Messages in this thread | | | From | Kaiwan N Billimoria <> | Date | Fri, 13 May 2022 08:52:45 +0530 | Subject | Re: [PATCH] scripts/faddr2line: Fix overlapping text section failures |
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Works perfectly! Thanks Josh, awaiting the merge into mainline ...
On Fri, May 13, 2022 at 12:35 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote: > > 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> > --- > 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 > -- > 2.34.1 >
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