bpf: remove stubs for cBPF from arch code

Remove the dummy bpf_jit_compile() stubs for eBPF JITs and make
that a single __weak function in the core that can be overridden
similarly to the eBPF one. Also remove stale pr_err() mentions
of bpf_jit_compile.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/arm64/net/bpf_jit_comp.c

@@ -813,11 +813,6 @@ static inline void bpf_flush_icache(void *start, void *end)
 	flush_icache_range((unsigned long)start, (unsigned long)end);
 }
 
-void bpf_jit_compile(struct bpf_prog *prog)
-{
-	/* Nothing to do here. We support Internal BPF. */
-}
-
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 {
 	struct bpf_prog *tmp, *orig_prog = prog;

arch/powerpc/net/bpf_jit_comp64.c

@@ -961,8 +961,6 @@ common_load:
 	return 0;
 }
 
-void bpf_jit_compile(struct bpf_prog *fp) { }
-
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 {
 	u32 proglen;

arch/s390/net/bpf_jit_comp.c

@@ -1262,14 +1262,6 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
 	return 0;
 }
 
-/*
- * Classic BPF function stub. BPF programs will be converted into
- * eBPF and then bpf_int_jit_compile() will be called.
- */
-void bpf_jit_compile(struct bpf_prog *fp)
-{
-}
-
 /*
  * Compile eBPF program "fp"
  */

arch/x86/net/bpf_jit_comp.c

@@ -1067,13 +1067,13 @@ common_load:
 
 		ilen = prog - temp;
 		if (ilen > BPF_MAX_INSN_SIZE) {
-			pr_err("bpf_jit_compile fatal insn size error\n");
+			pr_err("bpf_jit: fatal insn size error\n");
 			return -EFAULT;
 		}
 
 		if (image) {
 			if (unlikely(proglen + ilen > oldproglen)) {
-				pr_err("bpf_jit_compile fatal error\n");
+				pr_err("bpf_jit: fatal error\n");
 				return -EFAULT;
 			}
 			memcpy(image + proglen, temp, ilen);
@@ -1085,10 +1085,6 @@ common_load:
 	return proglen;
 }
 
-void bpf_jit_compile(struct bpf_prog *prog)
-{
-}
-
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 {
 	struct bpf_binary_header *header = NULL;

include/linux/filter.h

@@ -607,6 +607,7 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp);
 u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog);
+void bpf_jit_compile(struct bpf_prog *prog);
 bool bpf_helper_changes_pkt_data(void *func);
 
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
@@ -625,7 +626,6 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
 		     bpf_jit_fill_hole_t bpf_fill_ill_insns);
 void bpf_jit_binary_free(struct bpf_binary_header *hdr);
 
-void bpf_jit_compile(struct bpf_prog *fp);
 void bpf_jit_free(struct bpf_prog *fp);
 
 struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *fp);
@@ -669,10 +669,6 @@ static inline bool bpf_jit_blinding_enabled(void)
 	return true;
 }
 #else
-static inline void bpf_jit_compile(struct bpf_prog *fp)
-{
-}
-
 static inline void bpf_jit_free(struct bpf_prog *fp)
 {
 	bpf_prog_unlock_free(fp);

kernel/bpf/core.c

@@ -1154,12 +1154,22 @@ const struct bpf_func_proto bpf_tail_call_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
-/* For classic BPF JITs that don't implement bpf_int_jit_compile(). */
+/* Stub for JITs that only support cBPF. eBPF programs are interpreted.
+ * It is encouraged to implement bpf_int_jit_compile() instead, so that
+ * eBPF and implicitly also cBPF can get JITed!
+ */
 struct bpf_prog * __weak bpf_int_jit_compile(struct bpf_prog *prog)
 {
 	return prog;
 }
 
+/* Stub for JITs that support eBPF. All cBPF code gets transformed into
+ * eBPF by the kernel and is later compiled by bpf_int_jit_compile().
+ */
+void __weak bpf_jit_compile(struct bpf_prog *prog)
+{
+}
+
 bool __weak bpf_helper_changes_pkt_data(void *func)
 {
 	return false;