From: Nick Hu <nickhu@andestech.com>
To: Paul Walmsley <paul.walmsley@sifive.com>
Cc: "Palmer Dabbelt" <palmer@sifive.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Alan Quey-Liang Kao(高魁良)" <alankao@andestech.com>,
"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
"green.hu@gmail.com" <green.hu@gmail.com>,
"deanbo422@gmail.com" <deanbo422@gmail.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"aryabinin@virtuozzo.com" <aryabinin@virtuozzo.com>,
"glider@google.com" <glider@google.com>,
"dvyukov@google.com" <dvyukov@google.com>,
"Anup Patel" <Anup.Patel@wdc.com>,
"Greg KH" <gregkh@linuxfoundation.org>,
"alexios.zavras@intel.com" <alexios.zavras@intel.com>,
"Atish Patra" <Atish.Patra@wdc.com>,
"離職Zong Zong-Xian Li(李宗憲)" <zong@andestech.com>,
"kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>
Subject: Re: [PATCH 1/2] riscv: Add memmove string operation.
Date: Mon, 19 Aug 2019 14:29:19 +0800 [thread overview]
Message-ID: <20190819062919.GA6480@andestech.com> (raw)
In-Reply-To: <alpine.DEB.2.21.9999.1908151124450.18249@viisi.sifive.com>
Hi Paul,
On Thu, Aug 15, 2019 at 11:27:51AM -0700, Paul Walmsley wrote:
> 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
About pushing mem*() generic, let's start with the reason why in the first place
KASAN needs re-implement its own string operations:
In mm/kasan/common.c:
#undef memset
void *memset(void *addr, int c, size_t len)
{
check_memory_region((unsigned long)addr, len, true, _RET_IP_);
return __memset(addr, c, len);
}
KASAN would call the string operations with the prefix '__', which should be
just an alias to the proper one.
In the past, every architecture that supports KASAN does this in assembly.
E.g. ARM64:
In arch/arm64/lib/memset.S:
ENTRY(__memset)
ENTRY(memset)
...
...
EXPORT_SYMBOL(memset)
EXPORT_SYMBOL(__memset) // export this as an alias
In arch/arm64/include/asm/string.h
#define __HAVE_ARCH_MEMSET
extern void *memset(void *, int, __kernel_size_t);
extern void *__memset(void *, int, __kernel_size_t);
Now, if we are going to replace the current string operations with newlib ones
and let KASAN use them, we must provide something like this:
In lib/string.c:
void *___memset(...)
{
...
}
In include/linux/string.h:
#ifndef __HAVE_ARCH_MEMCPY
#ifdef CONFIG_KASAN
static inline void* __memset(...)
{
___memset(...);
}
extern void memset(...); // force those who include this header uses the
memset wrapped by KASAN
#else
static inline void *memset(...)
{
___memset(...);
}
#endif
#endif
Does this look OK to you?
Nick
next prev parent reply other threads:[~2019-08-19 6:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 7:19 [PATCH 0/2] KASAN support for RISC-V Nick Hu
2019-08-07 7:19 ` [PATCH 1/2] riscv: Add memmove string operation Nick Hu
2019-08-12 15:04 ` Christoph Hellwig
2019-08-13 23:50 ` Palmer Dabbelt
2019-08-14 2:22 ` Paul Walmsley
2019-08-14 3:27 ` Nick Hu
[not found] ` <alpine.DEB.2.21.9999.1908141002500.18249@viisi.sifive.com>
2019-08-15 3:12 ` Nick Hu
[not found] ` <alpine.DEB.2.21.9999.1908151124450.18249@viisi.sifive.com>
2019-08-19 6:29 ` Nick Hu [this message]
2019-08-14 18:33 ` Palmer Dabbelt
2019-08-22 15:59 ` Andrey Ryabinin
2019-08-27 9:07 ` Nick Hu
2019-08-27 9:33 ` Andrey Ryabinin
2019-08-28 3:06 ` Nick Hu
2019-08-07 7:19 ` [PATCH 2/2] riscv: Add KASAN support Nick Hu
2019-08-12 15:10 ` Christoph Hellwig
2019-08-14 7:44 ` Nick Hu
2019-08-22 17:08 ` Andrey Ryabinin
2019-09-03 15:08 ` Daniel Axtens
2019-09-04 2:24 ` Nick Hu
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