Re: PPC EABI, section explanation

[Bill Pringlemeir <bpringle@teklogix.com>]

"http://www3.chips.ibm.com/products/powerpc/library/eabi_app.pdf"
"http://www.esofta.com/pdfs/ppceabi.pdf"

If you need a .ps link, try a web search.

>>>>> "Kristian" == Kristian Otnes <ko@tandberg.no> writes:

    Kristian> Hi, I have downloaded GCC and PowerPC libraries from
    Kristian> www.objsw.com.  (Thanks for providing that...)

    Kristian> 1: Does anyone know where I can get a good explanation
    Kristian> of the EABI interface, I have looked a bit around and
    Kristian> can't say I have the full overview. I suppose I need to
    Kristian> know a bit about it due to the compiler register usage
    Kristian> and some existing assembly code that will be included.

    Kristian> 2: Can anyone tell me where to find some documentation
    Kristian> on some of the sections that gets included when I use
    Kristian> the libraries.  (I want to use stdio issues.)  Some of
    Kristian> them I know from earlier but some are not obvious to me
    Kristian> and I do not relly know what sort of setup is
    Kristian> required. The specific ones are:

    Kristian>    .fixup, .got, got2, sdata2

    Kristian>    I am currently working on a ROM based system, so I
    Kristian> have to know which are static and not, and what to setup
    Kristian> in the crt0 function.

.got stands for global offset table.
.sdata2 is short data.  global data of small size is put in an area
where it can be accessed quickly.  Most of these sections would be 
explained in a document on the EABI.  For instance R2 (no D2 on powerPC).
is used for 'const' small data area.  R13 is used for read/write small
data area.

The GOT sections aren't used in a typical embedded applications from what
I underdand.  They are more for when you have full blown operating system.
I believe they allow unresolved reference in your image.  Like a DLL or
shared library, but you should read the spec to be sure.


    Kristian> 3: So far I have been compiling with the -mno-eabi, if I
    Kristian> drop it I obviously get some more functionality included
    Kristian> (related to EABI setup etc.) But I also get a lot of
    Kristian> unresolved names from the linker, probably related to
    Kristian> start/end locations of sections:

    Kristian>    __SDATA_START__, __SBBS_END__, __GOT__START__,
    Kristian> __GOT2_END__ and so on.

    Kristian>    Should I define these in the linker file? Where do I
    Kristian> find any comments on them?

These are labels probably used by startup code. __SDATA_START__ start of
short RAM data.  __SBBS_END__ end of zero RAM data. __GOT__START__,
__GOT2_END__ global offset table defines.

hth,
Bill Pringlemeir


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