linux-kernel - Re: [PATCH] LoongArch: ptrace: Use UAPI types in UAPI header

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Message-ID: <4f8402e5-2bfa-4ee3-9123-fac887ed866d@t-8ch.de>
Date: Mon, 3 Nov 2025 10:27:22 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>, Jiaxun Yang <jiaxun.yang@...goat.com>, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: ptrace: Use UAPI types in UAPI header

Hi Huacai,

On 2025-11-03 17:12:58+0800, Huacai Chen wrote:
> On Wed, Oct 29, 2025 at 11:20 PM Thomas Weißschuh <linux@...ssschuh.net> wrote:
> >
> > The kernel UAPI headers already contain fixed-width integer types,
> > there is no need to rely on libc types. There may not be a libc
> > available or it may not provide <stdint.h>, like for example on nolibc.
> >
> > This also aligns the header with the rest of the LoongArch UAPI headers.

> Thank you for your patch, but could you please tell me some history
> and user guide about the three styles: u64, __u64 and unint64_t?

uint64_t -> userspace type, should not be used within the kernel
            can technically be used in UAPI it will be somewhat
	    nonstandard and introduce a dependency on libc with no
	    upsides.

u64      -> kernel-internal type, used for regular kernel code
            defined in include/linux/types.h

__u64    -> UAPI type usable from both kernel and userspace code
            defined in include/uapi/linux/types.

As a note: When applying the patch I want to clarify the commit message
a bit, as nolibc indeed has a stdint.h header. The real breakage comes
from a validation step we perform which does not add the libc include
directory to the include path.


Thomas