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scripts/faddr2line: Fix overlapping text section failures
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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‎scripts/faddr2line

Lines changed: 97 additions & 53 deletions
Original file line numberDiff line numberDiff line change
@@ -44,17 +44,6 @@
4444
set -o errexit
4545
set -o nounset
4646

47-
READELF="${CROSS_COMPILE:-}readelf"
48-
ADDR2LINE="${CROSS_COMPILE:-}addr2line"
49-
SIZE="${CROSS_COMPILE:-}size"
50-
NM="${CROSS_COMPILE:-}nm"
51-
52-
command -v awk >/dev/null 2>&1 || die "awk isn't installed"
53-
command -v ${READELF} >/dev/null 2>&1 || die "readelf isn't installed"
54-
command -v ${ADDR2LINE} >/dev/null 2>&1 || die "addr2line isn't installed"
55-
command -v ${SIZE} >/dev/null 2>&1 || die "size isn't installed"
56-
command -v ${NM} >/dev/null 2>&1 || die "nm isn't installed"
57-
5847
usage() {
5948
echo "usage: faddr2line [--list] <object file> <func+offset> <func+offset>..." >&2
6049
exit 1
@@ -69,14 +58,22 @@ die() {
6958
exit 1
7059
}
7160

61+
READELF="${CROSS_COMPILE:-}readelf"
62+
ADDR2LINE="${CROSS_COMPILE:-}addr2line"
63+
AWK="awk"
64+
65+
command -v ${AWK} >/dev/null 2>&1 || die "${AWK} isn't installed"
66+
command -v ${READELF} >/dev/null 2>&1 || die "${READELF} isn't installed"
67+
command -v ${ADDR2LINE} >/dev/null 2>&1 || die "${ADDR2LINE} isn't installed"
68+
7269
# Try to figure out the source directory prefix so we can remove it from the
7370
# addr2line output. HACK ALERT: This assumes that start_kernel() is in
7471
# init/main.c! This only works for vmlinux. Otherwise it falls back to
7572
# printing the absolute path.
7673
find_dir_prefix() {
7774
local objfile=$1
7875

79-
local start_kernel_addr=$(${READELF} -sW $objfile | awk '$8 == "start_kernel" {printf "0x%s", $2}')
76+
local start_kernel_addr=$(${READELF} --symbols --wide $objfile | ${AWK} '$8 == "start_kernel" {printf "0x%s", $2}')
8077
[[ -z $start_kernel_addr ]] && return
8178

8279
local file_line=$(${ADDR2LINE} -e $objfile $start_kernel_addr)
@@ -97,99 +94,146 @@ __faddr2line() {
9794
local dir_prefix=$3
9895
local print_warnings=$4
9996

100-
local func=${func_addr%+*}
97+
local sym_name=${func_addr%+*}
10198
local offset=${func_addr#*+}
10299
offset=${offset%/*}
103-
local size=
104-
[[ $func_addr =~ "/" ]] && size=${func_addr#*/}
100+
local user_size=
101+
[[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}
105102

106-
if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then
103+
if [[ -z $sym_name ]] || [[ -z $offset ]] || [[ $sym_name = $func_addr ]]; then
107104
warn "bad func+offset $func_addr"
108105
DONE=1
109106
return
110107
fi
111108

112109
# Go through each of the object's symbols which match the func name.
113-
# In rare cases there might be duplicates.
114-
file_end=$(${SIZE} -Ax $objfile | awk '$1 == ".text" {print $2}')
115-
while read symbol; do
116-
local fields=($symbol)
117-
local sym_base=0x${fields[0]}
118-
local sym_type=${fields[1]}
119-
local sym_end=${fields[3]}
120-
121-
# calculate the size
122-
local sym_size=$(($sym_end - $sym_base))
110+
# In rare cases there might be duplicates, in which case we print all
111+
# matches.
112+
while read line; do
113+
local fields=($line)
114+
local sym_addr=0x${fields[1]}
115+
local sym_elf_size=${fields[2]}
116+
local sym_sec=${fields[6]}
117+
118+
# Get the section size:
119+
local sec_size=$(${READELF} --section-headers --wide $objfile |
120+
sed 's/\[ /\[/' |
121+
${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print "0x" $6; exit }')
122+
123+
if [[ -z $sec_size ]]; then
124+
warn "bad section size: section: $sym_sec"
125+
DONE=1
126+
return
127+
fi
128+
129+
# Calculate the symbol size.
130+
#
131+
# Unfortunately we can't use the ELF size, because kallsyms
132+
# also includes the padding bytes in its size calculation. For
133+
# kallsyms, the size calculation is the distance between the
134+
# symbol and the next symbol in a sorted list.
135+
local sym_size
136+
local cur_sym_addr
137+
local found=0
138+
while read line; do
139+
local fields=($line)
140+
cur_sym_addr=0x${fields[1]}
141+
local cur_sym_elf_size=${fields[2]}
142+
local cur_sym_name=${fields[7]:-}
143+
144+
if [[ $cur_sym_addr = $sym_addr ]] &&
145+
[[ $cur_sym_elf_size = $sym_elf_size ]] &&
146+
[[ $cur_sym_name = $sym_name ]]; then
147+
found=1
148+
continue
149+
fi
150+
151+
if [[ $found = 1 ]]; then
152+
sym_size=$(($cur_sym_addr - $sym_addr))
153+
[[ $sym_size -lt $sym_elf_size ]] && continue;
154+
found=2
155+
break
156+
fi
157+
done < <(${READELF} --symbols --wide $objfile | ${AWK} -v sec=$sym_sec '$7 == sec' | sort --key=2)
158+
159+
if [[ $found = 0 ]]; then
160+
warn "can't find symbol: sym_name: $sym_name sym_sec: $sym_sec sym_addr: $sym_addr sym_elf_size: $sym_elf_size"
161+
DONE=1
162+
return
163+
fi
164+
165+
# If nothing was found after the symbol, assume it's the last
166+
# symbol in the section.
167+
[[ $found = 1 ]] && sym_size=$(($sec_size - $sym_addr))
168+
123169
if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then
124-
warn "bad symbol size: base: $sym_base end: $sym_end"
170+
warn "bad symbol size: sym_addr: $sym_addr cur_sym_addr: $cur_sym_addr"
125171
DONE=1
126172
return
127173
fi
174+
128175
sym_size=0x$(printf %x $sym_size)
129176

