On Fri, Jun 26, 2015 at 8:29 AM, Will Deacon <will.dea...@arm.com> wrote: > 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.dea...@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. >
Given that we've randomized the vdso load address on x86 for years, I don't see how perf ever worked here. There was a brief period during which we actually loaded the vdso at the address VDSO_PRELINK, but that's long gone. Is there a patch I should be looking at? --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/
