This is the mail archive of the
gdb@sources.redhat.com
mailing list for the GDB project.
Re: gdb support for Atmel AVR
- From: Andrew Cagney <ac131313 at cygnus dot com>
- To: "Theodore A. Roth" <troth at verinet dot com>
- Cc: Daniel Jacobowitz <drow at mvista dot com>, gdb at sources dot redhat dot com
- Date: Fri, 08 Feb 2002 17:56:40 -0500
- Subject: Re: gdb support for Atmel AVR
- References: <Pine.LNX.4.44.0202081432540.30447-100000@bozoland.mynet>
> On Fri, 8 Feb 2002, Daniel Jacobowitz wrote:
>
> :)I really do not think that TARGET_REMOTE_ADDR_BIT should be
> :)necessary... in what way was TARGET_ADDR_BIT/TARGET_POINTER_BIT
> :)inadequate? Do you have different sized code and data pointers?
>
> Code and data pointers are both 16-bit. The problem is we use some of the
> bits 31-16 to flag whether gdb is asking for code (flash) or data (sram)
> space. Using "remote_address_size = TARGET_ADDR_BIT;" in remote.c causes
> gdb to mask off the upper 16 bits thus removing the flag. Without the
> flag, the target will always think it is accessing code space.
TARGET_ADDR_BIT is the number of significant bits in a CORE_ADDR. For
your target that is 32. The remote protocol will use those 32 bits when
requesting raw memory.
Separatly, you've got 16 bit pointers you need TARGET_PTR_BIT=16. GDB
uses the functions pointer_to_address() and address_to_pointer() when
converting a C code/data pointer to/from a CORE_ADDR.
BTW, the d10v is even more fun. Data pointers are 16 bits and point to
an 8 bit byte. Code pointers are also 16 bits but point to a 16 bit
word. Consequently some shifting also occures when converting to/from
CORE_ADDRS. This all works with out cpu specific changes to core GDB.
> Basically, I've tricked gdb into storing ptrs and addresses into 32 bit
> numbers while it still thinks that they are both 16 bits. I need all 32
> bits sent to the target, but when gdb issues an 'm' packet for say a
> struct, it must request the right number of bytes from the remote target.
The d10v was doing something like that but has since been fixed.
> I got burned by this when I set remoteaddresssize to 32. Gdb would ask for
> 4 bytes at some address and then dereference the return value thinking the
> value was a ptr. Needless to say, the 32 ptr pointed to the wrong data.
I'd try the above.
enjoy,
Andrew