linux/arch/arm/include/asm/domain.h
Catalin Marinas 247055aa21 ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs
This patch removes the domain switching functionality via the set_fs and
__switch_to functions on cores that have a TLS register.

Currently, the ioremap and vmalloc areas share the same level 1 page
tables and therefore have the same domain (DOMAIN_KERNEL). When the
kernel domain is modified from Client to Manager (via the __set_fs or in
the __switch_to function), the XN (eXecute Never) bit is overridden and
newer CPUs can speculatively prefetch the ioremap'ed memory.

Linux performs the kernel domain switching to allow user-specific
functions (copy_to/from_user, get/put_user etc.) to access kernel
memory. In order for these functions to work with the kernel domain set
to Client, the patch modifies the LDRT/STRT and related instructions to
the LDR/STR ones.

The user pages access rights are also modified for kernel read-only
access rather than read/write so that the copy-on-write mechanism still
works. CPU_USE_DOMAINS gets disabled only if the hardware has a TLS register
(CPU_32v6K is defined) since writing the TLS value to the high vectors page
isn't possible.

The user addresses passed to the kernel are checked by the access_ok()
function so that they do not point to the kernel space.

Tested-by: Anton Vorontsov <cbouatmailru@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-11-04 15:44:31 +00:00

106 lines
2.6 KiB
C

/*
* arch/arm/include/asm/domain.h
*
* Copyright (C) 1999 Russell King.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef __ASM_PROC_DOMAIN_H
#define __ASM_PROC_DOMAIN_H
/*
* Domain numbers
*
* DOMAIN_IO - domain 2 includes all IO only
* DOMAIN_USER - domain 1 includes all user memory only
* DOMAIN_KERNEL - domain 0 includes all kernel memory only
*
* The domain numbering depends on whether we support 36 physical
* address for I/O or not. Addresses above the 32 bit boundary can
* only be mapped using supersections and supersections can only
* be set for domain 0. We could just default to DOMAIN_IO as zero,
* but there may be systems with supersection support and no 36-bit
* addressing. In such cases, we want to map system memory with
* supersections to reduce TLB misses and footprint.
*
* 36-bit addressing and supersections are only available on
* CPUs based on ARMv6+ or the Intel XSC3 core.
*/
#ifndef CONFIG_IO_36
#define DOMAIN_KERNEL 0
#define DOMAIN_TABLE 0
#define DOMAIN_USER 1
#define DOMAIN_IO 2
#else
#define DOMAIN_KERNEL 2
#define DOMAIN_TABLE 2
#define DOMAIN_USER 1
#define DOMAIN_IO 0
#endif
/*
* Domain types
*/
#define DOMAIN_NOACCESS 0
#define DOMAIN_CLIENT 1
#ifdef CONFIG_CPU_USE_DOMAINS
#define DOMAIN_MANAGER 3
#else
#define DOMAIN_MANAGER 1
#endif
#define domain_val(dom,type) ((type) << (2*(dom)))
#ifndef __ASSEMBLY__
#ifdef CONFIG_CPU_USE_DOMAINS
#define set_domain(x) \
do { \
__asm__ __volatile__( \
"mcr p15, 0, %0, c3, c0 @ set domain" \
: : "r" (x)); \
isb(); \
} while (0)
#define modify_domain(dom,type) \
do { \
struct thread_info *thread = current_thread_info(); \
unsigned int domain = thread->cpu_domain; \
domain &= ~domain_val(dom, DOMAIN_MANAGER); \
thread->cpu_domain = domain | domain_val(dom, type); \
set_domain(thread->cpu_domain); \
} while (0)
#else
#define set_domain(x) do { } while (0)
#define modify_domain(dom,type) do { } while (0)
#endif
/*
* Generate the T (user) versions of the LDR/STR and related
* instructions (inline assembly)
*/
#ifdef CONFIG_CPU_USE_DOMAINS
#define T(instr) #instr "t"
#else
#define T(instr) #instr
#endif
#else /* __ASSEMBLY__ */
/*
* Generate the T (user) versions of the LDR/STR and related
* instructions
*/
#ifdef CONFIG_CPU_USE_DOMAINS
#define T(instr) instr ## t
#else
#define T(instr) instr
#endif
#endif /* __ASSEMBLY__ */
#endif /* !__ASM_PROC_DOMAIN_H */