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![Josh Poimboeuf](/assets/img/avatar_default.png)
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: 67326666e2
("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
266 lines
7.4 KiB
Bash
Executable file
266 lines
7.4 KiB
Bash
Executable file
#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0
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#
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# Translate stack dump function offsets.
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#
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# addr2line doesn't work with KASLR addresses. This works similarly to
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# addr2line, but instead takes the 'func+0x123' format as input:
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#
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# $ ./scripts/faddr2line ~/k/vmlinux meminfo_proc_show+0x5/0x568
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# meminfo_proc_show+0x5/0x568:
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# meminfo_proc_show at fs/proc/meminfo.c:27
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#
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# If the address is part of an inlined function, the full inline call chain is
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# printed:
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#
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# $ ./scripts/faddr2line ~/k/vmlinux native_write_msr+0x6/0x27
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# native_write_msr+0x6/0x27:
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# arch_static_branch at arch/x86/include/asm/msr.h:121
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# (inlined by) static_key_false at include/linux/jump_label.h:125
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# (inlined by) native_write_msr at arch/x86/include/asm/msr.h:125
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#
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# The function size after the '/' in the input is optional, but recommended.
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# It's used to help disambiguate any duplicate symbol names, which can occur
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# rarely. If the size is omitted for a duplicate symbol then it's possible for
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# multiple code sites to be printed:
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#
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# $ ./scripts/faddr2line ~/k/vmlinux raw_ioctl+0x5
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# raw_ioctl+0x5/0x20:
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# raw_ioctl at drivers/char/raw.c:122
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#
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# raw_ioctl+0x5/0xb1:
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# raw_ioctl at net/ipv4/raw.c:876
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#
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# Multiple addresses can be specified on a single command line:
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#
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# $ ./scripts/faddr2line ~/k/vmlinux type_show+0x10/45 free_reserved_area+0x90
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# type_show+0x10/0x2d:
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# type_show at drivers/video/backlight/backlight.c:213
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#
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# free_reserved_area+0x90/0x123:
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# free_reserved_area at mm/page_alloc.c:6429 (discriminator 2)
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set -o errexit
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set -o nounset
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usage() {
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echo "usage: faddr2line [--list] <object file> <func+offset> <func+offset>..." >&2
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exit 1
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}
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warn() {
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echo "$1" >&2
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}
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die() {
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echo "ERROR: $1" >&2
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exit 1
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}
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READELF="${CROSS_COMPILE:-}readelf"
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ADDR2LINE="${CROSS_COMPILE:-}addr2line"
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AWK="awk"
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command -v ${AWK} >/dev/null 2>&1 || die "${AWK} isn't installed"
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command -v ${READELF} >/dev/null 2>&1 || die "${READELF} isn't installed"
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command -v ${ADDR2LINE} >/dev/null 2>&1 || die "${ADDR2LINE} isn't installed"
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# Try to figure out the source directory prefix so we can remove it from the
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# addr2line output. HACK ALERT: This assumes that start_kernel() is in
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# init/main.c! This only works for vmlinux. Otherwise it falls back to
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# printing the absolute path.
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find_dir_prefix() {
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local objfile=$1
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local start_kernel_addr=$(${READELF} --symbols --wide $objfile | ${AWK} '$8 == "start_kernel" {printf "0x%s", $2}')
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[[ -z $start_kernel_addr ]] && return
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local file_line=$(${ADDR2LINE} -e $objfile $start_kernel_addr)
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[[ -z $file_line ]] && return
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local prefix=${file_line%init/main.c:*}
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if [[ -z $prefix ]] || [[ $prefix = $file_line ]]; then
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return
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fi
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DIR_PREFIX=$prefix
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return 0
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}
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__faddr2line() {
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local objfile=$1
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local func_addr=$2
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local dir_prefix=$3
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local print_warnings=$4
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local sym_name=${func_addr%+*}
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local offset=${func_addr#*+}
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offset=${offset%/*}
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local user_size=
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[[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}
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if [[ -z $sym_name ]] || [[ -z $offset ]] || [[ $sym_name = $func_addr ]]; then
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warn "bad func+offset $func_addr"
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DONE=1
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return
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fi
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# Go through each of the object's symbols which match the func name.
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# In rare cases there might be duplicates, in which case we print all
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# matches.
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while read line; do
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local fields=($line)
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local sym_addr=0x${fields[1]}
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local sym_elf_size=${fields[2]}
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local sym_sec=${fields[6]}
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# Get the section size:
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local sec_size=$(${READELF} --section-headers --wide $objfile |
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sed 's/\[ /\[/' |
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${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print "0x" $6; exit }')
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if [[ -z $sec_size ]]; then
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warn "bad section size: section: $sym_sec"
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DONE=1
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return
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fi
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# Calculate the symbol size.
