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