PR/54876 CVS commit: src/sys/arch/sun68k/stand/libsa

["Izumi Tsutsui" <tsutsui%netbsd.org@localhost>]

The following reply was made to PR port-sun3/54876; it has been noted by GNATS.

From: "Izumi Tsutsui" <tsutsui%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/54876 CVS commit: src/sys/arch/sun68k/stand/libsa
Date: Wed, 19 Aug 2026 18:14:08 +0000

 Module Name:	src
 Committed By:	tsutsui
 Date:		Wed Aug 19 18:14:08 UTC 2026
 
 Modified Files:
 	src/sys/arch/sun68k/stand/libsa: sun3.c version
 
 Log Message:
 sun68k: avoid PROM DVMA map aliasing in sun3 bootloader
 
 NetBSD/sun3 11.0 GENERIC fails to boot from a SCSI disk on
 my Sun 3/60 with at least PROM revisions 2.8.3 and 3.0.1.
 
 It looks sun3 PROM SCSI driver allocates internal resources
 in DVMA space starting at 0xfff00000. The sun3 standalone
 DVMA setup currently aliases its local address range starting
 at 0x200000 to that same address.
 
 Since the alias is created by sharing PMEGs, PTE changes made by
 the PROM in its DVMA space also change the corresponding standalone
 mappings. These mappings are inherited by the loaded kernel.
 
 On Sun3, pmap_bootstrap() derives the first available PA from
 (nextva - KERNBASE3), assuming that the kernel bootstrap VA range
 is backed by the corresponding contiguous physical addresses.
 
 A leaked alias can instead map part of that range to an unrelated
 physical page, leaving that use unaccounted for. Then the page can
 be registered as available memory by uvm_page_physload() (via
 machine_init_common() in HEAD) even though it is already used for
 kernel bootstrap data such as the symbol table and kernel stack etc.
 Maybe this is the real reason that also caused PR/54876.
 
 Move the lower end of the standalone alias from 0x200000/0xfff00000
 to 0x240000/0xfff40000 to avoid aliasing the PROM DVMA mappings.
 Keep the upper limit unchanged, so existing local-to-DVMA address
 translations for the remaining range are preserved.
 
 Bump version to denote this fix.
 
 Should be pulled up to netbsd-11 and netbsd-10.
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.12 -r1.13 src/sys/arch/sun68k/stand/libsa/sun3.c
 cvs rdiff -u -r1.6 -r1.7 src/sys/arch/sun68k/stand/libsa/version
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.