linux/scripts/faddr2line
Josh Poimboeuf efdb4167e6 scripts/faddr2line: Fix "size mismatch" error
I'm not sure how we missed this problem before.  When I take a function
address and size from an oops and give it to faddr2line, it usually
complains about a size mismatch:

  $ scripts/faddr2line ~/k/vmlinux write_sysrq_trigger+0x51/0x60
  skipping write_sysrq_trigger address at 0xffffffff815731a1 due to size mismatch (0x60 != 83)
  no match for write_sysrq_trigger+0x51/0x60

The problem is caused by differences in how kallsyms and faddr2line
determine a function's size.

kallsyms calculates a function's size by parsing the output of 'nm -n'
and subtracting the next function's address from the current function's
address.  This means that nop instructions after the end of the function
are included in the size.

In contrast, faddr2line reads the size from the symbol table, which does
*not* include the ending nops in the function's size.

Change faddr2line to calculate the size from the output of 'nm -n' to be
consistent with kallsyms and oops outputs.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/bd313ed7c4003f6b1fda63e825325c44a9d837de.1477405374.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-25 18:40:37 +02:00

187 lines
5.1 KiB
Bash
Executable File

#!/bin/bash
#
# Translate stack dump function offsets.
#
# addr2line doesn't work with KASLR addresses. This works similarly to
# addr2line, but instead takes the 'func+0x123' format as input:
#
# $ ./scripts/faddr2line ~/k/vmlinux meminfo_proc_show+0x5/0x568
# meminfo_proc_show+0x5/0x568:
# meminfo_proc_show at fs/proc/meminfo.c:27
#
# If the address is part of an inlined function, the full inline call chain is
# printed:
#
# $ ./scripts/faddr2line ~/k/vmlinux native_write_msr+0x6/0x27
# native_write_msr+0x6/0x27:
# arch_static_branch at arch/x86/include/asm/msr.h:121
# (inlined by) static_key_false at include/linux/jump_label.h:125
# (inlined by) native_write_msr at arch/x86/include/asm/msr.h:125
#
# The function size after the '/' in the input is optional, but recommended.
# It's used to help disambiguate any duplicate symbol names, which can occur
# rarely. If the size is omitted for a duplicate symbol then it's possible for
# multiple code sites to be printed:
#
# $ ./scripts/faddr2line ~/k/vmlinux raw_ioctl+0x5
# raw_ioctl+0x5/0x20:
# raw_ioctl at drivers/char/raw.c:122
#
# raw_ioctl+0x5/0xb1:
# raw_ioctl at net/ipv4/raw.c:876
#
# Multiple addresses can be specified on a single command line:
#
# $ ./scripts/faddr2line ~/k/vmlinux type_show+0x10/45 free_reserved_area+0x90
# type_show+0x10/0x2d:
# type_show at drivers/video/backlight/backlight.c:213
#
# free_reserved_area+0x90/0x123:
# free_reserved_area at mm/page_alloc.c:6429 (discriminator 2)
set -o errexit
set -o nounset
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"
usage() {
echo "usage: faddr2line <object file> <func+offset> <func+offset>..." >&2
exit 1
}
warn() {
echo "$1" >&2
}
die() {
echo "ERROR: $1" >&2
exit 1
}
# 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
# kernel/init.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}')
[[ -z $start_kernel_addr ]] && return
local file_line=$(addr2line -e $objfile $start_kernel_addr)
[[ -z $file_line ]] && return
local prefix=${file_line%init/main.c:*}
if [[ -z $prefix ]] || [[ $prefix = $file_line ]]; then
return
fi
DIR_PREFIX=$prefix
return 0
}
__faddr2line() {
local objfile=$1
local func_addr=$2
local dir_prefix=$3
local print_warnings=$4
local func=${func_addr%+*}
local offset=${func_addr#*+}
offset=${offset%/*}
local size=
[[ $func_addr =~ "/" ]] && size=${func_addr#*/}
if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then
warn "bad func+offset $func_addr"
DONE=1
return
fi
# Go through each of the object's symbols which match the func name.
# In rare cases there might be duplicates.
while read symbol; do
local fields=($symbol)
local sym_base=0x${fields[0]}
local sym_type=${fields[1]}
local sym_end=0x${fields[3]}
# calculate the size
local sym_size=$(($sym_end - $sym_base))
if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then
warn "bad symbol size: base: $sym_base end: $sym_end"
DONE=1
return
fi
sym_size=0x$(printf %x $sym_size)
# calculate the address
local addr=$(($sym_base + $offset))
if [[ -z $addr ]] || [[ $addr = 0 ]]; then
warn "bad address: $sym_base + $offset"
DONE=1
return
fi
addr=0x$(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
[[ $print_warnings = 1 ]] &&
echo "skipping $func address at $addr due to size mismatch ($size != $sym_size)"
continue;
fi
# 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)"
continue
fi
# separate multiple entries with a blank line
[[ $FIRST = 0 ]] && echo
FIRST=0
# pass real address to addr2line
echo "$func+$offset/$sym_size:"
addr2line -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;"
DONE=1
done < <(nm -n $objfile | awk -v fn=$func '$3 == fn { found=1; line=$0; start=$1; next } found == 1 { found=0; print line, $1 }')
}
[[ $# -lt 2 ]] && usage
objfile=$1
[[ ! -f $objfile ]] && die "can't find objfile $objfile"
shift
DIR_PREFIX=supercalifragilisticexpialidocious
find_dir_prefix $objfile
FIRST=1
while [[ $# -gt 0 ]]; do
func_addr=$1
shift
# print any matches found
DONE=0
__faddr2line $objfile $func_addr $DIR_PREFIX 0
# if no match was found, print warnings
if [[ $DONE = 0 ]]; then
__faddr2line $objfile $func_addr $DIR_PREFIX 1
warn "no match for $func_addr"
fi
done