On Tue, Jun 16, 2020 at 3:05 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Adding support to generate .BTF_ids section that would
> hold various BTF IDs list for verifier.
>
> Adding macros help to define lists of BTF IDs placed in
> .BTF_ids section. They are initially filled with zeros
> (during compilation) and resolved later during the
> linking phase by btfid tool.
>
> Following defines list of one BTF ID that is accessible
> within kernel code as bpf_skb_output_btf_ids array.
>
> extern int bpf_skb_output_btf_ids[];
>
> BTF_ID_LIST(bpf_skb_output_btf_ids)
> BTF_ID(struct, sk_buff)
>
> Suggested-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> include/asm-generic/vmlinux.lds.h | 4 ++
> kernel/bpf/Makefile | 2 +-
> kernel/bpf/btf_ids.c | 3 ++
> kernel/bpf/btf_ids.h | 70 +++++++++++++++++++++++++++++++
> 4 files changed, 78 insertions(+), 1 deletion(-)
> create mode 100644 kernel/bpf/btf_ids.c
> create mode 100644 kernel/bpf/btf_ids.h
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index db600ef218d7..0be2ee265931 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -641,6 +641,10 @@
> __start_BTF = .; \
> *(.BTF) \
> __stop_BTF = .; \
> + } \
> + . = ALIGN(4); \
> + .BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) { \
> + *(.BTF_ids) \
> }
> #else
> #define BTF
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index 1131a921e1a6..21e4fc7c25ab 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -7,7 +7,7 @@ obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list
> obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
> obj-$(CONFIG_BPF_SYSCALL) += disasm.o
> obj-$(CONFIG_BPF_JIT) += trampoline.o
> -obj-$(CONFIG_BPF_SYSCALL) += btf.o
> +obj-$(CONFIG_BPF_SYSCALL) += btf.o btf_ids.o
> obj-$(CONFIG_BPF_JIT) += dispatcher.o
> ifeq ($(CONFIG_NET),y)
> obj-$(CONFIG_BPF_SYSCALL) += devmap.o
> diff --git a/kernel/bpf/btf_ids.c b/kernel/bpf/btf_ids.c
> new file mode 100644
> index 000000000000..e7f9d94ad293
> --- /dev/null
> +++ b/kernel/bpf/btf_ids.c
> @@ -0,0 +1,3 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include "btf_ids.h"
hm... what's the purpose of this btf_ids.c file?
> diff --git a/kernel/bpf/btf_ids.h b/kernel/bpf/btf_ids.h
> new file mode 100644
> index 000000000000..68aa5c38a37f
> --- /dev/null
> +++ b/kernel/bpf/btf_ids.h
[...]
