scripts/faddr2line: Fix overlapping text section failures
authorJosh Poimboeuf <jpoimboe@kernel.org>
Thu, 12 May 2022 19:05:27 +0000 (12:05 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 9 Jun 2022 08:22:57 +0000 (10:22 +0200)
[ 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

index 6c6439f..0e6268d 100755 (executable)
 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