[PATCH 5.4 090/348] Makefile: fix GDB warning with CONFIG_RELR

From: Greg Kroah-Hartman
Date: Mon Jul 12 2021 - 02:19:00 EST

From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

[ Upstream commit 27f2a4db76e8d8a8b601fc1c6a7a17f88bd907ab ]

GDB produces the following warning when debugging kernels built with

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

diff --git a/Makefile b/Makefile
index 5e8716dbbadc..78efac6021b6 100644
--- a/Makefile
+++ b/Makefile
@@ -937,7 +937,7 @@ LDFLAGS_vmlinux += $(call ld-option, -X,)

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

# make the checker run with the right architecture
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 $tmp_file.o >/dev/null 2>&1
void *p = &p;
-$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.