- qemu CVS, without using the kqemu module

- Solaris x86 guest

- I'm trying to debug a user program inside the Solaris x86 guest:

  $ mdb /bin/date
  > main:b
  > :r

  (note: mdb uses a breakpoint inside the target's dynamic linker
  ld.so.1 and single steps over that breakpoint during target
  program startup)




When kqemu isn't available, single stepping a user programm in the
/bin/mdb debugger in a Solaris x86 guest doesn't work.

The Solaris x86 kernel verifies that the "BS (single step) flag (bit
14)" in the DR6 debug status register is set when a user
program gets an exception #1 (EXCP01_SSTP).

qemu currently doesn't set this bit for exception #1 (EXCP01_SSTP).

The Solaris x86 kernel complains with the message:
    Unexpected INT 1 in user mode, dr6=0

At this point the Solaris x86 guest kernel is stuck in an endless
loop with "Unexpected INT 1 in user mode, dr6=0" messages.


Workaround:
===========

For the x86 platform only: use the kqemu module.


Suggested fix:
==============

Set the 0x4000 bit in DR6 when single stepping.

See the attached patch.  With this patch applied, debugging a user
program works.