Message ID | 20160615150558.GB7971@leverpostej (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
On Wed, Jun 15, 2016 at 5:05 PM, Mark Rutland <mark.rutland@arm.com> wrote: > On Wed, Jun 15, 2016 at 04:36:18PM +0200, Dmitry Vyukov wrote: >> > However, it looks like I missed a warning from the kernel build system, >> > and my toolchain doesn't actually support -fsanitize-coverage=trace-pc, >> > so I'm not going to be able to test that further. >> > >> > It would be great if we could deliberately not register the debugfs file >> > when there was no compiler support for the feature, for those like me >> > who miss the build time warning. We do something like that for the LSE >> > atomics on arm64. >> >> Hi Mark, >> >> It's a common problem and it would be great to detect this. >> But I think it's better to return ENOTSUP from open rather than not >> registering the file at all. This way higher level tools will be able >> to more easily diagnose the issue and properly report to user. A >> missing file looks like not mounted debugfs (which another common >> issue). > > I have no strong feeling either way, so long as we don't silently carry > on in a case that makes no sense. > >> I am not sure how to do it. >> Compiler does not provide any define for this option. And I am not >> familiar enough with kernel makefiles. Would it be possible to add a >> define to CLAGS in the makefile along with printing the warning? > > If you follow the arm64 LSE example, you can do something like the > below. > > Note that this relies on CFLAGS_KCOV being cleared when not supported by > the toolchain. I used ENOTSUPP rather than ENOTSUP as there's no > standard definition for the later in the Linux headers. > > Mark. > > ---->8---- > diff --git a/Makefile b/Makefile > index 0f70de6..e6ef260 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 -DCONFIG_KCOV_CC > > > # Use USERINCLUDE when you must reference the UAPI directories only. > diff --git a/kernel/kcov.c b/kernel/kcov.c > index a02f2dd..df2cafd 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 +161,13 @@ static int kcov_open(struct inode *inode, struct file *filep) > { > struct kcov *kcov; > > + /* > + * CONFIG_KCOV was selected, but the compiler does not support the > + * options KCOV requires. > + */ > + if (!IS_ENABLED(CONFIG_KCOV_CC)) > + return -ENOTSUPP; > + > kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); > if (!kcov) > return -ENOMEM; Looks great. Please mail it.
diff --git a/Makefile b/Makefile index 0f70de6..e6ef260 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 -DCONFIG_KCOV_CC # Use USERINCLUDE when you must reference the UAPI directories only. diff --git a/kernel/kcov.c b/kernel/kcov.c index a02f2dd..df2cafd 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 +161,13 @@ static int kcov_open(struct inode *inode, struct file *filep) { struct kcov *kcov; + /* + * CONFIG_KCOV was selected, but the compiler does not support the + * options KCOV requires. + */ + if (!IS_ENABLED(CONFIG_KCOV_CC)) + return -ENOTSUPP; + kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); if (!kcov) return -ENOMEM;