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Date: Sat, 6 Apr 2013 11:16:19 -0400 From: John David Anglin <dave.anglin@...l.net> To: James Bottomley <James.Bottomley@...senPartnership.com> CC: Rusty Russell <rusty@...tcorp.com.au>, Sebastian Wankerl <sisewank@....cs.fau.de>, linux-kernel@...r.kernel.org, Philip Kranz <philip.kranz@...glemail.com>, i4passt@...ts.informatik.uni-erlangen.de, linux-parisc@...r.kernel.org, corbet@....net Subject: Re: [PATCH] Add non-zero module sections to sysfs On 6-Apr-13, at 6:52 AM, James Bottomley wrote: > On Sat, 2013-04-06 at 15:22 +1030, Rusty Russell wrote: >>> The problem is our assumption that section names be unique. This >>> assumption is wrong. The ELF spec says (version 1.1 page 1-15): "An >>> object file may have more than one section with the same name." >>> We need >>> to fix the kernel not to rely on a bogus assumption ... but we had >>> no >>> idea how to do that in a way that preserved the backwards >>> compatibility >>> of sections subdirectory. >>> >>> I admit that 35dead4235e2b67da7275b4122fed37099c2f462 is a hack, >>> but now >>> the problem has got attention, can we fix it properly? >> >> Yep. The original patch didn't go through me, or we would have had >> this >> discussion back then... >> >> The use of section names in sysfs goes back to one Mr. Corbet. Why >> did >> he do it that way? Because gdb's add-symbol-file makes the same >> assumption. So if we fixed the sysfs somehow, it still wouldn't be >> useful, since there's no way to tell gdb :( >> >> The real answer don't use -ffunction-sections on modules: probably >> not >> as important as the rest of the kernel. And the new shiny is >> -flto anyway. >> >> And that leaves us with a PA-RISC specific issue, for which we should >> move the fix to PA-RISC. >> >> Thoughts? > > Well, we don't have much of a choice. Our ELF stub jump on 32 bits > is a > PCREL17. That means once a module size is over 128k there's a > chance we > might not be able to link it because the jump is too big for the > instruction. IPV6 is one such big module today, but I'm sure there > are > others. The only way I know to fix this is to allow the linker to > insert stubs between functions, so we only fail at linking if a single > function is >128k big. The way to do this is -ffunction-sections, > unless there's something else we could do (all we really need is a way > to ensure we can insert ELF stubs every 128k). There is now a config work around for this. See: http://www.spinics.net/lists/linux-parisc/msg04521.html Dave -- John David Anglin dave.anglin@...l.net -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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