LXR linux/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/vdso.h>
  14
  15static struct page *vdso_page;
  16
  17/* Create a vDSO page holding the signal trampoline.
  18 * We want this for a non-executable stack.
  19 */
  20static int __init vdso_init(void)
  21{
  22        struct hexagon_vdso *vdso;
  23
  24        vdso_page = alloc_page(GFP_KERNEL);
  25        if (!vdso_page)
  26                panic("Cannot allocate vdso");
  27
  28        vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  29        if (!vdso)
  30                panic("Cannot map vdso");
  31        clear_page(vdso);
  32
  33        /* Install the signal trampoline; currently looks like this:
  34         *      r6 = #__NR_rt_sigreturn;
  35         *      trap0(#1);
  36         */
  37        vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
  38        vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
  39
  40        vunmap(vdso);
  41
  42        return 0;
  43}
  44arch_initcall(vdso_init);
  45
  46/*
  47 * Called from binfmt_elf.  Create a VMA for the vDSO page.
  48 */
  49int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  50{
  51        int ret;
  52        unsigned long vdso_base;
  53        struct mm_struct *mm = current->mm;
  54
  55        if (mmap_write_lock_killable(mm))
  56                return -EINTR;
  57
  58        /* Try to get it loaded right near ld.so/glibc. */
  59        vdso_base = STACK_TOP;
  60
  61        vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
  62        if (IS_ERR_VALUE(vdso_base)) {
  63                ret = vdso_base;
  64                goto up_fail;
  65        }
  66
  67        /* MAYWRITE to allow gdb to COW and set breakpoints. */
  68        ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
  69                                      VM_READ|VM_EXEC|
  70                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  71                                      &vdso_page);
  72
  73        if (ret)
  74                goto up_fail;
  75
  76        mm->context.vdso = (void *)vdso_base;
  77
  78up_fail:
  79        mmap_write_unlock(mm);
  80        return ret;
  81}
  82
  83const char *arch_vma_name(struct vm_area_struct *vma)
  84{
  85        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  86                return "[vdso]";
  87        return NULL;
  88}
  89