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338d4f49d6
'Privileged Access Never' is a new arm8.1 feature which prevents
privileged code from accessing any virtual address where read or write
access is also permitted at EL0.
This patch enables the PAN feature on all CPUs, and modifies {get,put}_user
helpers temporarily to permit access.
This will catch kernel bugs where user memory is accessed directly.
'Unprivileged loads and stores' using ldtrb et al are unaffected by PAN.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
[will: use ALTERNATIVE in asm and tidy up pan_enable check]
Signed-off-by: Will Deacon <will.deacon@arm.com>
67 lines
1.7 KiB
ArmAsm
67 lines
1.7 KiB
ArmAsm
/*
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* Based on arch/arm/lib/clear_user.S
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*
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* Copyright (C) 2012 ARM Ltd.
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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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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/linkage.h>
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#include <asm/alternative.h>
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#include <asm/assembler.h>
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#include <asm/cpufeature.h>
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#include <asm/sysreg.h>
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.text
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/* Prototype: int __clear_user(void *addr, size_t sz)
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* Purpose : clear some user memory
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* Params : addr - user memory address to clear
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* : sz - number of bytes to clear
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* Returns : number of bytes NOT cleared
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*
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* Alignment fixed up by hardware.
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*/
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ENTRY(__clear_user)
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ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \
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CONFIG_ARM64_PAN)
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mov x2, x1 // save the size for fixup return
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subs x1, x1, #8
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b.mi 2f
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1:
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USER(9f, str xzr, [x0], #8 )
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subs x1, x1, #8
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b.pl 1b
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2: adds x1, x1, #4
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b.mi 3f
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USER(9f, str wzr, [x0], #4 )
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sub x1, x1, #4
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3: adds x1, x1, #2
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b.mi 4f
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USER(9f, strh wzr, [x0], #2 )
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sub x1, x1, #2
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4: adds x1, x1, #1
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b.mi 5f
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USER(9f, strb wzr, [x0] )
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5: mov x0, #0
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ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_HAS_PAN, \
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CONFIG_ARM64_PAN)
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ret
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ENDPROC(__clear_user)
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.section .fixup,"ax"
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.align 2
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9: mov x0, x2 // return the original size
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ret
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.previous
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