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Date: Fri, 5 Aug 2022 13:31:15 +0200 From: Artem Savkov <asavkov@...hat.com> To: Alexei Starovoitov <alexei.starovoitov@...il.com> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Andrea Arcangeli <aarcange@...hat.com>, Daniel Vacek <dvacek@...hat.com>, Jiri Olsa <olsajiri@...il.com>, Song Liu <song@...nel.org>, Daniel Xu <dxu@...uu.xyz> Subject: Re: [PATCH bpf-next v2 2/3] bpf: export crash_kexec() as destructive kfunc 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@...hat.com> wrote: > > > > Allow properly marked bpf programs to call crash_kexec(). > > > > Signed-off-by: Artem Savkov <asavkov@...hat.com> > > --- > > 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
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