mirror of
https://github.com/torvalds/linux.git
synced 2024-11-25 13:41:51 +00:00
344eb5539a
getuser() and putuser() (and there underscored variants) use two strb[t]/ldrb[t] instructions when they are asked to get/put 16-bits. This means that the read/write is not atomic even when performed to a 16-bit-aligned address. This leads to problems with vhost: vhost uses __getuser() to read the vring's 16-bit avail.index field, and if it happens to observe a partial update of the index, wrong descriptors will be used which will lead to a breakdown of the virtio communication. A similar problem exists for __putuser() which is used to write to the vring's used.index field. The reason these functions use strb[t]/ldrb[t] is because strht/ldrht instructions did not exist until ARMv6T2/ARMv7. So we should be easily able to fix this on ARMv7. Also, since all ARMv6 processors also don't actually use the unprivileged instructions anymore for uaccess (since CONFIG_CPU_USE_DOMAINS is not used) we can easily fix them too. Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
99 lines
2.1 KiB
ArmAsm
99 lines
2.1 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
|
|
* r1 contains the address limit, which must be preserved
|
|
* 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/assembler.h>
|
|
#include <asm/errno.h>
|
|
#include <asm/domain.h>
|
|
|
|
ENTRY(__put_user_1)
|
|
check_uaccess r0, 1, r1, ip, __put_user_bad
|
|
1: TUSER(strb) r2, [r0]
|
|
mov r0, #0
|
|
ret lr
|
|
ENDPROC(__put_user_1)
|
|
|
|
ENTRY(__put_user_2)
|
|
check_uaccess r0, 2, r1, ip, __put_user_bad
|
|
#if __LINUX_ARM_ARCH__ >= 6
|
|
|
|
2: TUSER(strh) r2, [r0]
|
|
|
|
#else
|
|
|
|
mov ip, r2, lsr #8
|
|
#ifndef __ARMEB__
|
|
2: TUSER(strb) r2, [r0], #1
|
|
3: TUSER(strb) ip, [r0]
|
|
#else
|
|
2: TUSER(strb) ip, [r0], #1
|
|
3: TUSER(strb) r2, [r0]
|
|
#endif
|
|
|
|
#endif /* __LINUX_ARM_ARCH__ >= 6 */
|
|
mov r0, #0
|
|
ret lr
|
|
ENDPROC(__put_user_2)
|
|
|
|
ENTRY(__put_user_4)
|
|
check_uaccess r0, 4, r1, ip, __put_user_bad
|
|
4: TUSER(str) r2, [r0]
|
|
mov r0, #0
|
|
ret lr
|
|
ENDPROC(__put_user_4)
|
|
|
|
ENTRY(__put_user_8)
|
|
check_uaccess r0, 8, r1, ip, __put_user_bad
|
|
#ifdef CONFIG_THUMB2_KERNEL
|
|
5: TUSER(str) r2, [r0]
|
|
6: TUSER(str) r3, [r0, #4]
|
|
#else
|
|
5: TUSER(str) r2, [r0], #4
|
|
6: TUSER(str) r3, [r0]
|
|
#endif
|
|
mov r0, #0
|
|
ret lr
|
|
ENDPROC(__put_user_8)
|
|
|
|
__put_user_bad:
|
|
mov r0, #-EFAULT
|
|
ret lr
|
|
ENDPROC(__put_user_bad)
|
|
|
|
.pushsection __ex_table, "a"
|
|
.long 1b, __put_user_bad
|
|
.long 2b, __put_user_bad
|
|
#if __LINUX_ARM_ARCH__ < 6
|
|
.long 3b, __put_user_bad
|
|
#endif
|
|
.long 4b, __put_user_bad
|
|
.long 5b, __put_user_bad
|
|
.long 6b, __put_user_bad
|
|
.popsection
|