Em Wed, Feb 04, 2009 at 05:16:18PM +0100, Petr Machata escreveu: > Hi, > > .debug_arange analysis shows that there's a lot of holes in .text. Turns > out these are NOP runs (for alignment purposes, I guess). First, is it > OK for the producer to leave NOP runs alone? If yes, dwarflint > shouldn't warn about it, but then there is a problem of how to detect > this. > > I think we can assume that the compiler actually emits literal "NOP" > instructions for padding purposes (i.e. not one of these contraptions > that look like they do something). But most of the time, we won't even > see contents of .text, will we? We are dealing with stripped > debuginfo-only files. Or are we going to do our debuginfo > transformation business on full files?
ftrace in the Linux kernel uses NOPs for leaving space for dynamic code patching, to insert calls to mcount, etc. I guess the alternatives code in the Linux kernel also uses NOPs to provide a dynamicly optimizable kernel depending on the processor the kernel is booted on. If curious, take a look at: arch/x86/include/asm/nops.h arch/x86/include/asm/alternative.h arch/um/sys-x86_64/shared/sysdep/system.h Look at rdtsc. in the Linux sources :-) - Arnaldo _______________________________________________ elfutils-devel mailing list [email protected] https://fedorahosted.org/mailman/listinfo/elfutils-devel
