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arm: arm11: allow unaligned memory access

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The UEFI spec mandates that unaligned memory access should be enabled if
supported by the CPU architecture.

This patch implements the function unaligned_access() to set the enable
unaligned data support flag and to clear the aligned flag in the system
control register (SCTLR). It is called when UEFI related commands like
bootefi are invoked.

Reported-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Tested-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Tested-by: Guillaume Gardet <Guillaume.Gardet@arm.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Heinrich Schuchardt 2019-11-19 04:02:10 +01:00
parent b20bb09b21
commit d47a774680
2 changed files with 29 additions and 0 deletions
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4
arch/arm/cpu/arm11/Makefile
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@ -4,3 +4,7 @@
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
obj-y = cpu.o
ifneq ($(CONFIG_SPL_BUILD),y)
obj-$(CONFIG_EFI_LOADER) += sctlr.o
endif

25
arch/arm/cpu/arm11/sctlr.S Normal file
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@ -0,0 +1,25 @@
/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Routines to access the system control register
*
* Copyright (c) 2019 Heinrich Schuchardt
*/
#include <linux/linkage.h>
/*
* void allow_unaligned(void) - allow unaligned access
*
* This routine sets the enable unaligned data support flag and clears the
* aligned flag in the system control register.
* After calling this routine unaligned access does no longer leads to a
* data abort or undefined behavior but is handled by the CPU.
* For details see the "ARM Architecture Reference Manual" for ARMv6.
*/
ENTRY(allow_unaligned)
mrc p15, 0, r0, c1, c0, 0 @ load system control register
orr r0, r0, #1 << 22 @ set unaligned data support flag
bic r0, r0, #2 @ clear aligned flag
mcr p15, 0, r0, c1, c0, 0 @ write system control register
bx lr @ return
ENDPROC(allow_unaligned)