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SubjectRe: Jettisoning init code (was: nfsroot anyone?)
On Mar 21,  7:15am, H. Peter Anvin wrote:
> Subject: Re: Jettisoning init code (was: nfsroot anyone?)
> It seems to me that the way to do it would be to have another segment
> for this. I *think* ELF can support more segments than .code and
> .data. Is there any way to get gas/gcc to use them, and if not, how
> hard would it be to hack them to support .initcode and .initdata
> segments?

This most certainly would work. I even made a half-hearted attempt
to implement something like this last May. When I did it, I ran across
assembler bugs which prevented the kernel from booting, but perhaps
these are fixed now. I suggest starting with a small user-mode
application first just to make sure that gas/ld work OK with multiple
text sections.

I still have the diffs - I can send them to people who want to
want to look into it to polish it up. They were based on 1.2.8
(most of the work involved is locating the functions which can
safely be moved to the .text.boot section).

The general approach is to use something like:

#ifdef __ELF__
#ifndef MODULE
#define SECTION_NAME(X) __attribute__((section(X)))
#endif
#endif

#ifndef SECTION_NAME
#define SECTION_NAME(X)
#endif

And then function declarations can be made like:

unsigned long inode_init(unsigned long start, unsigned long end)
SECTION_NAME(".text.boot");

unsigned long inode_init(unsigned long start, unsigned long end)
{
/* Function body here... */
}
When I was fooling with it, it looked like the attribute needed to be part
of the prototype and could not be part of the actual function declaration
itself. Maybe this is no longer true for newer compilers.

-Eric


--
"The woods are lovely, dark and deep. But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."


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