[v4] selftests/powerpc: New TM signal self test

[Michael Ellerman]

On Tue, 2019-01-08 at 11:31:21 UTC, Breno Leitao wrote:
> A new self test that forces MSR[TS] to be set without calling any TM
> instruction. This test also tries to cause a page fault at a signal
> handler, exactly between MSR[TS] set and tm_recheckpoint(), forcing
> thread->texasr to be rewritten with TEXASR[FS] = 0, which will cause a BUG
> when tm_recheckpoint() is called.
> 
> This test is not deterministic, since it is hard to guarantee that the page
> access will cause a page fault. In order to force more page faults at
> signal context, the signal handler and the ucontext are being mapped into a
> MADV_DONTNEED memory chunks.
> 
> Tests have shown that the bug could be exposed with few interactions in a
> buggy kernel. This test is configured to loop 5000x, having a good chance
> to hit the kernel issue in just one run.  This self test takes less than
> two seconds to run.
> 
> This test uses set/getcontext because the kernel will recheckpoint
> zeroed structures, causing the test to segfault, which is undesired because
> the test needs to rerun, so, there is a signal handler for SIGSEGV which
> will restart the test.
> 
> v2: Uses the MADV_DONTNEED memory advice
> v3: Fix memcpy and 32-bits compilation
> v4: Does not define unused macros
> 
> Signed-off-by: Breno Leitao <leitao at debian.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/a65329aa7d613288626275546074f1aa

cheers