#!/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