Re: port-vax/41139: pipe(2) seems broken on VAX

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

The following reply was made to PR port-vax/41139; it has been noted by GNATS.

From: Anders Magnusson <ragge%ludd.ltu.se@localhost>
To: Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, mhitch%lightning.msu.montana.edu@localhost,
        gnats-admin%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
Subject: Re: port-vax/41139: pipe(2) seems broken on VAX
Date: Fri, 10 Apr 2009 09:00:23 +0200

 Izumi Tsutsui wrote:
 > mhitch%lightning.msu.montana.edu@localhost wrote:
 > 
 >>  On Wed, 8 Apr 2009, Anders Magnusson wrote:
 >>  
 >>  > It may be worth trying, but it also may require significantly more code.
 >>  > The movc3 instruction handles overlapping copies, but if the data block 
 >> is
 >>  > larger than 64k then it must be done manually.  This is only a problem 
 >> for kcopy,
 >>  > copy{in,out} should not overlap :-)
 >>  
 >>     It's not all that much code, at least for copy{in,out}:
 >>  
 >>  ENTRY(copyout, 0)
 >>           movl    8(%ap),%r3
 >>           blss    3f              # kernel space
 >>           movl    4(%ap),%r1
 >>           brb     2f
 >>  
 >>  ENTRY(copyin, 0)
 >>           movl    4(%ap),%r1
 >>           blss    3f              # kernel space
 >>           movl    8(%ap),%r3
 >>  2:      mfpr    $PR_ESP,%r2
 >>           movab   1f,(%r2)
 >>  4:      tstw    14(%ap)         # check if >= 64K
 >>           bneq    5f
 >>           movc3   12(%ap),(%r1),(%r3)
 >>  1:      mfpr    $PR_ESP,%r2
 >>           clrl    (%r2)
 >>           ret
 >>  5:      movc3   $0xfffc,(%r1),(%r3)
 >>           subl2   $0xfffc,12(%ap)
 >>           brb     4b
 >>  
 >>  3:      mnegl   $1,%r0
 >>           ret
 > 
 > This fixes the pipe problem on 5.0.
 > Should we commit it and pull up to 5.0?
 >
 Please do.
 
 For an overlaying kcopy, it might be an idea to look at the memcpy code in 
libkern.
 
 -- Ragge