Recent tightening of the opcode table in binutils so as to consistently disallow the assembly or disassembly of CP0 instructions not supported by the processor architecture chosen has caused a regression like below:

arch/mips/dec/prom/locore.S: Assembler messages: arch/mips/dec/prom/locore.S:29: Error: opcode not supported on this processor: r4600 (mips3) `rfe'

in a piece of code used to probe for memory with PMAX DECstation models, which have non-REX firmware. Those computers always have an R2000 CPU and consequently the exception handler used in memory probing uses the RFE instruction, which those processors use.

While adding 64-bit support this code was correctly excluded for 64-bit configurations, however it should have also been excluded for irrelevant 32-bit configurations. Do this now then, and only enable PMAX memory probing for R3k systems.

Reported-by: Jan-Benedict Glaw jbglaw@lug-owl.de Reported-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Maciej W. Rozycki macro@orcam.me.uk Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org # v2.6.12+ --- Hi,

I'm assuming this won't go back beyond commit 2a11c8ea20bf ("kconfig: Introduce IS_ENABLED(), IS_BUILTIN() and IS_MODULE()") or any backport will have to be rewritten to avoid IS_ENABLED.

The original actual change named to fix ought to be commit dd82ef87e4c9 ("PROM interface rework to support a 64-bit kernel.") from the LMO repo: https://git.kernel.org/pub/scm/linux/kernel/git/ralf/linux.git/commit/?id=dd82ef87e4c9, which introduced the `prom_is_rex' macro, which guards this code. Said commit predates the history of our main repository though.

This change has actually been verified at runtime with a PMIN system (effectively a PMAX, but with a slower R2000 CPU) and a 4MAX+ system (an R4400SC-based machine), and naturally throughout the three possible build configurations: R3k, R4k/32-bit, R4k/64-bit.

It took longer than expected, but oh well... Sorry for the inconvenience caused.

Please apply,

Maciej --- arch/mips/dec/prom/Makefile | 2 +- arch/mips/include/asm/dec/prom.h | 15 +++++---------- 2 files changed, 6 insertions(+), 11 deletions(-)

linux-dec-locore-r3000.diff Index: linux-macro/arch/mips/dec/prom/Makefile =================================================================== --- linux-macro.orig/arch/mips/dec/prom/Makefile +++ linux-macro/arch/mips/dec/prom/Makefile @@ -6,4 +6,4 @@

lib-y += init.o memory.o cmdline.o identify.o console.o

-lib-$(CONFIG_32BIT) += locore.o +lib-$(CONFIG_CPU_R3000) += locore.o Index: linux-macro/arch/mips/include/asm/dec/prom.h =================================================================== --- linux-macro.orig/arch/mips/include/asm/dec/prom.h +++ linux-macro/arch/mips/include/asm/dec/prom.h @@ -43,16 +43,11 @@ */ #define REX_PROM_MAGIC 0x30464354

-#ifdef CONFIG_64BIT - -#define prom_is_rex(magic) 1 /* KN04 and KN05 are REX PROMs. */ - -#else /* !CONFIG_64BIT */ - -#define prom_is_rex(magic) ((magic) == REX_PROM_MAGIC) - -#endif /* !CONFIG_64BIT */ - +/* KN04 and KN05 are REX PROMs, so only do the check for R3k systems. */ +static inline bool prom_is_rex(u32 magic) +{ + return !IS_ENABLED(CONFIG_CPU_R3000) || magic == REX_PROM_MAGIC; +}

/* * 3MIN/MAXINE PROM entry points for DS5000/1xx's, DS5000/xx's and