Q.
Can you provide some quick GDB commands for a newbie?
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A.
This is a quick FAQ written in a typical debug sequence and is only meant for beginners. I just extracted the contents of the uploaded file in Doc Site:
http://docs.blackfin.uclinux.org/lib/exe/fetch.php?media=presentations:toolchain:gdb_for_dummies.pdf
Fact Sheet
What is GDB? http://shop.fsf.org/product/debugging-gdb-gnu-source-level-debugger/
“GDB, the GNU Project debugger, allows you to see what is going on `inside' another program while it executes -- or what another program was doing at the moment it crashed. GDB can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act:
What is GDB Server? http://en.wikipedia.org/wiki/Gdbserver
“gdb-server is a computer program that makes it possible to remotely debug other programs.Running on the same system as the program to be debugged, it allows the GNU Debugger to connect from another system; that is, only the executable to be debugged needs to be resident on the target system, while the source code and a copy of the binary file to be debugged reside on the developer’s local computer. The connection can be either TCP or a serial line”
What is GDB Proxy? https://docs.blackfin.uclinux.org/doku.php?id=toolchain:debug:gdbproxy
When debugging under the gdb environment, the debugger needs to know what target to connect to. This target is a tiny server daemon, typically running on the host computer. It is equivalent to a gdbserver, although it does not run on the target hardware. This server is called gdbproxy and is derived from rproxy-0.7.
What is Eclipse? http://en.wikipedia.org/wiki/Eclipse_(software)
Eclipse is a multi-language software development environment comprising an integrated development environment (IDE) and an extensible plug-in system. It is written mostly in Java and can be used to develop applications in Java and, by means of various plug-ins, other programming languages including Ada, C, C++, COBOL, Perl, PHP, Python, R. Ruby (including Ruby on Rails framework), Scala, Clojure, and Scheme.
What is GDB/mi Interface? http://sourceware.org/gdb/onlinedocs/gdb/GDB_002fMI.html#GDB_002fMI
GDB/MI is a line based machine oriented text interface to GDB and is activated by specifying using the --interpreter command line option (see Mode Options). It is specifically intended to support the development of systems which use the debugger as just one small component as a larger system {Eclipse}.
Lets learn from a simple no-hardware code as below. All following gdb commands are sequentially tested…
int global_data = 1111;
void func1();
void func2();
int main(void);
int main(void)
{
func1();
return 0;
}
void func1()
int local_data = 1234;
global_data = 5678;
func2();
void func2()
Start the GDB first:
C:\Program Files\Analog Devices\GNU Toolchain\2010R1\elf\bin>bfin-elf-gdb.exe gdb_debugging
GNU gdb 6.6
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "--host=i386-mingw32msvc --target=bfin-elf"...
(gdb) target remote localhost:2000
Remote debugging using localhost:2000
main () at ../src/gdb_debugging.c:9
9 func1();
(gdb) load
Loading section .rodata, size 0x8 lma 0xff800000
Loading section .eh_frame, size 0x4 lma 0xff800008
Loading section .ctors, size 0x8 lma 0xff80000c
Loading section .dtors, size 0x8 lma 0xff800014
Loading section .jcr, size 0x4 lma 0xff80001c
Loading section .data, size 0x40c lma 0xff800020
Loading section .text, size 0x510 lma 0xffa00000
Loading section .init, size 0x12 lma 0xffa00510
Loading section .fini, size 0xe lma 0xffa00522
Start address 0xffa00000, load size 2396
Transfer rate: 140941 bits/sec, 266 bytes/write.
Insert some break points – at the entry of each function:
(gdb) break main
Breakpoint 1 at 0xffa00274: file ../src/gdb_debugging.c, line 9.
(gdb) break func1
Breakpoint 2 at 0xffa00284: file ../src/gdb_debugging.c, line 17.
(gdb) break func2
Breakpoint 3 at 0xffa002ac: file ../src/gdb_debugging.c, line 28.
Run the code and it should hit breakpoints.
(gdb) continue
Continuing.
Breakpoint 1, main () at ../src/gdb_debugging.c:9
Breakpoint 2, func1 () at ../src/gdb_debugging.c:17
17 int local_data = 1234;
Let’s play with breakpoints. See the information of the breakpoints, how it can be disabled.
