Re: [PATCH] pop previous section in alternative.c

[Linus Torvalds <torvalds@linux-foundation.org>]

On Thu, 10 Apr 2008, Andi Kleen wrote:
> 
> A simple way to detect it on the assembler level would be checking
> that the section is the same after #NO_APP as before #APP

That would mark gcc itself as buggy, because gcc will move some things 
into the #APP/#NO_APP thing, and sometimes doesn't end the #APP at all!

Try gcc -S on this this trivial "program"

	asm("Hello world");

and at least I personally get

	        .file   "bug.c"
	#APP
	        Hello world
	        .ident  "GCC: (GNU) 4.1.2 20070925 (Red Hat 4.1.2-33)"
	        .section        .note.GNU-stack,"",@progbits

and nothing else. Note the lack of #NO_APP ;)

(I also swear I've seen code or data move _into_ the #NO_APP - ie gcc did 
eventually close the #APP section, but did it too late, after it had 
emitted other things itself - but maybe I just dreamed it because I can't 
seem to reproduce it now. Or maybe it's just a historical gcc bug that got 
fixed)

			Linus