linux/arch/powerpc/kernel/prom_init_check.sh
Benjamin Herrenschmidt 7191b61575 powerpc/pmac: Early debug output on screen on 64-bit macs
We have a bunch of CONFIG_PPC_EARLY_DEBUG_* options that are intended
for bringup/debug only. They hard wire a machine specific udbg backend
very early on (before we even probe the platform), and use whatever
tricks are available on each machine/cpu to be able to get some kind
of output out there early on.

So far, on powermac with no serial ports, we have CONFIG_PPC_EARLY_DEBUG_BOOTX
to use the low-level btext engine on the screen, but it doesn't do much, at
least on 64-bit. It only really gets enabled after the platform has been
probed and the MMU enabled.

This adds a way to enable it much earlier. From prom_init.c (while still
running with Open Firmware), we grab the screen details and set things up
using the physical address of the frame buffer.

Then btext itself uses the "rm_ci" feature of the 970 processor (Real
Mode Cache Inhibited) to access it while in real mode.

We need to do a little bit of reorg of the btext code to inline things
better, in order to limit how much we touch memory while in this mode as
the consequences might be ... interesting.

This successfully allowed me to debug problems early on with the G5
(related to gold being broken vs. ppc64 kernels).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-08-14 14:57:40 +10:00

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#!/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 kernstart_addr memstart_addr linux_banner _stext
opal_query_takeover opal_do_takeover opal_enter_rtas opal_secondary_entry
boot_command_line __prom_init_toc_start __prom_init_toc_end
btext_setup_display"
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" = "$WHITE" ]; then
OK=1
break
fi
done
# ignore register save/restore funcitons
if [ "${UNDEF:0:9}" = "_restgpr_" ]; then
OK=1
fi
if [ "${UNDEF:0:10}" = "_restgpr0_" ]; then
OK=1
fi
if [ "${UNDEF:0:11}" = "_rest32gpr_" ]; then
OK=1
fi
if [ "${UNDEF:0:9}" = "_savegpr_" ]; then
OK=1
fi
if [ "${UNDEF:0:10}" = "_savegpr0_" ]; then
OK=1
fi
if [ "${UNDEF:0:11}" = "_save32gpr_" ]; then
OK=1
fi
if [ $OK -eq 0 ]; then
ERROR=1
echo "Error: External symbol '$UNDEF' referenced" \
"from prom_init.c" >&2
fi
done
exit $ERROR