vdso32-setup.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * (C) Copyright 2002 Linus Torvalds
 4 * Portions based on the vdso-randomization code from exec-shield:
 5 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
 6 *
 7 * This file contains the needed initializations to support sysenter.
 8 */
 9
10#include <linux/init.h>
11#include <linux/smp.h>
12#include <linux/kernel.h>
13#include <linux/mm_types.h>
14#include <linux/elf.h>
15
16#include <asm/processor.h>
17#include <asm/vdso.h>
18
19#ifdef CONFIG_COMPAT_VDSO
20#define VDSO_DEFAULT	0
21#else
22#define VDSO_DEFAULT	1
23#endif
24
25/*
26 * Should the kernel map a VDSO page into processes and pass its
27 * address down to glibc upon exec()?
28 */
29unsigned int __read_mostly vdso32_enabled = VDSO_DEFAULT;
30
31static int __init vdso32_setup(char *s)
32{
33	vdso32_enabled = simple_strtoul(s, NULL, 0);
34
35	if (vdso32_enabled > 1) {
36		pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
37		vdso32_enabled = 0;
38	}
39
40	return 1;
41}
42
43/*
44 * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
45 * behavior on both 64-bit and 32-bit kernels.
46 * On 32-bit kernels, vdso=[012] means the same thing.
47 */
48__setup("vdso32=", vdso32_setup);
49
50#ifdef CONFIG_X86_32
51__setup_param("vdso=", vdso_setup, vdso32_setup, 0);
52#endif
53
54
55#ifdef CONFIG_SYSCTL
56#include <linux/sysctl.h>
57
58static const struct ctl_table vdso_table[] = {
59	{
60#ifdef CONFIG_X86_64
61		.procname	= "vsyscall32",
62#else
63		.procname	= "vdso_enabled",
64#endif
65		.data		= &vdso32_enabled,
66		.maxlen		= sizeof(int),
67		.mode		= 0644,
68		.proc_handler	= proc_dointvec_minmax,
69		.extra1		= SYSCTL_ZERO,
70		.extra2		= SYSCTL_ONE,
71	},
72};
73
74static __init int ia32_binfmt_init(void)
75{
76#ifdef CONFIG_X86_64
77	/* Register vsyscall32 into the ABI table */
78	register_sysctl("abi", vdso_table);
79#else
80	register_sysctl_init("vm", vdso_table);
81#endif
82	return 0;
83}
84__initcall(ia32_binfmt_init);
85#endif /* CONFIG_SYSCTL */
86