Re: [PATCH] Fix prefetch patching in 2.5-bk

[Linus Torvalds]

On Thu, 1 May 2003, Andi Kleen wrote:
> 
> If your machine BUG()s in apply_alternatives at booting 
> or module loading you need this patch.

I applied it, but I don't have to like it..

How about doing this differently, and having something like this:

	#define nop_alternative(newinstr, feature)		\
		".section .altinstructions,\"a\"\n"		\
		"  .align 4\n"
		"    .long 660f\n"
		"    .long 663f\n"
		"    .byte %c0\n"
		"    .byte 0\n"
		"    .byte 664f-663f\n"
		".previous\n"
		".section .altinstr_replacement",\"ax\"\n"
		"663:\n\t" newinstr "\n664:\n"
		".previous"
		"660:\n\t"
		".rept  664b-663b, 0x90\n\t"

and making "sourcelen==0" a special case for replacement (replace with the 
proper destination length nop, instead of having that "0x90 0x90 0x90" 
sequence).

This allows you to use arbitrary-sized things without having to worry 
about having to have the size right, or without having to use 
unnecessarily long nop-sequences. You'll always get the right-size nop.

		Linus