libbpf: Add support for field size relocations (94f060e9) · Commits · 戴 / test

tools/lib/bpf/bpf_core_read.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -96,6 +96,13 @@ enum bpf_field_info_kind {
		#define bpf_core_field_exists(field) \
		__builtin_preserve_field_info(field, BPF_FIELD_EXISTS)

		/*
		* Convenience macro to get byte size of a field. Works for integers,
		* struct/unions, pointers, arrays, and enums.
		*/
		#define bpf_core_field_size(field) \
		__builtin_preserve_field_info(field, BPF_FIELD_BYTE_SIZE)

		/*
		* bpf_core_read() abstracts away bpf_probe_read() call and captures offset
		* relocation for source address using __builtin_preserve_access_index()

tools/lib/bpf/libbpf.c

+32 −8

Original line number	Diff line number	Diff line
		@@ -2704,8 +2704,10 @@ err_out:
		/* Check two types for compatibility, skipping const/volatile/restrict and
		* typedefs, to ensure we are relocating compatible entities:
		* - any two STRUCTs/UNIONs are compatible and can be mixed;
		* - any two FWDs are compatible;
		* - any two FWDs are compatible, if their names match (modulo flavor suffix);
		* - any two PTRs are always compatible;
		* - for ENUMs, names should be the same (ignoring flavor suffix) or at
		* least one of enums should be anonymous;
		* - for ENUMs, check sizes, names are ignored;
		* - for INT, size and signedness are ignored;
		* - for ARRAY, dimensionality is ignored, element types are checked for
		@@ -2733,11 +2735,23 @@ recur:
		return 0;

		switch (btf_kind(local_type)) {
		case BTF_KIND_FWD:
		case BTF_KIND_PTR:
		return 1;
		case BTF_KIND_ENUM:
		return local_type->size == targ_type->size;
		case BTF_KIND_FWD:
		case BTF_KIND_ENUM: {
		const char local_name, targ_name;
		size_t local_len, targ_len;

		local_name = btf__name_by_offset(local_btf,
		local_type->name_off);
		targ_name = btf__name_by_offset(targ_btf, targ_type->name_off);
		local_len = bpf_core_essential_name_len(local_name);
		targ_len = bpf_core_essential_name_len(targ_name);
		/* one of them is anonymous or both w/ same flavor-less names */
		return local_len == 0 \|\| targ_len == 0 \|\|
		(local_len == targ_len &&
		strncmp(local_name, targ_name, local_len) == 0);
		}
		case BTF_KIND_INT:
		/* just reject deprecated bitfield-like integers; all other
		* integers are by default compatible between each other
		@@ -2926,16 +2940,23 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
		const struct btf_member *m;
		const struct btf_type *mt;
		bool bitfield;
		__s64 sz;

		/* a[n] accessor needs special handling */
		if (!acc->name) {
		if (relo->kind != BPF_FIELD_BYTE_OFFSET) {
		pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access'\n",
		if (relo->kind == BPF_FIELD_BYTE_OFFSET) {
		*val = spec->bit_offset / 8;
		} else if (relo->kind == BPF_FIELD_BYTE_SIZE) {
		sz = btf__resolve_size(spec->btf, acc->type_id);
		if (sz < 0)
		return -EINVAL;
		*val = sz;
		} else {
		pr_warn("prog '%s': relo %d at insn #%d can't be applied to array access\n",
		bpf_program__title(prog, false),
		relo->kind, relo->insn_off / 8);
		return -EINVAL;
		}
		*val = spec->bit_offset / 8;
		if (validate)
		*validate = true;
		return 0;
		@@ -2963,7 +2984,10 @@ static int bpf_core_calc_field_relo(const struct bpf_program *prog,
		byte_off = bit_off / 8 / byte_sz * byte_sz;
		}
		} else {
		byte_sz = mt->size;
		sz = btf__resolve_size(spec->btf, m->type);
		if (sz < 0)
		return -EINVAL;
		byte_sz = sz;
		byte_off = spec->bit_offset / 8;
		bit_sz = byte_sz * 8;
		}

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