linux-kernel - [PATCH AUTOSEL 5.5 07/28] int128: fix __uint128

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Date:   Thu, 26 Mar 2020 19:23:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        George Spelvin <lkml@....org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.5 07/28] int128: fix __uint128_t compiler test in Kconfig

From: Masahiro Yamada <masahiroy@...nel.org>

[ Upstream commit 3a7c733165a4799fa1beb262fe244bfbcdd1c163 ]

The support for __uint128_t is dependent on the target bit size.

GCC that defaults to the 32-bit can still build the 64-bit kernel
with -m64 flag passed.

However, $(cc-option,-D__SIZEOF_INT128__=0) is evaluated against the
default machine bit, which may not match to the kernel it is building.

Theoretically, this could be evaluated separately for 64BIT/32BIT.

  config CC_HAS_INT128
          bool
          default !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) if 64BIT
          default !$(cc-option,$(m32-flag) -D__SIZEOF_INT128__=0)

I simplified it more because the 32-bit compiler is unlikely to support
__uint128_t.

Fixes: c12d3362a74b ("int128: move __uint128_t compiler test to Kconfig")
Reported-by: George Spelvin <lkml@....org>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Tested-by: George Spelvin <lkml@....org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 init/Kconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 47d40f3990005..74297c392dd49 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -767,8 +767,7 @@ config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 	bool
 
 config CC_HAS_INT128
-	def_bool y
-	depends on !$(cc-option,-D__SIZEOF_INT128__=0)
+	def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
 
 #
 # For architectures that know their GCC __int128 support is sound
-- 
2.20.1