Re: optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.

Re: optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.

[Alexandre Oliva]

The following reply was made to PR optimization/3329; it has been noted by GNATS.

From: Alexandre Oliva <aoliva@redhat.com>
To: dorian.araneda@intel.com
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.
Date: 21 Jun 2001 16:46:39 -0300

 Do -fno-builtin or -ffreestanding help?
 
 -- 
 Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
 Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
 CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
 Free Software Evangelist    *Please* write to mailing lists, not to me

Re: optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.

[rth]

Synopsis: optimization large memory copies uses kernel memcpy function without user's knowledge.

State-Changed-From-To: open->closed
State-Changed-By: rth
State-Changed-When: Tue Apr  2 02:09:39 2002
State-Changed-Why:
    GCC requires that the memcpy symbol (among others) exist.
    I believe you'll find that at some point the x86 Linux kernel
    maintainers were convinced of this, and now that symbol does
    exist to be exported to your module.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=3329

RE: optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.

[Araneda, Dorian]

The following reply was made to PR optimization/3329; it has been noted by GNATS.

From: "Araneda, Dorian" <dorian.araneda@intel.com>
To: "'Alexandre Oliva'" <aoliva@redhat.com>
Cc: gcc-gnats@gcc.gnu.org
Subject: RE: optimization/3329: optimization large memory copies uses kern
	el memcpy function without user's knowledge.
Date: Thu, 21 Jun 2001 12:50:52 -0700

 i will investigate these flags.
 and thier effects on this optimization
 
 it will not be any time soon but 
 i will get back to you eventually.
 
 thanks for the reply.
 
 -----Original Message-----
 From: Alexandre Oliva [ mailto:aoliva@redhat.com ]
 Sent: Thursday, June 21, 2001 3:47 PM
 To: dorian.araneda@intel.com
 Cc: gcc-gnats@gcc.gnu.org
 Subject: Re: optimization/3329: optimization large memory copies uses
 kernel memcpy function without user's knowledge.
 
 
 Do -fno-builtin or -ffreestanding help?
 
 -- 
 Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
 Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
 CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
 Free Software Evangelist    *Please* write to mailing lists, not to me
 

optimization/3329: optimization large memory copies uses kernel memcpy function without user's knowledge.

[dorian.araneda]

>Number:         3329
>Category:       optimization
>Synopsis:       optimization large memory copies uses kernel memcpy function without user's knowledge.
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 21 08:16:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Dorian S. Araneda
>Release:        unknown-1.0,  version that comes with SuSE 7.1
>Organization:
>Environment:
SuSE 7.1, Pentium II, kernel module compiled with: cc -Wall -O   
>Description:
if I do an assignment of one large structure to another, "myLargeStruct1 = myLargeStruct2", compiler optimization will
choose to use kernel memcpy() instead of generating its own assembly language.  this causes problems for compiled code that must remain
kernel generic and never intend to use kernel calls. Object code will contain mismatched memcpy symbols between
kernels implementing symbol version signatures.  I do not know at what structure size the optimizer looks for to decide whether to use memcpy or
not.  All I know is that the user is unaware that this linkage is occurring and the only way to discover what the compiler did is recognizing the
error and examining the ".s" files.
>How-To-Repeat:
create some large structues. i dont know what size to use.
and do an assignment   "largestruct_1 = largestruct_2"
>Fix:
I correct the problem by using my own function that implements the functionality of memcpy.

>Release-Note:
>Audit-Trail:
>Unformatted: