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kaiser: tidied up asm/kaiser.h somewhat

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Mainly deleting a surfeit of blank lines, and reflowing header comment.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hugh Dickins 2017-09-03 19:18:07 -07:00 committed by Greg Kroah-Hartman
parent 407c3ff6a2
commit 5fbd46c4be
1 changed files with 13 additions and 19 deletions
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32
arch/x86/include/asm/kaiser.h
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@ -1,15 +1,17 @@
#ifndef _ASM_X86_KAISER_H
#define _ASM_X86_KAISER_H
/* 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 shodow-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 chaches are freed, and the user may not attack the whole kernel memory.
/*
* 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, as the entry/exit functions
* of the user space, or the stacks.
* 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.
*/
#ifdef __ASSEMBLY__
#ifdef CONFIG_KAISER
@ -48,13 +50,10 @@ _SWITCH_TO_KERNEL_CR3 %rax
movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
.endm
.macro SWITCH_USER_CR3_NO_STACK
movq %rax, PER_CPU_VAR(unsafe_stack_register_backup)
_SWITCH_TO_USER_CR3 %rax
movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
.endm
#else /* CONFIG_KAISER */
@ -72,7 +71,6 @@ movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
#else /* __ASSEMBLY__ */
#ifdef CONFIG_KAISER
/*
* Upon kernel/user mode switch, it may happen that the address
@ -80,7 +78,6 @@ movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
* 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);
/**
@ -95,7 +92,6 @@ DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
*/
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
@ -104,12 +100,12 @@ extern int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned l
extern void kaiser_remove_mapping(unsigned long start, unsigned long size);
/**
* kaiser_initialize_mapping - Initalize the shadow mapping
* 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 nevertunmapped.
* time mappings are permanent and never unmapped.
*/
extern void kaiser_init(void);
@ -117,6 +113,4 @@ extern void kaiser_init(void);
#endif /* __ASSEMBLY */
#endif /* _ASM_X86_KAISER_H */