On Mon, 2011-01-17 at 22:35 -0800, David Miller wrote: > From: Steven Rostedt <rost...@goodmis.org> > Date: Mon, 17 Jan 2011 09:15:41 -0500 > > > Again, this is to help the linker keep arrays in tacked. Tracepoints are > > allocated into the tracepoint section, and then read like an array. If > > the linker adds holes as it links sections into one big one, then the > > reading of the array breaks. > > > > We either need to compact it (with the align(4)) which is undesirable, > > or add our own holes like the above does. > > Just take away all of the align directives, it should just work.
If that was the case, we would have never added it :-) > > If it doesn't, then we should investigate to find out the real reason > why. OK, we can remove it and I can see what breaks. > > The linker has no reason to add holes, and in fact if we are to believe > the commit message for 86c38a31aa7f2dd6e74a262710bf8ebf7455acc5 > ("tracing: Fix ftrace_event_call alignment for use with gcc 4.5"), with > gcc-4.x where x < 5, it did work even though some ftrace_event_call > declarations lacked the align directive. > > If this align thing is so critical, why don't we need it for the > exception table entries which live in the "__ex_table" section in the > kernel? It's the same _exact_ kind of thing, and the asm sequence we > use to populate it is identical to what GCC emits for the tracing > object declarations in question. But aren't the __ex_table entries just two words? Which would align nicely regardless. The ftrace_event_call is a relatively large structure, as it may end on a 4 byte alignement, the linker may start the next section with more space to get it back to a 8 byte alignment. This is assuming that x86_64 packs the array in 4 bytes. Hmm, perhaps changing the alignment in vmlinux.lds.h would fix that. Anyway, I'll revert that commit and see if I can break it again. If so, then I'll look for other solutions. Thanks! -- Steve -- To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1295371856.12215.29.ca...@gandalf.stny.rr.com