4 First, load the sg kernel module.
7 To run the gdb server, do (you do not need sudo if you have set up
8 permissions correctly):
9 $ make -C build && sudo ./build/st-util 1234 /dev/sg1
12 (gdb) target remote :1234
16 Resetting the chip from GDB
17 ===========================
19 You may reset the chip using GDB if you want. You'll need to use `target
20 extended-remote' command like in this session:
21 (gdb) target extended-remote localhost:1111
22 Remote debugging using localhost:1111
23 0x080007a8 in _startup ()
25 Kill the program being debugged? (y or n) y
27 Starting program: /home/whitequark/ST/apps/bally/firmware.elf
29 Remember that you can shorten the commands. `tar ext :1111' is good enough
35 For convenience, you may install udev rules file, 10-stlink.rules, located
36 in the root of repository. You will need to copy it to /etc/udev/rules.d,
37 and then either reboot or execute
38 $ udevadm control --reload-rules
40 Udev will now create a /dev/stlink file, which will point at appropriate
41 /dev/sgX device. Good to not accidentally start debugging your flash drive.
43 Running programs from SRAM
44 ==========================
46 You can run your firmware directly from SRAM if you want to. Just link
47 it at 0x20000000 and do
48 (gdb) load firmware.elf
50 It will be loaded, and pc will be adjusted to point to start of the
51 code, if it is linked correctly (i.e. ELF has correct entry point).
56 The GDB stub ships with a correct memory map, including the flash area.
57 If you would link your executable to 0x08000000 and then do
58 (gdb) load firmware.elf
59 then it would be written to the memory.
64 Q: My breakpoints do not work at all or only work once.
66 A: Optimizations can cause severe instruction reordering. For example,
67 if you are doing something like `REG = 0x100;' in a loop, the code may
68 be split into two parts: loading 0x100 into some intermediate register
69 and moving that value to REG. When you set up a breakpoint, GDB will
70 hook to the first instruction, which may be called only once if there are
71 enough unused registers. In my experience, -O3 causes that frequently.
73 Q: At some point I use GDB command `next', and it hangs.
75 A: Sometimes when you will try to use GDB `next' command to skip a loop,
76 it will use a rather inefficient single-stepping way of doing that.
77 Set up a breakpoint manually in that case and do `continue'.