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#ifndef _ASM_X86_KAISER_H
#define _ASM_X86_KAISER_H
#include <uapi/asm/processor-flags.h> /* For PCID constants */
/*
* This file includes the definitions for the KAISER feature.
* KAISER is a counter measure against x86_64 side channel attacks on
* the kernel virtual memory. It has a shadow pgd for every process: the
* shadow pgd has a minimalistic kernel-set mapped, but includes the whole
* user memory. Within a kernel context switch, or when an interrupt is handled,
* the pgd is switched to the normal one. When the system switches to user mode,
* the shadow pgd is enabled. By this, the virtual memory caches are freed,
* and the user may not attack the whole kernel memory.
*
* A minimalistic kernel mapping holds the parts needed to be mapped in user
* mode, such as the entry/exit functions of the user space, or the stacks.
*/
#define KAISER_SHADOW_PGD_OFFSET 0x1000
#ifdef __ASSEMBLY__
#ifdef CONFIG_PAGE_TABLE_ISOLATION
.macro _SWITCH_TO_KERNEL_CR3 reg
movq %cr3, \reg
andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg
/* If PCID enabled, set X86_CR3_PCID_NOFLUSH_BIT */
ALTERNATIVE "", "bts $63, \reg", X86_FEATURE_PCID
movq \reg, %cr3
.endm
.macro _SWITCH_TO_USER_CR3 reg regb
/*
* regb must be the low byte portion of reg: because we have arranged
* for the low byte of the user PCID to serve as the high byte of NOFLUSH
* (0x80 for each when PCID is enabled, or 0x00 when PCID and NOFLUSH are
* not enabled): so that the one register can update both memory and cr3.
*/
movq %cr3, \reg
orq PER_CPU_VAR(x86_cr3_pcid_user), \reg
js 9f
/* If PCID enabled, FLUSH this time, reset to NOFLUSH for next time */
movb \regb, PER_CPU_VAR(x86_cr3_pcid_user+7)
9:
movq \reg, %cr3
.endm
.macro SWITCH_KERNEL_CR3
ALTERNATIVE "jmp 8f", "pushq %rax", X86_FEATURE_KAISER
_SWITCH_TO_KERNEL_CR3 %rax
popq %rax
8:
.endm
.macro SWITCH_USER_CR3
ALTERNATIVE "jmp 8f", "pushq %rax", X86_FEATURE_KAISER
_SWITCH_TO_USER_CR3 %rax %al
popq %rax
8:
.endm
.macro SWITCH_KERNEL_CR3_NO_STACK
ALTERNATIVE "jmp 8f", \
__stringify(movq %rax, PER_CPU_VAR(unsafe_stack_register_backup)), \
X86_FEATURE_KAISER
_SWITCH_TO_KERNEL_CR3 %rax
movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
8:
.endm
#else /* CONFIG_PAGE_TABLE_ISOLATION */
.macro SWITCH_KERNEL_CR3
.endm
.macro SWITCH_USER_CR3
.endm
.macro SWITCH_KERNEL_CR3_NO_STACK
.endm
#endif /* CONFIG_PAGE_TABLE_ISOLATION */
#else /* __ASSEMBLY__ */
#ifdef CONFIG_PAGE_TABLE_ISOLATION
/*
* Upon kernel/user mode switch, it may happen that the address
* space has to be switched before the registers have been
* stored. To change the address space, another register is
* needed. A register therefore has to be stored/restored.
*/
DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
DECLARE_PER_CPU(unsigned long, x86_cr3_pcid_user);
extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[];
extern int kaiser_enabled;
extern void __init kaiser_check_boottime_disable(void);
#else
#define kaiser_enabled 0
static inline void __init kaiser_check_boottime_disable(void) {}
#endif /* CONFIG_PAGE_TABLE_ISOLATION */
/*
* Kaiser function prototypes are needed even when CONFIG_PAGE_TABLE_ISOLATION is not set,
* so as to build with tests on kaiser_enabled instead of #ifdefs.
*/
/**
* kaiser_add_mapping - map a virtual memory part to the shadow (user) mapping
* @addr: the start address of the range
* @size: the size of the range
* @flags: The mapping flags of the pages
*
* The mapping is done on a global scope, so no bigger
* synchronization has to be done. the pages have to be
* manually unmapped again when they are not needed any longer.
*/
extern int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);
/**
* kaiser_remove_mapping - unmap a virtual memory part of the shadow mapping
* @addr: the start address of the range
* @size: the size of the range
*/
extern void kaiser_remove_mapping(unsigned long start, unsigned long size);
/**
* kaiser_init - Initialize the shadow mapping
*
* Most parts of the shadow mapping can be mapped upon boot
* time. Only per-process things like the thread stacks
* or a new LDT have to be mapped at runtime. These boot-
* time mappings are permanent and never unmapped.
*/
extern void kaiser_init(void);
#endif /* __ASSEMBLY */
#endif /* _ASM_X86_KAISER_H */