On Wed, Jul 03, 2013 at 08:22:35PM -0400, Paul Gortmaker wrote: > [Re: [PATCH] ARM: move body of head-common.S back to text section] On 03/07/2013 (Wed 18:20) Russell King - ARM Linux wrote: > > > On Wed, Jul 03, 2013 at 11:30:12AM -0400, Paul Gortmaker wrote: > > > [Re: [PATCH] ARM: move body of head-common.S back to text section] On 03/07/2013 (Wed 11:00) Russell King - ARM Linux wrote: > > > > > > > On Wed, Jul 03, 2013 at 01:19:07AM -0400, Paul Gortmaker wrote: > > > > > As an aside, I'm now thinking any __INIT that implicitly rely on EOF for > > > > > closure are nasty traps waiting to happen and it might be worthwhile to > > > > > audit and explicitly __FINIT them before someone appends to the file... > > > > > > > > That hides a different kind of bug though - I hate __FINIT for exactly > > > > that reason. Consider this: > > > > > > Agreed - perhaps masking that it is a ".previous" just hides the fact > > > that it is more like a pop operation vs. an on/off operation, or per > > > function as we have in C. > > > > I read the info pages, because I thought it was a pop operation too. > > I was concerned that .section didn't push the previous section onto the > > stack. > > > > However, .popsection is the pseudio-op which pops. .previous just toggles > > the current section with the section immediately before it. > > > > So: > > > > .text > > .data > > .previous > > /* this is .text */ > > .previous > > /* this is .data */ > > .previous > > /* this is .text */ > > .previous > > /* this is .data */ > > Cool -- I bet we weren't the only ones thinking it was a pop. Thanks. > > Does that make __FINIT less evil than we previously assumed? I think > your example was the following pseudo-patch: > > > .text > <some text> > + .data > + <some data> > __INIT > <big hunk of init> > __FINIT > /* this below used to be text */ > <more stuff that was originally meant for text> > > Even if it is a toggle (vs. pop), the end text will now become data, > so the no-op __FINIT with an explicit section called out just below > it may still be the most unambiguous way to indicate what is going on. > > > > > > That seems reasonable to me. I can't think of any self auditing that is > > > reasonably simple to implement. One downside of __FINIT as a no-op vs. > > > what it is today, is that a dangling __FINIT in a file with no other > > > previous sections will emit a warning. But that is a small low value > > > corner case I think. > > > > That warning from __FINIT will only happen if there has been no section > > or .text or .data statement in the file at all. As soon as you have any > > statement setting any kind of section, .previous doesn't warn. > > > > So: > > > > .text > > ... > > __FINIT > > > > produces no warning.o > > Yep -- we are both saying the same thing here - hence why I called it a > small low value corner case. Note that .previous has another important gotcha. Consider: __INIT /* now in .text.init */ ALT_UP(...) /* now in .text.init */ __FINIT /* now in .alt.smp.text! */ .previous (or macros containing a dangling .previous) shouldn't be used unless you're absolutely certain what the previous section was. In general: label: <stuff> .previous restores to the section which was current at label, only if there are no section directives in <stuff>, nor anything which could contain a section directive after macro expansion. The same goes for the hidden, dangling .previous embedded in __FINIT and friends. Cheers ---Dave -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
