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Message-ID: <f2661969-a0d8-45e1-4334-c9b74d08f143@gmail.com> Date: Fri, 21 Dec 2018 20:46:48 +0200 From: Igor Stoppa <igor.stoppa@...il.com> To: Matthew Wilcox <willy@...radead.org> Cc: Andy Lutomirski <luto@...capital.net>, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Mimi Zohar <zohar@...ux.vnet.ibm.com>, Thiago Jung Bauermann <bauerman@...ux.ibm.com>, igor.stoppa@...wei.com, Nadav Amit <nadav.amit@...il.com>, Kees Cook <keescook@...omium.org>, Ahmed Soliman <ahmedsoliman@...a.vt.edu>, linux-integrity@...r.kernel.org, kernel-hardening@...ts.openwall.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 01/12] x86_64: memset_user() On 21/12/2018 20:25, Matthew Wilcox wrote: > On Fri, Dec 21, 2018 at 08:14:12PM +0200, Igor Stoppa wrote: >> +unsigned long __memset_user(void __user *addr, int c, unsigned long size) >> +{ >> + long __d0; >> + unsigned long pattern = 0; >> + int i; >> + >> + for (i = 0; i < 8; i++) >> + pattern = (pattern << 8) | (0xFF & c); > > That's inefficient. > > pattern = (unsigned char)c; > pattern |= pattern << 8; > pattern |= pattern << 16; > pattern |= pattern << 32; ok, thank you -- igor
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