svn commit: r360537 - head/stand/powerpc/boot1.chrp

[Brandon Bergren]

Author: bdragon
Date: Fri May  1 16:56:36 2020
New Revision: 360537
URL: https://svnweb.freebsd.org/changeset/base/360537

Log:
  [PowerPC] Set fixed boot1.elf load address
  
  Due to the way claiming works, we need to ensure on AIM OFW machines that
  we don't have overlapping ranges on any step of the load.
  
  Load boot1.elf at 0x38000 so it will not overlap with anything even if the
  entire PReP partition gets loaded by OFW.
  
  Tested on an iBook G4, a PowerBook G4, a PowerMac G5, and qemu pseries.
  (qemu pseries is broken without this patch due to the high address used
  by lld10.)
  
  Reviewed by:	adalava
  Sponsored by:	Tag1 Consulting, Inc.
  Differential Revision:	https://reviews.freebsd.org/D24623

Modified:
  head/stand/powerpc/boot1.chrp/Makefile

Modified: head/stand/powerpc/boot1.chrp/Makefile
==============================================================================
--- head/stand/powerpc/boot1.chrp/Makefile	Fri May  1 16:47:54 2020	(r360536)
+++ head/stand/powerpc/boot1.chrp/Makefile	Fri May  1 16:56:36 2020	(r360537)
@@ -10,7 +10,20 @@ FILES=		boot1.hfs
 SRCS=		boot1.c ashldi3.c syncicache.c
 
 CFLAGS+=-I${LDRSRC}
-LDFLAGS=-nostdlib -static -Wl,-N
+# Load boot1.elf below kernel.
+#
+# Due to limitiations in the way we load stuff, we have to avoid reusing
+# memory until the kernel MMU code has taken over.
+#
+# 0x38000 is high enough to not interfere with the trap area, but low
+# enough that it doesn't bump into the kernel area starting at 0x100000,
+# even if the entire partition gets used as the load size by a buggy OFW.
+#
+# In theory 0xf0000 would work too under the current 64k size limit for
+# boot1.elf defined in the HFS template, but sometimes boot1.elf is written
+# directly to the PReP partition.
+#
+LDFLAGS=-nostdlib -static -Wl,-N -Wl,-Ttext=0x38000
 
 .PATH:  ${SYSDIR}/libkern ${SRCTOP}/lib/libc/powerpc/gen ${.CURDIR}