Add QEMU+GDB instruction to docs

docs/qemu-debug.md

@@ -1,12 +1,58 @@
 # Debugging with QEMU
 
-> This page is work in progress
-
-This toolchain provides `qemu-system-tricore` and `tricore-elf-gdb` executable
-that can be used to run and debug your code in a simulated environment.
+This toolchain provides `qemu-system-tricore` and `tricore-elf-gdb` for running
+and debugging your code in a simulated environment.
 
 > QEMU support for Tricore architecture is incomplete. It provides only basic
 > CPU instruction decode (no interrupts or multi-core) and no peripheral is
 > available. Only core architecture from tc1.3 up to tc1.6.2 is supported
 
-TODO..
+The code below uses ELF executable built from
+[aurix-cmake-code-sample](https://github.com/NoMore201/aurix-cmake-code-sample)
+in debug mode (no optimizations and debug symbols enabled). It should work with
+any Tricore ELF file built with DWARF v3 debug symbols.
+
+First step is to run QEMU providing the ELF executable, enabling gdb stub for
+remote debugging and enable startup freeze option to be able to connect before
+running the emulation.
+
+```
+$ qemu-system-tricore -machine KIT_AURIX_TC277_TRB -kernel ./out/debug/src/aurix_sample_tc33x.elf -s -S
+```
+
+Next we run tricore-elf-gdb, set the architecture version to 1.6.2 and connect
+to QEMU gdb stub:
+
+```
+$ tricore-elf-gdb ./out/debug/src/aurix_sample_tc33x.elf
+
+GNU gdb (GDB) 14.0.50.20230607-git
+Copyright (C) 2023 Free Software Foundation, Inc.
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
+Type "show copying" and "show warranty" for details.
+This GDB was configured as "--host=x86_64-pc-linux-gnu --target=tricore-elf".
+Type "show configuration" for configuration details.
+For bug reporting instructions, please see:
+<https://www.gnu.org/software/gdb/bugs/>.
+Find the GDB manual and other documentation resources online at:
+    <http://www.gnu.org/software/gdb/documentation/>.
+
+For help, type "help".
+Type "apropos word" to search for commands related to "word"...
+Reading symbols from /mnt/c/git/aurix-cmake-code-sample/out/debug/src/aurix_sample_tc33x.elf...
+
+(gdb) set architecture TriCore:V1_6_2
+The target architecture is set to "TriCore:V1_6_2".
+
+(gdb) target remote localhost:1234
+Remote debugging using localhost:1234
+Ifx_Ssw_jumpToFunction (fun=<optimized out>)
+    at /home/nomore/Workspace/aurix-cmake-code-sample/third_party/infineon/Libraries/Infra/Ssw/TC33A/Tricore/Ifx_Ssw_CompilersGnuc.h:183
+183         __asm__ volatile ("ji %0" ::"a" (fun));
+```
+
+Now you can start debugging your code through QEMU.
+
+![gdb example](./gdb-screen.png)