On Wed, Aug 30, 2017 at 9:08 PM, Dmitry Vyukov <[email protected]> wrote: > On Wed, Aug 30, 2017 at 8:23 PM, Mark Rutland <[email protected]> wrote: >> Hi, >> >> On Wed, Aug 30, 2017 at 06:23:29PM +0200, Dmitry Vyukov wrote: >>> From: Victor Chibotaru <[email protected]> >>> >>> 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). >> >> What's needed to build the kernel with Clang these days? >> >> I was under the impression that it still wasn't possible to build arm64 >> with clang due to a number of missing features (e.g. the %a assembler >> output template). >> >>> 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. >>> >>> Signed-off-by: Victor Chibotaru <[email protected]> >>> Cc: Andrew Morton <[email protected]> >>> Cc: Mark Rutland <[email protected]> >>> Cc: Alexander Popov <[email protected]> >>> Cc: Andrey Ryabinin <[email protected]> >>> Cc: Kees Cook <[email protected]> >>> Cc: Vegard Nossum <[email protected]> >>> Cc: Quentin Casasnovas <[email protected]> >>> Cc: [email protected] >>> Cc: [email protected] >>> Cc: [email protected] >>> --- >>> Clang instrumentation: >>> https://clang.llvm.org/docs/SanitizerCoverage.html#tracing-data-flow >> >> How stable is this? >> >> The comment at the end says "This interface is a subject to change." > > > The intention is that this is not subject to change anymore (since we > are using it in kernel). > I've mailed change to docs: https://reviews.llvm.org/D37303 > > FWIW, there is patch in flight that adds this instrumentation to gcc: > https://groups.google.com/forum/#!topic/syzkaller/CSLynn6nI-A > It seems to be stalled on review phase, though.
Good news is that this is submitted to gcc in 251801.
