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Subject[PATCH AUTOSEL 5.13 49/85] Makefile: fix GDB warning with CONFIG_RELR
Date
From: Nick Desaulniers <ndesaulniers@google.com>

[ Upstream commit 27f2a4db76e8d8a8b601fc1c6a7a17f88bd907ab ]

GDB produces the following warning when debugging kernels built with
CONFIG_RELR:

BFD: /android0/linux-next/vmlinux: unknown type [0x13] section `.relr.dyn'

when loading a kernel built with CONFIG_RELR into GDB. It can also
prevent debugging symbols using such relocations.

Peter sugguests:
[That flag] means that lld will use dynamic tags and section type
numbers in the OS-specific range rather than the generic range. The
kernel itself doesn't care about these numbers; it determines the
location of the RELR section using symbols defined by a linker script.

Link: https://github.com/ClangBuiltLinux/linux/issues/1057
Suggested-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20210522012626.2811297-1-ndesaulniers@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Makefile | 2 +-
scripts/tools-support-relr.sh | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 0565caea0362..88888fff4c62 100644
--- a/Makefile
+++ b/Makefile
@@ -1039,7 +1039,7 @@ LDFLAGS_vmlinux += $(call ld-option, -X,)
endif

ifeq ($(CONFIG_RELR),y)
-LDFLAGS_vmlinux += --pack-dyn-relocs=relr
+LDFLAGS_vmlinux += --pack-dyn-relocs=relr --use-android-relr-tags
endif

# We never want expected sections to be placed heuristically by the
diff --git a/scripts/tools-support-relr.sh b/scripts/tools-support-relr.sh
index 45e8aa360b45..cb55878bd5b8 100755
--- a/scripts/tools-support-relr.sh
+++ b/scripts/tools-support-relr.sh
@@ -7,7 +7,8 @@ trap "rm -f $tmp_file.o $tmp_file $tmp_file.bin" EXIT
cat << "END" | $CC -c -x c - -o $tmp_file.o >/dev/null 2>&1
void *p = &p;
END
-$LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr -o $tmp_file
+$LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr \
+ --use-android-relr-tags -o $tmp_file

# Despite printing an error message, GNU nm still exits with exit code 0 if it
# sees a relr section. So we need to check that nothing is printed to stderr.
--
2.30.2
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