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Message-ID: <CA+mdN-HLgwVoP9yq3fu_5_9Oru=WTh82P6jkRcg_8S4tx21sDA@mail.gmail.com>
Date: Tue, 10 May 2016 23:05:01 -0700
From: Gry Gunvor <gry.gunvor@...il.com>
To: musl@...ts.openwall.com
Subject: porting musl to RISCV-64
I am interested in compiling for RISCV-64 (http://riscv.org/) using a
libc that I compile myself so that I can run it through some
source-to-source transformations before compiling it. The default
RISCV tools will target their ports of either gnu libc or newlib. Gnu
libc is huge, so I would rather avoid it; also I would rather use
something released under a permissive open source license (BSD).
Newlib is small, but I am not interested in multithreading and the
multithreading/reentrancy support they have built into the library is
causing me problems. So I thought I would try musl.
I'm running on a vanilla Ubuntu 14.04 x86 machine and muscl builds out
of the box. Using your gcc wrapper, hello world links and runs. I
tried wrapping malloc at link time and that worked. Thus, so far,
muscl is working great.
FYI: You might want to know that this recent post on the subject of
teaching C speaks of musl as "high-quality":
http://blog.regehr.org/archives/1393
"We’ll want some lecture material about C’s place in the modern world
and we also need to spend time reading some high-quality C code,
perhaps starting with Redis, Musl, or Xv6. Musl, in particular, is a
good match for teaching since it contains lots of cute little
functions that can be understood in isolation."
Anyway, suppose I want to port musl to RISCV-64 and cross-compile it.
MIPS is a RISC architecture that is rather close to RISCV, but your
MIPS support says 32-bit (and big-endian), so I take it you have some
dependencies on what used to be called the "machine word size" (RISCV
is 64-bit, but the RISCV docs still call a 32-bit unit a "word"; ugh;
so now we need a new word for "word"). Thus I suspect that this is
going to be non-trival. How much work is this going to be? Hints?
More generally, any comments on what do you recommend as the easiest
thing to do? Port musl to RISCV-64? Use a different libc? For those
of you who know newlib, hack newlib to remove reentrancy goop?
Gry
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