Re: [PATCH v2 1/4] Add helper functions to trad_frame to support register cache maps.

[Simon Marchi <simon dot marchi at ericsson dot com>]

On 2018-09-24 04:51 PM, John Baldwin wrote:
> Currently, signal frame handlers require explicitly coded calls to
> trad_frame_set_reg_addr() to describe the location of saved registers
> within a signal frame.  This change permits the regcache_map_entry
> arrays used with regcache::supply_regset and regcache::collect_regset
> to be used to describe a block of saved registers given an initial
> address for the register block.
> 
> Some systems use the same layout for registers in core dump notes,
> native register sets with ptrace(), and the register contexts saved in
> signal frames.  On these systems, a single register map can now be
> used to describe the layout of registers in all three places.
> 
> If a register map entry's size does not match the native size of a
> register, try to match the semantics used by
> regcache::transfer_regset.  If a register slot is too large, assume
> that the register's value is stored in the first N bytes and ignore
> the remaning bytes.  If the register slot is smaller than the
> register, assume the slot holds the low N bytes of the register's
> value.  Read these low N bytes from the target and zero-extend them to
> generate a register value.

LGTM.  It sounds very good to de-duplicate the knowledge of the register
layout in those structures.

Simon