linux-kernel - [PATCH] ARM: replace the sole use of a symbol with its definition

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Date:   Tue,  7 Apr 2020 12:05:57 -0700
From:   Jian Cai <caij2003@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     caij2003@...il.com, ndesaulniers@...gle.com, manojgupta@...gle.com,
        stefan@...er.ch, Russell King <linux@...linux.org.uk>,
        Enrico Weigelt <info@...ux.net>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] ARM: replace the sole use of a symbol with its definition

ALT_UP_B macro sets symbol up_b_offset via .equ to an expression
involving another symbol. The macro gets expanded twice when
arch/arm/kernel/sleep.S is assembled, creating a scenario where
up_b_offset is set to another expression involving symbols while its
current value is based on symbols. LLVM integrated assembler does not
allow such cases, and based on the documentation of binutils, "Values
that are based on expressions involving other symbols are allowed, but
some targets may restrict this to only being done once per assembly", so
it may be better to avoid such cases as it is not clearly stated which
targets should support or disallow them. The fix in this case is simple,
as up_b_offset has only one use, so we can replace the use with the
definition and get rid of up_b_offset.

Signed-off-by: Jian Cai <caij2003@...il.com>
---
 arch/arm/include/asm/assembler.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 99929122dad7..adee13126c62 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -269,10 +269,9 @@
 	.endif							;\
 	.popsection
 #define ALT_UP_B(label)					\
-	.equ	up_b_offset, label - 9998b			;\
 	.pushsection ".alt.smp.init", "a"			;\
 	.long	9998b						;\
-	W(b)	. + up_b_offset					;\
+	W(b)	. + (label - 9998b)					;\
 	.popsection
 #else
 #define ALT_SMP(instr...)
-- 
2.26.0.292.g33ef6b2f38-goog