On Wed, Jun 15, 2016 at 7:04 PM, Mark Rutland <[email protected]> wrote: > If the toolchain does not support -fsanitize-coverage=trace-pc, we blat > this option from CFLAGS_KCOV, and build the kernel without > instrumentation, even if CONFIG_KCOV was selected. However, we still > build the rest of the kcov infrastructure, and expose a kcov file under > debugfs. This can be confusing, as the kernel will appear to support > kcov, yet will never manage to sample any trace PC values. While we do > note this fact at build time, this may be missed, and a user may not > have access to build logs. > > This patch ensures that CC_HAVE_SANCOV_TRACE_PC is defined when the > toolchain supports -fsanitize-coverage=trace-pc, and is not defined > otherwise. When CC_HAVE_SANCOV_TRACE_PC is not defined, the kernel will > return -ENOTSUPP if userspace attempts to open the kcov debugfs file, > indicating that kcov functionality is unavailable. > > Signed-off-by: Mark Rutland <[email protected]> > Cc: Alexander Potapenko <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Dmitry Vyukov <[email protected]> > Cc: James Morse <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Michal Marek <[email protected]> > Cc: [email protected] > --- > Makefile | 2 +- > kernel/kcov.c | 9 +++++++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > > Since v1 [1]: > * Use CC_HAVE_SANCOV_TRACE_PC rather than CONFIG_KCOV_CC > > [1] lkml.kernel.org/r/[email protected] > > diff --git a/Makefile b/Makefile > index 0f70de6..3785a63 100644 > --- a/Makefile > +++ b/Makefile > @@ -369,7 +369,7 @@ LDFLAGS_MODULE = > CFLAGS_KERNEL = > AFLAGS_KERNEL = > CFLAGS_GCOV = -fprofile-arcs -ftest-coverage -fno-tree-loop-im > -Wno-maybe-uninitialized > -CFLAGS_KCOV = -fsanitize-coverage=trace-pc > +CFLAGS_KCOV = -fsanitize-coverage=trace-pc -DCC_HAVE_SANCOV_TRACE_PC > > > # Use USERINCLUDE when you must reference the UAPI directories only. > diff --git a/kernel/kcov.c b/kernel/kcov.c > index a02f2dd..0a0b164 100644 > --- a/kernel/kcov.c > +++ b/kernel/kcov.c > @@ -3,6 +3,7 @@ > #define DISABLE_BRANCH_PROFILING > #include <linux/compiler.h> > #include <linux/types.h> > +#include <linux/errno.h> > #include <linux/file.h> > #include <linux/fs.h> > #include <linux/mm.h> > @@ -160,6 +161,14 @@ static int kcov_open(struct inode *inode, struct file > *filep) > { > struct kcov *kcov; > > +#ifndef CC_HAVE_SANCOV_TRACE_PC > + /* > + * CONFIG_KCOV was selected, but the compiler does not support the > + * options KCOV requires. > + */ > + return -ENOTSUPP; > +#endif /* CC_HAVE_SANCOV_TRACE_PC */ > + > kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); > if (!kcov) > return -ENOMEM;
Looks good to me.
