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... > + > +#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
