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Getting Started
===============

The simplest demonstration of the unwinder is to use the simulation client
and supplied memory image.  Building and running this can be done on the PC
in the following way:

    $ make unwind

This will use GCC to build the unwinder and the simulation client that is
already configured to read the memory image provided in memhigh.dat
and memlow.dat.  The simulation can be ran under a debugger, Valgrind etc...
and can be ran as follows:

    $ ./unwind
    [ Lots of ouput removed ] 
    Read 0x680ae800 H
    fread() failed: : No error
    A: 0x0000a904
    A: 0x0000a97c
    A: 0x0000a9e8
    A: 0x0000a9d8
    A: 0x0000a9d8
    A: 0x0000a9d8
    A: 0x0000a9d8
    T: 0x0000ab0e
    T: 0x0000ab28
    A: 0x0000aabc
    A: 0x0000aad8
    A: 0x0000b4bc
    A: 0xe800e800

    Result: 8
    
This shows the unwound stack addresses and processor mode (A = ARM, T = Thumb).
The supplied sym file gives the addresses of the functions, making it possible
to lookup the function names on the stack.

NOTE: If you have ran make without the 'unwind' target specified, it will have
defaulted to building the ARM target, and depending on the environment may 
have produced some object files that are incompatible with GCC.  Executing
'make clean' will remove these objects.


Building an ARM Image
=====================

You will need ARM tools installed as well as an emulator.  I use RVCT with the
ARMSD emulator from the SDT version of the tool chain (RVD, the newer debugger
is very expensive, and the older debugger is fine for this purpose).

To build an executable ARM image, do the following:

    $ make clean
    $ make 
    
This will delete any old PC format objects, and then compile a version of the
code that can be executed in ARMSD in the following manner:

    $ armsd unwind.axf
    ARM Source-level Debugger vsn 4.60 (ARM Ltd SDT2.51) [Build number 128]
    RDI 1.5->1.0 Protocol converter vsn 0.1 [Feb 12 2000]
    ARMulator SDT2.51 [Build number 128]
    ARM7TDMI, Tracer, 4GB, Dummy MMU, Soft Angel 1.4 [Angel SWIs], FPE,
      Profiler, Pagetables, Little endian.
    Object program file unwind.axf
    armsd: go
    [ Lots of ouput removed ] 
    A: 0x0000ac4c
    A: 0x0000acc4
    A: 0x0000ad20
    A: 0x0000ad20
    A: 0x0000ad20
    A: 0x0000ad20
    T: 0x0000ae56
    T: 0x0000ae70
    A: 0x0000ae04
    A: 0x0000ae20
    A: 0x0000b420
    
    Result: 1
    2525 9Program terminated normally at PC = 0x0000bd50 (_sys_exit + 0x8)
    +0008 0x0000bd50: 0xef123456  V4.. :    swi      0x123456
    armsd:
    
Since a target image is available, the resulting addresses can be converted 
into function names by using the binutils 'addr2line' tool.  Looking up the
addresses in the symbol file, produced via fromElf, is also possible, as is
using a debugger or any other tool you may have to hand.  For example, I made 
a small program callled addr2sym which serves a similar purpose to addr2line, 
but formats output in a similar manner to the stack result.  Processing the
above stack trace gives the following output:

$ addr2sym unwind.axf 0x0000ac4c 0x0000acc4 0x0000ad20 0x0000ad20 0x0000ad2
0 0x0000ad20  0x0000ae56 0x0000ae70 0x0000ae04 0x0000ae20 0x0000b420 0xe800e800
0: 0x0000ac4c: tailCall() + 0xc
1: 0x0000acc4: testStackResize() + 0x48
2: 0x0000ad20: testRecurse() + 0x18
3: 0x0000ad20: testRecurse() + 0x18
4: 0x0000ad20: testRecurse() + 0x18
5: 0x0000ad20: testRecurse() + 0x18
6: 0x0000ae56: testThumb1() + 0x11
7: 0x0000ae70: testThumb() + 0x13
8: 0x0000ae04: testPrintf() + 0x1c
9: 0x0000ae20: main() + 0x8
a: 0x0000b420: __rt_entry() + 0x3c


Moving to a Target
==================

If you have a target and wish to use the unwinder on it, you will probably 
need to modify the client code to display the unwind information in a way
more suitable to an embedded target; for example to a display or via a
serial port.  Building without UNW_DEBUG is advised, as the debug strings
will consume a lot of ROM and are only really of interest if unwinding does
not correctly handle some situation that needs investigating.


Changelog
=========

12/07/2007: Correct instruction decoding error.
            Add new stop cause to catch jump through zero.
21/01/2006: Initial revision.


Michael McTernan
[email protected]

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