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libbpf: Support kfunc detection in light skeleton.

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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: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230321203854.3035-4-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov
2023-03-21 13:38:53 -07:00
committed by Andrii Nakryiko
parent a5464a5b0e
commit 68cd7cd386
3 changed files with 27 additions and 22 deletions
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38
src/gen_loader.c
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@@ -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--;
}
}