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[U-Boot,1/2] arm: arm11: allow unaligned memory access

Message ID 20191119033557.16056-2-xypron.glpk@gmx.de
State Accepted, archived
Commit d47a774680d18ee5dea43d8b631048c3dc1a2b5f
Delegated to: Heinrich Schuchardt
Headers show
Series efi_loader: enable unaligned access on arm11 | expand

Commit Message

Heinrich Schuchardt Nov. 19, 2019, 3:35 a.m. UTC 
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>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
 arch/arm/cpu/arm11/Makefile |  4 ++++
 arch/arm/cpu/arm11/sctlr.S  | 25 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 arch/arm/cpu/arm11/sctlr.S

--
2.24.0
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Patch

diff --git a/arch/arm/cpu/arm11/Makefile b/arch/arm/cpu/arm11/Makefile
index 5d721fce12..5dfa01ae8d 100644
--- a/arch/arm/cpu/arm11/Makefile
+++ b/arch/arm/cpu/arm11/Makefile
@@ -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
diff --git a/arch/arm/cpu/arm11/sctlr.S b/arch/arm/cpu/arm11/sctlr.S
new file mode 100644
index 0000000000..74a7fc4a25
--- /dev/null
+++ b/arch/arm/cpu/arm11/sctlr.S
@@ -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)