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Commit 67fab0d4 authored by Hugh Dickins's avatar Hugh Dickins Committed by Greg Kroah-Hartman
Browse files

kaiser: tidied up asm/kaiser.h somewhat 




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

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f43f386f

arch/x86/include/asm/kaiser.h

+13 −19
Original line number Diff line number Diff line 
#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 */