bpf: Add PTR_TO_BTF_ID_OR_NULL support

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_iter_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 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.

Yonghong Song committed 6 years ago

Commit b121b341 parent eaaacd23 files · +18 −5Browse files

Showing the changes to include/linux (1 of 3 files). Show all

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include/linux/bpf.h+2−0

@@ -320,6 +320,7 @@ enum bpf_reg_type { · 319 unmodified lines
320	320	PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
321	321	PTR_TO_XDP_SOCK, /* reg points to struct xdp_sock */
322	322	PTR_TO_BTF_ID, /* reg points to kernel struct */
	323	+ PTR_TO_BTF_ID_OR_NULL, /* reg points to kernel struct or NULL */
323	324	};
324	325
325	326	/* The information passed from prog-specific *_is_valid_access
@@ -658,6 +659,7 @@ struct bpf_prog_aux { · 332 unmodified lines
658	659	bool offload_requested;
659	660	bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */
660	661	bool func_proto_unreliable;
	662	+ bool btf_id_or_null_non0_off;
661	663	enum bpf_tramp_prog_type trampoline_prog_type;
662	664	struct bpf_trampoline *trampoline;
663	665	struct hlist_node tramp_hlist;