include/linux/stackprotector.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_STACKPROTECTOR_H
#define _LINUX_STACKPROTECTOR_H 1

#include <linux/compiler.h>
#include <linux/sched.h>
#include <linux/random.h>

/*
 * On 64-bit architectures, protect against non-terminated C string overflows
 * by zeroing out the first byte of the canary; this leaves 56 bits of entropy.
 */
#ifdef CONFIG_64BIT
# ifdef __LITTLE_ENDIAN
#  define CANARY_MASK 0xffffffffffffff00UL
# else /* big endian, 64 bits: */
#  define CANARY_MASK 0x00ffffffffffffffUL
# endif
#else /* 32 bits: */
# define CANARY_MASK 0xffffffffUL
#endif

static inline unsigned long get_random_canary(void)
{
	return get_random_long() & CANARY_MASK;
}

#if defined(CONFIG_STACKPROTECTOR) || defined(CONFIG_ARM64_PTR_AUTH)
# include <asm/stackprotector.h>
#else
static inline void boot_init_stack_canary(void)
{
}
#endif

#endif