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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>
171 lines
3.5 KiB
ArmAsm
171 lines
3.5 KiB
ArmAsm
/*
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* linux/arch/arm/lib/getuser.S
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*
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* Copyright (C) 2001 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Idea from x86 version, (C) Copyright 1998 Linus Torvalds
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*
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* These functions have a non-standard call interface to make them more
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* efficient, especially as they return an error value in addition to
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* the "real" return value.
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*
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* __get_user_X
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*
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* Inputs: r0 contains the address
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* r1 contains the address limit, which must be preserved
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* Outputs: r0 is the error code
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* r2, r3 contains the zero-extended value
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* lr corrupted
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*
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* No other registers must be altered. (see <asm/uaccess.h>
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* for specific ASM register usage).
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*
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* Note that ADDR_LIMIT is either 0 or 0xc0000000.
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* Note also that it is intended that __get_user_bad is not global.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/errno.h>
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#include <asm/domain.h>
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ENTRY(__get_user_1)
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check_uaccess r0, 1, r1, r2, __get_user_bad
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1: TUSER(ldrb) r2, [r0]
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mov r0, #0
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ret lr
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ENDPROC(__get_user_1)
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_ASM_NOKPROBE(__get_user_1)
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ENTRY(__get_user_2)
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check_uaccess r0, 2, r1, r2, __get_user_bad
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#if __LINUX_ARM_ARCH__ >= 6
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2: TUSER(ldrh) r2, [r0]
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#else
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#ifdef CONFIG_CPU_USE_DOMAINS
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rb .req ip
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2: ldrbt r2, [r0], #1
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3: ldrbt rb, [r0], #0
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#else
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rb .req r0
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2: ldrb r2, [r0]
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3: ldrb rb, [r0, #1]
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#endif
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#ifndef __ARMEB__
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orr r2, r2, rb, lsl #8
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#else
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orr r2, rb, r2, lsl #8
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#endif
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#endif /* __LINUX_ARM_ARCH__ >= 6 */
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mov r0, #0
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ret lr
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ENDPROC(__get_user_2)
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_ASM_NOKPROBE(__get_user_2)
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ENTRY(__get_user_4)
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check_uaccess r0, 4, r1, r2, __get_user_bad
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4: TUSER(ldr) r2, [r0]
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mov r0, #0
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ret lr
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ENDPROC(__get_user_4)
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_ASM_NOKPROBE(__get_user_4)
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ENTRY(__get_user_8)
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check_uaccess r0, 8, r1, r2, __get_user_bad8
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#ifdef CONFIG_THUMB2_KERNEL
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5: TUSER(ldr) r2, [r0]
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6: TUSER(ldr) r3, [r0, #4]
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#else
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5: TUSER(ldr) r2, [r0], #4
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6: TUSER(ldr) r3, [r0]
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#endif
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mov r0, #0
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ret lr
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ENDPROC(__get_user_8)
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_ASM_NOKPROBE(__get_user_8)
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#ifdef __ARMEB__
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ENTRY(__get_user_32t_8)
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check_uaccess r0, 8, r1, r2, __get_user_bad
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#ifdef CONFIG_CPU_USE_DOMAINS
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add r0, r0, #4
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7: ldrt r2, [r0]
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#else
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7: ldr r2, [r0, #4]
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#endif
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mov r0, #0
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ret lr
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ENDPROC(__get_user_32t_8)
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_ASM_NOKPROBE(__get_user_32t_8)
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ENTRY(__get_user_64t_1)
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check_uaccess r0, 1, r1, r2, __get_user_bad8
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8: TUSER(ldrb) r3, [r0]
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mov r0, #0
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ret lr
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ENDPROC(__get_user_64t_1)
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_ASM_NOKPROBE(__get_user_64t_1)
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ENTRY(__get_user_64t_2)
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check_uaccess r0, 2, r1, r2, __get_user_bad8
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#ifdef CONFIG_CPU_USE_DOMAINS
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rb .req ip
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9: ldrbt r3, [r0], #1
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10: ldrbt rb, [r0], #0
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#else
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rb .req r0
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9: ldrb r3, [r0]
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10: ldrb rb, [r0, #1]
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#endif
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orr r3, rb, r3, lsl #8
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mov r0, #0
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ret lr
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ENDPROC(__get_user_64t_2)
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_ASM_NOKPROBE(__get_user_64t_2)
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ENTRY(__get_user_64t_4)
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check_uaccess r0, 4, r1, r2, __get_user_bad8
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11: TUSER(ldr) r3, [r0]
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mov r0, #0
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ret lr
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ENDPROC(__get_user_64t_4)
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_ASM_NOKPROBE(__get_user_64t_4)
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#endif
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__get_user_bad8:
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mov r3, #0
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__get_user_bad:
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mov r2, #0
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mov r0, #-EFAULT
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ret lr
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ENDPROC(__get_user_bad)
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ENDPROC(__get_user_bad8)
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_ASM_NOKPROBE(__get_user_bad)
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_ASM_NOKPROBE(__get_user_bad8)
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.pushsection __ex_table, "a"
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.long 1b, __get_user_bad
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.long 2b, __get_user_bad
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#if __LINUX_ARM_ARCH__ < 6
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.long 3b, __get_user_bad
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#endif
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.long 4b, __get_user_bad
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.long 5b, __get_user_bad8
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.long 6b, __get_user_bad8
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#ifdef __ARMEB__
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.long 7b, __get_user_bad
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.long 8b, __get_user_bad8
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.long 9b, __get_user_bad8
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.long 10b, __get_user_bad8
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.long 11b, __get_user_bad8
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#endif
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.popsection
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