Re: [avr-gcc-list] avarice again

[Theodore Roth]

I just looked through the gdb code in simulavr and found this:

        /* NOTE: from what I've read on the gdb lists, gdb never uses the
           "continue at address" functionality. That may change, so let's
           catch that case. */

The "continue at address" is the cAAAA or sAAAA command.

You should be able to set PC to anything you want like this:

  (gdb) set $pc = 0xXXXX

where XXXX is the address. Note the the address should be 2 times what the
real flash address is since gdb thinks all addresses are bytes but the
avr addresses the flash space by words.

Of course, I decided to test this before I sent this message and, alas, it
doesn't work. :-(

(gdb) break main
Breakpoint 1 at 0x390: file memtest.c, line 294.
(gdb) c
Continuing.

Breakpoint 1, main () at memtest.c:294
294         MCUCR = _BV (SRE);          /* Enable External SRAM/XMEM */
(gdb) set debug remote 1
(gdb) set $pc = 0x0
Sending packet: $P22=00000000#71...Ack
Packet received: E01
Remote failure reply: E01


It looks like 'P' packets are not implemented in avarice. Plus, I see that
the 'P' packet code that is there isn't handling the PC register
correctly.

What should really happen is avarice should complete ignore 'P' packets
for now and just send gdb an empty reply. Then gdb could try another
method of setting the register if possible. If I can find some time this
weekend, I'll see what I can come up with on this. Not Likely though. :-(

And looking at what simulavr does, I see that I forgot to update it to
handle the change from 2 to 4 bytes for the PC. D'oh! ... Fixed.

Ted Roth

On Thu, 1 Aug 2002, Klaus Rudolph wrote:

:) Hallo all,
:)
:) I took a short look inside the avarice sources and found
:) no function to set the PC. So I must not
:) wonder that I am not able to set PC from gdb. Or have
:) I overseen something?
:)
:) I think that there must be a 'cAAAA' command which
:) set PC to new execution position and
:) therefor must be a way to get the AAAA to the device via
:) jtag. But inside the remote.cc i found:
:)
:)     240     case 'c':  // cAA..AA    Continue from address AA..AA(optional)
:)     241     // try to read optional parameter, pc unchanged if no parm
:)     242 #if 0 // not yet supported
:)     243     if(hexToInt(&ptr, &addr))
:)     244     {
:)     245         registers[PC] = addr;
:)     246     }
:)     247 #endif
:)     248     if (jtagContinue())
:)     249     {
:)     250         strcpy(remcomOutBuffer, "S05"); // Just tell it a break
:) happened.
:)     251     }
:)     252     else
:)     253     {
:)     254         // A breakpoint did not occur. Assume that GDB sent a break.
:)     255
:)     256         // NEED SOMETHING MORE CLEVER THAN THIS!!
:)     257
:)     258         // Flush the GDB command buffer.
:)     259         (void)tcflush(gdbFileDescriptor, TCIFLUSH);
:)     260         // Halt the target.
:)     261         finishCommand();
:)     262         // Send signal up to gdb. Sadly, I can't find in the GDB
:) manual,
:)     263         // which signal to send up. When you run GDB locally under
:)     264         // Linux, a CTRL-C results in GDB saying "Program received
:)     265         // signal SIGINT, Interrupt." This should mean that the
:)     266         // following should work. So far, I can only get GDB to
:) either
:)     267         // declare that "The program no longer exists" or simply not
:)     268         // return the GDB prompt to me :-(.
:)     269 //      strcpy(remcomOutBuffer, "W02"); // Just tell it interrupt
:) occured.
:)     270         strcpy(remcomOutBuffer, "S05"); // Just tell it a break
:) happened.
:)     271 //      strcpy(remcomOutBuffer, "W07"); // Just tell it a break
:) happened.
:)     272 //      strcpy(remcomOutBuffer, "S03"); // Just tell it interrupt
:) occured.
:)     273 //      strcpy(remcomOutBuffer, "S17"); // Just tell it processed
:) stoped.
:)     274 //      strcpy(remcomOutBuffer, "W00"); // Just tell it processed
:) stoped.
:)     275     }
:)     276     break;
:)
:) This seems not to be working way to set PC, or?
:)
:) Same I found with single step instructions: 'sAAAA'
:) Also only set a breakpoint here :-(
:)
:) How do you set the execution position with gdb and avarice?
:) Which gdb commands can I use to debug?
:)
:)
:) Thanks
:)     Klaus
:)
:) --
:) GMX - Die Kommunikationsplattform im Internet.
:) http://www.gmx.net
:)
:) avr-gcc-list at http://avr1.org
:)


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