Re: Displaying more than 16 registers with GDB for ARM targets

[Andrew Cagney <ac131313 at cygnus dot com>]

> 	PROBLEM 1:
> 	GDB uses a #define called NUM_REGS to determine how many
> 	registers a target has, this #define uses gdbarch_num_regs()
> 	to return the number of registers for a specific target.
> 	For ARM targets, the number of registers is set by calling
> 	set_gdbarch_num_regs() in arm-tdep.c the value passed is
> 	NUM_GREGS + NUM_FREGS + NUM_SREGS which totals about 26.
> 
> 	NUM_REGS is used to allocate memory for the register_valid,
> 	and registers variables in regcache.c. Since my target returns 
> 	37 registers, there is not enough space to store them all
> 	using supply_register().

> 	SOLUTION:
> 	Add a #define to arm-tdep.h called MAX_ARM_REGS, this #define
> 	is the max number of registers for all ARM targets, currently
> 	I'm using a value of 48, which is is enough for the currently
> 	supported ARM registers, plus the extra ones I need.
> 	This #define is then used in arm-tdep.c to set the number
> 	of registers for the ARM target with the call to
> 	set_gdbarch_num_regs(). Now when space is allocated for the
> 	register_valid and registers variables, there is enough
> 	space for my extra registers so I can call supply_register()
> 	with out a core dump.


As a rule of thumb[er groan] with GDB, adding #define's to headers 
suggests something going wrong.

Have a closer look at arm_gdbarch_init().  You can change each of these 
parameters, as required from that function without adding extra #defines.

> 	PROBLEM 2:
> 	There is no way to dynamically change the register names
> 	based on a target selection. For example, lets say I create
> 	a remote target interface based on remote.c, when I read the
> 	target registers by issuing the remote 'g' command I get
> 	all 37 registers back from the target and inform GDB by calling
> 	supply_register().
> 	Since GDB only displays registers that it has names for, and
> 	my extra registers have no names, they are not displayed by
> 	GDB.



> 	SOLUTION:
> 	I have expanded on GDBs 'set disassembly-flavor' command which
> 	allows the selection of different names for the standard ARM
> 	registers R0-R15.

I don't think this is the way to do it.  Per above, you simply want to 
modify arm_gdbarch_init() so that it correctly describes your new 
architecture.

Separate to this, you may want to consider mechanisms for having the 
target (via gdbarch_update_p() et.al.) notifing core gdb of the current 
architecture (for instance your new architecture).

enjoy,
Andrew