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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
16static struct page *vdso_page;
17
18/* Create a vDSO page holding the signal trampoline.
19 * We want this for a non-executable stack.
20 */
21static 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}
45arch_initcall(vdso_init);
46
47/*
48 * Called from binfmt_elf. Create a VMA for the vDSO page.
49 */
50int 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;
85up_fail:
86 mmap_write_unlock(mm);
87 return ret;
88}
89
90const 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}