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#
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# Unfortunately we can't use the ELF size, because kallsyms
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# also includes the padding bytes in its size calculation. For
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# kallsyms, the size calculation is the distance between the
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# symbol and the next symbol in a sorted list.
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local sym_size
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local cur_sym_addr
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local found=0
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while read line; do
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local fields=($line)
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cur_sym_addr=0x${fields[1]}
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local cur_sym_elf_size=${fields[2]}
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local cur_sym_name=${fields[7]:-}
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if [[ $cur_sym_addr = $sym_addr ]] &&
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[[ $cur_sym_elf_size = $sym_elf_size ]] &&
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[[ $cur_sym_name = $sym_name ]]; then
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found=1
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continue
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fi
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if [[ $found = 1 ]]; then
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sym_size=$(($cur_sym_addr - $sym_addr))
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[[ $sym_size -lt $sym_elf_size ]] && continue;
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found=2
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break
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fi
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done < <(${READELF} --symbols --wide $objfile | ${AWK} -v sec=$sym_sec '$7 == sec' | sort --key=2)
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if [[ $found = 0 ]]; then
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warn "can't find symbol: sym_name: $sym_name sym_sec: $sym_sec sym_addr: $sym_addr sym_elf_size: $sym_elf_size"
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DONE=1
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return
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fi
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# If nothing was found after the symbol, assume it's the last
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# symbol in the section.
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[[ $found = 1 ]] && sym_size=$(($sec_size - $sym_addr))
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if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then
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warn "bad symbol size: sym_addr: $sym_addr cur_sym_addr: $cur_sym_addr"
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DONE=1
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return
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fi
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sym_size=0x$(printf %x $sym_size)
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# Calculate the section address from user-supplied offset:
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local addr=$(($sym_addr + $offset))
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if [[ -z $addr ]] || [[ $addr = 0 ]]; then
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warn "bad address: $sym_addr + $offset"
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DONE=1
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return
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fi
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addr=0x$(printf %x $addr)
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# If the user provided a size, make sure it matches the symbol's size:
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if [[ -n $user_size ]] && [[ $user_size -ne $sym_size ]]; then
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[[ $print_warnings = 1 ]] &&
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echo "skipping $sym_name address at $addr due to size mismatch ($user_size != $sym_size)"
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continue;
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fi
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# Make sure the provided offset is within the symbol's range:
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if [[ $offset -gt $sym_size ]]; then
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[[ $print_warnings = 1 ]] &&
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echo "skipping $sym_name address at $addr due to size mismatch ($offset > $sym_size)"
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continue
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fi
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# In case of duplicates or multiple addresses specified on the
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# cmdline, separate multiple entries with a blank line:
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[[ $FIRST = 0 ]] && echo
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FIRST=0
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echo "$sym_name+$offset/$sym_size:"
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# Pass section address to addr2line and strip absolute paths
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# from the output:
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local output=$(${ADDR2LINE} -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;")
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[[ -z $output ]] && continue
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# Default output (non --list):
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if [[ $LIST = 0 ]]; then
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echo "$output" | while read -r line
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do
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echo $line
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done
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DONE=1;
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continue
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fi
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# For --list, show each line with its corresponding source code:
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echo "$output" | while read -r line
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do
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echo
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echo $line
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n=$(echo $line | sed 's/.*:\([0-9]\+\).*/\1/g')
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n1=$[$n-5]
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n2=$[$n+5]
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f=$(echo $line | sed 's/.*at \(.\+\):.*/\1/g')
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${AWK} 'NR>=strtonum("'$n1'") && NR<=strtonum("'$n2'") { if (NR=='$n') printf(">%d<", NR); else printf(" %d ", NR); printf("\t%s\n", $0)}' $f
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done
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DONE=1
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done < <(${READELF} --symbols --wide $objfile | ${AWK} -v fn=$sym_name '$4 == "FUNC" && $8 == fn')
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}
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[[ $# -lt 2 ]] && usage
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objfile=$1
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LIST=0
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[[ "$objfile" == "--list" ]] && LIST=1 && shift && objfile=$1
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[[ ! -f $objfile ]] && die "can't find objfile $objfile"
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shift
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DIR_PREFIX=supercalifragilisticexpialidocious
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find_dir_prefix $objfile
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FIRST=1
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while [[ $# -gt 0 ]]; do
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func_addr=$1
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shift
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# print any matches found
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DONE=0
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__faddr2line $objfile $func_addr $DIR_PREFIX 0
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# if no match was found, print warnings
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if [[ $DONE = 0 ]]; then
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__faddr2line $objfile $func_addr $DIR_PREFIX 1
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warn "no match for $func_addr"
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fi
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done
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