From: Alexandre Ghiti alex@ghiti.fr
[ Upstream commit 43e76cd368fbb67e767da5363ffeaa3989993c8c ]
Commit 8580ac9404f6 ("bpf: Process in-kernel BTF") introduced two weak symbols that may be unresolved at link time which result in an absolute relocation to 0. relocs_check.sh emits the following warning:
"WARNING: 2 bad relocations c000000001a41478 R_PPC64_ADDR64 _binary__btf_vmlinux_bin_start c000000001a41480 R_PPC64_ADDR64 _binary__btf_vmlinux_bin_end"
whereas those relocations are legitimate even for a relocatable kernel compiled with -pie option.
relocs_check.sh already excluded some weak unresolved symbols explicitly: remove those hardcoded symbols and add some logic that parses the symbols using nm, retrieves all the weak unresolved symbols and excludes those from the list of the potential bad relocations.
Reported-by: Stephen Rothwell sfr@canb.auug.org.au Signed-off-by: Alexandre Ghiti alex@ghiti.fr Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20200118170335.21440-1-alex@ghiti.fr Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/Makefile.postlink | 4 ++-- arch/powerpc/tools/relocs_check.sh | 20 ++++++++++++-------- 2 files changed, 14 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/Makefile.postlink b/arch/powerpc/Makefile.postlink index 134f12f89b92b..2268396ff4bba 100644 --- a/arch/powerpc/Makefile.postlink +++ b/arch/powerpc/Makefile.postlink @@ -17,11 +17,11 @@ quiet_cmd_head_check = CHKHEAD $@ quiet_cmd_relocs_check = CHKREL $@ ifdef CONFIG_PPC_BOOK3S_64 cmd_relocs_check = \ - $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$@" ; \ + $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@" ; \ $(BASH) $(srctree)/arch/powerpc/tools/unrel_branch_check.sh "$(OBJDUMP)" "$@" else cmd_relocs_check = \ - $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$@" + $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@" endif
# `@true` prevents complaint when there is nothing to be done diff --git a/arch/powerpc/tools/relocs_check.sh b/arch/powerpc/tools/relocs_check.sh index 7b9fe0a567cf3..014e00e74d2b6 100755 --- a/arch/powerpc/tools/relocs_check.sh +++ b/arch/powerpc/tools/relocs_check.sh @@ -10,14 +10,21 @@ # based on relocs_check.pl # Copyright © 2009 IBM Corporation
-if [ $# -lt 2 ]; then - echo "$0 [path to objdump] [path to vmlinux]" 1>&2 +if [ $# -lt 3 ]; then + echo "$0 [path to objdump] [path to nm] [path to vmlinux]" 1>&2 exit 1 fi
-# Have Kbuild supply the path to objdump so we handle cross compilation. +# Have Kbuild supply the path to objdump and nm so we handle cross compilation. objdump="$1" -vmlinux="$2" +nm="$2" +vmlinux="$3" + +# Remove from the bad relocations those that match an undefined weak symbol +# which will result in an absolute relocation to 0. +# Weak unresolved symbols are of that form in nm output: +# " w _binary__btf_vmlinux_bin_end" +undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')
bad_relocs=$( $objdump -R "$vmlinux" | @@ -26,8 +33,6 @@ $objdump -R "$vmlinux" | # These relocations are okay # On PPC64: # R_PPC64_RELATIVE, R_PPC64_NONE - # R_PPC64_ADDR64 mach_<name> - # R_PPC64_ADDR64 __crc_<name> # On PPC: # R_PPC_RELATIVE, R_PPC_ADDR16_HI, # R_PPC_ADDR16_HA,R_PPC_ADDR16_LO, @@ -39,8 +44,7 @@ R_PPC_ADDR16_HI R_PPC_ADDR16_HA R_PPC_RELATIVE R_PPC_NONE' | - grep -E -v '<R_PPC64_ADDR64[[:space:]]+mach_' | - grep -E -v '<R_PPC64_ADDR64[[:space:]]+__crc_' + ([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat) )
if [ -z "$bad_relocs" ]; then