Kernel related (?) user space crash at ARM11 MPCore
catalin.marinas at arm.com
Mon Sep 7 12:43:30 EDT 2009
On Mon, 2009-09-07 at 17:56 +0200, Dirk Behme wrote:
> Catalin Marinas wrote:
> > There is a glibc patch to allow fully position-independent code and
> > avoid CoW for text pages:
> > http://sourceware.org/ml/libc-ports/2008-10/msg00009.html
> > We tested it and it seems to solve the problem without requiring a
> > kernel patch.
> Regarding "fix the tool chain/libc and not the kernel":
> The initial issue we are discussing here was found with a user space
> application downloaded as binary. Namely Ubuntu-ARM. While we could
> try to fix some tool chains, we never will be able to fix all tool
> chains out there. There will be ever some binaries compiled with a
> non-patched tool chain, resulting in ARM11 MPCore failures.
Please don't get me wrong, I'm in favour of a kernel fix even though
future toolchains may avoid this problem. I'm just trying clarify the
issue and get another opinion from Russell or others on this list.
> Additionally, this Ubuntu ARM port runs fine on single core ARM11
> (e.g. N800) or Cortex A8 (e.g OMAP3 based BeagleBoard). It's my
> understanding that the issue we are discussing here is ARM11 MPCore
> kernel (cache handling?) specific, then.
It's a problem with write-allocate caches, it isn't related to SMP. When
CONFIG_SMP is enabled, the kernel sets the cache policy to writealloc.
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