NetBSD Problem Report #35597

From dyoung@cuw.ojctech.com  Wed Feb 14 09:36:58 2007
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Date: Wed, 14 Feb 2007 02:31:58 -0600 (CST)
From: dyoung@cuw.ojctech.com
Reply-To: dyoung@cuw.ojctech.com
To: gnats-bugs@NetBSD.org
Cc: dyoung@netbsd.org
Subject: cross-gdb does not grok NetBSD target kcore/kvm
X-Send-Pr-Version: 3.95

>Number:         35597
>Category:       toolchain
>Synopsis:       cross-gdb does not grok NetBSD target kcore/kvm
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 14 09:40:00 +0000 2007
>Last-Modified:  Tue Apr 17 05:05:04 +0000 2007
>Originator:     David Young
>Release:        NetBSD 4.99.9
>Organization:
CUWiN
>Environment:
System: NetBSD cuw 4.99.9 NetBSD 4.99.9 (nfsgeode) #8: Wed Feb 14 00:39:39 CST 2007  dyoung@cuw.ojctech.com:/u4/dyoung-scratch/scratch-new/i386/O/sys/arch/i386/compile/nfsgeode i386
Architecture: i386
Machine: i386
>Description:
As built by 'env MKCROSSGDB=yes build.sh tools', gdb does not understand
'target kcore' or 'target kvm', so it is not possible to use it to examine
a system dump.
>How-To-Repeat:
Compare the debug targets understood by $TOOLDIR/bin/i386--netbsdelf-gdb,

	% /u4/dyoung-scratch/scratch-new/T/bin/i386--netbsdelf-gdb
	GNU gdb 6.5
        Copyright (C) 2006 Free Software Foundation, Inc.
        GDB is free software, covered by the GNU General Public
        License, and you are welcome to change it and/or distribute
        copies of it under certain conditions.
        Type "show copying" to see the conditions.
        There is absolutely no warranty for GDB.  Type "show
        warranty" for details.  This GDB was configured as
        "--host=i386-unknown-netbsdelf2.99.10 --target=i386--netbsdelf".
        (gdb) help target
        Connect to a target machine or process.
        The first argument is the type or protocol of the target machine.
        Remaining arguments are interpreted by the target protocol.  For more
        information on the arguments for a particular protocol, type
        `help target ' followed by the protocol name.

        List of target subcommands:

        target async -- Use a remote computer via a serial line
        target core -- Use a core file as a target
        target exec -- Use an executable file as a target
        target extended-async -- Use a remote computer via a serial line
        target extended-remote -- Use a remote computer via a serial line
        target remote -- Use a remote computer via a serial line

        Type "help target" followed by target subcommand name for
        full documentation.
        Command name abbreviations are allowed if unambiguous.
        (gdb) 

with the debug targets understood by $DESTDIR/usr/bin/gdb (run on
the target system):

        # gdb
        GNU gdb 6.5
        Copyright (C) 2006 Free Software Foundation, Inc.
        GDB is free software, covered by the GNU General Public
        License, and you are welcome to change it and/or distribute
        copies of it under certain conditions.
        Type "show copying" to see the conditions.
        There is absolutely no warranty for GDB.  Type "show
        warranty" for details.
        This GDB was configured as "i386--netbsdelf".
        (gdb) help target
        Connect to a target machine or process.
        The first argument is the type or protocol of the target machine.
        Remaining arguments are interpreted by the target protocol.  For more
        information on the arguments for a particular protocol, type
        `help target ' followed by the protocol name.

        List of target subcommands:

        target async -- Use a remote computer via a serial line
        target child -- Unix child process (started by the "run" command)
        target core -- Use a core file as a target
        target exec -- Use an executable file as a target
        target extended-async -- Use a remote computer via a serial line
        target extended-remote -- Use a remote computer via a serial line
        target kvm -- Use a kernel virtual memory image as a target
        target remote -- Use a remote computer via a serial line

        Type "help target" followed by target subcommand name for
        full documentation.
        Command name abbreviations are allowed if unambiguous.
        (gdb) 

>Fix:
Unknown.

>Audit-Trail:
From: Jason Thorpe <thorpej@shagadelic.org>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: toolchain/35597: cross-gdb does not grok NetBSD target kcore/kvm
Date: Mon, 16 Apr 2007 22:01:31 -0700

 The issue is that "target kcore" / "target kvm" depend on the native  
 libkvm.  Because we can't build a cross-targeted libkvm, we can't use  
 that functionality.

 To fix this, gdb would need to be taught about the crash dump format  
 and how to parse the page tables in the crash dump to do the KVA ->  
 file offset mapping (basically, replace the dead-kernel functionality  
 that we get from libkvm), and do so in a cross-safe way.

 -- thorpej

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