scs.h
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Shadow Call Stack support.
*
* Copyright (C) 2019 Google LLC
*/
#ifndef _LINUX_SCS_H
#define _LINUX_SCS_H
#include <linux/gfp.h>
#include <linux/sched.h>
#include <asm/page.h>
#ifdef CONFIG_SHADOW_CALL_STACK
#ifdef CONFIG_SHADOW_CALL_STACK_VMAP
#define SCS_SIZE PAGE_SIZE
#else
/*
* In testing, 1 KiB shadow stack size (i.e. 128 stack frames on a 64-bit
* architecture) provided ~40% safety margin on stack usage while keeping
* memory allocation overhead reasonable.
*/
#define SCS_SIZE 1024UL
#endif
#define GFP_SCS (GFP_KERNEL | __GFP_ZERO)
/*
* A random number outside the kernel's virtual address space to mark the
* end of the shadow stack.
*/
#define SCS_END_MAGIC 0xaf0194819b1635f6UL
#define task_scs(tsk) (task_thread_info(tsk)->shadow_call_stack)
static inline void task_set_scs(struct task_struct *tsk, void *s)
{
task_scs(tsk) = s;
}
extern void scs_init(void);
extern void scs_task_reset(struct task_struct *tsk);
extern int scs_prepare(struct task_struct *tsk, int node);
extern bool scs_corrupted(struct task_struct *tsk);
extern void scs_release(struct task_struct *tsk);
#else /* CONFIG_SHADOW_CALL_STACK */
#define task_scs(tsk) NULL
static inline void task_set_scs(struct task_struct *tsk, void *s) {}
static inline void scs_init(void) {}
static inline void scs_task_reset(struct task_struct *tsk) {}
static inline int scs_prepare(struct task_struct *tsk, int node) { return 0; }
static inline bool scs_corrupted(struct task_struct *tsk) { return false; }
static inline void scs_release(struct task_struct *tsk) {}
#endif /* CONFIG_SHADOW_CALL_STACK */
#endif /* _LINUX_SCS_H */