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
  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 (down_write_killable(&mm->mmap_sem))
  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         up_write(&mm->mmap_sem);
  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 }