arch/sh/kernel/vsyscall/vsyscall.c

   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 static struct vm_special_mapping vdso_mapping = {
  40         .name = "[vdso]",
  41         .pages = syscall_pages,
  42 };
  43
  44 int __init vsyscall_init(void)
  45 {
  46         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
  47         syscall_pages[0] = virt_to_page(syscall_page);
  48
  49         /*
  50          * XXX: Map this page to a fixmap entry if we get around
  51          * to adding the page to ELF core dumps
  52          */
  53
  54         memcpy(syscall_page,
  55                &vsyscall_trapa_start,
  56                &vsyscall_trapa_end - &vsyscall_trapa_start);
  57
  58         return 0;
  59 }
  60
  61 /* Setup a VMA at program startup for the vsyscall page */
  62 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  63 {
  64         struct mm_struct *mm = current->mm;
  65         struct vm_area_struct *vma;
  66         unsigned long addr;
  67         int ret;
  68
  69         if (mmap_write_lock_killable(mm))
  70                 return -EINTR;
  71
  72         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
  73         if (IS_ERR_VALUE(addr)) {
  74                 ret = addr;
  75                 goto up_fail;
  76         }
  77
  78         vdso_mapping.pages = syscall_pages;
  79         vma = _install_special_mapping(mm, addr, PAGE_SIZE,
  80                                       VM_READ | VM_EXEC |
  81                                       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
  82                                       &vdso_mapping);
  83         ret = PTR_ERR(vma);
  84         if (IS_ERR(vma))
  85                 goto up_fail;
  86
  87         current->mm->context.vdso = (void *)addr;
  88         ret = 0;
  89
  90 up_fail:
  91         mmap_write_unlock(mm);
  92         return ret;
  93 }
  94
  95 const char *arch_vma_name(struct vm_area_struct *vma)
  96 {
  97         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  98                 return "[vdso]";
  99
 100         return NULL;
 101 }