[Qemu-devel] Re: Resume Flag support on i386/x86_64?

[Jan Kiszka <jan.kiszka@siemens.com>]

Alex Smith wrote:
> Hi,
> 
> Recently support for hardware breakpoint support on i386/x86_64 was
> added (revision 5747 -
> http://lists.gnu.org/archive/html/qemu-devel/2008-11/msg01025.html).
> I've been using hardware breakpoints while writing a debugger for my
> hobby OS kernel, however I've discovered that despite support being
> added for them in QEMU, the Resume Flag (bit 16 in EFLAGS) is not
> supported. When this flag is set on return from an interrupt, the CPU
> should ignore instruction breakpoints for the next instruction, and
> then clear the flag after checking for breakpoints (there's a
> description on page 18-10 of the Intel Software Developer's Manual
> Volume 3B).

Mmh, guess I missed this...

> 
> Would it be possible to implement support for this?

I think so. Will take some fiddling within the code generator, will see
what I can do, but you have to be patient (long to-do list...) -- or
look into this on your own. ;)

Well, in the meantime you may also find a correct behavior by running
qemu in kvm mode because then the real hardware is used, and that should
already work as expected.

Jan

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