5ac47f7a6e
The ppc64 kernel can get loaded at any address which means our very early init code in prom_init.c must be relocatable. We do this with a pretty nasty RELOC() macro that we wrap accesses of variables with. It is very fragile and sometimes we forget to add a RELOC() to an uncommon path or sometimes a compiler change breaks it. 32bit has a much more elegant solution where we build prom_init.c with -mrelocatable and then process the relocations manually. Unfortunately we can't do the equivalent on 64bit and we would have to build the entire kernel relocatable (-pie), resulting in a large increase in kernel footprint (megabytes of relocation data). The relocation data will be marked __initdata but it still creates more pressure on our already tight memory layout at boot. Alan Modra pointed out that the 64bit ABI is relocatable even if we don't build with -pie, we just need to relocate the TOC. This patch implements that idea and relocates the TOC entries of prom_init.c. An added bonus is there are very few relocations to process which helps keep boot times on simulators down. gcc does not put 64bit integer constants into the TOC but to be safe we may want a build time script which passes through the prom_init.c TOC entries to make sure everything looks reasonable. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
81 lines
2 KiB
Bash
81 lines
2 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 kernstart_addr memstart_addr linux_banner _stext
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opal_query_takeover opal_do_takeover opal_enter_rtas opal_secondary_entry
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boot_command_line __prom_init_toc_start __prom_init_toc_end"
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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" = "$WHITE" ]; then
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OK=1
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break
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fi
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done
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# ignore register save/restore funcitons
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if [ "${UNDEF:0:9}" = "_restgpr_" ]; then
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OK=1
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fi
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if [ "${UNDEF:0:10}" = "_restgpr0_" ]; then
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OK=1
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fi
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if [ "${UNDEF:0:11}" = "_rest32gpr_" ]; then
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OK=1
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fi
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if [ "${UNDEF:0:9}" = "_savegpr_" ]; then
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OK=1
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fi
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if [ "${UNDEF:0:10}" = "_savegpr0_" ]; then
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OK=1
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fi
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if [ "${UNDEF:0:11}" = "_save32gpr_" ]; then
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OK=1
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fi
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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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