linux-kernel - [PATCH v2 1/4] arm64: vdso32: drop the test for dmb ishld

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Message-Id: <20211019223646.1146945-2-ndesaulniers@google.com>
Date:   Tue, 19 Oct 2021 15:36:43 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Christian Biesinger <cbiesinger@...gle.com>,
        Simon Marchi <simon.marchi@...ymtl.ca>
Subject: [PATCH v2 1/4] arm64: vdso32: drop the test for dmb ishld

Binutils added support for this instruction in commit
e797f7e0b2bedc9328d4a9a0ebc63ca7a2dbbebc which shipped in 2.24 (just
missing the 2.33 release) but was cherry-picked into 2.23 in commit
27a50d6755bae906bc73b4ec1a8b448467f0bea1. Thanks to Christian and Simon
for helping me with the patch archaeology.

According to Documentation/process/changes.rst, the minimum supported
version of binutils is 2.23. Since all supported versions of GAS support
this instruction, drop the assembler invocation, preprocessor
flags/guards, and the cross assembler macro that's now unused.

This also avoids a recursive self reference in a follow up cleanup
patch.

Cc: Christian Biesinger <cbiesinger@...gle.com>
Cc: Simon Marchi <simon.marchi@...ymtl.ca>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
Changes v1 -> v2:
* Fix typos (2.33 -> 2.23, 2.34 -> 2.24) as per Christian.

 arch/arm64/include/asm/vdso/compat_barrier.h | 2 +-
 arch/arm64/kernel/vdso32/Makefile            | 8 --------
 2 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/vdso/compat_barrier.h b/arch/arm64/include/asm/vdso/compat_barrier.h
index 3fd8fd6d8fc2..fb60a88b5ed4 100644
--- a/arch/arm64/include/asm/vdso/compat_barrier.h
+++ b/arch/arm64/include/asm/vdso/compat_barrier.h
@@ -20,7 +20,7 @@
 
 #define dmb(option) __asm__ __volatile__ ("dmb " #option : : : "memory")
 
-#if __LINUX_ARM_ARCH__ >= 8 && defined(CONFIG_AS_DMB_ISHLD)
+#if __LINUX_ARM_ARCH__ >= 8
 #define aarch32_smp_mb()	dmb(ish)
 #define aarch32_smp_rmb()	dmb(ishld)
 #define aarch32_smp_wmb()	dmb(ishst)
diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index 3dba0c4f8f42..89299a26638b 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -29,8 +29,6 @@ cc32-option = $(call try-run,\
         $(CC_COMPAT) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
 cc32-disable-warning = $(call try-run,\
 	$(CC_COMPAT) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1)))
-cc32-as-instr = $(call try-run,\
-	printf "%b\n" "$(1)" | $(CC_COMPAT) $(VDSO_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
 
 # We cannot use the global flags to compile the vDSO files, the main reason
 # being that the 32-bit compiler may be older than the main (64-bit) compiler
@@ -113,12 +111,6 @@ endif
 VDSO_AFLAGS := $(VDSO_CAFLAGS)
 VDSO_AFLAGS += -D__ASSEMBLY__
 
-# Check for binutils support for dmb ishld
-dmbinstr := $(call cc32-as-instr,dmb ishld,-DCONFIG_AS_DMB_ISHLD=1)
-
-VDSO_CFLAGS += $(dmbinstr)
-VDSO_AFLAGS += $(dmbinstr)
-
 # From arm vDSO Makefile
 VDSO_LDFLAGS += -Bsymbolic --no-undefined -soname=linux-vdso.so.1
 VDSO_LDFLAGS += -z max-page-size=4096 -z common-page-size=4096
-- 
2.33.0.1079.g6e70778dc9-goog