130-
# calculate the address
131-
local addr=$(($sym_base + $offset))
177+
# Calculate the section address from user-supplied offset:
178+
local addr=$(($sym_addr + $offset))
132179
if [[ -z $addr ]] || [[ $addr = 0 ]]; then
133-
warn "bad address: $sym_base + $offset"
180+
warn "bad address: $sym_addr + $offset"
134181
DONE=1
135182
return
136183
fi
137184
addr=0x$(printf %x $addr)
138185

139-
# weed out non-function symbols
140-
if [[ $sym_type != t ]] && [[ $sym_type != T ]]; then
141-
[[ $print_warnings = 1 ]] &&
142-
echo "skipping $func address at $addr due to non-function symbol of type '$sym_type'"
143-
continue
144-
fi
145-
146-
# if the user provided a size, make sure it matches the symbol's size
147-
if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then
186+
# If the user provided a size, make sure it matches the symbol's size:
187+
if [[ -n $user_size ]] && [[ $user_size -ne $sym_size ]]; then
148188
[[ $print_warnings = 1 ]] &&
149-
echo "skipping $func address at $addr due to size mismatch ($size != $sym_size)"
189+
echo "skipping $sym_name address at $addr due to size mismatch ($user_size != $sym_size)"
150190
continue;
151191
fi
152192

153-
# make sure the provided offset is within the symbol's range
193+
# Make sure the provided offset is within the symbol's range:
154194
if [[ $offset -gt $sym_size ]]; then
155195
[[ $print_warnings = 1 ]] &&
156-
echo "skipping $func address at $addr due to size mismatch ($offset > $sym_size)"
196+
echo "skipping $sym_name address at $addr due to size mismatch ($offset > $sym_size)"
157197
continue
158198
fi
159199

160-
# separate multiple entries with a blank line
200+
# In case of duplicates or multiple addresses specified on the
201+
# cmdline, separate multiple entries with a blank line:
161202
[[ $FIRST = 0 ]] && echo
162203
FIRST=0
163204

164-
# pass real address to addr2line
165-
echo "$func+$offset/$sym_size:"
166-
local file_lines=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
167-
[[ -z $file_lines ]] && return
205+
echo "$sym_name+$offset/$sym_size:"
168206

207+
# Pass section address to addr2line and strip absolute paths
208+
# from the output:
209+
local output=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
210+
[[ -z $output ]] && continue
211+
212+
# Default output (non --list):
169213
if [[ $LIST = 0 ]]; then
170-
echo "$file_lines" | while read -r line
214+
echo "$output" | while read -r line
171215
do
172216
echo $line
173217
done
174218
DONE=1;
175-
return
219+
continue
176220
fi
177221

178-
# show each line with context
179-
echo "$file_lines" | while read -r line
222+
# For --list, show each line with its corresponding source code:
223+
echo "$output" | while read -r line
180224
do
181225
echo
182226
echo $line
183227
n=$(echo $line | sed 's/.*:\([0-9]\+\).*/\1/g')
184228
n1=$[$n-5]
185229
n2=$[$n+5]
186230
f=$(echo $line | sed 's/.*at \(.\+\):.*/\1/g')
187-
awk 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
231+
${AWK} 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
188232
done
189233

190234
DONE=1
191235

192-
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"$1 } END {if (found == 1) print line, end; }')
236+
done < <(${READELF} --symbols --wide $objfile | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
193237
}
194238

195239
[[ $# -lt 2 ]] && usage

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