bpf: Use prog->jited_len in bpf_prog_ksym_set_addr()

Using prog->jited_len is simpler and more accurate than current
estimation (header + header->size).

Also, fix missing prog->jited_len with multi function program. This hasn't
been a real issue before this.
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220204185742.271030-5-song@kernel.org

kernel/bpf/core.c

@@ -537,13 +537,10 @@ long bpf_jit_limit_max __read_mostly;
 static void
 bpf_prog_ksym_set_addr(struct bpf_prog *prog)
 {
-	const struct bpf_binary_header *hdr = bpf_jit_binary_hdr(prog);
-	unsigned long addr = (unsigned long)hdr;
-
 	WARN_ON_ONCE(!bpf_prog_ebpf_jited(prog));
 
 	prog->aux->ksym.start = (unsigned long) prog->bpf_func;
-	prog->aux->ksym.end   = addr + hdr->size;
+	prog->aux->ksym.end   = prog->aux->ksym.start + prog->jited_len;
 }
 
 static void

kernel/bpf/verifier.c

@@ -13067,6 +13067,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 
 	prog->jited = 1;
 	prog->bpf_func = func[0]->bpf_func;
+	prog->jited_len = func[0]->jited_len;
 	prog->aux->func = func;
 	prog->aux->func_cnt = env->subprog_cnt;
 	bpf_prog_jit_attempt_done(prog);