arch/powerpc/tools/head_check.sh

   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