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Date: Thu, 21 Jan 2021 18:45:55 +0000
From: Alexander Lobakin <alobakin@...me>
To: Kees Cook <keescook@...omium.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>, Michal Marek <michal.lkml@...kovi.net>, Alexander Lobakin <alobakin@...me>, kernel-hardening@...ts.openwall.com, linux-hardening@...r.kernel.org, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH kspp-next] kbuild: prevent CC_FLAGS_LTO self-bloating on recursive rebuilds
CC_FLAGS_LTO gets initialized only via +=, never with := or =.
When building with CONFIG_TRIM_UNUSED_KSYMS, Kbuild may perform
several kernel rebuilds to satisfy symbol dependencies. In this
case, value of CC_FLAGS_LTO is concatenated each time, which
triggers a full rebuild.
Initialize it with := to fix this.
Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO")
Signed-off-by: Alexander Lobakin <alobakin@...me>
---
Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 668909e7a460..2233951666f7 100644
--- a/Makefile
+++ b/Makefile
@@ -895,10 +895,10 @@ endif
ifdef CONFIG_LTO_CLANG
ifdef CONFIG_LTO_CLANG_THIN
-CC_FLAGS_LTO += -flto=thin -fsplit-lto-unit
+CC_FLAGS_LTO := -flto=thin -fsplit-lto-unit
KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod-prefix).thinlto-cache
else
-CC_FLAGS_LTO += -flto
+CC_FLAGS_LTO := -flto
endif
CC_FLAGS_LTO += -fvisibility=hidden
--
2.30.0
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