NetBSD Problem Report #39110

From www@NetBSD.org  Sun Jul  6 13:40:17 2008
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Date: Sun,  6 Jul 2008 13:40:16 +0000 (UTC)
From: paul@whooppee.com
Reply-To: paul@whooppee.com
To: gnats-bugs@NetBSD.org
Subject: Suspect typecast in src/sys/dev/ld.c
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>Number:         39110
>Category:       kern
>Synopsis:       Suspect typecast in src/sys/dev/ld.c
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jul 06 13:45:00 +0000 2008
>Closed-Date:    Sun Jul 06 14:26:45 +0000 2008
>Last-Modified:  Sun Jul 06 14:26:45 +0000 2008
>Originator:     Paul Goyette
>Release:        4.99.67
>Organization:
>Environment:
quicky:dev {285} uname -a
NetBSD quicky.whooppee.com 4.99.66 NetBSD 4.99.66 (QUICKY (ASUS M2N32 WS) 2008-06-20 03:02:36) #1: Fri Jun 20 04:58:08 PDT 2008  paul@speedy.whooppee.com:/build/obj/amd64/sys/arch/amd64/compile/QUICKY amd64
quicky:dev {286} 

>Description:
In src/sys/dev/ld.c there is a typecast of a "struct device *" to a "struct ld_softc *".  While this may work today due to fortuitous alignment of the structures, it is likely to cause problems in the future, especially if the "separate softc from device_t" project reaches this driver.
>How-To-Repeat:
Inspect the code
>Fix:
The following patch replaces the typecast with use of device_private().  Although it adds a couple of instructions, it's not on a commonly-used code path so will have negligible performance or memory-footprint impact.

Index: ld.c
===================================================================
RCS file: /build/cvsroot/src/sys/dev/ld.c,v
retrieving revision 1.59
diff -u -p -r1.59 ld.c
--- ld.c        11 Jun 2008 12:41:22 -0000      1.59
+++ ld.c        5 Jul 2008 15:28:47 -0000
@@ -915,6 +915,6 @@ ld_set_properties(struct ld_softc *ld)
 static void
 ld_config_interrupts (struct device *d)
 {
-       struct ld_softc *sc = (struct ld_softc *)d;
+       struct ld_softc *sc = (struct ld_softc *)device_private(d);
        dkwedge_discover(&sc->sc_dk);
 }

>Release-Note:

>Audit-Trail:
From: Quentin Garnier <cube@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/39110 CVS commit: src/sys/dev
Date: Sun,  6 Jul 2008 14:07:44 +0000 (UTC)

 Module Name:	src
 Committed By:	cube
 Date:		Sun Jul  6 14:07:44 UTC 2008

 Modified Files:
 	src/sys/dev: ld.c

 Log Message:
 Use device_private() where appropriate.

 Noted by Paul Goyette in PR#39110.


 To generate a diff of this commit:
 cvs rdiff -r1.59 -r1.60 src/sys/dev/ld.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: cube@NetBSD.org
State-Changed-When: Sun, 06 Jul 2008 14:26:45 +0000
State-Changed-Why:
Considering that none of the ld drivers are "devcei_t-splitted", it didn't really
matter but changing it doesn't hurt.
Note that it's no longer necessary to cast:  that's the whole idea, actually.


>Unformatted:

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