remote GDB problem reading instructions from FLASH (IXP425)

remote GDB problem reading instructions from FLASH (IXP425)

[Jonathan Wurtz]

Hello,

I'm trying to debug code running from Flash on an IXDP425 (XScale) board.  To do 
this, I'm using xscale-elf-gdb on the host, which communicates with the target 
via the Abatron BDI200 JTAG interface unit.  Whenever the code hits a breakpoint 
in flash (which, I assume is a HW breakpoint, since it's in flash, and the code 
does stop), GDB on the host requests to read target memory for that 32-bit 
instruction.  Unfortunately, this instruction resides in flash, which only 
supports 16-data reads.

I've observed this with "set debug remote" turned on:

  > /* Code hits hardware (I assume) breakpoint set at 0x50013b3c */
  >   Sending packet: $m50013b3c,4#be...Ack
  >   Packet received: E01
  >   Cannot access memory at address 0x50013b3c

Is there any way to get GDB to limit reads from within a certain memory range to 
16-bits at a time?  Or, at least to manually set the read size for instruction 
fetches to either 16 or 32, based on where I know I'm executing code?

I've tried setting the GDB variables 'set remote memory-read-packet-size' and 
'set remote memory-write-packet-size' both to 2 (bytes), but it seemed to have 
no effect on GDB instruction fetches.


This is my interpretation of the evidence.  Please correct me if I'm wrong.

Any help appreciated :-)
--Jon


-- 
Jonathan Wurtz
Senior Software Engineer
WorldGate Communications
Phone: (215) 354-5135