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![Will Deacon](/assets/img/avatar_default.png)
Mapping symbols emitted in the readelf output can confuse the 'faddr2line' symbol size calculation, resulting in the erroneous rejection of valid offsets. This is especially prevalent when building an arm64 kernel with CONFIG_CFI_CLANG=y, where most functions are prefixed with a 32-bit data value in a '$d.n' section. For example: 447538: ffff800080014b80 548 FUNC GLOBAL DEFAULT 2 do_one_initcall 104: ffff800080014c74 0 NOTYPE LOCAL DEFAULT 2 $x.73 106: ffff800080014d30 0 NOTYPE LOCAL DEFAULT 2 $x.75 111: ffff800080014da4 0 NOTYPE LOCAL DEFAULT 2 $d.78 112: ffff800080014da8 0 NOTYPE LOCAL DEFAULT 2 $x.79 36: ffff800080014de0 200 FUNC LOCAL DEFAULT 2 run_init_process Adding a warning to do_one_initcall() results in: | WARNING: CPU: 0 PID: 1 at init/main.c:1236 do_one_initcall+0xf4/0x260 Which 'faddr2line' refuses to accept: $ ./scripts/faddr2line vmlinux do_one_initcall+0xf4/0x260 skipping do_one_initcall address at 0xffff800080014c74 due to size mismatch (0x260 != 0x224) no match for do_one_initcall+0xf4/0x260 Filter out these entries from readelf using a shell reimplementation of is_mapping_symbol(), so that the size of a symbol is calculated as a delta to the next symbol present in ksymtab. Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Will Deacon <will@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/r/20231002165750.1661-4-will@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
314 lines
8.6 KiB
Bash
Executable file
314 lines
8.6 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: $1" >&2
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exit 1
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}
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UTIL_SUFFIX=""
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if [[ "${LLVM:-}" == "" ]]; then
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UTIL_PREFIX=${CROSS_COMPILE:-}
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else
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UTIL_PREFIX=llvm-
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if [[ "${LLVM}" == *"/" ]]; then
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UTIL_PREFIX=${LLVM}${UTIL_PREFIX}
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elif [[ "${LLVM}" == "-"* ]]; then
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UTIL_SUFFIX=${LLVM}
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fi
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fi
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READELF="${UTIL_PREFIX}readelf${UTIL_SUFFIX}"
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ADDR2LINE="${UTIL_PREFIX}addr2line${UTIL_SUFFIX}"
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AWK="awk"
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GREP="grep"
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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 | sed 's/\[.*\]//' |
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${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 func_offset=${func_addr#*+}
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func_offset=${func_offset%/*}
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local user_size=
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local file_type
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local is_vmlinux=0
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[[ $func_addr =~ "/" ]] && user_size=${func_addr#*/}
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if [[ -z $sym_name ]] || [[ -z $func_offset ]] || [[ $sym_name = $func_addr ]]; then
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warn "bad func+offset $func_addr"
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DONE=1
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return
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fi
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# vmlinux uses absolute addresses in the section table rather than
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# section offsets.
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local file_type=$(${READELF} --file-header $objfile |
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${AWK} '$1 == "Type:" { print $2; exit }')
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if [[ $file_type = "EXEC" ]] || [[ $file_type == "DYN" ]]; then
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is_vmlinux=1
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fi
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# Go through each of the object's symbols which match the func name.
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# In rare cases there might be duplicates, in which case we print all
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# matches.
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while read line; do
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local fields=($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=${fields[6]}
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local sec_size
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local sec_name
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# Get the section size:
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sec_size=$(${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: $sym_sec"
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DONE=1
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return
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fi
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# Get the section name:
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sec_name=$(${READELF} --section-headers --wide $objfile |
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sed 's/\[ /\[/' |
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${AWK} -v sec=$sym_sec '$1 == "[" sec "]" { print $2; exit }')
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if [[ -z $sec_name ]]; then
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warn "bad section name: 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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# is_mapping_symbol(cur_sym_name)
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if [[ ${cur_sym_name} =~ ^(\.L|L0|\$) ]]; then
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continue
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fi
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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 | sed 's/\[.*\]//' | ${AWK} -v sec=$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 $sym_size)
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# Calculate the address from user-supplied offset:
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local addr=$(($sym_addr + $func_offset))
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if [[ -z $addr ]] || [[ $addr = 0 ]]; then
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warn "bad address: $sym_addr + $func_offset"
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DONE=1
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return
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fi
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addr=0x$(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 [[ $func_offset -gt $sym_size ]]; then
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[[ $print_warnings = 1 ]] &&
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echo "skipping $sym_name address at $addr due to size mismatch ($func_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+$func_offset/$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 args="--functions --pretty-print --inlines --exe=$objfile"
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[[ $is_vmlinux = 0 ]] && args="$args --section=$sec_name"
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local output=$(${ADDR2LINE} $args $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 | sed 's/\[.*\]//' | ${AWK} -v fn=$sym_name '$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 $objfile"
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shift
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${READELF} --section-headers --wide $objfile | ${GREP} -q '\.debug_info' || die "CONFIG_DEBUG_INFO not enabled"
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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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