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
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}