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authorMichael Ellerman <michael@ellerman.id.au>2008-04-24 12:08:22 +1000
committerPaul Mackerras <paulus@samba.org>2008-04-24 20:58:03 +1000
commit5c02cd2fb83bd4a11270eeb6682e507f04897837 (patch)
treed2b2a294dfab46543232dc0d6082abe71398186b /arch/powerpc
parentd9e9d82c24e55b8a0fcc89032fdf9f58f1fb56d7 (diff)
[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')
-rw-r--r--arch/powerpc/kernel/Makefile9
-rw-r--r--arch/powerpc/kernel/prom_init_check.sh58
2 files changed, 67 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index ce1e8d24e74..9177b21b1a9 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -106,4 +106,13 @@ PHONY += systbl_chk
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
diff --git a/arch/powerpc/kernel/prom_init_check.sh b/arch/powerpc/kernel/prom_init_check.sh
new file mode 100644
index 00000000000..8e24fc1821e
--- /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