1#!/bin/sh 2# Copyright © 2016 IBM Corporation 3 4# This program is free software; you can redistribute it and/or 5# modify it under the terms of the GNU General Public License 6# as published by the Free Software Foundation; either version 7# 2 of the License, or (at your option) any later version. 8 9# This script checks the head of a vmlinux for linker stubs that 10# break our placement of fixed-location code for 64-bit. 11 12# based on relocs_check.pl 13# Copyright © 2009 IBM Corporation 14 15# NOTE! 16# 17# If the build dies here, it's likely code in head_64.S/exception-64*.S or 18# nearby, is branching to labels it can't reach directly, which results in the 19# linker inserting branch stubs. This can move code around in ways that break 20# the fixed section calculations (head-64.h). To debug this, disassemble the 21# vmlinux and look for branch stubs (long_branch, plt_branch, etc.) in the 22# fixed section region (0 - 0x8000ish). Check what code is calling those stubs, 23# and perhaps change so a direct branch can reach. 24# 25# A ".linker_stub_catch" section is used to catch some stubs generated by 26# early .text code, which tend to get placed at the start of the section. 27# If there are too many such stubs, they can overflow this section. Expanding 28# it may help (or reducing the number of stub branches). 29# 30# Linker stubs use the TOC pointer, so even if fixed section code could 31# tolerate them being inserted into head code, they can't be allowed in low 32# level entry code (boot, interrupt vectors, etc) until r2 is set up. This 33# could cause the kernel to die in early boot. 34 35# Allow for verbose output 36if [ "$V" = "1" ]; then 37 set -x 38fi 39 40if [ $# -lt 2 ]; then 41 echo "$0 [path to nm] [path to vmlinux]" 1>&2 42 exit 1 43fi 44 45# Have Kbuild supply the path to nm so we handle cross compilation. 46nm="$1" 47vmlinux="$2" 48 49# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T 50$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" > .tmp_symbols.txt 51 52 53vma=$(grep -e " [TA] _stext$" .tmp_symbols.txt | cut -d' ' -f1) 54 55expected_start_head_addr="$vma" 56 57start_head_addr=$(grep " t start_first_256B$" .tmp_symbols.txt | cut -d' ' -f1) 58 59if [ "$start_head_addr" != "$expected_start_head_addr" ]; then 60 echo "ERROR: head code starts at $start_head_addr, should be $expected_start_head_addr" 1>&2 61 echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" 1>&2 62 echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" 1>&2 63 64 exit 1 65fi 66 67top_vma=$(echo "$vma" | cut -d'0' -f1) 68 69expected_start_text_addr=$(grep " a text_start$" .tmp_symbols.txt | cut -d' ' -f1 | sed "s/^0/$top_vma/") 70 71start_text_addr=$(grep " t start_text$" .tmp_symbols.txt | cut -d' ' -f1) 72 73if [ "$start_text_addr" != "$expected_start_text_addr" ]; then 74 echo "ERROR: start_text address is $start_text_addr, should be $expected_start_text_addr" 1>&2 75 echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" 1>&2 76 echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" 1>&2 77 78 exit 1 79fi 80 81rm -f .tmp_symbols.txt 82