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

[Eduardo Habkost <ehabkost@redhat.com>]

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?


>   */
> -#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
> 

-- 
Eduardo