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.