linux-kernel - [PATCH 4.9 088/128] x86/build: Keep local relocations with ld.lld

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Message-Id: <20190530030450.680146839@linuxfoundation.org>
Date:   Wed, 29 May 2019 20:07:00 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        clang-built-linux@...glegroups.com, x86-ml <x86@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 088/128] x86/build: Keep local relocations with ld.lld

[ Upstream commit 7c21383f3429dd70da39c0c7f1efa12377a47ab6 ]

The LLVM linker (ld.lld) defaults to removing local relocations, which
causes KASLR boot failures. ld.bfd and ld.gold already handle this
correctly. This adds the explicit instruction "--discard-none" during
the link phase. There is no change in output for ld.bfd and ld.gold,
but ld.lld now produces an image with all the needed relocations.

Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: clang-built-linux@...glegroups.com
Cc: x86-ml <x86@...nel.org>
Link: https://lkml.kernel.org/r/20190404214027.GA7324@beast
Link: https://github.com/ClangBuiltLinux/linux/issues/404
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index b5226a009973f..2996a1d0a410a 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -47,7 +47,7 @@ export REALMODE_CFLAGS
 export BITS
 
 ifdef CONFIG_X86_NEED_RELOCS
-        LDFLAGS_vmlinux := --emit-relocs
+        LDFLAGS_vmlinux := --emit-relocs --discard-none
 endif
 
 #
-- 
2.20.1