On 4/29/20 1:46 PM, Andrii Nakryiko wrote:
On Mon, Apr 27, 2020 at 1:13 PM Yonghong Song <yhs@xxxxxx> wrote:Add bpf_reg_type PTR_TO_BTF_ID_OR_NULL support. For tracing/iter program, the bpf program context definition, e.g., for previous bpf_map target, looks like struct bpf_iter_bpf_map { struct bpf_dump_meta *meta; struct bpf_map *map; }; The kernel guarantees that meta is not NULL, but map pointer maybe NULL. The NULL map indicates that all objects have been traversed, so bpf program can take proper action, e.g., do final aggregation and/or send final report to user space. Add btf_id_or_null_non0_off to prog->aux structure, to indicate that for tracing programs, if the context access offset is not 0, set to PTR_TO_BTF_ID_OR_NULL instead of PTR_TO_BTF_ID. This bit is set for tracing/iter program. Signed-off-by: Yonghong Song <yhs@xxxxxx> --- include/linux/bpf.h | 2 ++ kernel/bpf/btf.c | 5 ++++- kernel/bpf/verifier.c | 19 ++++++++++++++----- 3 files changed, 20 insertions(+), 6 deletions(-)[...]static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg) @@ -410,7 +411,8 @@ static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type) return type == PTR_TO_SOCKET || type == PTR_TO_SOCKET_OR_NULL || type == PTR_TO_TCP_SOCK || - type == PTR_TO_TCP_SOCK_OR_NULL; + type == PTR_TO_TCP_SOCK_OR_NULL || + type == PTR_TO_BTF_ID_OR_NULL;BTF_ID is not considered to be refcounted for the purpose of verifier, unless I'm missing something?
You are correct. PTR_TO_BTF_ID is not there is a clear sign PTR_TO_BTF_ID_OR_NULL should not be there either.
} static bool arg_type_may_be_refcounted(enum bpf_arg_type type) @@ -462,6 +464,7 @@ static const char * const reg_type_str[] = { [PTR_TO_TP_BUFFER] = "tp_buffer", [PTR_TO_XDP_SOCK] = "xdp_sock", [PTR_TO_BTF_ID] = "ptr_", + [PTR_TO_BTF_ID_OR_NULL] = "ptr_or_null_", };[...]
