arch/x86/entry/vdso/vdso32-setup.c

// SPDX-License-Identifier: GPL-2.0
/*
 * (C) Copyright 2002 Linus Torvalds
 * Portions based on the vdso-randomization code from exec-shield:
 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
 *
 * This file contains the needed initializations to support sysenter.
 */

#include <linux/init.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/mm_types.h>
#include <linux/elf.h>

#include <asm/processor.h>
#include <asm/vdso.h>

#ifdef CONFIG_COMPAT_VDSO
#define VDSO_DEFAULT	0
#else
#define VDSO_DEFAULT	1
#endif

/*
 * Should the kernel map a VDSO page into processes and pass its
 * address down to glibc upon exec()?
 */
unsigned int __read_mostly vdso32_enabled = VDSO_DEFAULT;

static int __init vdso32_setup(char *s)
{
	vdso32_enabled = simple_strtoul(s, NULL, 0);

	if (vdso32_enabled > 1) {
		pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
		vdso32_enabled = 0;
	}

	return 1;
}

/*
 * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
 * behavior on both 64-bit and 32-bit kernels.
 * On 32-bit kernels, vdso=[012] means the same thing.
 */
__setup("vdso32=", vdso32_setup);

#ifdef CONFIG_X86_32
__setup_param("vdso=", vdso_setup, vdso32_setup, 0);
#endif

#ifdef CONFIG_X86_64

#ifdef CONFIG_SYSCTL
/* Register vsyscall32 into the ABI table */
#include <linux/sysctl.h>

static struct ctl_table abi_table2[] = {
	{
		.procname	= "vsyscall32",
		.data		= &vdso32_enabled,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_minmax,
		.extra1		= SYSCTL_ZERO,
		.extra2		= SYSCTL_ONE,
	},
	{}
};

static __init int ia32_binfmt_init(void)
{
	register_sysctl("abi", abi_table2);
	return 0;
}
__initcall(ia32_binfmt_init);
#endif /* CONFIG_SYSCTL */

#endif	/* CONFIG_X86_64 */