Re: [PATCH 1/2] riscv: Add memmove string operation.

From: Paul Walmsley <paul.walmsley@sifive.com>
To: Nick Hu <nickhu@andestech.com>
Cc: "離職Zong Zong-Xian Li(李宗憲)" <zong@andestech.com>,
	"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	"Alan Quey-Liang Kao(高魁良)" <alankao@andestech.com>,
	"Atish Patra" <Atish.Patra@wdc.com>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Palmer Dabbelt" <palmer@sifive.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	"alexios.zavras@intel.com" <alexios.zavras@intel.com>,
	"Anup Patel" <Anup.Patel@wdc.com>,
	"glider@google.com" <glider@google.com>,
	"green.hu@gmail.com" <green.hu@gmail.com>,
	"aryabinin@virtuozzo.com" <aryabinin@virtuozzo.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"deanbo422@gmail.com" <deanbo422@gmail.com>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"dvyukov@google.com" <dvyukov@google.com>
Subject: Re: [PATCH 1/2] riscv: Add memmove string operation.
Date: Thu, 15 Aug 2019 11:27:51 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.9999.1908151124450.18249@viisi.sifive.com> (raw)
In-Reply-To: <20190815031225.GA5666@andestech.com>

On Thu, 15 Aug 2019, Nick Hu wrote:

> On Wed, Aug 14, 2019 at 10:03:39AM -0700, Paul Walmsley wrote:
>
> > Thanks for the explanation.  What do you think about Palmer's idea to 
> > define a generic C set of KASAN string operations, derived from the newlib 
> > code?
> 
> That sounds good to me. But it should be another topic. We need to investigate
> it further about replacing something generic and fundamental in lib/string.c
> with newlib C functions.  Some blind spots may exist.  So I suggest, let's
> consider KASAN for now.

OK.  Here is the problem for us as maintainers.  You, Palmer, and I all 
agree that a C-language version would be better.  We'd rather not merge a 
pure assembly-language version unless it had significant advantages, and 
right now we're not anticipating that.  So that suggests that a C-language 
memmove() is the right way to go.

But if we merge a C-language memmove() into arch/riscv, other kernel 
developers would probably ask us why we're doing that, since there's 
nothing RISC-V-specific about it.  So do you think you might reconsider 
sending patches to add a generic C-language memmove()?

- Paul

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