Messages in this thread | | | Date | Fri, 26 Jun 2015 16:29:52 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] perf tools: don't adjust symbols in vDSO |
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On Fri, Jun 26, 2015 at 04:18:59PM +0100, Andy Lutomirski wrote: > On Fri, Jun 26, 2015 at 7:58 AM, Will Deacon <will.deacon@arm.com> wrote: > > (CC'ing Andy, since the removal of VDSO_PRELINK is user-visible here) > > What arch is this? I removed VDSO_PRELINK entirely from x86 a while > back, and now x86's vdso has a base address of 0 before relocations, > and everything works just fine.
I think this is only x86, since it's the removal of VDSO_PRELINK that has changed things.
> (Except one ancient glibc, which fails if the vdso is relocated at > all. We no longer support that version of glibc unless you turn off > the vdso entirely.)
The problem is that perf expects to objdump portions of the vdso using --start-address=foo and --stop-address=bar, but these addresses have changed from being offset by VDSO_PRELINK to 0x0.
Thankfully, it looks like perf tool was always broken in this regard, but I figured you might like to be aware of the issue. I guess perf just needs to add on the load address of the vdso .text section to its relative addresses before passing them to objdump.
Will
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