linux-kernel - Re: [PATCH 0/3] LoongArch: initial 32-bit UAPI

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Message-Id: <6b2e8382-e4d6-46ce-9d1d-02ddbae76ad3@app.fastmail.com>
Date: Sun, 05 Jan 2025 10:27:25 +0000
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Arnd Bergmann" <arnd@...db.de>, "Xi Ruoyao" <xry111@...111.site>,
 "Huacai Chen" <chenhuacai@...nel.org>, "Xuerui Wang" <kernel@...0n.name>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 0/3] LoongArch: initial 32-bit UAPI



在2025年1月5日一月 上午4:43，Arnd Bergmann写道：
[...]
> If both the ISA and the ABI get it right, it should be possible to
> build 32-bit userspace that is compatible with both when targeting
> a 32-bit hardware, but still use 64-bit registers inside a single
> function when the compiler is building for a 64-bit capable CPU
> (e.g. "-march=la464 -m32"). There is a small cost in the calling
> conventions for passing u64 arguments in pairs of registers
> (unlike n32/x32/aarch64ilp32/rv64ilp32), but a huge benefit in
> not maintaining two incompatible ABIs.

Thanks Arnd for elaborating this!

I actually more or less have this in mind when I was designing this ABI,
thus GRs were designed to be 64bit in sigcontext. But I never look into
that closely.

I'll try to explore that option, maybe come up with a COMPAT implementation
first.

Thanks
>
>      Arnd

-- 
- Jiaxun