Re: .init .text .fini

[Erik Christiansen <erik at dd dot nec dot com dot au>]

On Wed, May 04, 2005 at 09:33:35PM -0700, Shaun Jackman wrote:
> Why do the symbols _init and _fini sit in their own segments .init and
> .fini rather than in .text? 

Because initialisation normally precedes the main act (.text), and
finish comes after? ;)

> I'm trying to generate a binary suitable for a flash image in an
> embedded system where the start symbol is at the first address, but
> with the default linker script -- armelf.xc in my case -- _init from
> .init is being placed before _mainCRTStartup from .text.

Err .. that sounds perfectly normal doesn't it?. Anything in .text is
post-init code, since your compiler/assembler directives will have
placed initialisation in a .init section? As just one example, avr-gcc
default linker script offers ten init sections:

    *(.init0)  /* Start here after reset.  */
    *(.init1)
    *(.init2)  /* Clear __zero_reg__, set up stack pointer.  */
    *(.init3)
    *(.init4)  /* Initialize data and BSS.  */
    *(.init5)
    *(.init6)  /* C++ constructors.  */
    *(.init7)
    *(.init8)
    *(.init9)  /* Call main().  */
    *(.text)

Of course, one's own init stuff can be placed wherever it does the most
good.

> Could the default order in ld/scripttempl/elf.sc be changed to .text
> .init .fini rather than the current .init .text .fini, or would this
> break something? 

If it is OK to have the code at _init run when/if execution falls off
the end of .text, then by all means you could modify your linker script
to do that. (But running a system's initialisation just before it shuts
down does look a little odd. ;)

hth
Erik