[PATCH] efi_loader: define allow_unaligned as 'asm volatile'

[Ilias Apalodimas]

Tom reports that compiling with LTO & EFI breaks armv7 and arm11*
builds.  The reason is that LTO (maybe a binutils bug?) replaces the
asm version of allow_unaligned() with the __weak definition of the
function.  As a result EFI code ends up running with unaligned accesses
disabled and eventually crashes.

allow_unaligned() hardware specific variants are usually defined in .S
files.  Switching those to inline assembly fixes the problem and the
linker keeps the correct version in the final binary

Reported-by: Tom Rini <trini at konsulko.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
This is an alternative approach to https://lore.kernel.org/u-boot/ZBRy1oSZ5iVFqrdV@hera/
since enabling unaligned accesses by default has been rejected in the past

 arch/arm/cpu/arm11/Makefile |  4 ----
 arch/arm/cpu/arm11/cpu.c    | 13 +++++++++++++
 arch/arm/cpu/arm11/sctlr.S  | 25 -------------------------
 arch/arm/cpu/armv7/Makefile |  1 -
 arch/arm/cpu/armv7/cpu.c    | 11 +++++++++++
 arch/arm/cpu/armv7/sctlr.S  | 22 ----------------------
 6 files changed, 24 insertions(+), 52 deletions(-)
 delete mode 100644 arch/arm/cpu/arm11/sctlr.S
 delete mode 100644 arch/arm/cpu/armv7/sctlr.S

diff --git a/arch/arm/cpu/arm11/Makefile b/arch/arm/cpu/arm11/Makefile
index 5dfa01ae8d05..5d721fce12b5 100644
--- a/arch/arm/cpu/arm11/Makefile
+++ b/arch/arm/cpu/arm11/Makefile
@@ -4,7 +4,3 @@
 # Wolfgang Denk, DENX Software Engineering, wd at 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/cpu.c b/arch/arm/cpu/arm11/cpu.c
index ffe35111d589..b19c4fc4a6c2 100644
--- a/arch/arm/cpu/arm11/cpu.c
+++ b/arch/arm/cpu/arm11/cpu.c
@@ -111,3 +111,16 @@ void enable_caches(void)
 #endif
 }
 #endif
+
+#if !IS_ENABLED(CONFIG_SPL_BUILD)
+void allow_unaligned(void)
+{
+	asm volatile(
+	"mrc	p15, 0, r0, c1, c0, 0\n" //load system control register
+	"orr	r0, r0, #1 << 22\n"	 //set unaligned data support flag
+	"bic	r0, r0, #2\n"		 //clear aligned flag
+	"mcr	p15, 0, r0, c1, c0, 0\n" // write system control register
+	"bx	lr\n"			 //return
+	);
+}
+#endif
diff --git a/arch/arm/cpu/arm11/sctlr.S b/arch/arm/cpu/arm11/sctlr.S
deleted file mode 100644
index 74a7fc4a25b6..000000000000
--- a/arch/arm/cpu/arm11/sctlr.S
+++ /dev/null
@@ -1,25 +0,0 @@
-/* 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)
diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
index 653eef8ad79e..ca50f6e93e10 100644
--- a/arch/arm/cpu/armv7/Makefile
+++ b/arch/arm/cpu/armv7/Makefile
@@ -13,7 +13,6 @@ obj-y	+= syslib.o
 obj-$(CONFIG_SYS_ARM_MPU) += mpu_v7r.o

 ifneq ($(CONFIG_SPL_BUILD),y)
-obj-$(CONFIG_EFI_LOADER) += sctlr.o
 obj-$(CONFIG_ARMV7_NONSEC) += exception_level.o
 endif

diff --git a/arch/arm/cpu/armv7/cpu.c b/arch/arm/cpu/armv7/cpu.c
index 68807d209978..9742fa65e3cf 100644
--- a/arch/arm/cpu/armv7/cpu.c
+++ b/arch/arm/cpu/armv7/cpu.c
@@ -83,3 +83,14 @@ int cleanup_before_linux(void)
 {
 	return cleanup_before_linux_select(CBL_ALL);
 }
+
+#if !IS_ENABLED(CONFIG_SPL_BUILD)
+void allow_unaligned(void)
+{
+	asm volatile(
+	"mrc	p15, 0, r0, c1, c0, 0\n" //load system control register
+	"bic	r0, r0, #2\n"		 //clear aligned flag
+	"mcr	p15, 0, r0, c1, c0, 0\n" //write system control register
+	);
+}
+#endif
diff --git a/arch/arm/cpu/armv7/sctlr.S b/arch/arm/cpu/armv7/sctlr.S
deleted file mode 100644
index bd56e41afe18..000000000000
--- a/arch/arm/cpu/armv7/sctlr.S
+++ /dev/null
@@ -1,22 +0,0 @@
-/* SPDX-License-Identifier:     GPL-2.0+ */
-/*
- *  Routines to access the system control register
- *
- *  Copyright (c) 2018 Heinrich Schuchardt
- */
-
-#include <linux/linkage.h>
-
-/*
- * void allow_unaligned(void) - allow unaligned access
- *
- * This routine clears the aligned flag in the system control register.
- * After calling this routine unaligned access does no longer lead to a
- * data abort but is handled by the CPU.
- */
-ENTRY(allow_unaligned)
-	mrc	p15, 0, r0, c1, c0, 0	@ load system control register
-	bic	r0, r0, #2		@ clear aligned flag
-	mcr	p15, 0, r0, c1, c0, 0	@ write system control register
-	bx	lr			@ return
-ENDPROC(allow_unaligned)
--
2.39.2