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    Subject[PATCH 5.18 426/879] scripts/faddr2line: Fix overlapping text section failures
    Date
    From: Josh Poimboeuf <jpoimboe@kernel.org>

    [ Upstream commit 1d1a0e7c5100d332583e20b40aa8c0a8ed3d7849 ]

    There have been some recent reports of faddr2line failures:

    $ scripts/faddr2line sound/soundcore.ko sound_devnode+0x5/0x35
    bad symbol size: base: 0x0000000000000000 end: 0x0000000000000000

    $ ./scripts/faddr2line vmlinux.o enter_from_user_mode+0x24
    bad symbol size: base: 0x0000000000005fe0 end: 0x0000000000005fe0

    The problem is that faddr2line is based on 'nm', which has a major
    limitation: it doesn't know how to distinguish between different text
    sections. So if an offset exists in multiple text sections in the
    object, it may fail.

    Rewrite faddr2line to be section-aware, by basing it on readelf.

    Fixes: 67326666e2d4 ("scripts: add script for translating stack dump function offsets")
    Reported-by: Kaiwan N Billimoria <kaiwan.billimoria@gmail.com>
    Reported-by: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
    Link: https://lore.kernel.org/r/29ff99f86e3da965b6e46c1cc2d72ce6528c17c3.1652382321.git.jpoimboe@kernel.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    scripts/faddr2line | 150 +++++++++++++++++++++++++++++----------------
    1 file changed, 97 insertions(+), 53 deletions(-)

    diff --git a/scripts/faddr2line b/scripts/faddr2line
    index 6c6439f69a72..0e6268d59883 100755
    --- a/scripts/faddr2line
    +++ b/scripts/faddr2line
    @@ -44,17 +44,6 @@
    set -o errexit
    set -o nounset

    -READELF="${CROSS_COMPILE:-}readelf"
    -ADDR2LINE="${CROSS_COMPILE:-}addr2line"
    -SIZE="${CROSS_COMPILE:-}size"
    -NM="${CROSS_COMPILE:-}nm"
    -
    -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"
    -command -v ${SIZE} >/dev/null 2>&1 || die "size isn't installed"
    -command -v ${NM} >/dev/null 2>&1 || die "nm isn't installed"
    -
    usage() {
    echo "usage: faddr2line [--list] <object file> <func+offset> <func+offset>..." >&2
    exit 1
    @@ -69,6 +58,14 @@ die() {
    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
    @@ -76,7 +73,7 @@ die() {
    find_dir_prefix() {
    local objfile=$1

    - local start_kernel_addr=$(${READELF} -sW $objfile | awk '$8 == "start_kernel" {printf "0x%s", $2}')
    + local start_kernel_addr=$(${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)
    @@ -97,86 +94,133 @@ __faddr2line() {
    local dir_prefix=$3
    local print_warnings=$4

    - local func=${func_addr%+*}
    + local sym_name=${func_addr%+*}
    local offset=${func_addr#*+}
    offset=${offset%/*}
    - local size=
    - [[ $func_addr =~ "/" ]] && size=${func_addr#*/}
    + local user_size=
    + [[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}

    - if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then
    + if [[ -z $sym_name ]] || [[ -z $offset ]] || [[ $sym_name = $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.
    - file_end=$(${SIZE} -Ax $objfile | awk '$1 == ".text" {print $2}')
    - while read symbol; do
    - local fields=($symbol)
    - local sym_base=0x${fields[0]}
    - local sym_type=${fields[1]}
    - local sym_end=${fields[3]}
    -
    - # calculate the size
    - local sym_size=$(($sym_end - $sym_base))
    + # In rare cases there might be duplicates, in which case we print all
    + # matches.
    + while read line; do
    + local fields=($line)
    + local sym_addr=0x${fields[1]}
    + local sym_elf_size=${fields[2]}
    + local sym_sec=${fields[6]}
    +
    + # Get the section size:
    + local sec_size=$(${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: $sym_sec"
    + DONE=1
    + return
    + fi
    +
    + # Calculate the symbol size.
    + #
    + # Unfortunately we can't use the ELF size, because kallsyms
    + # also includes the padding bytes in its size calculation. For
    + # kallsyms, the size calculation is the distance between the
    + # symbol and the next symbol in a sorted list.
    + local sym_size
    + local cur_sym_addr
    + local found=0
    + while read line; do
    + local fields=($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: base: $sym_base end: $sym_end"
    + 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
    - local addr=$(($sym_base + $offset))
    + # Calculate the section address from user-supplied offset:
    + local addr=$(($sym_addr + $offset))
    if [[ -z $addr ]] || [[ $addr = 0 ]]; then
    - warn "bad address: $sym_base + $offset"
    + warn "bad address: $sym_addr + $offset"
    DONE=1
    return
    fi
    addr=0x$(printf %x $addr)

    - # weed out non-function symbols
    - if [[ $sym_type != t ]] && [[ $sym_type != T ]]; then
    - [[ $print_warnings = 1 ]] &&
    - echo "skipping $func address at $addr due to non-function symbol of type '$sym_type'"
    - continue
    - fi
    -
    - # if the user provided a size, make sure it matches the symbol's size
    - if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then
    + # 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 $func address at $addr due to size mismatch ($size != $sym_size)"
    + 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
    + # 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 $addr due to size mismatch ($offset > $sym_size)"
    + echo "skipping $sym_name address at $addr due to size mismatch ($offset > $sym_size)"
    continue
    fi

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

    - # pass real address to addr2line
    - echo "$func+$offset/$sym_size:"
    - local file_lines=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
    - [[ -z $file_lines ]] && return
    + echo "$sym_name+$offset/$sym_size:"

    + # Pass section address to addr2line and strip absolute paths
    + # from the output:
    + local output=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
    + [[ -z $output ]] && continue
    +
    + # Default output (non --list):
    if [[ $LIST = 0 ]]; then
    - echo "$file_lines" | while read -r line
    + echo "$output" | while read -r line
    do
    echo $line
    done
    DONE=1;
    - return
    + continue
    fi

    - # show each line with context
    - echo "$file_lines" | while read -r line
    + # For --list, show each line with its corresponding source code:
    + echo "$output" | while read -r line
    do
    echo
    echo $line
    @@ -184,12 +228,12 @@ __faddr2line() {
    n1=$[$n-5]
    n2=$[$n+5]
    f=$(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
    + ${AWK} 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
    done

    DONE=1

    - done < <(${NM} -n $objfile | awk -v fn=$func -v end=$file_end '$3 == fn { found=1; line=$0; start=$1; next } found == 1 { found=0; print line, "0x"$1 } END {if (found == 1) print line, end; }')
    + done < <(${READELF} --symbols --wide $objfile | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
    }

    [[ $# -lt 2 ]] && usage
    --
    2.35.1


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