Date: Thu, 9 Jun 2016 10:40:21 -0700 From: Andy Lutomirski <luto@...capital.net> To: Alexander Monakov <amonakov@...ras.ru> Cc: fREW Schmidt <frioux@...il.com>, Linux Kernel <linux-kernel@...r.kernel.org>, "musl@...ts.openwall.com" <musl@...ts.openwall.com> Subject: Re: Broken vDSO on built kernel On Wed, Jun 8, 2016 at 2:36 PM, Alexander Monakov <amonakov@...ras.ru> wrote: > On Wed, 8 Jun 2016, fREW Schmidt wrote: >> I was debugging an issue I ran into ( >> https://github.com/docker/docker/issues/23378) and after chatting with the >> folks in #musl and we triaged it down to a broken vDSO (tested by running >> `strace date` and seeing a clock_gettime call.) > > To provide a bit more detail, we've found that the vdso mappend into the > application has no dynamic symbols; Glibc ignores the vdso, so it continues to > work, but musl segfaults since the vdso is invalid. > > I'm pasting below `readelf -aW` output on the vdso dumped on the affected > system (via 'fwrite((void*)getauxval(AT_SYSINFO_EHDR), 8192, 1, stdout)'; > as you can see, there's no dynamic symbols and symbol hash tables. It may > be a toolchain bug since there was no issue with 4.6 kernel (and reportedly > there were no significant vdso changes merged into 4.7 -- the issue is seen > on Ubuntu's 4.7rc2). Hmm. The vdso64.so in /lib/firmware in that image has the same problem, so this isn't vdso2c's fault. I added this to my -next queue to help diagnose it: https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/vdso&id=6436d4c1a83cbe083e54c53bb2b16efaab9b62f4 --Andy
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