Re: [Qemu-devel] [PATCH] dump: add kernel_gs_base to QEMU CPU state

[Viktor Prutyanov <viktor.prutyanov@virtuozzo.com>]

On Wed, 11 Jul 2018 13:00:25 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Tue, Jul 10, 2018 at 06:21:09PM +0300, Viktor Prutyanov wrote:
> > This patch adds field with content of KERNEL_GS_BASE MSR to QEMU
> > note in ELF dump.
> > 
> > On Windows, if all vCPUs are running usermode tasks at the time the
> > dump is created, this can be helpful in the discovery of guest
> > system structures during conversion ELF dump to MEMORY.DMP dump.
> > 
> > Signed-off-by: Viktor Prutyanov <viktor.prutyanov@virtuozzo.com>
> > ---
> >  target/i386/arch_dump.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/target/i386/arch_dump.c b/target/i386/arch_dump.c
> > index 35b55fc..a702138 100644
> > --- a/target/i386/arch_dump.c
> > +++ b/target/i386/arch_dump.c
> > @@ -237,7 +237,7 @@ int
> > x86_cpu_write_elf32_note(WriteCoreDumpFunction f, CPUState *cs,
> >   * please count up QEMUCPUSTATE_VERSION if you have changed
> > definition of
> >   * QEMUCPUState, and modify the tools using this information
> > accordingly.  
> 
> Where are the tools using this information, that need to be
> updated?  Won't this break existing versions of those tools?
> 
> Is the dump format and pointers to available tools documented
> somewhere?

I hope that someone from community knows about those tools because I
can't find such tools.

> 
> >   */
> > -#define QEMUCPUSTATE_VERSION (1)
> > +#define QEMUCPUSTATE_VERSION (2)
> >  
> >  struct QEMUCPUSegment {
> >      uint32_t selector;
> > @@ -258,6 +258,7 @@ struct QEMUCPUState {
> >      QEMUCPUSegment cs, ds, es, fs, gs, ss;
> >      QEMUCPUSegment ldt, tr, gdt, idt;
> >      uint64_t cr[5];
> > +    uint64_t kernel_gs_base;
> >  };
> >  
> >  typedef struct QEMUCPUState QEMUCPUState;
> > @@ -315,6 +316,8 @@ static void qemu_get_cpustate(QEMUCPUState *s,
> > CPUX86State *env) s->cr[2] = env->cr[2];
> >      s->cr[3] = env->cr[3];
> >      s->cr[4] = env->cr[4];
> > +
> > +    s->kernel_gs_base = env->kernelgsbase;
> >  }
> >  
> >  static inline int cpu_write_qemu_note(WriteCoreDumpFunction f,
> > -- 
> > 2.7.4
> >   
>