1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * arch/sh/kernel/vsyscall/vsyscall.c 4 * 5 * Copyright (C) 2006 Paul Mundt 6 * 7 * vDSO randomization 8 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar 9 */ 10 #include <linux/mm.h> 11 #include <linux/kernel.h> 12 #include <linux/init.h> 13 #include <linux/gfp.h> 14 #include <linux/module.h> 15 #include <linux/elf.h> 16 #include <linux/sched.h> 17 #include <linux/err.h> 18 19 /* 20 * Should the kernel map a VDSO page into processes and pass its 21 * address down to glibc upon exec()? 22 */ 23 unsigned int __read_mostly vdso_enabled = 1; 24 EXPORT_SYMBOL_GPL(vdso_enabled); 25 26 static int __init vdso_setup(char *s) 27 { 28 vdso_enabled = simple_strtoul(s, NULL, 0); 29 return 1; 30 } 31 __setup("vdso=", vdso_setup); 32 33 /* 34 * These symbols are defined by vsyscall.o to mark the bounds 35 * of the ELF DSO images included therein. 36 */ 37 extern const char vsyscall_trapa_start, vsyscall_trapa_end; 38 static struct page *syscall_pages[1]; 39 40 int __init vsyscall_init(void) 41 { 42 void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC); 43 syscall_pages[0] = virt_to_page(syscall_page); 44 45 /* 46 * XXX: Map this page to a fixmap entry if we get around 47 * to adding the page to ELF core dumps 48 */ 49 50 memcpy(syscall_page, 51 &vsyscall_trapa_start, 52 &vsyscall_trapa_end - &vsyscall_trapa_start); 53 54 return 0; 55 } 56 57 /* Setup a VMA at program startup for the vsyscall page */ 58 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 59 { 60 struct mm_struct *mm = current->mm; 61 unsigned long addr; 62 int ret; 63 64 if (mmap_write_lock_killable(mm)) 65 return -EINTR; 66 67 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); 68 if (IS_ERR_VALUE(addr)) { 69 ret = addr; 70 goto up_fail; 71 } 72 73 ret = install_special_mapping(mm, addr, PAGE_SIZE, 74 VM_READ | VM_EXEC | 75 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, 76 syscall_pages); 77 if (unlikely(ret)) 78 goto up_fail; 79 80 current->mm->context.vdso = (void *)addr; 81 82 up_fail: 83 mmap_write_unlock(mm); 84 return ret; 85 } 86 87 const char *arch_vma_name(struct vm_area_struct *vma) 88 { 89 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) 90 return "[vdso]"; 91 92 return NULL; 93 } 94