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| 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 | + |
| 37 | +if [ $# -lt 2 ]; then |
| 38 | + echo "$0 [path to nm] [path to vmlinux]" 1>&2 |
| 39 | + exit 1 |
| 40 | +fi |
| 41 | + |
| 42 | +# Have Kbuild supply the path to nm so we handle cross compilation. |
| 43 | +nm="$1" |
| 44 | +vmlinux="$2" |
| 45 | + |
| 46 | +# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T |
| 47 | +$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" -m4 > .tmp_symbols.txt |
| 48 | + |
| 49 | + |
| 50 | +vma=$(cat .tmp_symbols.txt | grep -e " [TA] _stext$" | cut -d' ' -f1) |
| 51 | + |
| 52 | +expected_start_head_addr=$vma |
| 53 | + |
| 54 | +start_head_addr=$(cat .tmp_symbols.txt | grep " t start_first_256B$" | cut -d' ' -f1) |
| 55 | + |
| 56 | +if [ "$start_head_addr" != "$expected_start_head_addr" ]; then |
| 57 | + echo "ERROR: head code starts at $start_head_addr, should be $expected_start_head_addr" |
| 58 | + echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" |
| 59 | + echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" |
| 60 | + |
| 61 | + exit 1 |
| 62 | +fi |
| 63 | + |
| 64 | +top_vma=$(echo $vma | cut -d'0' -f1) |
| 65 | + |
| 66 | +expected_start_text_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/") |
| 67 | + |
| 68 | +start_text_addr=$(cat .tmp_symbols.txt | grep " t start_text$" | cut -d' ' -f1) |
| 69 | + |
| 70 | +if [ "$start_text_addr" != "$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 |
| 76 | +fi |
| 77 | + |
| 78 | +rm -f .tmp_symbols.txt |
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