xref: /openbmc/linux/arch/x86/entry/vdso/vdso32-setup.c (revision 3f6cc47f)
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  */
29 unsigned int __read_mostly vdso32_enabled = VDSO_DEFAULT;
30 
vdso32_setup(char * s)31 static 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 #ifdef CONFIG_X86_64
55 
56 #ifdef CONFIG_SYSCTL
57 /* Register vsyscall32 into the ABI table */
58 #include <linux/sysctl.h>
59 
60 static struct ctl_table abi_table2[] = {
61 	{
62 		.procname	= "vsyscall32",
63 		.data		= &vdso32_enabled,
64 		.maxlen		= sizeof(int),
65 		.mode		= 0644,
66 		.proc_handler	= proc_dointvec_minmax,
67 		.extra1		= SYSCTL_ZERO,
68 		.extra2		= SYSCTL_ONE,
69 	},
70 	{}
71 };
72 
ia32_binfmt_init(void)73 static __init int ia32_binfmt_init(void)
74 {
75 	register_sysctl("abi", abi_table2);
76 	return 0;
77 }
78 __initcall(ia32_binfmt_init);
79 #endif /* CONFIG_SYSCTL */
80 
81 #endif	/* CONFIG_X86_64 */
82