(gdb) info breakpoints
Num Type Disp Enb Address What
1 breakpoint keep y 0xffa00274 in main at ../src/gdb_debugging.c:9
breakpoint already hit 1 time
2 breakpoint keep y 0xffa00284 in func1 at ../src/gdb_debugging.c:17
3 breakpoint keep y 0xffa002ac in func2 at ../src/gdb_debugging.c:28
(gdb) disable 2
2 breakpoint keep n 0xffa00284 in func1 at ../src/gdb_debugging.c:17
#0 func1 () at ../src/gdb_debugging.c:17
#1 0xffa00278 in main () at ../src/gdb_debugging.c:9
Single stepping the code…
(gdb) step
19 global_data = 5678;
Let’s print the local variable..
(gdb) info local
local_data = 1234
And the global variable…
(gdb) print/x global_data
$1 = 0x457
Check out the dis-assembly
(gdb) disassemble 0xffa00280 0xffa002a0
Dump of assembler code from 0xffa00280 to 0xffa002a0:
0xffa00280 <func1+0>: LINK 0x10; /* (16) */
0xffa00284 <func1+4>: R0 = 0x4d2 (X); /* R0=0x0x4d2(1234) */
0xffa00288 <func1+8>: [FP -0x4] = R0;
0xffa0028a <func1+10>: P2.H = 0xff80; /* (-128) P2=0x0xff800000<_global_impure_ptr> */
0xffa0028e <func1+14>: P2.L = 0x24; /* ( 36) P2=0x0xff800024<global_data> */
0xffa00292 <func1+18>: R0 = 0x162e (X); /* R0=0x0x162e(5678) */
0xffa00296 <func1+22>: [P2] = R0;
0xffa00298 <func1+24>: CALL 0x0xffa002a4 <func2>;
0xffa0029c <func1+28>: UNLINK;
End of assembler dump.
We run again…
Breakpoint 3, func2 () at ../src/gdb_debugging.c:28
28 }
Look at the back-trace info of function calls and frame info.
(gdb) bt
#0 func2 () at ../src/gdb_debugging.c:28
#1 0xffa0029c in func1 () at ../src/gdb_debugging.c:21
#2 0xffa00278 in main () at ../src/gdb_debugging.c:9
(gdb) backtrace full
No locals.
(gdb) frame
Core register information...
(gdb) info registers
r0 0x162e 5678
r1 0xff80042c -8387540
r2 0x0 0A
r3 0x0 0
r4 0x8000 32768
r5 0x989680 10000000
r6 0x0 0
r7 0x0 0
p0 0xff800178 0xff800178
p1 0x1 0x1
p2 0xff800024 0xff800024
p3 0x3f1ff80 0x3f1ff80
p4 0x3f22148 0x3f22148
p5 0xffc03060 0xffc03060
sp 0xffb00f9c 0xffb00f9c
fp 0xffb00f9c 0xffb00f9c
i0 0xffe01300 -2092288
i1 0xffe00300 -2096384
i2 0x7d801048 2105544776
i3 0x7f900840 2140145728
m0 0x0 0
m1 0x0 0
m2 0xff807ffc -8355844
m3 0x0 0
b0 0x7fa7e73e 2141710142
b1 0xb5025ff6 -1258135562
b2 0x5b4597f7 1531287543
b3 0x4c3dac51 1279110225
l0 0x0 0
l1 0x0 0
l2 0x0 0
l3 0x0 0
a0x 0x0 0
a0w 0x3200000 52428800
a1x 0x0 0
a1w 0x2b53 11091
astat 0x2001025 33558565
rets 0xffa0029c 0xffa0029c <func1+28>
lc0 0x0 0
lt0 0xffa0005c -6291364
lb0 0xffa0005d -6291363
lc1 0x0 0
lt1 0xffa00366 -6290586
lb1 0xffa00367 -6290585
cycles 0xa07d46a4 -1602402652
cycles2 0x0 0
usp 0xffb00ff4 0xffb00ff4
seqstat 0x0 0
syscfg 0x32 50
reti 0xffa000e8 -6291224
retx 0xffa004d6 -6290218
retn 0x986b21f 159822367
rete 0xffa002ac -6290772
pc 0xffa002ac 0xffa002ac <func2+8>
cc 0x1 1
text_addr 0x0 0
text_end_addr 0x0 0
data_addr 0x0 0
fdpic_exec 0x0 0
fdpic_interp 0x0 0
ipend 0x0 0
Set some global data
(gdb) set global_data = 9999
(gdb) print global_data
$2 = 9999
GDB/MI interface is meant for IDDE such as Eclipse. There are of course some simple useful commands. But beware – the console out seems terribly bad, when these commands are invoked directly.
