4 First, load the sg kernel module.
7 On Ubuntu you need to install the package libsgutils2-dev:
8 # sudo apt-get install libsgutils2-dev
10 To run the gdb server, do (you do not need sudo if you have set up
11 permissions correctly):
12 $ make -C build && sudo ./build/st-util 1234 /dev/sg1
15 (gdb) target remote :1234
19 Resetting the chip from GDB
20 ===========================
22 You may reset the chip using GDB if you want. You'll need to use `target
23 extended-remote' command like in this session:
24 (gdb) target extended-remote localhost:1111
25 Remote debugging using localhost:1111
26 0x080007a8 in _startup ()
28 Kill the program being debugged? (y or n) y
30 Starting program: /home/whitequark/ST/apps/bally/firmware.elf
32 Remember that you can shorten the commands. `tar ext :1111' is good enough
38 For convenience, you may install udev rules file, 10-stlink.rules, located
39 in the root of repository. You will need to copy it to /etc/udev/rules.d,
40 and then either reboot or execute
41 $ udevadm control --reload-rules
43 Udev will now create a /dev/stlink file, which will point at appropriate
44 /dev/sgX device. Good to not accidentally start debugging your flash drive.
46 Running programs from SRAM
47 ==========================
49 You can run your firmware directly from SRAM if you want to. Just link
50 it at 0x20000000 and do
51 (gdb) load firmware.elf
53 It will be loaded, and pc will be adjusted to point to start of the
54 code, if it is linked correctly (i.e. ELF has correct entry point).
59 The GDB stub ships with a correct memory map, including the flash area.
60 If you would link your executable to 0x08000000 and then do
61 (gdb) load firmware.elf
62 then it would be written to the memory.
67 Q: My breakpoints do not work at all or only work once.
69 A: Optimizations can cause severe instruction reordering. For example,
70 if you are doing something like `REG = 0x100;' in a loop, the code may
71 be split into two parts: loading 0x100 into some intermediate register
72 and moving that value to REG. When you set up a breakpoint, GDB will
73 hook to the first instruction, which may be called only once if there are
74 enough unused registers. In my experience, -O3 causes that frequently.
76 Q: At some point I use GDB command `next', and it hangs.
78 A: Sometimes when you will try to use GDB `next' command to skip a loop,
79 it will use a rather inefficient single-stepping way of doing that.
80 Set up a breakpoint manually in that case and do `continue'.