diff options
Diffstat (limited to 'include/linux/scs.h')
| -rw-r--r-- | include/linux/scs.h | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/include/linux/scs.h b/include/linux/scs.h new file mode 100644 index 000000000000..18122d9e17ff --- /dev/null +++ b/include/linux/scs.h @@ -0,0 +1,68 @@ +/* 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/poison.h> +#include <linux/sched.h> +#include <linux/sizes.h> + +#ifdef CONFIG_SHADOW_CALL_STACK + +#define SCS_ORDER 0 +#define SCS_SIZE (PAGE_SIZE << SCS_ORDER) +#define GFP_SCS (GFP_KERNEL | __GFP_ZERO) + +/* An illegal pointer value to mark the end of the shadow stack. */ +#define SCS_END_MAGIC (0x5f6UL + POISON_POINTER_DELTA) + +#define task_scs(tsk) (task_thread_info(tsk)->scs_base) +#define task_scs_sp(tsk) (task_thread_info(tsk)->scs_sp) + +void *scs_alloc(int node); +void scs_free(void *s); +void scs_init(void); +int scs_prepare(struct task_struct *tsk, int node); +void scs_release(struct task_struct *tsk); + +static inline void scs_task_reset(struct task_struct *tsk) +{ + /* + * Reset the shadow stack to the base address in case the task + * is reused. + */ + task_scs_sp(tsk) = task_scs(tsk); +} + +static inline unsigned long *__scs_magic(void *s) +{ + return (unsigned long *)(s + SCS_SIZE) - 1; +} + +static inline bool task_scs_end_corrupted(struct task_struct *tsk) +{ + unsigned long *magic = __scs_magic(task_scs(tsk)); + unsigned long sz = task_scs_sp(tsk) - task_scs(tsk); + + return sz >= SCS_SIZE - 1 || READ_ONCE_NOCHECK(*magic) != SCS_END_MAGIC; +} + +#else /* CONFIG_SHADOW_CALL_STACK */ + +static inline void *scs_alloc(int node) { return NULL; } +static inline void scs_free(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 void scs_release(struct task_struct *tsk) {} +static inline bool task_scs_end_corrupted(struct task_struct *tsk) { return false; } + +#endif /* CONFIG_SHADOW_CALL_STACK */ + +#endif /* _LINUX_SCS_H */ |