Re: Adding backtrace to an arm-based on-target debugger

[Nagender Telkar <ntelkar@gmail.com>]

Hello All,

I am trying to get the back trace working for an arm-based target
debugger. The remote gdb protocol does not specify about the
handshakes that go on between the gdb and the remote  target.

I am using GNU gdb 6.0 configured as  "--host=i686-pc-cygwin --target=arm-elf".

Can someone tell me which registers does the gdb use when it is trying
to do a backtrace?
On what basis does it send out the "$m" command?
What is the protocol involved? 
What happens if the enviornment in which the application being
debugged is compiled by "armcc", but the debuggable application is
compiled in "arm-elf-gcc"?
The application being debugged(by arm-elf-gcc) jumps in and out of the
armcc compiled code.

The following is the set of register values shown on the gdb prompt. I
have also shown what happens after I do a "bt" at the command prompt.

Any help would be greatly appreciated. Thanks in advance.
Nagender

 (gdb) i r
r0             0xd380c0 13861056
r1             0xb0c478 11584632
r2             0xd11a68 13703784
r3             0x0      0
r4             0xd38124 13861156
r5             0xd50aec 13961964
r6             0xb0c494 11584660
r7             0xb0c978 11585912
r8             0x0      0
r9             0xd3da98 13884056
r10            0x69817c 6914428
r11            0xb00fb0 11538352
r12            0xb00fb4 11538356
sp             0xb00d44 11537732
lr             0x602c   24620
pc             0x2058   8280
fps            0x0      0
cpsr           0x0      0

(gdb) bt
Sending packet: $mb00f98,4#66...Ack
Packet received: c080d300
#0  ET_SaveReport (pApp=0xd380c0) at et_dbfunctions.c:732
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fa4,4#8a...Ack
Packet received: cc0fb000
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fcc,4#bb...Ack
Packet received: fc0ad500
Sending packet: $md50af4,4#91...Ack
Packet received: 04b04ce2
Sending packet: $md50af8,4#95...Ack
Packet received: 08d04de2
Sending packet: $md50afc,4#c0...Ack
Packet received: 14000be5
Sending packet: $md50b00,4#58...Ack
Packet received: 14301be5
Sending packet: $md50b04,4#5c...Ack
Packet received: 18300be5
Sending packet: $md50b08,4#60...Ack
Packet received: 18001be5
Sending packet: $md50b0c,4#8b...Ack
Packet received: 01f0ffeb
Sending packet: $md50b10,4#59...Ack
Packet received: 18001be5
Sending packet: $md50b14,4#5d...Ack
Packet received: e7eeffeb
Sending packet: $md50b18,4#61...Ack
Packet received: 18301be5
Sending packet: $md50b1c,4#8c...Ack
Packet received: 0c3093e5
Sending packet: $md50b20,4#5a...Ack
Packet received: 003093e5
Sending packet: $md50b24,4#5e...Ack
Packet received: 18201be5
Sending packet: $md50b28,4#62...Ack
Packet received: 2c4093e5
Sending packet: $md50b2c,4#8d...Ack
Packet received: 0c0092e5
Sending packet: $md50b30,4#5b...Ack
Packet received: bb1fa0e3
Sending packet: $mb00fa4,4#8a...Ack
Packet received: cc0fb000
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
#1  0x00d50b10 in ?? ()
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fa4,4#8a...Ack
Packet received: cc0fb000
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
Sending packet: $mb00fcc,4#bb...Ack
Packet received: fc0ad500
Sending packet: $md50af4,4#91...Ack
Packet received: 04b04ce2
Sending packet: $md50af8,4#95...Ack
Packet received: 08d04de2
Sending packet: $md50afc,4#c0...Ack
Packet received: 14000be5
Sending packet: $md50b00,4#58...Ack
Packet received: 14301be5
Sending packet: $md50b04,4#5c...Ack
Packet received: 18300be5
Sending packet: $md50b08,4#60...Ack
Packet received: 18001be5
Sending packet: $md50b0c,4#8b...Ack
Packet received: 01f0ffeb
Sending packet: $md50b10,4#59...Ack
Packet received: 18001be5
Sending packet: $md50b14,4#5d...Ack
Packet received: e7eeffeb
Sending packet: $md50b18,4#61...Ack
Packet received: 18301be5
Sending packet: $md50b1c,4#8c...Ack
Packet received: 0c3093e5
Sending packet: $md50b20,4#5a...Ack
Packet received: 003093e5
Sending packet: $md50b24,4#5e...Ack
Packet received: 18201be5
Sending packet: $md50b28,4#62...Ack
Packet received: 2c4093e5
Sending packet: $md50b2c,4#8d...Ack
Packet received: 0c0092e5
Sending packet: $md50b30,4#5b...Ack
Packet received: bb1fa0e3
Sending packet: $mb00fac,4#b9...Ack
Packet received: 100bd500
(gdb)



On Mon, 05 Jul 2004 10:04:44 +0530, Ramana Radhakrishnan
<ramana.radhakrishnan@codito.com> wrote:
> 
> >I am working on developing an on-target debugger for applications on
> >an arm-based target. I need to add a backtrace feature to it.
> >
> >Can someone tell me where to look for the gdb serial protocol?
> >
> >
> 1. info gdbint.
> 2. gdb/remote.c
> 
> >When I do a "bt" on the gdb prompt I get only the current frame. It
> >does not go beyond the current frame. It is as shown below.
> >
> >#0  Test_Func(nValue=525, psValueBuf=0xb00f0c,
> >Sending packet: $mb00ee0,4#89...Ack
> >Packet received: 14000000
> >   nValueBufSize=20) at et_amountctl.c:390
> >#1  0x00d4b9e4 in ?? ()
> >
> >Can you tell me what do I need to do in the target-side stub?
> >
> >
> >
> Please submit your problem with a script of your debug session showing
> exactly all that you did before this and a small testcase mentioning the
> version of gdb , gcc and binutils that you are currently using for this.
> 
> You could take a look at the script command in bash or you could use
> emacs to capture the debug session using M-x gdb .
> 
> cheers
> Ramana
>