On Thu, Aug 04, 2022 at 01:41:53PM -0700, Alexei Starovoitov wrote:
> On Tue, Aug 2, 2022 at 2:10 AM Artem Savkov <asavkov@xxxxxxxxxx> wrote:
> >
> > Allow properly marked bpf programs to call crash_kexec().
> >
> > Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
> > ---
> > kernel/kexec_core.c | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> >
> > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> > index 4d34c78334ce..9259ea3bd693 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -39,6 +39,8 @@
> > #include <linux/hugetlb.h>
> > #include <linux/objtool.h>
> > #include <linux/kmsg_dump.h>
> > +#include <linux/btf.h>
> > +#include <linux/btf_ids.h>
> >
> > #include <asm/page.h>
> > #include <asm/sections.h>
> > @@ -1238,3 +1240,22 @@ void __weak arch_kexec_protect_crashkres(void)
> >
> > void __weak arch_kexec_unprotect_crashkres(void)
> > {}
> > +
> > +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> > +BTF_SET8_START(kexec_btf_ids)
> > +BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> > +BTF_SET8_END(kexec_btf_ids)
> > +
> > +static const struct btf_kfunc_id_set kexec_kfunc_set = {
> > + .owner = THIS_MODULE,
> > + .set = &kexec_btf_ids,
> > +};
> > +
> > +static int __init crash_kfunc_init(void)
> > +{
> > + register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
> > + return 0;
> > +}
> > +
> > +subsys_initcall(crash_kfunc_init);
> > +#endif
>
> It feels there will be a bunch of such boiler plate code
> in different .c files in many places in the kernel
> if we go with this approach.
>
> Maybe we should do one call:
> register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING
> from kernel/bpf/helper.c
> to register all tracing kfuncs ?
>
> And gate
> BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> with #ifdef CONFIG_KEXEC_CORE.
>
> We have such a pattern in verifier.c already.
Good idea, thanks for the pointers. I'll do that in next version.
--
Artem
