Re: [PATCH v7 10/25] arm64: compat: Add vDSO

[Thomas Gleixner]

On Tue, 9 Jul 2019, John Stultz wrote:
> Though unfortunately, it seems the arm64 vdso code that just landed is
> breaking AOSP for me.
> 
> I see a lot of the following errors:
> 01-01 01:22:14.097   755   755 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 755 (cameraserver),
> pid 755 (cameraserver)
> 01-01 01:22:14.112   759   759 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 759
> (android.hardwar), pid 759 (android.hardwar)
> 01-01 01:22:14.120   756   756 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 756 (drmserver),
> pid 756 (drmserver)
> 
> Which go away if I revert the vdso merge that went in via tip/timers.
> 
> I tried to bisect things down a bit, but as some later fixes are
> required (at one point, date was returning the start epoch and never
> increasing), this hasn't worked too well. But I'm guessing since I
> see: "CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will
> not be built", and the system is half working, I'm guessing this is an
> issue with just the 32bit code failing.  While I can try to sort out
> the proper CROSS_COMPILE_COMPAT in my build environment, I assume
> userland shouldn't be crashing if that value isn't set.

The obvious question is whether the VDSO is mapped to the 32bit process in
that case. It shouldn't...

Thanks,

	tglx