From: David Miller <davem@davemloft.net>
To: pasha.tatashin@oracle.com
Cc: linux-mm@kvack.org, sparclinux@vger.kernel.org
Subject: Re: [PATCH v1 1/3] sparc64: NG4 memset/memcpy 32 bits overflow
Date: Tue, 28 Feb 2017 10:12:18 -0500 (EST) [thread overview]
Message-ID: <20170228.101218.983689349992464602.davem@davemloft.net> (raw)
In-Reply-To: <1488293746-965735-2-git-send-email-pasha.tatashin@oracle.com>
From: Pavel Tatashin <pasha.tatashin@oracle.com>
Date: Tue, 28 Feb 2017 09:55:44 -0500
> @@ -252,19 +248,16 @@ FUNC_NAME: /* %o0=dst, %o1=src, %o2=len */
> #ifdef MEMCPY_DEBUG
> wr %g0, 0x80, %asi
> #endif
> - srlx %o2, 31, %g2
> - cmp %g2, 0
> - tne %XCC, 5
> PREAMBLE
> mov %o0, %o3
> brz,pn %o2, .Lexit
This limitation was placed here intentionally, because huge values
are %99 of the time bugs and unintentional.
You will see that every assembler optimized memcpy on sparc64 has
this bug trap, not just NG4.
This is a very useful way to find bugs and length {over,under}flows.
Please do not remove it.
If you have to do 4GB or larger copies, do it in pieces or similar.
Thank you.
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next prev parent reply other threads:[~2017-02-28 15:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-28 14:55 [PATCH v1 0/3] Zeroing hash tables in allocator Pavel Tatashin
2017-02-28 14:55 ` [PATCH v1 1/3] sparc64: NG4 memset/memcpy 32 bits overflow Pavel Tatashin
2017-02-28 15:12 ` David Miller [this message]
2017-02-28 15:56 ` Pasha Tatashin
2017-02-28 18:59 ` Matthew Wilcox
2017-02-28 19:34 ` Pasha Tatashin
2017-02-28 19:58 ` Matthew Wilcox
2017-02-28 14:55 ` [PATCH v1 2/3] mm: Zeroing hash tables in allocator Pavel Tatashin
2017-02-28 14:55 ` [PATCH v1 3/3] mm: Updated callers to use HASH_ZERO flag Pavel Tatashin
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