android_kernel_xiaomi_sm8350/arch/powerpc/tools/relocs_check.sh
Alexandre Ghiti a531e6ba85 powerpc: Do not consider weak unresolved symbol relocations as bad
[ 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>
2020-02-24 08:37:00 +01:00

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#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-or-later
# Copyright © 2015 IBM Corporation
# This script checks the relocations of a vmlinux for "suspicious"
# relocations.
# based on relocs_check.pl
# Copyright © 2009 IBM Corporation
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 and nm so we handle cross compilation.
objdump="$1"
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" |
# Only look at relocation lines.
grep -E '\<R_' |
# These relocations are okay
# On PPC64:
# R_PPC64_RELATIVE, R_PPC64_NONE
# On PPC:
# R_PPC_RELATIVE, R_PPC_ADDR16_HI,
# R_PPC_ADDR16_HA,R_PPC_ADDR16_LO,
# R_PPC_NONE
grep -F -w -v 'R_PPC64_RELATIVE
R_PPC64_NONE
R_PPC_ADDR16_LO
R_PPC_ADDR16_HI
R_PPC_ADDR16_HA
R_PPC_RELATIVE
R_PPC_NONE' |
([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat)
)
if [ -z "$bad_relocs" ]; then
exit 0
fi
num_bad=$(echo "$bad_relocs" | wc -l)
echo "WARNING: $num_bad bad relocations"
echo "$bad_relocs"
# If we see this type of relocation it's an idication that
# we /may/ be using an old version of binutils.
if echo "$bad_relocs" | grep -q -F -w R_PPC64_UADDR64; then
echo "WARNING: You need at least binutils >= 2.19 to build a CONFIG_RELOCATABLE kernel"
fi