linux-kernel - [PATCH AUTOSEL 4.19 010/106] efi/libstub/x86: Work around LLVM ELF quirk build regression

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Message-Id: <20200608232238.3368589-10-sashal@kernel.org>
Date:   Mon,  8 Jun 2020 19:21:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Fangrui Song <maskray@...gle.com>,
        Sasha Levin <sashal@...nel.org>, linux-efi@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH AUTOSEL 4.19 010/106] efi/libstub/x86: Work around LLVM ELF quirk build regression

From: Ard Biesheuvel <ardb@...nel.org>

[ Upstream commit f77767ed5f4d398b29119563155e4ece2dfeee13 ]

When building the x86 EFI stub with Clang, the libstub Makefile rules
that manipulate the ELF object files may throw an error like:

    STUBCPY drivers/firmware/efi/libstub/efi-stub-helper.stub.o
  strip: drivers/firmware/efi/libstub/efi-stub-helper.stub.o: Failed to find link section for section 10
  objcopy: drivers/firmware/efi/libstub/efi-stub-helper.stub.o: Failed to find link section for section 10

This is the result of a LLVM feature [0] where symbol references are
stored in a LLVM specific .llvm_addrsig section in a non-transparent way,
causing generic ELF tools such as strip or objcopy to choke on them.

So force the compiler not to emit these sections, by passing the
appropriate command line option.

[0] https://sourceware.org/bugzilla/show_bug.cgi?id=23817

Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Peter Collingbourne <pcc@...gle.com>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Reported-by: Arnd Bergmann <arnd@...db.de>
Suggested-by: Fangrui Song <maskray@...gle.com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/firmware/efi/libstub/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index d9845099635e..d3777d754984 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -28,6 +28,7 @@ KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
 				   -D__NO_FORTIFY \
 				   $(call cc-option,-ffreestanding) \
 				   $(call cc-option,-fno-stack-protector) \
+				   $(call cc-option,-fno-addrsig) \
 				   -D__DISABLE_EXPORTS
 
 GCOV_PROFILE			:= n
-- 
2.25.1