linux/arch/powerpc/tools/unrel_branch_check.sh

#!/bin/bash
# Copyright © 2016 IBM Corporation
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version
# 2 of the License, or (at your option) any later version.
#
# This script checks the relocations of a vmlinux for "suspicious"
# branches from unrelocated code (head_64.S code).

# Turn this on if you want more debug output:
# set -x

# Have Kbuild supply the path to objdump so we handle cross compilation.
objdump="$1"
vmlinux="$2"

#__end_interrupts should be located within the first 64K
kstart=0xc000000000000000
printf -v kend '0x%x' $(( kstart + 0x10000 ))

end_intr=0x$(
$objdump -R -d --start-address="$kstart" --stop-address="$kend" "$vmlinux" |
awk '$2 == "<__end_interrupts>:" { print $1 }'
)

BRANCHES=$(
$objdump -R -D --no-show-raw-insn --start-address="$kstart" --stop-address="$end_intr" "$vmlinux" |
sed -E -n '
# match lines that start with a kernel address
/^c[0-9a-f]*:\s*b/ {
	# drop a target that we do not care about
	/\<__start_initialization_multiplatform>/d
	# drop branches via ctr or lr
	/\<b.?.?(ct|l)r/d
	# cope with some differences between Clang and GNU objdumps
	s/\<bt.?\s*[[:digit:]]+,/beq/
	s/\<bf.?\s*[[:digit:]]+,/bne/
	# tidy up
	s/\s0x/ /
	s/://
	# format for the loop below
	s/^(\S+)\s+(\S+)\s+(\S+)\s*(\S*).*$/\1:\2:0x\3:\4/
	# strip out condition registers
	s/:0xcr[0-7],/:0x/
	p
}'
)

for tuple in $BRANCHES; do
	from=$(echo "$tuple" | cut -d':' -f1)
	branch=$(echo "$tuple" | cut -d':' -f2)
	to=$(echo "$tuple" | cut -d':' -f3)
	sym=$(echo "$tuple" | cut -d':' -f4)

	if (( to > end_intr )); then
		if [ -z "$bad_branches" ]; then
			echo "WARNING: Unrelocated relative branches"
			bad_branches="yes"
		fi
		echo "$from $branch-> $to $sym"
	fi
done

if [ -z "$bad_branches" ]; then
	exit 0
fi