Commit 708cdc57 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Andrii Nakryiko
Browse files

libbpf: Support kfunc detection in light skeleton. 



Teach gen_loader to find {btf_id, btf_obj_fd} of kernel variables and kfuncs
and populate corresponding ld_imm64 and bpf_call insns.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230321203854.3035-4-alexei.starovoitov@gmail.com
parent 1057d299

tools/lib/bpf/bpf_gen_internal.h

+3 −1
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ struct ksym_relo_desc { 
	int insn_idx;

	bool is_weak;

	bool is_typeless;

	bool is_ld64;

};



struct ksym_desc {
@@ -24,6 +25,7 @@ struct ksym_desc { 
		bool typeless;

	};

	int insn;

	bool is_ld64;

};



struct bpf_gen {
@@ -65,7 +67,7 @@ void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u 
void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx);

void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *name, enum bpf_attach_type type);

void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,

			    bool is_typeless, int kind, int insn_idx);

			    bool is_typeless, bool is_ld64, int kind, int insn_idx);

void bpf_gen__record_relo_core(struct bpf_gen *gen, const struct bpf_core_relo *core_relo);

void bpf_gen__populate_outer_map(struct bpf_gen *gen, int outer_map_idx, int key, int inner_map_idx);

tools/lib/bpf/gen_loader.c

+19 −19
Original line number Diff line number Diff line
@@ -560,7 +560,7 @@ static void emit_find_attach_target(struct bpf_gen *gen) 
}



void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,

			    bool is_typeless, int kind, int insn_idx)

			    bool is_typeless, bool is_ld64, int kind, int insn_idx)

{

	struct ksym_relo_desc *relo;
@@ -574,6 +574,7 @@ void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak, 
	relo->name = name;

	relo->is_weak = is_weak;

	relo->is_typeless = is_typeless;

	relo->is_ld64 = is_ld64;

	relo->kind = kind;

	relo->insn_idx = insn_idx;

	gen->relo_cnt++;
@@ -586,9 +587,11 @@ static struct ksym_desc *get_ksym_desc(struct bpf_gen *gen, struct ksym_relo_des 
	int i;



	for (i = 0; i < gen->nr_ksyms; i++) {

		if (!strcmp(gen->ksyms[i].name, relo->name)) {

			gen->ksyms[i].ref++;

			return &gen->ksyms[i];

		kdesc = &gen->ksyms[i];

		if (kdesc->kind == relo->kind && kdesc->is_ld64 == relo->is_ld64 &&

		    !strcmp(kdesc->name, relo->name)) {

			kdesc->ref++;

			return kdesc;

		}

	}

	kdesc = libbpf_reallocarray(gen->ksyms, gen->nr_ksyms + 1, sizeof(*kdesc));
@@ -603,6 +606,7 @@ static struct ksym_desc *get_ksym_desc(struct bpf_gen *gen, struct ksym_relo_des 
	kdesc->ref = 1;

	kdesc->off = 0;

	kdesc->insn = 0;

	kdesc->is_ld64 = relo->is_ld64;

	return kdesc;

}
@@ -864,23 +868,17 @@ static void emit_relo(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn 
{

	int insn;



	pr_debug("gen: emit_relo (%d): %s at %d\n", relo->kind, relo->name, relo->insn_idx);

	pr_debug("gen: emit_relo (%d): %s at %d %s\n",

		 relo->kind, relo->name, relo->insn_idx, relo->is_ld64 ? "ld64" : "call");

	insn = insns + sizeof(struct bpf_insn) * relo->insn_idx;

	emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_8, BPF_PSEUDO_MAP_IDX_VALUE, 0, 0, 0, insn));

	switch (relo->kind) {

	case BTF_KIND_VAR:

	if (relo->is_ld64) {

		if (relo->is_typeless)

			emit_relo_ksym_typeless(gen, relo, insn);

		else

			emit_relo_ksym_btf(gen, relo, insn);

		break;

	case BTF_KIND_FUNC:

	} else {

		emit_relo_kfunc_btf(gen, relo, insn);

		break;

	default:

		pr_warn("Unknown relocation kind '%d'\n", relo->kind);

		gen->error = -EDOM;

		return;

	}

}
@@ -903,18 +901,20 @@ static void cleanup_core_relo(struct bpf_gen *gen) 


static void cleanup_relos(struct bpf_gen *gen, int insns)

{

	struct ksym_desc *kdesc;

	int i, insn;



	for (i = 0; i < gen->nr_ksyms; i++) {

		kdesc = &gen->ksyms[i];

		/* only close fds for typed ksyms and kfuncs */

		if (gen->ksyms[i].kind == BTF_KIND_VAR && !gen->ksyms[i].typeless) {

		if (kdesc->is_ld64 && !kdesc->typeless) {

			/* close fd recorded in insn[insn_idx + 1].imm */

			insn = gen->ksyms[i].insn;

			insn = kdesc->insn;

			insn += sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm);

			emit_sys_close_blob(gen, insn);

		} else if (gen->ksyms[i].kind == BTF_KIND_FUNC) {

			emit_sys_close_blob(gen, blob_fd_array_off(gen, gen->ksyms[i].off));

			if (gen->ksyms[i].off < MAX_FD_ARRAY_SZ)

		} else if (!kdesc->is_ld64) {

			emit_sys_close_blob(gen, blob_fd_array_off(gen, kdesc->off));

			if (kdesc->off < MAX_FD_ARRAY_SZ)

				gen->nr_fd_array--;

		}

	}

tools/lib/bpf/libbpf.c

+5 −2
Original line number Diff line number Diff line
@@ -7070,18 +7070,21 @@ static int bpf_program_record_relos(struct bpf_program *prog) 
	for (i = 0; i < prog->nr_reloc; i++) {

		struct reloc_desc *relo = &prog->reloc_desc[i];

		struct extern_desc *ext = &obj->externs[relo->sym_off];

		int kind;



		switch (relo->type) {

		case RELO_EXTERN_LD64:

			if (ext->type != EXT_KSYM)

				continue;

			kind = btf_is_var(btf__type_by_id(obj->btf, ext->btf_id)) ?

				BTF_KIND_VAR : BTF_KIND_FUNC;

			bpf_gen__record_extern(obj->gen_loader, ext->name,

					       ext->is_weak, !ext->ksym.type_id,

					       BTF_KIND_VAR, relo->insn_idx);

					       true, kind, relo->insn_idx);

			break;

		case RELO_EXTERN_CALL:

			bpf_gen__record_extern(obj->gen_loader, ext->name,

					       ext->is_weak, false, BTF_KIND_FUNC,

					       ext->is_weak, false, false, BTF_KIND_FUNC,

					       relo->insn_idx);

			break;

		case RELO_CORE: {