Re: weirdo panic

[Thomas Schwinge]

On Wed, Feb 23, 2005 at 02:43:35PM +0100, Alfred M. Szmidt wrote:
>    > Could you remind me abit more about that thread?
> 
>    Shall I send you the messages or does that
>    <URL:http://lists.gnu.org/archive/html/bug-hurd/2004-10/msg00365.html>
>    suffice?
> 
> Ah, CS thingy...  Try the patch and see if it crashes the program or
> crashes the kernel.

After adding '#include "ldt.h" /* for USER_CS */' to i386/i386/trap.c
I got GNU Mach to compile having Roland's patch applied, but it didn't
help: at the time glibc's build system tries to load an executable using
the newly created loader (.../elf/ld.so.1) the kernel crashes:
#v+
Kernel General protection trap, eip 0x17649c
Kernel: General protection (13), code=14
Stopped at 0x17649c: mov %ax,%fs
db> trace
0x17649c(10617454)
>>>>> General protection (13) at 0x10bdb02 <<<<<
0x10bdb02(6ec6003)
>>>>> Divide error (0) at 0 <<<<<
#v-

#v+
$ addr2line -fe gnumach 0x17649c
inst_fetch
i386/i386/locore.S:1647
#v-

#v+
$ cat -n i386/i386/locore.S | grep -C 10 ^\ \ 1647
  1637          ret                             /* exit */
  1638  
  1639  
  1640  /*
  1641   * int inst_fetch(int eip, int cs);
  1642   *
  1643   * Fetch instruction byte.  Return -1 if invalid address.
  1644   */
  1645  ENTRY(inst_fetch)
  1646          movl    S_ARG1, %eax            /* get segment */
  1647          movw    %ax,%fs                 /* into FS */
  1648          movl    S_ARG0, %eax            /* get offset */
  1649          RETRY(EXT(inst_fetch))          /* re-load FS on retry */
  1650          RECOVER(_inst_fetch_fault)
  1651          movzbl  %fs:(%eax),%eax         /* load instruction byte */
  1652          ret
  1653  
  1654  _inst_fetch_fault:
  1655          movl    $-1,%eax                /* return -1 if error */
  1656          ret
  1657  
#v-


> I don't recall if the patch in question was applied, if you can check
> that it does help, then we can apply it.

It doesn't seem to.


Regards,
 Thomas


P.S. For posterity:
To get debugging symbols in the object files compiled from Assembler
source files, you have to add '-g' to '$ASFLAGS' before configuring
GNU Mach.  I used
#v+
$ CFLAGS="$CFLAGS -O0 -g" ASFLAGS="${ASFLAGS-$CFLAGS} -O0 -g" ./configure [...]
#v-