On Mon, Mar 10, 2014 at 8:09 PM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Mon, Mar 10, 2014 at 7:37 PM, Andy Lutomirski <l...@amacapital.net> wrote: >> >> It does. My patch breaks OpenSuSE 9 when >> CONFIG_ENABLE_VDSO32_BY_DEFAULT=y unless it's overridden by sysctl or >> boot option. > > Oh, I missed that "when =y" part. > > But why do we then want to have that "=y" as an option at all? > > If the situation is that everybody is fine with that being disabled by > default, let's just make it the default. And I'd even be ok with > removing it as an option *entirely*. > > That would seem to be *much* preferable that having an option that > nobody really wants anyway, and where the default value would break > some users. THAT just seems completely insane.
I suspect that a lot of 32-bit Linux users want syscall and/or sysenter, and Stefani certainly wants the fast timing that the vDSO can provide. Also, presumably __kernel_sigreturn serves some purpose :) The basic issue is that most old glibc versions (and all versions that were ever tagged in a release) work correctly regardless of whether there is a vDSO, and newer glibc versions (since 2004) will take advantage of a vDSO if one exists, but OpenSuSE 9 shipped with a creatively broken version that blows up if presented with a vDSO that's not prelinked to its actual address. Currently there are three options: sane vDSO, no vDSO, and OpenSuSE 9-compatible vDSO. The latter is a mess to maintain and breaks ASLR (even for users of modern glibc), and having a vDSO is apparently important enough that people are willing to pay to enhance it. The default is OpenSuSE 9-compatible vDSO, which is IMO an odd choice. ISTM the right solution is to make OpenSuSE 9 users turn off the vDSO (which is a performance hit for them, but not a correctness issue) and let everyone else have a simpler kernel that has no ASLR issues. I'm a bit heartened by the fact that the failure mode on OpenSuSE 9 is a rather distinctive and easily Googlable message. Most of the hits offer abi.vsyscall32=0 or vdso=0 as suggestions, both of which continue to work with my patch. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
