From: "Keith Packard" <keithp@keithp.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
"QEMU Developers" <qemu-devel@nongnu.org>
Subject: Re: [PATCH] Semihost SYS_READC implementation (v4)
Date: Fri, 25 Oct 2019 12:15:45 -0700 [thread overview]
Message-ID: <87mudo4owu.fsf@keithp.com> (raw)
In-Reply-To: <CAFEAcA-g+RkvYjseDE=1Z=gnLum0Cjvn_7bqB3ti+cBq9UZ3Eg@mail.gmail.com>
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Peter Maydell <peter.maydell@linaro.org> writes:
> Is there a specification for RISC-V semihosting? This is
> likely to be my first question when the support comes
> round for review, so you can have it early :-) We'd
> prefer to implement specified interfaces, not random
> ad-hoc "this seems to be what newlib wants to see,
> which is turn got hacked together by copying some other
> architecture's code".
There seems to be convergence on a pretty simple interface which uses
ebreak surrounded by a couple of specific no-ops:
slli x0, x0, 0x1f
ebreak
srai x0, x0, 0x7
There are implementations in rust and openocd, and I've got one for
picolibc. The risc-v semihosting code is sitting on a branch in my repo
on github:
https://github.com/keith-packard/qemu/tree/riscv-semihost
> (describing a mechanism to avoid stopping the emulator)
> This feels to me like it's a bit overcomplicated unless it turns out
> we actually require it though.
Would also be nice for multi-core setups. I'd like to start with the
simple plan for now.
> Isn't the answer to this "don't use a command line that tries
> to connect stdio to multiple things" ?
Uh, we do that all the time? The mux device is designed to handle this
so that you can use stdio for both monitor commands and application
I/O. It's very convenient, the only issue is that the last device that
hooks to the mux ends up getting input first (you use ^Ac to rotate
among the selected devices).
--
-keith
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next prev parent reply other threads:[~2019-10-25 19:18 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-23 19:26 [PATCH] Semihost SYS_READC implementation (v3) Keith Packard
2019-10-24 17:33 ` no-reply
2019-10-24 18:54 ` Paolo Bonzini
2019-10-24 22:46 ` [PATCH] Semihost SYS_READC implementation (v4) Keith Packard
2019-10-25 9:51 ` Alex Bennée
2019-10-25 16:36 ` Keith Packard
2019-10-25 16:49 ` Peter Maydell
2019-10-25 19:15 ` Keith Packard [this message]
2019-10-25 20:53 ` Peter Maydell
2019-10-25 23:18 ` Keith Packard
2019-11-04 20:42 ` [PATCH] Semihost SYS_READC implementation (v6) Keith Packard
2019-12-17 8:38 ` Alex Bennée
2019-12-17 9:08 ` Paolo Bonzini
2019-12-17 9:51 ` Alex Bennée
2019-12-17 10:04 ` Paolo Bonzini
2019-12-17 12:14 ` [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP) Alex Bennée
2019-12-17 12:22 ` Paolo Bonzini
2019-12-17 13:42 ` Alex Bennée
2019-12-17 13:48 ` Paolo Bonzini
2019-12-17 14:18 ` Alex Bennée
2019-12-17 14:39 ` Paolo Bonzini
2019-12-17 14:39 ` Paolo Bonzini
2019-12-18 17:36 ` Alex Bennée
2019-12-18 21:23 ` Paolo Bonzini
2019-11-05 5:10 ` [PATCH] Semihost SYS_READC implementation (v4) Keith Packard
2019-11-11 14:51 ` Peter Maydell
2019-11-14 15:46 ` Alistair Francis
2019-11-14 17:43 ` Keith Packard
2019-11-14 17:39 ` Keith Packard
2019-11-14 17:47 ` Peter Maydell
2019-11-14 19:20 ` Peter Maydell
2019-11-14 16:14 ` Peter Maydell
2019-11-14 18:05 ` Keith Packard
2019-11-14 18:18 ` Peter Maydell
2019-11-14 19:18 ` Richard Henderson
2019-11-14 19:29 ` Peter Maydell
2019-11-14 20:52 ` Richard Henderson
2019-11-14 21:04 ` Peter Maydell
2019-11-14 22:26 ` Keith Packard
2019-11-15 10:54 ` Peter Maydell
2019-11-15 23:40 ` Keith Packard
2019-10-25 17:02 ` Alex Bennée
2019-10-25 18:17 ` no-reply
2019-10-25 18:20 ` no-reply
2019-10-24 17:43 ` [PATCH] Semihost SYS_READC implementation (v3) no-reply
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