83 vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len, 84 VM_READ|VM_EXEC| 85 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 86 vdso_mapping); 87 if (IS_ERR(vma)) { 88 do_munmap(mm, vdso_text_start, PAGE_SIZE, NULL); 89 rc = PTR_ERR(vma); 90 } else { 91 current->mm->context.vdso_base = vdso_text_start; 92 rc = 0; 93 } 94 95 mmap_write_unlock(mm); 96 return rc; 97 } 98 99 static struct page ** __init vdso_setup_pages(void *start, void *end) 100 { 101 int pages = (end - start) >> PAGE_SHIFT; 102 struct page **pagelist; 103 int i; 104 105 pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL); 106 if (!pagelist) 107 panic("%s: Cannot allocate page list for VDSO", __func__); 108 for (i = 0; i < pages; i++) 109 pagelist[i] = virt_to_page(start + i * PAGE_SIZE); 110 return pagelist; 111 } 112 113 static int __init vdso_init(void) 114 { 115 #ifdef CONFIG_64BIT 116 vdso64_mapping.pages = vdso_setup_pages(&vdso64_start, &vdso64_end); 117 #endif 118 if (IS_ENABLED(CONFIG_COMPAT) || !IS_ENABLED(CONFIG_64BIT)) 119 vdso32_mapping.pages = vdso_setup_pages(&vdso32_start, &vdso32_end); 120 return 0; 121 } 122 arch_initcall(vdso_init); 123