arch/hexagon/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * vDSO implementation for Hexagon
   4  *
   5  * Copyright (c) 2011, The Linux Foundation. All rights reserved.
   6  */
   7
   8 #include <linux/err.h>
   9 #include <linux/mm.h>
  10 #include <linux/vmalloc.h>
  11 #include <linux/binfmts.h>
  12
  13 #include <asm/elf.h>
  14 #include <asm/vdso.h>
  15
  16 static struct page *vdso_page;
  17
  18 /* Create a vDSO page holding the signal trampoline.
  19  * We want this for a non-executable stack.
  20  */
  21 static int __init vdso_init(void)
  22 {
  23         struct hexagon_vdso *vdso;
  24
  25         vdso_page = alloc_page(GFP_KERNEL);
  26         if (!vdso_page)
  27                 panic("Cannot allocate vdso");
  28
  29         vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  30         if (!vdso)
  31                 panic("Cannot map vdso");
  32         clear_page(vdso);
  33
  34         /* Install the signal trampoline; currently looks like this:
  35          *      r6 = #__NR_rt_sigreturn;
  36          *      trap0(#1);
  37          */
  38         vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
  39         vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
  40
  41         vunmap(vdso);
  42
  43         return 0;
  44 }
  45 arch_initcall(vdso_init);
  46
  47 /*
  48  * Called from binfmt_elf.  Create a VMA for the vDSO page.
  49  */
  50 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  51 {
  52         int ret;
  53         unsigned long vdso_base;
  54         struct vm_area_struct *vma;
  55         struct mm_struct *mm = current->mm;
  56         static struct vm_special_mapping vdso_mapping = {
  57                 .name = "[vdso]",
  58         };
  59
  60         if (mmap_write_lock_killable(mm))
  61                 return -EINTR;
  62
  63         /* Try to get it loaded right near ld.so/glibc. */
  64         vdso_base = STACK_TOP;
  65
  66         vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
  67         if (IS_ERR_VALUE(vdso_base)) {
  68                 ret = vdso_base;
  69                 goto up_fail;
  70         }
  71
  72         /* MAYWRITE to allow gdb to COW and set breakpoints. */
  73         vdso_mapping.pages = &vdso_page;
  74         vma = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
  75                                       VM_READ|VM_EXEC|
  76                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  77                                       &vdso_mapping);
  78
  79         ret = PTR_ERR(vma);
  80         if (IS_ERR(vma))
  81                 goto up_fail;
  82
  83         mm->context.vdso = (void *)vdso_base;
  84         ret = 0;
  85 up_fail:
  86         mmap_write_unlock(mm);
  87         return ret;
  88 }
  89
  90 const char *arch_vma_name(struct vm_area_struct *vma)
  91 {
  92         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  93                 return "[vdso]";
  94         return NULL;
  95 }