um: Support kcov

This adds support for kcov to UML.

There is a small problem where UML will randomly segfault during boot;
this is because current_thread_info() occasionally returns an invalid
(non-NULL) pointer and we try to dereference it in
__sanitizer_cov_trace_pc(). I consider this a bug in UML itself and this
patch merely exposes it.

[v2: disable instrumentation in UML-specific code]

Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: user-mode-linux-devel <user-mode-linux-devel@lists.sourceforge.net>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
index 08d931c98621..f8530d866c9f 100644
--- a/arch/um/Kconfig.common
+++ b/arch/um/Kconfig.common
@@ -1,6 +1,7 @@
 config UML
         bool
         default y
+        select ARCH_HAS_KCOV
         select HAVE_ARCH_AUDITSYSCALL
         select HAVE_ARCH_SECCOMP_FILTER
         select HAVE_UID16