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Revision be0f272bfc83797f70d44faca86954df62e2bbc0 authored by Ard Biesheuvel on 20 November 2017, 17:41:30 UTC, committed by Will Deacon on 01 December 2017, 13:04:59 UTC 
arm64: ftrace: emit ftrace-mod.o contents through code
 
When building the arm64 kernel with both CONFIG_ARM64_MODULE_PLTS and
CONFIG_DYNAMIC_FTRACE enabled, the ftrace-mod.o object file is built
with the kernel and contains a trampoline that is linked into each
module, so that modules can be loaded far away from the kernel and
still reach the ftrace entry point in the core kernel with an ordinary
relative branch, as is emitted by the compiler instrumentation code
dynamic ftrace relies on.

In order to be able to build out of tree modules, this object file
needs to be included into the linux-headers or linux-devel packages,
which is undesirable, as it makes arm64 a special case (although a
precedent does exist for 32-bit PPC).

Given that the trampoline essentially consists of a PLT entry, let's
not bother with a source or object file for it, and simply patch it
in whenever the trampoline is being populated, using the existing
PLT support routines.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
1 parent 7e8b9c1
Raw File
decodecode 
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
# Disassemble the Code: line in Linux oopses
# usage: decodecode < oops.file
#
# options: set env. variable AFLAGS=options to pass options to "as";
# e.g., to decode an i386 oops on an x86_64 system, use:
# AFLAGS=--32 decodecode < 386.oops

cleanup() {
	rm -f $T $T.s $T.o $T.oo $T.aa $T.dis
	exit 1
}

die() {
	echo "$@"
	exit 1
}

trap cleanup EXIT

T=`mktemp` || die "cannot create temp file"
code=

while read i ; do

case "$i" in
*Code:*)
	code=$i
	;;
esac

done

if [ -z "$code" ]; then
	rm $T
	exit
fi

echo $code
code=`echo $code | sed -e 's/.*Code: //'`

width=`expr index "$code" ' '`
width=$((($width-1)/2))
case $width in
1) type=byte ;;
2) type=2byte ;;
4) type=4byte ;;
esac

disas() {
	${CROSS_COMPILE}as $AFLAGS -o $1.o $1.s > /dev/null 2>&1

	if [ "$ARCH" = "arm" ]; then
		if [ $width -eq 2 ]; then
			OBJDUMPFLAGS="-M force-thumb"
		fi

		${CROSS_COMPILE}strip $1.o
	fi

	${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $1.o | \
		grep -v "/tmp\|Disassembly\|\.text\|^$" > $1.dis 2>&1
}

marker=`expr index "$code" "\<"`
if [ $marker -eq 0 ]; then
	marker=`expr index "$code" "\("`
fi

touch $T.oo
if [ $marker -ne 0 ]; then
	echo All code >> $T.oo
	echo ======== >> $T.oo
	beforemark=`echo "$code"`
	echo -n "	.$type 0x" > $T.s
	echo $beforemark | sed -e 's/ /,0x/g; s/[<>()]//g' >> $T.s
	disas $T
	cat $T.dis >> $T.oo
	rm -f $T.o $T.s $T.dis

# and fix code at-and-after marker
	code=`echo "$code" | cut -c$((${marker} + 1))-`
fi
echo Code starting with the faulting instruction  > $T.aa
echo =========================================== >> $T.aa
code=`echo $code | sed -e 's/ [<(]/ /;s/[>)] / /;s/ /,0x/g; s/[>)]$//'`
echo -n "	.$type 0x" > $T.s
echo $code >> $T.s
disas $T
cat $T.dis >> $T.aa

# (lines of whole $T.oo) - (lines of $T.aa, i.e. "Code starting") + 3,
# i.e. the title + the "===..=" line (sed is counting from 1, 0 address is
# special)
faultlinenum=$(( $(wc -l $T.oo  | cut -d" " -f1) - \
		 $(wc -l $T.aa  | cut -d" " -f1) + 3))

faultline=`cat $T.dis | head -1 | cut -d":" -f2-`
faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`

cat $T.oo | sed -e "${faultlinenum}s/^\(.*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
echo
cat $T.aa
cleanup
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