linux-kernel - Re: [PATCH] Loongarch: entry: fix syscall_get

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Message-ID: <1145a7c66dde1157f8c8dd6fd073164edfce744c.camel@xry111.site>
Date: Thu, 28 Aug 2025 15:14:06 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Huacai Chen <chenhuacai@...nel.org>, Wentao Guan
 <guanwentao@...ontech.com>
Cc: WANG Xuerui <kernel@...0n.name>, linux-kernel
 <linux-kernel@...r.kernel.org>,  loongarch <loongarch@...ts.linux.dev>,
 占俊 <zhanjun@...ontech.com>
Subject: Re: [PATCH] Loongarch: entry: fix syscall_get_arguments() VS
 no-bultin-memcpy

On Thu, 2025-08-28 at 15:11 +0800, Xi Ruoyao wrote:
> On Thu, 2025-08-28 at 15:09 +0800, Huacai Chen wrote:
> > On Thu, Aug 28, 2025 at 3:06 PM Wentao Guan
> > <guanwentao@...ontech.com>
> > wrote:
> > > 
> > > Hello Ruoyao,
> > > 
> > > Thanks for your review.
> > > I will test and send test results later.
> > > (use different gcc verions and remove the three flags.)
> > I think kernel's memcpy is still needed for CPUs without UAL.
> 
> GCC memcpy expansion correctly understands no-UAL case.  It won't
> generate unaligned access unless -mno-strict-align.

P.S. kernel's memcpy is indeed still needed because when GCC deduces
it's not beneficial to expand the __builtin_memcpy into ld/st sequeces,
it'll just call memcpy.

-- 
Xi Ruoyao <xry111@...111.site>