Re: [Qemu-devel] [PATCH v2] dump: add kernel_gs_base to QEMU CPU state

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Jul 12, 2018 at 08:29:27PM +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>
> ---
>  v2: keep version 1 in QEMUCPUState and document the extension procedure
> 
>  target/i386/arch_dump.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/target/i386/arch_dump.c b/target/i386/arch_dump.c
> index 35b55fc..cc8750f 100644
> --- a/target/i386/arch_dump.c
> +++ b/target/i386/arch_dump.c
> @@ -258,6 +258,12 @@ struct QEMUCPUState {
>      QEMUCPUSegment cs, ds, es, fs, gs, ss;
>      QEMUCPUSegment ldt, tr, gdt, idt;
>      uint64_t cr[5];
> +    /*
> +     * Fields below are optional and are being added at the end without
> +     * changing the version. External tools may identify their presence
> +     * by checking 'size' field.
> +     */
> +    uint64_t kernel_gs_base;
>  };
>  
>  typedef struct QEMUCPUState QEMUCPUState;
> @@ -315,6 +321,8 @@ 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;

This breaks i386-softmmu:

/home/travis/build/ehabkost/qemu/target/i386/arch_dump.c: In function ‘qemu_get_cpustate’:
/home/travis/build/ehabkost/qemu/target/i386/arch_dump.c:325:28: error: ‘CPUX86State’ has no member named ‘kernelgsbase’
     s->kernel_gs_base = env->kernelgsbase;
                            ^
make[1]: *** [target/i386/arch_dump.o] Error 1
make: *** [subdir-i386-softmmu] Error 2
make: *** Waiting for unfinished jobs....

-- 
Eduardo