scripts/faddr2line

#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
#
# 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

usage() {
echo "usage: faddr2line [--list] <object file> <func+offset> <func+offset>..." >&2
exit 1
}

warn() {
echo "$1" >&2
}

die() {
echo "ERROR: $1" >&2
exit 1
}

READELF="${CROSS_COMPILE:-}readelf"
ADDR2LINE="${CROSS_COMPILE:-}addr2line"
AWK="awk"

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"

# 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
# init/main.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} --symbols --wide $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 sym_name=${func_addr%+*}
local func_offset=${func_addr#*+}
func_offset=${func_offset%/*}
local user_size=
local file_type
local is_vmlinux=0
[[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}

if [[ -z $sym_name ]] || [[ -z $func_offset ]] || [[ $sym_name = $func_addr ]]; then
warn "bad func+offset $func_addr"
DONE=1
return
fi

# vmlinux uses absolute addresses in the section table rather than
# section offsets.
local file_type=$(${READELF} --file-header $objfile |
${AWK} '$1 == "Type:" { print $2; exit }')
if [[ $file_type = "EXEC" ]] || [[ $file_type == "DYN" ]]; then
is_vmlinux=1
fi

# Go through each of the object's symbols which match the func name.
# In rare cases there might be duplicates, in which case we print all
# matches.
while read line; do
local fields=($line)
local sym_addr=0x${fields[1]}
local sym_elf_size=${fields[2]}
local sym_sec=${fields[6]}
local sec_size
local sec_name

# Get the section size:
sec_size=$(${READELF} --section-headers --wide $objfile |
sed 's/\[ /\[/' |
${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print "0x" $6; exit }')

if [[ -z $sec_size ]]; then
warn "bad section size: section: $sym_sec"
DONE=1
return
fi

# Get the section name:
sec_name=$(${READELF} --section-headers --wide $objfile |
sed 's/\[ /\[/' |
${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print $2; exit }')

if [[ -z $sec_name ]]; then
warn "bad section name: section: $sym_sec"
DONE=1
return
fi

# Calculate the symbol size.
#
# Unfortunately we can't use the ELF size, because kallsyms
# also includes the padding bytes in its size calculation. For
# kallsyms, the size calculation is the distance between the
# symbol and the next symbol in a sorted list.
local sym_size
local cur_sym_addr
local found=0
while read line; do
local fields=($line)
cur_sym_addr=0x${fields[1]}
local cur_sym_elf_size=${fields[2]}
local cur_sym_name=${fields[7]:-}

if [[ $cur_sym_addr = $sym_addr ]] &&
 [[ $cur_sym_elf_size = $sym_elf_size ]] &&
 [[ $cur_sym_name = $sym_name ]]; then
found=1
continue
fi

if [[ $found = 1 ]]; then
sym_size=$(($cur_sym_addr - $sym_addr))
[[ $sym_size -lt $sym_elf_size ]] && continue;
found=2
break
fi
done < <(${READELF} --symbols --wide $objfile | ${AWK} -v sec=$sym_sec '$7 == sec' | sort --key=2)

if [[ $found = 0 ]]; then
warn "can't find symbol: sym_name: $sym_name sym_sec: $sym_sec sym_addr: $sym_addr sym_elf_size: $sym_elf_size"
DONE=1
return
fi

# If nothing was found after the symbol, assume it's the last
# symbol in the section.
[[ $found = 1 ]] && sym_size=$(($sec_size - $sym_addr))

if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then
warn "bad symbol size: sym_addr: $sym_addr cur_sym_addr: $cur_sym_addr"
DONE=1
return
fi

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

# Calculate the address from user-supplied offset:
local addr=$(($sym_addr + $func_offset))
if [[ -z $addr ]] || [[ $addr = 0 ]]; then
warn "bad address: $sym_addr + $func_offset"
DONE=1
return
fi
addr=0x$(printf %x $addr)

# If the user provided a size, make sure it matches the symbol's size:
if [[ -n $user_size ]] && [[ $user_size -ne $sym_size ]]; then
[[ $print_warnings = 1 ]] &&
echo "skipping $sym_name address at $addr due to size mismatch ($user_size != $sym_size)"
continue;
fi

# Make sure the provided offset is within the symbol's range:
if [[ $func_offset -gt $sym_size ]]; then
[[ $print_warnings = 1 ]] &&
echo "skipping $sym_name address at $addr due to size mismatch ($func_offset > $sym_size)"
continue
fi

# In case of duplicates or multiple addresses specified on the
# cmdline, separate multiple entries with a blank line:
[[ $FIRST = 0 ]] && echo
FIRST=0

echo "$sym_name+$func_offset/$sym_size:"

# Pass section address to addr2line and strip absolute paths
# from the output:
local args="--functions --pretty-print --inlines --exe=$objfile"
[[ $is_vmlinux = 0 ]] && args="$args --section=$sec_name"
local output=$(${ADDR2LINE} $args $addr | sed "s; $dir_prefix\(\./\)*; ;")
[[ -z $output ]] && continue

# Default output (non --list):
if [[ $LIST = 0 ]]; then
echo "$output" | while read -r line
do
echo $line
done
DONE=1;
continue
fi

# For --list, show each line with its corresponding source code:
echo "$output" | while read -r line
do
echo
echo $line
n=$(echo $line | sed 's/.*:\([0-9]\+\).*/\1/g')
n1=$[$n-5]
n2=$[$n+5]
f=$(echo $line | sed 's/.*at \(.\+\):.*/\1/g')
${AWK} 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
done

DONE=1

done < <(${READELF} --symbols --wide $objfile | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
}

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

objfile=$1

LIST=0
[[ "$objfile" == "--list" ]] && LIST=1 && shift && 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