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Date: Thu, 9 Jun 2016 10:40:21 -0700
From: Andy Lutomirski <>
To: Alexander Monakov <>
Cc: fREW Schmidt <>, Linux Kernel <>, 
	"" <>
Subject: Re: Broken vDSO on built kernel

On Wed, Jun 8, 2016 at 2:36 PM, Alexander Monakov <> wrote:
> On Wed, 8 Jun 2016, fREW Schmidt wrote:
>> I was debugging an issue I ran into (
>> 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 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:


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