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# Allow for verbose output 35if [ "$V" = "1" ]; then 36 set -x 37fi 38 39if [ $# -lt 2 ]; then 40 echo "$0 [path to nm] [path to vmlinux]" 1>&2 41 exit 1 42fi 43 44# Have Kbuild supply the path to nm so we handle cross compilation. 45nm="$1" 46vmlinux="$2" 47 48# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T 49$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" > .tmp_symbols.txt 50 51 52vma=$(cat .tmp_symbols.txt | grep -e " [TA] _stext$" | cut -d' ' -f1) 53 54expected_start_head_addr=$vma 55 56start_head_addr=$(cat .tmp_symbols.txt | grep " t start_first_256B$" | cut -d' ' -f1) 57 58if [ "$start_head_addr" != "$expected_start_head_addr" ]; then 59 echo "ERROR: head code starts at $start_head_addr, should be $expected_start_head_addr" 60 echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" 61 echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" 62 63 exit 1 64fi 65 66top_vma=$(echo $vma | cut -d'0' -f1) 67 68expected_start_text_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/") 69 70start_text_addr=$(cat .tmp_symbols.txt | grep " t start_text$" | cut -d' ' -f1) 71 72if [ "$start_text_addr" != "$expected_start_text_addr" ]; then 73 echo "ERROR: start_text address is $start_text_addr, should be $expected_start_text_addr" 74 echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" 75 echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" 76 77 exit 1 78fi 79 80rm -f .tmp_symbols.txt 81