On Tue, Aug 17, 2021 at 12:54:32PM +0100, Sudip Mukherjee wrote:
While I was testing v5.4.142-rc2 I noticed mips build of decstation_r4k_defconfig fails with binutils-2_37. The error is:
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'
I have also reported this at https://sourceware.org/bugzilla/show_bug.cgi?id=28241
It would appear gas got more anal about ISA checking for the RFE instructions which did only exist in MIPS I and II; MIPS III and later use ERET for returning from an exception.
The older gas I've got installed here happily accepts RFE in MIPS III/R4000 mode:
$ cat s.s rfe eret $ mips-linux-as -o s.o s.s s.s: Assembler messages: s.s:2: Error: opcode not supported on this processor: mips1 (mips1) `eret' $ mips-linux-as -march=r4000 -o s.o s.s $ mips-linux-objdump -d s.o
s.o: file format elf32-tradbigmips
Disassembly of section .text:
00000000 <.text>: 0: 42000010 c0 0x10 # <- RFE 4: 42000018 eret ... $
It's easy to find arguments for why this gas change is the right thing to do - and not the right thing to do.
It should be fixable by simply putting gas into mips1 mode. Can you test below patch?
Ralf
Signed-off-by: Ralf Baechle ralf@linux-mips.org
diff --git a/arch/mips/dec/prom/locore.S b/arch/mips/dec/prom/locore.S index 0eb8fab62ab0..8d00ca8872f9 100644 --- a/arch/mips/dec/prom/locore.S +++ b/arch/mips/dec/prom/locore.S @@ -16,6 +16,7 @@ NESTED(genexcept_early, 0, sp) .set noat .set noreorder + .set mips1
mfc0 k0, CP0_STATUS la k1, mem_err