xref: /openbmc/linux/arch/powerpc/tools/head_check.sh (revision d2ba09c1) 
1# Copyright © 2016 IBM Corporation
2
3# This program is free software; you can redistribute it and/or
4# modify it under the terms of the GNU General Public License
5# as published by the Free Software Foundation; either version
6# 2 of the License, or (at your option) any later version.
7
8# This script checks the head of a vmlinux for linker stubs that
9# break our placement of fixed-location code for 64-bit.
10
11# based on relocs_check.pl
12# Copyright © 2009 IBM Corporation
13
14# NOTE!
15#
16# If the build dies here, it's likely code in head_64.S/exception-64*.S or
17# nearby, is branching to labels it can't reach directly, which results in the
18# linker inserting branch stubs. This can move code around in ways that break
19# the fixed section calculations (head-64.h). To debug this, disassemble the
20# vmlinux and look for branch stubs (long_branch, plt_branch, etc.) in the
21# fixed section region (0 - 0x8000ish). Check what code is calling those stubs,
22# and perhaps change so a direct branch can reach.
23#
24# A ".linker_stub_catch" section is used to catch some stubs generated by
25# early .text code, which tend to get placed at the start of the section.
26# If there are too many such stubs, they can overflow this section. Expanding
27# it may help (or reducing the number of stub branches).
28#
29# Linker stubs use the TOC pointer, so even if fixed section code could
30# tolerate them being inserted into head code, they can't be allowed in low
31# level entry code (boot, interrupt vectors, etc) until r2 is set up. This
32# could cause the kernel to die in early boot.
33
34# Turn this on if you want more debug output:
35# set -x
36
37if [ $# -lt 2 ]; then
38	echo "$0 [path to nm] [path to vmlinux]" 1>&2
39	exit 1
40fi
41
42# Have Kbuild supply the path to nm so we handle cross compilation.
43nm="$1"
44vmlinux="$2"
45
46# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T
47$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" -m4 > .tmp_symbols.txt
48
49
50vma=$(cat .tmp_symbols.txt | grep -e " [TA] _stext$" | cut -d' ' -f1)
51
52expected_start_head_addr=$vma
53
54start_head_addr=$(cat .tmp_symbols.txt | grep " t start_first_256B$" | cut -d' ' -f1)
55
56if [ "$start_head_addr" != "$expected_start_head_addr" ]; then
57	echo "ERROR: head code starts at $start_head_addr, should be $expected_start_head_addr"
58	echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option"
59	echo "ERROR: see comments in arch/powerpc/tools/head_check.sh"
60
61	exit 1
62fi
63
64top_vma=$(echo $vma | cut -d'0' -f1)
65
66expected_start_text_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/")
67
68start_text_addr=$(cat .tmp_symbols.txt | grep " t start_text$" | cut -d' ' -f1)
69
70if [ "$start_text_addr" != "$expected_start_text_addr" ]; then
71	echo "ERROR: start_text address is $start_text_addr, should be $expected_start_text_addr"
72	echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option"
73	echo "ERROR: see comments in arch/powerpc/tools/head_check.sh"
74
75	exit 1
76fi
77
78rm -f .tmp_symbols.txt
79