[PATCH 2/2] scripts/gdb: Support getting current task struct in UML

[Jan Kiszka]

On 15.02.23 00:35, Glenn Washburn wrote:
> A running x86 UML kernel reports with architecture "i386:x86-64" as
> it is a sub-architecture. However, a difference with bare-metal x86
> kernels is in how it manages tasks and the current task struct. To
> identify that the inferior is a UML kernel and not bare-metal, the
> symbol "uml_kmalloc" is checked for. If it exists, then do the UML
> specific way of getting the current task struct.
> 
> Signed-off-by: Glenn Washburn <development at efficientek.com>
> ---
>  scripts/gdb/linux/cpus.py | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
> index 289f0bf4d2a1..90908653f6c7 100644
> --- a/scripts/gdb/linux/cpus.py
> +++ b/scripts/gdb/linux/cpus.py
> @@ -163,8 +163,12 @@ def get_current_task(cpu):
>      task_ptr_type = task_type.get_type().pointer()
>  
>      if utils.is_target_arch("x86"):
> -        var_ptr = gdb.parse_and_eval("&current_task")
> -        return per_cpu(var_ptr, cpu).dereference()
> +        if gdb.lookup_global_symbol("uml_kmalloc"):
> +            var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")

Can't we use an UML indicator that is related to the topic? Why not
cpu_tasks itself?

> +            return var_ptr.dereference()
> +        else:
> +            var_ptr = gdb.parse_and_eval("&current_task")
> +            return per_cpu(var_ptr, cpu).dereference()
>      elif utils.is_target_arch("aarch64"):
>          current_task_addr = gdb.parse_and_eval("$SP_EL0")
>          if((current_task_addr >> 63) != 0):

Jan

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