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