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43e76cd368
Commit 8580ac9404 ("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
63 lines
1.6 KiB
Bash
Executable File
63 lines
1.6 KiB
Bash
Executable File
#!/bin/sh
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# SPDX-License-Identifier: GPL-2.0-or-later
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# Copyright © 2015 IBM Corporation
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# This script checks the relocations of a vmlinux for "suspicious"
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# relocations.
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# based on relocs_check.pl
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# Copyright © 2009 IBM Corporation
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if [ $# -lt 3 ]; then
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echo "$0 [path to objdump] [path to nm] [path to vmlinux]" 1>&2
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exit 1
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fi
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# Have Kbuild supply the path to objdump and nm so we handle cross compilation.
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objdump="$1"
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nm="$2"
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vmlinux="$3"
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# Remove from the bad relocations those that match an undefined weak symbol
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# which will result in an absolute relocation to 0.
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# Weak unresolved symbols are of that form in nm output:
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# " w _binary__btf_vmlinux_bin_end"
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undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')
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bad_relocs=$(
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$objdump -R "$vmlinux" |
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# Only look at relocation lines.
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grep -E '\<R_' |
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# These relocations are okay
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# On PPC64:
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# R_PPC64_RELATIVE, R_PPC64_NONE
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# On PPC:
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# R_PPC_RELATIVE, R_PPC_ADDR16_HI,
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# R_PPC_ADDR16_HA,R_PPC_ADDR16_LO,
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# R_PPC_NONE
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grep -F -w -v 'R_PPC64_RELATIVE
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R_PPC64_NONE
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R_PPC_ADDR16_LO
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R_PPC_ADDR16_HI
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R_PPC_ADDR16_HA
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R_PPC_RELATIVE
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R_PPC_NONE' |
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([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat)
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)
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if [ -z "$bad_relocs" ]; then
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exit 0
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fi
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num_bad=$(echo "$bad_relocs" | wc -l)
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echo "WARNING: $num_bad bad relocations"
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echo "$bad_relocs"
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# If we see this type of relocation it's an idication that
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# we /may/ be using an old version of binutils.
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if echo "$bad_relocs" | grep -q -F -w R_PPC64_UADDR64; then
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echo "WARNING: You need at least binutils >= 2.19 to build a CONFIG_RELOCATABLE kernel"
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fi
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