linux-kernel - [PATCH 2/2] int128: fix __uint128

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Message-Id: <20200310101250.22374-2-masahiroy@kernel.org>
Date:   Tue, 10 Mar 2020 19:12:50 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Ard Biesheuvel <ardb@...nel.org>, George Spelvin <lkml@....org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        David Howells <dhowells@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Patrick Bellasi <patrick.bellasi@....com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] int128: fix __uint128_t compiler test in Kconfig

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>
---

 init/Kconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 20a6ac33761c..4f717bfdbfe2 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
-- 
2.17.1