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author | Michael Ellerman <michael@ellerman.id.au> | 2008-04-24 12:08:22 +1000 |
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committer | Paul Mackerras <paulus@samba.org> | 2008-04-24 20:58:03 +1000 |
commit | 5c02cd2fb83bd4a11270eeb6682e507f04897837 (patch) | |
tree | d2b2a294dfab46543232dc0d6082abe71398186b /arch/powerpc/kernel/prom_init_check.sh | |
parent | d9e9d82c24e55b8a0fcc89032fdf9f58f1fb56d7 (diff) | |
download | linux-5c02cd2fb83bd4a11270eeb6682e507f04897837.tar.bz2 |
[POWERPC] Discourage people from fiddling with kernel data from prom_init
As BenH said the other day, it is an "accident" that prom_init.o is
linked with the rest of the kernel. The truth is a little more
subtle, prom_init isn't truly bootloader, it does access kernel data
in a few places.
What we can do is discourage people from adding new code that accesses
data outside of prom_init. And hence this patch; from the script:
# 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.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/prom_init_check.sh')
-rw-r--r-- | arch/powerpc/kernel/prom_init_check.sh | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/prom_init_check.sh b/arch/powerpc/kernel/prom_init_check.sh new file mode 100644 index 000000000000..8e24fc1821e8 --- /dev/null +++ b/arch/powerpc/kernel/prom_init_check.sh @@ -0,0 +1,58 @@ +#!/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 |