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Date:      2 Dec 1999 17:25:48 -0000
From:      gary@aaa-mainstreet.nl
To:        freebsd-emulation@freebsd.org
Subject:   Emulation kernel bug (linux)
Message-ID:  <19991202172548.2955.qmail@abc.aaa-mainstreet.nl>
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Hi,

I'm trying to get linux Visual-Age for Java from IBM running under BSD 3.3.
I get a core dump:

	% ./ide
	zsh: segmentation fault  ./ide              

A ktrace gives this:

	   792 ide      CALL  mkdir(0)
	   792 ide      RET   mkdir 0
	   792 ide      CALL  getpid
	   792 ide      RET   getpid 792/0x318
	   792 ide      CALL  getpid
	   792 ide      RET   getpid 792/0x318
	   792 ide      CALL  obs_vread(0xa,0xbfbfdb20
	   792 ide      RET   obs_vread 0
	   792 ide      CALL  obs_vread(0xc,0xbfbfdb14
	   792 ide      RET   obs_vread 0
	   792 ide      CALL  setreuid(0,0xbfbfdb50,0)
	   792 ide      RET   setreuid 0
	   792 ide      PSIG  SIGSEGV SIG_DFL
	   792 ide      NAMI  "ide.core"                         

So I took a look at setreuid (which is not necessary anyway - why not
run with the standard ids?).  So I wrote this:

	main()
	{
		setreuid(-1, -1);
	}                        

Runs fine as a BSD binary.   I compile it under linux, though, and this happens:

	% ./lx
	zsh: segmentation fault (core dumped)  ./lx               

Does it look familiar?  Looks like the Visual Age problem.  And I assume
it is a bug, yes?


My system looks like this:

	%uname
	FreeBSD  3.3-RELEASE FreeBSD 3.3-RELEASE #0: Thu Sep 16 23:40:35 GMT 1999     jkh@highwing.cdrom.com:/usr/src/sys/compile/GENERIC  i386                                     
	% kldstat
	Id Refs Address    Size     Name
	 1    6 0xc0100000 277038   kernel
	 2    1 0xc0a32000 4000     kernfs.ko
	 3    2 0xc0a4d000 a000     ibcs2.ko
	 4    1 0xc0a5b000 3000     ibcs2_coff.ko
	 5    1 0xc0a61000 e000     linux.ko

 5    1 0xc0a61000 e000     linux.ko   

	Tail end of kldstat -v:

		Contains modules:
			Id Name
			20 linuxelf
			21 linuxaout                               


So,  is this a known problem?

If so, let me know how to fix it.

If not, can someone give me some help in solving this - I have starting
playing around with .ko files, and want to write one to override the
setreuid call for linux so that it does nothing.  I have just compiled
my fist .ko file, and successfully loaded it (the helloworld example).

Now, this got loaded at 210, and seems to work fine.  Is there I can
load this at 70, so that it removes setreuid functionaility?

Would I do that by changing NO_SYSCALL in the helloworld example?

But of course this is the wrong approach - I really want to override
the linux setreuid, don't I.  But that is currently mapped to BSD
setreuid().  So, how do I override the linux setreuid(), but not the
BSD version?


Any help much appreciated - and I'll gladly put in time to help improve the
emulation - hey, you help me solve the kernel problems, and I'll make
a port for the IBM program, OK?


Thanks,

Gary <gary@hotlava.com>


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