kcov: support comparison operands collection
authorVictor Chibotaru <tchibo@google.com>
Fri, 17 Nov 2017 23:30:46 +0000 (15:30 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 18 Nov 2017 00:10:04 +0000 (16:10 -0800)
commitded97d2c2b2c5f1dcced0bc57133f7753b037dfc
tree2929f22e810fcd3573892b8124735a3afb6c3058
parentfcf4edac049a8bca41658970292e2dfdbc9d5f62
kcov: support comparison operands collection

Enables kcov to collect comparison operands from instrumented code.
This is done by using Clang's -fsanitize=trace-cmp instrumentation
(currently not available for GCC).

The comparison operands help a lot in fuzz testing.  E.g.  they are used
in Syzkaller to cover the interiors of conditional statements with way
less attempts and thus make previously unreachable code reachable.

To allow separate collection of coverage and comparison operands two
different work modes are implemented.  Mode selection is now done via a
KCOV_ENABLE ioctl call with corresponding argument value.

Link: http://lkml.kernel.org/r/20171011095459.70721-1-glider@google.com
Signed-off-by: Victor Chibotaru <tchibo@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Popov <alex.popov@linux.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: <syzkaller@googlegroups.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/kcov.h
include/uapi/linux/kcov.h
kernel/kcov.c