[Qemu-devel] s390 host support

[Bastian Blank]

Hi folks

Thimo Seufer asked me to check if the s390 host supports works at all.
It did not even build, dyngen failed. I digged into the problem and
found the following:
gcc for s390 generates a data table after each function if necessary
instead of immediate loads. (g5, the oldest supported processor only
suports one halfword immediate load.) dyngen is not prepared for that
and fails. I found that gcc moves this data into the .rodata section if
generating code for z900 and above, which looked like a possible way to
support this.

The attached patch makes qemu build on a s390 host and able to run i386
kernels and userspace. powerpc did not boot, mips failed to start new
processes, the process reports illegal instruction, but the qemu log
does not reflect this.

It does the following changes:
- Hardcode -march=z900 to generate usable op code.
- Add redirection for parameter expansion in op code.
- Cleanup GOTO_LABEL_PARAM.
- Accept any return from function (like "br %r5").
- Support R_390_PC32DBL relocation, including relocations into sections.
- Disable special GOTO_TB handler, it segfaults.

Bastian

-- 
Each kiss is as the first.
                -- Miramanee, Kirk's wife, "The Paradise Syndrome",
                   stardate 4842.6

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