On Fri, Sep 22, 2023 at 5:50 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > On Fri, Sep 22, 2023 at 04:55:02PM +0200, KP Singh wrote: > > These macros are a clever trick to determine a count of the number of > > LSMs that are enabled in the config to ascertain the maximum number of > > static calls that need to be configured per LSM hook. > > > > Without this one would need to generate static calls for the total > > number of LSMs in the kernel (even if they are not compiled) times the > > number of LSM hooks which ends up being quite wasteful. > > > > Suggested-by: Kui-Feng Lee <sinquersw@xxxxxxxxx> > > Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > > Acked-by: Song Liu <song@xxxxxxxxxx> > > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx> > > Thought below, but regardless of result: > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > > > > --- > > include/linux/lsm_count.h | 107 ++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 107 insertions(+) > > create mode 100644 include/linux/lsm_count.h > > > > diff --git a/include/linux/lsm_count.h b/include/linux/lsm_count.h > > new file mode 100644 > > index 000000000000..4d6dac6efb75 > > --- /dev/null > > +++ b/include/linux/lsm_count.h > > @@ -0,0 +1,107 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > + > > +/* > > + * Copyright (C) 2023 Google LLC. > > + */ > > + > > +#ifndef __LINUX_LSM_COUNT_H > > +#define __LINUX_LSM_COUNT_H > > + > > +#include <linux/args.h> > > + > > +#ifdef CONFIG_SECURITY > > + > > +/* > > + * Macros to count the number of LSMs enabled in the kernel at compile time. > > + */ > > + > > +/* > > + * Capabilities is enabled when CONFIG_SECURITY is enabled. > > + */ > > +#if IS_ENABLED(CONFIG_SECURITY) > > +#define CAPABILITIES_ENABLED 1, > > +#else > > +#define CAPABILITIES_ENABLED > > +#endif > > We're in an #ifdef CONFIG_SECURITY, so CAPABILITIES_ENABLED will always > be set. As such, we could leave off the trailing comma and list it > _last_ in the macro, and then ... > > > +/* > > + * There is a trailing comma that we need to be accounted for. This is done by > > + * using a skipped argument in __COUNT_LSMS > > + */ > > +#define __COUNT_LSMS(skipped_arg, args...) COUNT_ARGS(args) > > +#define COUNT_LSMS(args...) __COUNT_LSMS(args) > > This wouldn't be needed... Slight preference for explicitly having the capabilities listed than implicitly over counting. But no strong opinion, fine with either approches. > > > + > > +#define MAX_LSM_COUNT \ > > + COUNT_LSMS( \ > > + CAPABILITIES_ENABLED \ > > + SELINUX_ENABLED \ > > + SMACK_ENABLED \ > > + APPARMOR_ENABLED \ > > + TOMOYO_ENABLED \ > > + YAMA_ENABLED \ > > + LOADPIN_ENABLED \ > > + LOCKDOWN_ENABLED \ > > + BPF_LSM_ENABLED \ > > + LANDLOCK_ENABLED) > > > COUNT_ARGS( \ > SELINUX_ENABLED \ > SMACK_ENABLED \ > ... > CAPABILITIES_ENABLED) > > -Kees > > -- > Kees Cook
