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