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scripts/faddr2line: Fix overlapping text section failures
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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: 6732666 ("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
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@jpoimboe
jpoimboe committed May 12, 2022
1 parent 21e3502 commit 1d1a0e7
Showing 1 changed file with 97 additions and 53 deletions.
150 changes: 97 additions & 53 deletions scripts/faddr2line
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -69,14 +58,22 @@ 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
# printing the absolute path.
find_dir_prefix() {
local objfile=$1

local start_kernel_addr=$(${READELF} -sW $objfile | awk '$8 == "start_kernel" {printf "0x%s", $2}')
local start_kernel_addr=$(${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)
Expand All @@ -97,99 +94,146 @@ __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 $line
n=$(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
${AWK} 'NR>=strtonum("'$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
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