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ARM: 8723/2: always assume the "unified" syntax for assembly code

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The GNU assembler has implemented the "unified syntax" parsing since
2005. This "unified" syntax is required when the kernel is built in
Thumb2 mode. However the "unified" syntax is a mixed bag of features,
including not requiring a `#' prefix with immediate operands. This leads
to situations where some code builds just fine in Thumb2 mode and fails
to build in ARM mode if that prefix is missing. This behavior
discrepancy makes build tests less valuable, forcing both ARM and Thumb2
builds for proper coverage.

Let's "fix" this issue by always using the "unified" syntax for both ARM
and Thumb2 mode. Given that the documented minimum binutils version that
properly builds the kernel is version 2.20 released in 2010, we can
assume that any toolchain capable of building the latest kernel is also
"unified syntax" capable.

Whith this, a bunch of macros used to mask some differences between both
syntaxes can be removed, with the side effect of making LTO easier.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Nicolas Pitre 2017-11-29 07:52:52 +01:00 committed by Russell King
parent 55e7cff44c
commit 75fea300d7
3 changed files with 8 additions and 82 deletions
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7
arch/arm/Kconfig
View File

@ -1524,12 +1524,10 @@ config THUMB2_KERNEL
bool "Compile the kernel in Thumb-2 mode" if !CPU_THUMBONLY
depends on (CPU_V7 || CPU_V7M) && !CPU_V6 && !CPU_V6K
default y if CPU_THUMBONLY
select ARM_ASM_UNIFIED
select ARM_UNWIND
help
By enabling this option, the kernel will be compiled in
Thumb-2 mode. A compiler/assembler that understand the unified
ARM-Thumb syntax is needed.
Thumb-2 mode.
If unsure, say N.
@ -1564,9 +1562,6 @@ config THUMB2_AVOID_R_ARM_THM_JUMP11
Unless you are sure your tools don't have this problem, say Y.
config ARM_ASM_UNIFIED
bool
config ARM_PATCH_IDIV
bool "Runtime patch udiv/sdiv instructions into __aeabi_{u}idiv()"
depends on CPU_32v7 && !XIP_KERNEL

6
arch/arm/Makefile
View File

@ -115,9 +115,11 @@ ifeq ($(CONFIG_ARM_UNWIND),y)
CFLAGS_ABI +=-funwind-tables
endif
# Accept old syntax despite ".syntax unified"
AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
ifeq ($(CONFIG_THUMB2_KERNEL),y)
AFLAGS_AUTOIT :=$(call as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it)
AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
CFLAGS_ISA :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb
# Work around buggy relocation from gas if requested:
@ -125,7 +127,7 @@ ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)
KBUILD_CFLAGS_MODULE +=-fno-optimize-sibling-calls
endif
else
CFLAGS_ISA :=$(call cc-option,-marm,)
CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN)
AFLAGS_ISA :=$(CFLAGS_ISA)
endif

77
arch/arm/include/asm/unified.h
View File

@ -20,8 +20,10 @@
#ifndef __ASM_UNIFIED_H
#define __ASM_UNIFIED_H
#if defined(__ASSEMBLY__) && defined(CONFIG_ARM_ASM_UNIFIED)
#if defined(__ASSEMBLY__)
.syntax unified
#else
__asm__(".syntax unified");
#endif
#ifdef CONFIG_CPU_V7M
@ -64,77 +66,4 @@
#endif /* CONFIG_THUMB2_KERNEL */
#ifndef CONFIG_ARM_ASM_UNIFIED
/*
* If the unified assembly syntax isn't used (in ARM mode), these
* macros expand to an empty string
*/
#ifdef __ASSEMBLY__
.macro it, cond
.endm
.macro itt, cond
.endm
.macro ite, cond
.endm
.macro ittt, cond
.endm
.macro itte, cond
.endm
.macro itet, cond
.endm
.macro itee, cond
.endm
.macro itttt, cond
.endm
.macro ittte, cond
.endm
.macro ittet, cond
.endm
.macro ittee, cond
.endm
.macro itett, cond
.endm
.macro itete, cond
.endm
.macro iteet, cond
.endm
.macro iteee, cond
.endm
#else /* !__ASSEMBLY__ */
__asm__(
" .macro it, cond\n"
" .endm\n"
" .macro itt, cond\n"
" .endm\n"
" .macro ite, cond\n"
" .endm\n"
" .macro ittt, cond\n"
" .endm\n"
" .macro itte, cond\n"
" .endm\n"
" .macro itet, cond\n"
" .endm\n"
" .macro itee, cond\n"
" .endm\n"
" .macro itttt, cond\n"
" .endm\n"
" .macro ittte, cond\n"
" .endm\n"
" .macro ittet, cond\n"
" .endm\n"
" .macro ittee, cond\n"
" .endm\n"
" .macro itett, cond\n"
" .endm\n"
" .macro itete, cond\n"
" .endm\n"
" .macro iteet, cond\n"
" .endm\n"
" .macro iteee, cond\n"
" .endm\n");
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_ARM_ASM_UNIFIED */
#endif /* !__ASM_UNIFIED_H */