scripts: add script for translating stack dump function offsets

#!/bin/bash

#

# Translate stack dump function offsets.

#

# addr2line doesn't work with KASLR addresses.  This works similarly to

# addr2line, but instead takes the 'func+0x123' format as input:

#

#   $ ./scripts/faddr2line ~/k/vmlinux meminfo_proc_show+0x5/0x568

#   meminfo_proc_show+0x5/0x568:

#   meminfo_proc_show at fs/proc/meminfo.c:27

#

# If the address is part of an inlined function, the full inline call chain is

# printed:

#

#   $ ./scripts/faddr2line ~/k/vmlinux native_write_msr+0x6/0x27

#   native_write_msr+0x6/0x27:

#   arch_static_branch at arch/x86/include/asm/msr.h:121

#    (inlined by) static_key_false at include/linux/jump_label.h:125

#    (inlined by) native_write_msr at arch/x86/include/asm/msr.h:125

#

# The function size after the '/' in the input is optional, but recommended.

# It's used to help disambiguate any duplicate symbol names, which can occur

# rarely.  If the size is omitted for a duplicate symbol then it's possible for

# multiple code sites to be printed:

#

#   $ ./scripts/faddr2line ~/k/vmlinux raw_ioctl+0x5

#   raw_ioctl+0x5/0x20:

#   raw_ioctl at drivers/char/raw.c:122

#

#   raw_ioctl+0x5/0xb1:

#   raw_ioctl at net/ipv4/raw.c:876

#

# Multiple addresses can be specified on a single command line:

#

#   $ ./scripts/faddr2line ~/k/vmlinux type_show+0x10/45 free_reserved_area+0x90

#   type_show+0x10/0x2d:

#   type_show at drivers/video/backlight/backlight.c:213

#

#   free_reserved_area+0x90/0x123:

#   free_reserved_area at mm/page_alloc.c:6429 (discriminator 2)

set -o errexit

set -o nounset

command -v awk >/dev/null 2>&1 || die "awk isn't installed"

command -v readelf >/dev/null 2>&1 || die "readelf isn't installed"

command -v addr2line >/dev/null 2>&1 || die "addr2line isn't installed"

usage() {

	echo "usage: faddr2line <object file> <func+offset> <func+offset>..." >&2

	exit 1

}

warn() {

	echo "$1" >&2

}

die() {

	echo "ERROR: $1" >&2

	exit 1

}

# Try to figure out the source directory prefix so we can remove it from the

# addr2line output.  HACK ALERT: This assumes that start_kernel() is in

# kernel/init.c!  This only works for vmlinux.  Otherwise it falls back to

# printing the absolute path.

find_dir_prefix() {

	local objfile=$1

	local start_kernel_addr=$(readelf -sW $objfile | awk '$8 == "start_kernel" {printf "0x%s", $2}')

	[[ -z $start_kernel_addr ]] && return

	local file_line=$(addr2line -e $objfile $start_kernel_addr)

	[[ -z $file_line ]] && return

	local prefix=${file_line%init/main.c:*}

	if [[ -z $prefix ]] || [[ $prefix = $file_line ]]; then

		return

	fi

	DIR_PREFIX=$prefix

	return 0

}

__faddr2line() {

	local objfile=$1

	local func_addr=$2

	local dir_prefix=$3

	local print_warnings=$4

	local func=${func_addr%+*}

	local offset=${func_addr#*+}

	offset=${offset%/*}

	local size=

	[[ $func_addr =~ "/" ]] && size=${func_addr#*/}

	if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then

		warn "bad func+offset $func_addr"

		DONE=1

		return

	fi

	# Go through each of the object's symbols which match the func name.

	# In rare cases there might be duplicates.

	while read symbol; do

		local fields=($symbol)

		local sym_base=0x${fields[1]}

		local sym_size=${fields[2]}

		local sym_type=${fields[3]}

		# calculate the address

		local addr=$(($sym_base + $offset))

		if [[ -z $addr ]] || [[ $addr = 0 ]]; then

			warn "bad address: $sym_base + $offset"

			DONE=1

			return

		fi

		local hexaddr=0x$(printf %x $addr)

		# weed out non-function symbols

		if [[ $sym_type != "FUNC" ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to non-function symbol"

			continue

		fi

		# if the user provided a size, make sure it matches the symbol's size

		if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to size mismatch ($size != $sym_size)"

			continue;

		fi

		# make sure the provided offset is within the symbol's range

		if [[ $offset -gt $sym_size ]]; then

			[[ $print_warnings = 1 ]] &&

				echo "skipping $func address at $hexaddr due to size mismatch ($offset > $sym_size)"

			continue

		fi

		# separate multiple entries with a blank line

		[[ $FIRST = 0 ]] && echo

		FIRST=0

		local hexsize=0x$(printf %x $sym_size)

		echo "$func+$offset/$hexsize:"

		addr2line -fpie $objfile $hexaddr | sed "s;$dir_prefix;;"

		DONE=1

	done < <(readelf -sW $objfile | awk -v f=$func '$8 == f {print}')

}

[[ $# -lt 2 ]] && usage

objfile=$1

[[ ! -f $objfile ]] && die "can't find objfile $objfile"

shift

DIR_PREFIX=supercalifragilisticexpialidocious

find_dir_prefix $objfile

FIRST=1

while [[ $# -gt 0 ]]; do

	func_addr=$1

	shift

	# print any matches found

	DONE=0

	__faddr2line $objfile $func_addr $DIR_PREFIX 0

	# if no match was found, print warnings

	if [[ $DONE = 0 ]]; then

		__faddr2line $objfile $func_addr $DIR_PREFIX 1

		warn "no match for $func_addr"

	fi

done