linux/arch/arm/lib/putuser.S
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

92 lines
1.9 KiB
ArmAsm

/*
* linux/arch/arm/lib/putuser.S
*
* Copyright (C) 2001 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.
*
* Idea from x86 version, (C) Copyright 1998 Linus Torvalds
*
* These functions have a non-standard call interface to make
* them more efficient, especially as they return an error
* value in addition to the "real" return value.
*
* __put_user_X
*
* Inputs: r0 contains the address
* r2, r3 contains the value
* Outputs: r0 is the error code
* lr corrupted
*
* No other registers must be altered. (see <asm/uaccess.h>
* for specific ASM register usage).
*
* Note that ADDR_LIMIT is either 0 or 0xc0000000
* Note also that it is intended that __put_user_bad is not global.
*/
#include <linux/linkage.h>
#include <asm/errno.h>
#include <asm/domain.h>
ENTRY(__put_user_1)
1: T(strb) r2, [r0]
mov r0, #0
mov pc, lr
ENDPROC(__put_user_1)
ENTRY(__put_user_2)
mov ip, r2, lsr #8
#ifdef CONFIG_THUMB2_KERNEL
#ifndef __ARMEB__
2: T(strb) r2, [r0]
3: T(strb) ip, [r0, #1]
#else
2: T(strb) ip, [r0]
3: T(strb) r2, [r0, #1]
#endif
#else /* !CONFIG_THUMB2_KERNEL */
#ifndef __ARMEB__
2: T(strb) r2, [r0], #1
3: T(strb) ip, [r0]
#else
2: T(strb) ip, [r0], #1
3: T(strb) r2, [r0]
#endif
#endif /* CONFIG_THUMB2_KERNEL */
mov r0, #0
mov pc, lr
ENDPROC(__put_user_2)
ENTRY(__put_user_4)
4: T(str) r2, [r0]
mov r0, #0
mov pc, lr
ENDPROC(__put_user_4)
ENTRY(__put_user_8)
#ifdef CONFIG_THUMB2_KERNEL
5: T(str) r2, [r0]
6: T(str) r3, [r0, #4]
#else
5: T(str) r2, [r0], #4
6: T(str) r3, [r0]
#endif
mov r0, #0
mov pc, lr
ENDPROC(__put_user_8)
__put_user_bad:
mov r0, #-EFAULT
mov pc, lr
ENDPROC(__put_user_bad)
.pushsection __ex_table, "a"
.long 1b, __put_user_bad
.long 2b, __put_user_bad
.long 3b, __put_user_bad
.long 4b, __put_user_bad
.long 5b, __put_user_bad
.long 6b, __put_user_bad
.popsection