[POWERPC] Discourage people from fiddling with kernel data from prom_init

systbl_chk: $(src)/systbl_chk.sh $(obj)/systbl_chk.i

	$(call cmd,systbl_chk)

$(obj)/built-in.o:		prom_init_check

quiet_cmd_prom_init_check = CALL    $<

      cmd_prom_init_check = $(CONFIG_SHELL) $< "$(NM)" "$(obj)/prom_init.o"

PHONY += prom_init_check

prom_init_check: $(src)/prom_init_check.sh $(obj)/prom_init.o

	$(call cmd,prom_init_check)

clean-files := vmlinux.lds

#!/bin/sh

#

# Copyright © 2008 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 prom_init.o to see what external symbols it

# is using, if it finds symbols not in the whitelist it returns

# an error. The point of this is to discourage people from

# intentionally or accidentally adding new code to prom_init.c

# which has side effects on other parts of the kernel.

# If you really need to reference something from prom_init.o add

# it to the list below:

WHITELIST="add_reloc_offset __bss_start __bss_stop copy_and_flush

_end enter_prom memcpy memset reloc_offset __secondary_hold

__secondary_hold_acknowledge __secondary_hold_spinloop __start

strcmp strcpy strlcpy strlen strncmp strstr logo_linux_clut224

reloc_got2"

NM="$1"

OBJ="$2"

ERROR=0

for UNDEF in $($NM -u $OBJ | awk '{print $2}')

do

	# On 64-bit nm gives us the function descriptors, which have

	# a leading . on the name, so strip it off here.

	UNDEF="${UNDEF#.}"

	if [ $KBUILD_VERBOSE ]; then

		if [ $KBUILD_VERBOSE -ne 0 ]; then

			echo "Checking prom_init.o symbol '$UNDEF'"

		fi

	fi

	OK=0

	for WHITE in $WHITELIST

	do

		if [ "$UNDEF" = "$WHITE" ]; then

			OK=1

			break

		fi

	done

	if [ $OK -eq 0 ]; then

		ERROR=1

		echo "Error: External symbol '$UNDEF' referenced" \

		     "from prom_init.c" >&2

	fi

done

exit $ERROR