Re: [PATCH 01/24] gdb: don't handle i386 k registers as pseudo registers

[John Baldwin <jhb@FreeBSD.org>]

On 11/7/23 9:00 PM, Simon Marchi wrote:
> From: Simon Marchi <simon.marchi@efficios.com>
> 
> I think that i386 k registers are raw registers, and therefore shouldn't
> be handled in the various functions handling pseudo registers.
> 
> What tipped me off is the code in i386_pseudo_register_read_into_value:
> 
>        else if (i386_k_regnum_p (gdbarch, regnum))
> 	{
> 	  regnum -= tdep->k0_regnum;
> 
> 	  /* Extract (always little endian).  */
> 	  status = regcache->raw_read (tdep->k0_regnum + regnum, raw_buf);
> 
> We take regnum (the pseudo register number we want to read), subtract
> k0_regnum, add k0_regnum, and pass the result to raw_read.  So we would
> end up calling raw_read with the same regnum as the function received
> which is supposedly a pseudo register number.
> 
> Other hints are:
> 
>   - The command `maint print raw-registers` shows the k registers.
>   - Printing $k0 doesn't cause i386_pseudo_register_read_into_value to be
>     called.
>   - There's code in i387-tdep.c to save/restore the k registers.

Also, the bottom of i386_gdbarch_init (where all of the pseudo register numbers
are allocated) doesn't allocate any pseudo register numbers for the k registers.
I think this bit of code in i386_gdbarch_init is the definitive set of what
counts as pseudo registers on i386/amd64.
  
> Remove handling of the k registers from:
> 
>   - i386_pseudo_register_read_into_value
>   - i386_pseudo_register_write
>   - i386_ax_pseudo_register_collect

Reviewed-by: John Baldwin <jhb@FreeBSD.org>

-- 
John Baldwin