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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>
59 lines
1.5 KiB
Bash
59 lines
1.5 KiB
Bash
#!/bin/sh
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#
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# Copyright © 2008 IBM Corporation
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License
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# as published by the Free Software Foundation; either version
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# 2 of the License, or (at your option) any later version.
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# This script checks prom_init.o to see what external symbols it
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# is using, if it finds symbols not in the whitelist it returns
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# an error. The point of this is to discourage people from
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# intentionally or accidentally adding new code to prom_init.c
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# which has side effects on other parts of the kernel.
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# If you really need to reference something from prom_init.o add
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# it to the list below:
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WHITELIST="add_reloc_offset __bss_start __bss_stop copy_and_flush
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_end enter_prom memcpy memset reloc_offset __secondary_hold
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__secondary_hold_acknowledge __secondary_hold_spinloop __start
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strcmp strcpy strlcpy strlen strncmp strstr logo_linux_clut224
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reloc_got2"
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NM="$1"
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OBJ="$2"
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ERROR=0
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for UNDEF in $($NM -u $OBJ | awk '{print $2}')
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do
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# On 64-bit nm gives us the function descriptors, which have
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# a leading . on the name, so strip it off here.
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UNDEF="${UNDEF#.}"
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if [ $KBUILD_VERBOSE ]; then
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if [ $KBUILD_VERBOSE -ne 0 ]; then
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echo "Checking prom_init.o symbol '$UNDEF'"
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fi
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fi
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OK=0
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for WHITE in $WHITELIST
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do
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if [ "$UNDEF" = "$WHITE" ]; then
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OK=1
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break
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fi
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done
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if [ $OK -eq 0 ]; then
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ERROR=1
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echo "Error: External symbol '$UNDEF' referenced" \
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"from prom_init.c" >&2
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fi
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done
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exit $ERROR
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