linux-kernel - [PATCH V3 01/13] selftests/x86/sgx: Fix a benign linker warning

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Message-Id: <ca0f8a81fc1e78af9bdbc6a88e0f9c37d82e53f2.1636997631.git.reinette.chatre@intel.com>
Date:   Mon, 15 Nov 2021 10:35:14 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     jarkko@...nel.org, linux-sgx@...r.kernel.org, shuah@...nel.org,
        dave.hansen@...ux.intel.com
Cc:     seanjc@...gle.com, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH V3 01/13] selftests/x86/sgx: Fix a benign linker warning

From: Sean Christopherson <sean.j.christopherson@...el.com>

The enclave binary (test_encl.elf) is built with only three sections (tcs,
text, and data) as controlled by its custom linker script.

If gcc is built with "--enable-linker-build-id" (this appears to be a
common configuration even if it is by default off) then gcc
will pass "--build-id" to the linker that will prompt it (the linker) to
write unique bits identifying the linked file to a ".note.gnu.build-id"
section.

The section ".note.gnu.build-id" does not exist in the test enclave
resulting in the following warning emitted by the linker:

/usr/bin/ld: warning: .note.gnu.build-id section discarded, --build-id
ignored

The test enclave does not use the build id within the binary so fix the
warning by passing a build id of "none" to the linker that will disable the
setting from any earlier "--build-id" options and thus disable the attempt
to write the build id to a ".note.gnu.build-id" section that does not
exist.

Link: https://lore.kernel.org/linux-sgx/20191017030340.18301-2-sean.j.christopherson@intel.com/
Suggested-by: Cedric Xing <cedric.xing@...el.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
---
Changes since V2:
- Rewrite commit message (Dave).

Changes since V1:
- Change Cedric's signature to a "Suggested-by" (Jarkko and Cedric).
- Add signatures from Jarkko and Dave.

 tools/testing/selftests/sgx/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/sgx/Makefile b/tools/testing/selftests/sgx/Makefile
index 7f12d55b97f8..2956584e1e37 100644
--- a/tools/testing/selftests/sgx/Makefile
+++ b/tools/testing/selftests/sgx/Makefile
@@ -45,7 +45,7 @@ $(OUTPUT)/sign_key.o: sign_key.S
 	$(CC) $(HOST_CFLAGS) -c $< -o $@

 $(OUTPUT)/test_encl.elf: test_encl.lds test_encl.c test_encl_bootstrap.S
-	$(CC) $(ENCL_CFLAGS) -T $^ -o $@
+	$(CC) $(ENCL_CFLAGS) -T $^ -o $@ -Wl,--build-id=none

 EXTRA_CLEAN := \
 	$(OUTPUT)/test_encl.elf \
-- 
2.25.1