Re: illegal hardware instruction during MIPS-I ELF linux useremulation

["Libo Zhou" <zhlb29@foxmail.com>]

> If you look at the mips_defs[] array in
> target/mips/translate_init.inc.c, the older ISA implemented is MIPS-II:

> $ git grep .insn_flags target/mips/translate_init.inc.c
> translate_init.inc.c:75:        .insn_flags = CPU_MIPS32,
> translate_init.inc.c:97:        .insn_flags = CPU_MIPS32 | ASE_MIPS16,
> translate_init.inc.c:117:        .insn_flags = CPU_MIPS32,
> translate_init.inc.c:137:        .insn_flags = CPU_MIPS32 | ASE_MIPS16,
> translate_init.inc.c:158:        .insn_flags = CPU_MIPS32R2,
> translate_init.inc.c:179:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
> translate_init.inc.c:201:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
> translate_init.inc.c:223:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP,
> translate_init.inc.c:249:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16,
> translate_init.inc.c:297:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP | ASE_MT,
> translate_init.inc.c:323:        .insn_flags = CPU_MIPS32R2 | ASE_MIPS16 | ASE_DSP | ASE_DSP_R2,
> translate_init.inc.c:343:        .insn_flags = CPU_MIPS32R2 | ASE_MICROMIPS,
> translate_init.inc.c:364:        .insn_flags = CPU_MIPS32R2 | ASE_MICROMIPS,
> translate_init.inc.c:410:        .insn_flags = CPU_MIPS32R5 | ASE_MSA,
> translate_init.inc.c:449:        .insn_flags = CPU_MIPS32R6 | ASE_MICROMIPS,
> translate_init.inc.c:488:        .insn_flags = CPU_NANOMIPS32 | ASE_DSP | ASE_DSP_R2 | ASE_DSP_R3 |
> translate_init.inc.c:511:        .insn_flags = CPU_MIPS3,
> translate_init.inc.c:531:        .insn_flags = CPU_VR54XX,
> translate_init.inc.c:552:        .insn_flags = CPU_MIPS64,
> translate_init.inc.c:578:        .insn_flags = CPU_MIPS64,
> translate_init.inc.c:607:        .insn_flags = CPU_MIPS64 | ASE_MIPS3D,
> translate_init.inc.c:636:        .insn_flags = CPU_MIPS64R2 | ASE_MIPS3D,
> translate_init.inc.c:657:        .insn_flags = CPU_MIPS64R2,
> translate_init.inc.c:681:        .insn_flags = CPU_MIPS64R2,
> translate_init.inc.c:721:        .insn_flags = CPU_MIPS64R6 | ASE_MSA,
> translate_init.inc.c:761:        .insn_flags = CPU_MIPS64R6 | ASE_MSA,
> translate_init.inc.c:781:        .insn_flags = CPU_LOONGSON2E,
> translate_init.inc.c:801:        .insn_flags = CPU_LOONGSON2F,
> translate_init.inc.c:830:        .insn_flags = CPU_MIPS64R2 | ASE_DSP | ASE_DSP_R2,

> So currently there is no MIPS-I only CPU.
> Note that the code got written with MIPS32 in mind, and implementing
> MIPS-I requires a considerable amount of change in the codebase.

Hi Philippe,

I just figured out what the problem was. The custom compiler I used just modified the opcode fields of sw and lw instructions of MIPS, so QEMU didn't recognize them out of the box.
I just added the support in decode_opc function in translate.c, and I also added my own CPU model in translate_init.inc.c. However, the illegal instruction exception is still there.

I am suspecting that the way I added my own CPU model in translate_init.inc.c is wrong. Below is what I added:
...
+{
+    .name = "MyCPU",
+    .insn_flags = CPU_MIPS1 | INSN_MYCPU,
+},
...
I just need to simulate it's instruction set in linux user emulation, I didn't include CP0* items in the list. Is this good enough to add a new CPU model?

Thanks,
Libo Zhou