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![Josh Poimboeuf](/assets/img/avatar_default.png)
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>
186 lines
5.1 KiB
Bash
Executable file
186 lines
5.1 KiB
Bash
Executable file
#!/bin/bash
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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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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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usage() {
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echo "usage: faddr2line <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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# 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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# kernel/init.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 -sW $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=$4
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local func=${func_addr%+*}
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local offset=${func_addr#*+}
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offset=${offset%/*}
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local size=
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[[ $func_addr =~ "/" ]] && size=${func_addr#*/}
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if [[ -z $func ]] || [[ -z $offset ]] || [[ $func = $func_addr ]]; then
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warn "bad func+offset $func_addr"
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DONE=1
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return
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fi
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# Go through each of the object's symbols which match the func name.
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# In rare cases there might be duplicates.
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while read symbol; do
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local fields=($symbol)
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local sym_base=0x${fields[0]}
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local sym_type=${fields[1]}
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local sym_end=0x${fields[3]}
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# calculate the size
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local sym_size=$(($sym_end - $sym_base))
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if [[ -z $sym_size ]] || [[ $sym_size -le 0 ]]; then
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warn "bad symbol size: base: $sym_base end: $sym_end"
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DONE=1
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return
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fi
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sym_size=0x$(printf %x $sym_size)
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# calculate the address
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local addr=$(($sym_base + $offset))
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if [[ -z $addr ]] || [[ $addr = 0 ]]; then
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warn "bad address: $sym_base + $offset"
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DONE=1
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return
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fi
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addr=0x$(printf %x $addr)
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# weed out non-function symbols
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if [[ $sym_type != t ]] && [[ $sym_type != T ]]; then
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[[ $print_warnings = 1 ]] &&
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echo "skipping $func address at $addr due to non-function symbol of type '$sym_type'"
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continue
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fi
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# if the user provided a size, make sure it matches the symbol's size
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if [[ -n $size ]] && [[ $size -ne $sym_size ]]; then
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[[ $print_warnings = 1 ]] &&
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echo "skipping $func address at $addr due to size mismatch ($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 $func address at $addr due to size mismatch ($offset > $sym_size)"
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continue
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fi
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# separate multiple entries with a blank line
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[[ $FIRST = 0 ]] && echo
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FIRST=0
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# pass real address to addr2line
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echo "$func+$offset/$sym_size:"
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addr2line -fpie $objfile $addr | sed "s; $dir_prefix\(\./\)*; ;"
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DONE=1
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done < <(nm -n $objfile | awk -v fn=$func '$3 == fn { found=1; line=$0; start=$1; next } found == 1 { found=0; print line, $1 }')
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}
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[[ $# -lt 2 ]] && usage
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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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