# rvbacktrace_fp

## Overview

This example demonstrates the use of frame pointer to perform stack backtracking for interrupts, function calls and exception on a riscv32 machine.

## Hardware Configuration

No special configuration is required.

## Running the example

Once this program runs correctly, the function call information corresponding to the situation will be output on the console. In case of an exception, the register values saved in the stack when the exception occurs will be output.

- interrupt

    ``` console

    ENTER ISR

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87f10 - 0x87f40] ra 0x800090f8
    [1]Stack interval :[0x87f40 - 0x87f50] ra 0x80006072
    [2]Stack interval :[0x87f50 - 0x87f60] ra 0x230
    [3]Stack interval :[0x87f60 - 0x87f70] ra 0x282
    [4]Stack interval :[0x87f70 - 0x87fd0] ra 0x800061c8
    [5]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 800090f8 80006072 230 282 800061c8 8000664c
    ---- RV_Backtrace Call Frame End:----

    ```

- caller and callee

    ``` console

    F[function_recursion]: recursion cycle[1]

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87f70 - 0x87fa0] ra 0x800090f8
    [1]Stack interval :[0x87fa0 - 0x87fb0] ra 0x80005fca
    [2]Stack interval :[0x87fb0 - 0x87fd0] ra 0x800061de
    [3]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 800090f8 80005fca 800061de 8000664c
    ---- RV_Backtrace Call Frame End:----
    F[function_recursion]: recursion cycle[2]

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87f50 - 0x87f80] ra 0x800090f8
    [1]Stack interval :[0x87f80 - 0x87f90] ra 0x80005fca
    [2]Stack interval :[0x87f90 - 0x87fb0] ra 0x80005fd4
    [3]Stack interval :[0x87fb0 - 0x87fd0] ra 0x800061de
    [4]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 800090f8 80005fca 80005fd4 800061de 8000664c
    ---- RV_Backtrace Call Frame End:----
    F[function_recursion]: recursion cycle[3]

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87f30 - 0x87f60] ra 0x800090f8
    [1]Stack interval :[0x87f60 - 0x87f70] ra 0x80005fca
    [2]Stack interval :[0x87f70 - 0x87f90] ra 0x80005fd4
    [3]Stack interval :[0x87f90 - 0x87fb0] ra 0x80005fd4
    [4]Stack interval :[0x87fb0 - 0x87fd0] ra 0x800061de
    [5]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 800090f8 80005fca 80005fd4 80005fd4 800061de 8000664c
    ---- RV_Backtrace Call Frame End:----
    F[function_recursion]: recursion cycle[4]

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87f10 - 0x87f40] ra 0x800090f8
    [1]Stack interval :[0x87f40 - 0x87f50] ra 0x80005fca
    [2]Stack interval :[0x87f50 - 0x87f70] ra 0x80005fd4
    [3]Stack interval :[0x87f70 - 0x87f90] ra 0x80005fd4
    [4]Stack interval :[0x87f90 - 0x87fb0] ra 0x80005fd4
    [5]Stack interval :[0x87fb0 - 0x87fd0] ra 0x800061de
    [6]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 800090f8 80005fca 80005fd4 80005fd4 80005fd4 800061de 8000664c
    ---- RV_Backtrace Call Frame End:----

    ```

- exception

    ``` console

    GET FAULT ADDRESS, ENTER TRAP

    ---- RV_Backtrace Call Frame Start: ----
    [0]Stack interval :[0x87e80 - 0x87eb0] ra 0x8000911c
    [1]Stack interval :[0x87eb0 - 0x87ed0] ra 0x80006052
    [2]Stack interval :[0x87ed0 - 0x87ef0] ra 0x422
    [3]Stack interval :[0x87ef0 - 0x87f80] ra 0x80005ff8
    [4]Stack interval :[0x87f80 - 0x87fb0] ra 0x80006026
    [5]Stack interval :[0x87fb0 - 0x87fd0] ra 0x800061e0
    [6]Stack interval :[0x87fd0 - 0x87ff0] ra 0x8000664c

    addr2line -e xxx.elf -a -f 8000911c 80006052 422 80005ff8 80006026 800061e0 8000664c
    ---- RV_Backtrace Call Frame End:----
    ---- RV Core Dump:----
        mcause: 	 0x5
        mepc: 		 0x80005ffc
        ra: 		 0x80005ff8
        t0: 		 0x0
        t1: 		 0x87ed3
        t2: 		 0x20
        s0: 		 0x87fb0
        a0: 		 0x1e
        a1: 		 0xa
        a2: 		 0x1e
        a3: 		 0xf0040000
        a4: 		 0x6e1
        a5: 		 0xffffffff
        a6: 		 0x8000f158
        a7: 		 0x73
        t3: 		 0x271a
        t4: 		 0x10bacb8
        t5: 		 0x3acb8
        t6: 		 0x10bf9e0
    ---- RV Core Dump End:----

    ```

## note

- The first stack frame of the print information is the stack frame of the stack backtrace API, and the call starts at ``[1]Stack interval``.

- In exception situations, ``rvbacktrace_trap()`` needs to be used. For interrupts and function calls, ``rvbacktrace()`` is used.

- To view the call chain of function names, the ``addr2line`` tool needs to be used

    ``` terminal
    addr2line -e xxx.elf -a -f <addr1> <addr2> ...
    ```

- This component is generally used for software debugging. It is recommended to use it under the debug level.