Setting up as usual.
C:\Program Files\Analog Devices\GNU Toolchain\2010R1\elf\bin>bfin-elf-gdb.exe --interpreter=mi gdb_debugging
~"GNU gdb 6.6\n"
~"Copyright (C) 2006 Free Software Foundation, Inc.\n"
~"GDB is free software, covered by the GNU General Public License, and you are\n"
~"welcome to change it and/or distribute copies of it under certain conditions.\n"
~"Type \"show copying\" to see the conditions.\n"
~"There is absolutely no warranty for GDB. Type \"show warranty\" for details.\n"
~"This GDB was configured as \"--host=i386-mingw32msvc --target=bfin-elf\"...\n"
(gdb)
target remote localhost:2000
&"target remote localhost:2000\n"
~"Remote debugging using localhost:2000\n"
~"main () at ../src/gdb_debugging.c:9\n"
~"9\t\tfunc1();\n"
^done
Dis-assembly
-data-disassemble -f gdb_debugging.c -l 15 -n 3 -- 0
^done,asm_insns=
[{address="0xffa00280",func-name="func1",offset="0",inst="LINK 0x10;\t\t/* (16) */"},
{address="0xffa00284",func-name="func1",offset="4",inst="R0 = 0x4d2 (X);\t\t/*\t\tR0=0x0x4d2(1234) */"},
{address="0xffa00288",func-name="func1",offset="8",inst="[FP -0x4] = R0;"}]
Reading and writing data
-data-read-memory 0xff800000 x 1 3 3
^done,addr="0xff800000",nr-bytes="9",total-bytes="9",next-row="0xff800003",prev-row="0xff7ffffd",next-page="0xff800009",prev-page="0xff7ffff7",
memory=[{addr="0xff800000",data=["0x00","0x00","0x00"]},
{addr="0xff800003",data=["0x00","0x43","0x00"]},
{addr="0xff800006",data=["0x00","0x00","0xff"]}]
-data-write-memory 0xff800000 x 1 0x11
-data-write-memory 0xff800001 x 1 0x22
-data-write-memory 0xff800001 x 1 0x33
memory=[{addr="0xff800000",data=["0x11","0x33","0x00"]},
Hi Ken,
I’m going to email you from processor.tools.support@analog.com so that we can discuss the problems you’re having with VisualDSP++, and what’s blocking you right now. We may also be able to figure out a plan for trading in your HPUSBs for ICE-100Bs.
Regards,
Linda
Linda Gray
Processor Tools Support Manager
Prasanth, that's a non sequitir. Just because open source tools are inexpensive or no cost, doesn't mean they're not the best. When you're company pays top dollar for a tools like HPUSB-ICEs, you shouldn't have to suffer with VDSP, but right now that's the only option.
At the bottom of http://docs.blackfin.uclinux.org/doku.php?id=hw:jtag , it lists all the jtag devices gdbproxy supports now. If you happen to have some in the list, you can try. I would recommend ICE-100B and gnICE+ .
You can look up where to buy them here:
http://docs.blackfin.uclinux.org/doku.php?id=buy_stuff
Yes, we could use some other ICE if our company had not already spent beaucoup bucks on loads of HPUSB-ICEs. But since it has, it's difficult to go back and ask for yet another. It sure would be nice if we could get gdbproxy support for HPUSB-ICE. Or perhaps some documentation so someone else could do it.
As I see it, HP USB is way too costly, so it doesn't align with the low cost concept in open source development. Besides ICE 100B is a low cost product.