Thank you very much for this! On 10 Sep 2017, David Miller verbalised: > From: David Miller <davem@xxxxxxxxxxxxx> > Date: Mon, 14 Aug 2017 22:35:53 -0700 (PDT) > >> From: Nick Alcock <nick.alcock@xxxxxxxxxx> >> Date: Fri, 11 Aug 2017 13:23:26 +0100 >> >>> unless you have a really serious linker bug, >> >> Open your mind a little bit. > > Looking at the actual details, how did this ever work for anyone? Probably chance. It did seem to work, though. > The arch/sparc/vdso/vdso.lds file says: > > vvar_start = . -(1 << 12); > > And "1 << 12" is 4096, therefore a multiple of 4096 and not 8192. Uh. Yeah. How the heck did I miss that? 50% chance it'll end up correctly aligned *anyway*, of course, and I must have been lucky. Blasted machine-variable page sizes. (You can tell this was derived from the x86 code :/ ) > So, as requested, the object built gets: > > davem@patience:~/src/GIT/sparc-next$ nm -n arch/sparc/vdso/vdso64.so.dbg > fffffffffffff000 a vvar_data > fffffffffffff000 a vvar_start > > So why is vdso2c requiring an 8192 byte aligned value for the address > of 'vvar_start'? Because it has to be page-aligned. It's just, uh, the wrong alignment for this architecture. Mea culpa. > Nick, I will be honest and sat that I'm kinda irritated that I had to > track this down and the best you could come up with was blaming the > linker... :-( It's been two years since I looked at that code, and when Nagarathnam sent his email I was at the wrong end of a high-latency satellite link on holiday and then knee-deep in other time-critical stuff, I'm afraid. I entirely forgot this thread was still alive. On 11 Sep 2017, David Miller said: > Breaking this down further, the linker scripts are written assuming > they will be built by a host compiler that generates 64-bit target > code by default. > > This is not a safe assumption. One presumes it's not safe on x86-64 either, then. > My system generates 32-bit binaries from gcc by default, and that's > why you end up with a value of PAGE_SIZE which is 4096 propagating > through all of the generated linker scripts. *This* is down to distro variance, I'm afraid. (And yes, I think your machine is correctly configured, and I should have tested on a -m32-by-default GCC, but I didn't think of it.) -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
