_text vs _start

_text vs _start

[Hollis Blanchard]

Hi Magnus, xen/common/kexec.c references _text, which is not provided by
PowerPC's linker script.

Given that you do arithmetic with _end, can you explain why you're not
using _start, which is a standard symbol provided by the default linker
script?

Outside of Linux, kexec is the only code referencing _text.

-- 
Hollis Blanchard
IBM Linux Technology Center

Re: _text vs _start

[Hollis Blanchard]

On Wed, 2007-01-03 at 15:07 -0600, Hollis Blanchard wrote:
> Given that you do arithmetic with _end, can you explain why you're not
> using _start, which is a standard symbol provided by the default linker
> script?

My mistake; _start of course isn't a linker script symbol at all, but
rather the entry point code.

-- 
Hollis Blanchard
IBM Linux Technology Center

Re: _text vs _start

[Keir Fraser]

On 3/1/07 9:22 pm, "Hollis Blanchard" <hollisb@us.ibm.com> wrote:

> On Wed, 2007-01-03 at 15:07 -0600, Hollis Blanchard wrote:
>> Given that you do arithmetic with _end, can you explain why you're not
>> using _start, which is a standard symbol provided by the default linker
>> script?
> 
> My mistake; _start of course isn't a linker script symbol at all, but
> rather the entry point code.

There is an unnecessary disagreement among architectures over what symbols
should be used to mark section and image boundaries. We could reasonably
agree on at least _start/_end and _stext/_etext I think. This would allow
functions like is_kernel_text() to become generic, and make it obvious which
labels kexec should be using.

 -- Keir

Re: _text vs _start

[Hollis Blanchard]

On Wed, 2007-01-03 at 21:32 +0000, Keir Fraser wrote:
> On 3/1/07 9:22 pm, "Hollis Blanchard" <hollisb@us.ibm.com> wrote:
> 
> > On Wed, 2007-01-03 at 15:07 -0600, Hollis Blanchard wrote:
> >> Given that you do arithmetic with _end, can you explain why you're not
> >> using _start, which is a standard symbol provided by the default linker
> >> script?
> >
> > My mistake; _start of course isn't a linker script symbol at all, but
> > rather the entry point code.
> 
> There is an unnecessary disagreement among architectures over what symbols
> should be used to mark section and image boundaries. We could reasonably
> agree on at least _start/_end and _stext/_etext I think. This would allow
> functions like is_kernel_text() to become generic, and make it obvious which
> labels kexec should be using.

Sounds great to me.

PowerPC already arranges for _start to be at the very beginning
of .text, which is at the beginning of the first PT_LOAD segment... so
the end result is that the address of _start is the same as our link
address.

We also provide _etext, and _end, but not _stext (currently).

-- 
Hollis Blanchard
IBM Linux Technology Center

Re: _text vs _start

[Magnus Damm]

On 1/4/07, Keir Fraser <Keir.Fraser@cl.cam.ac.uk> wrote:
> There is an unnecessary disagreement among architectures over what symbols
> should be used to mark section and image boundaries. We could reasonably
> agree on at least _start/_end and _stext/_etext I think. This would allow
> functions like is_kernel_text() to become generic, and make it obvious which
> labels kexec should be using.

I was about to suggest to move the prototypes to a generic header file
while at it, but it seems like that someone already done that...
Thanks!

/ magnus