diff options
| -rw-r--r-- | arch/powerpc/Makefile.postlink | 8 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/head-64.h | 4 | ||||
| -rw-r--r-- | arch/powerpc/kernel/vmlinux.lds.S | 22 | ||||
| -rw-r--r-- | arch/powerpc/tools/head_check.sh | 78 |
4 files changed, 87 insertions, 25 deletions
diff --git a/arch/powerpc/Makefile.postlink b/arch/powerpc/Makefile.postlink index 50336930e6f7..5db43ebbe2df 100644 --- a/arch/powerpc/Makefile.postlink +++ b/arch/powerpc/Makefile.postlink @@ -10,6 +10,9 @@ __archpost: -include include/config/auto.conf include scripts/Kbuild.include +quiet_cmd_head_check = CHKHEAD $@ + cmd_head_check = $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/head_check.sh "$(NM)" "$@" + quiet_cmd_relocs_check = CHKREL $@ ifdef CONFIG_PPC_BOOK3S_64 cmd_relocs_check = \ @@ -24,6 +27,9 @@ endif vmlinux: FORCE @true +ifdef CONFIG_PPC64 + $(call cmd,head_check) +endif ifdef CONFIG_RELOCATABLE $(call if_changed,relocs_check) endif @@ -32,7 +38,7 @@ endif @true clean: - @true + rm -f .tmp_symbols.txt PHONY += FORCE clean diff --git a/arch/powerpc/include/asm/head-64.h b/arch/powerpc/include/asm/head-64.h index 68828aa6e056..7ab95798f170 100644 --- a/arch/powerpc/include/asm/head-64.h +++ b/arch/powerpc/include/asm/head-64.h @@ -49,8 +49,8 @@ * CLOSE_FIXED_SECTION() or elsewhere, there may be something * unexpected being added there. Remove the '. = x_len' line, rebuild, and * check what is pushing the section down. - * - If the build dies in linking, check arch/powerpc/kernel/vmlinux.lds.S - * for instructions. + * - If the build dies in linking, check arch/powerpc/tools/head_check.sh + * comments. * - If the kernel crashes or hangs in very early boot, it could be linker * stubs at the start of the main text. */ diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index be8578e02ab6..e69155f0db36 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -58,7 +58,6 @@ SECTIONS #ifdef CONFIG_PPC64 KEEP(*(.head.text.first_256B)); #ifdef CONFIG_PPC_BOOK3E -# define END_FIXED 0x100 #else KEEP(*(.head.text.real_vectors)); *(.head.text.real_trampolines); @@ -66,12 +65,8 @@ SECTIONS *(.head.text.virt_trampolines); # if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_PPC_POWERNV) KEEP(*(.head.data.fwnmi_page)); -# define END_FIXED 0x8000 -# else -# define END_FIXED 0x7000 # endif #endif - ASSERT((. == END_FIXED), "vmlinux.lds.S: fixed section overflow error"); #else /* !CONFIG_PPC64 */ HEAD_TEXT #endif @@ -79,23 +74,6 @@ SECTIONS __head_end = .; - /* - * If the build dies here, it's likely code in head_64.S is referencing - * labels it can't reach, and the linker inserting stubs without the - * assembler's knowledge. To debug, remove the above assert and - * rebuild. Look for branch stubs in the fixed section region. - * - * Linker stub generation could be allowed in "trampoline" - * sections if absolutely necessary, but this would require - * some rework of the fixed sections. Before resorting to this, - * consider references that have sufficient addressing range, - * (e.g., hand coded trampolines) so the linker does not have - * to add stubs. - * - * Linker stubs at the top of the main text section are currently not - * detected, and will result in a crash at boot due to offsets being - * wrong. - */ #ifdef CONFIG_PPC64 /* * BLOCK(0) overrides the default output section alignment because diff --git a/arch/powerpc/tools/head_check.sh b/arch/powerpc/tools/head_check.sh new file mode 100644 index 000000000000..ad9e57209aa4 --- /dev/null +++ b/arch/powerpc/tools/head_check.sh @@ -0,0 +1,78 @@ +# Copyright © 2016 IBM Corporation + +# This program is free software; you can redistribute it and/or +# modify it under the terms of the GNU General Public License +# as published by the Free Software Foundation; either version +# 2 of the License, or (at your option) any later version. + +# This script checks the head of a vmlinux for linker stubs that +# break our placement of fixed-location code for 64-bit. + +# based on relocs_check.pl +# Copyright © 2009 IBM Corporation + +# NOTE! +# +# If the build dies here, it's likely code in head_64.S/exception-64*.S or +# nearby, is branching to labels it can't reach directly, which results in the +# linker inserting branch stubs. This can move code around in ways that break +# the fixed section calculations (head-64.h). To debug this, disassemble the +# vmlinux and look for branch stubs (long_branch, plt_branch, etc.) in the +# fixed section region (0 - 0x8000ish). Check what code is calling those stubs, +# and perhaps change so a direct branch can reach. +# +# A ".linker_stub_catch" section is used to catch some stubs generated by +# early .text code, which tend to get placed at the start of the section. +# If there are too many such stubs, they can overflow this section. Expanding +# it may help (or reducing the number of stub branches). +# +# Linker stubs use the TOC pointer, so even if fixed section code could +# tolerate them being inserted into head code, they can't be allowed in low +# level entry code (boot, interrupt vectors, etc) until r2 is set up. This +# could cause the kernel to die in early boot. + +# Turn this on if you want more debug output: +# set -x + +if [ $# -lt 2 ]; then + echo "$0 [path to nm] [path to vmlinux]" 1>&2 + exit 1 +fi + +# Have Kbuild supply the path to nm so we handle cross compilation. +nm="$1" +vmlinux="$2" + +# gcc-4.6-era toolchain make _stext an A (absolute) symbol rather than T +$nm "$vmlinux" | grep -e " [TA] _stext$" -e " t start_first_256B$" -e " a text_start$" -e " t start_text$" -m4 > .tmp_symbols.txt + + +vma=$(cat .tmp_symbols.txt | grep -e " [TA] _stext$" | cut -d' ' -f1) + +expected_start_head_addr=$vma + +start_head_addr=$(cat .tmp_symbols.txt | grep " t start_first_256B$" | cut -d' ' -f1) + +if [ "$start_head_addr" != "$expected_start_head_addr" ]; then + echo "ERROR: head code starts at $start_head_addr, should be $expected_start_head_addr" + echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" + echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" + + exit 1 +fi + +top_vma=$(echo $vma | cut -d'0' -f1) + +expected_start_text_addr=$(cat .tmp_symbols.txt | grep " a text_start$" | cut -d' ' -f1 | sed "s/^0/$top_vma/") + +start_text_addr=$(cat .tmp_symbols.txt | grep " t start_text$" | cut -d' ' -f1) + +if [ "$start_text_addr" != "$expected_start_text_addr" ]; then + echo "ERROR: start_text address is $start_text_addr, should be $expected_start_text_addr" + echo "ERROR: try to enable LD_HEAD_STUB_CATCH config option" + echo "ERROR: see comments in arch/powerpc/tools/head_check.sh" + + exit 1 +fi + +rm -f .tmp_symbols.txt |