[PATCH bpf-next v5 1/5] bpf: Move JIT for single-subprog programs to verifier

[Xu Kuohai]

From: Xu Kuohai <xukuohai@xxxxxxxxxx>

JIT for single-subprog programs is done after the verification stage. This
prevents the JIT stage from accessing the verifier's internal datas, like
env->insn_aux_data. So move it to the verifier. After the movement, all bpf
progs loaded with bpf_prog_load() are JITed in the verifier. The JIT in
bpf_prog_select_runtime() is preserved for bpf_migrate_filter() and test
cases.

Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
---
 include/linux/filter.h |  2 ++
 kernel/bpf/core.c      | 51 +++++++++++++++++++++++++++---------------
 kernel/bpf/syscall.c   |  2 +-
 kernel/bpf/verifier.c  |  7 +++++-
 4 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 44d7ae95ddbc..632c03e126d9 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1108,6 +1108,8 @@ static inline int sk_filter_reason(struct sock *sk, struct sk_buff *skb,
 	return sk_filter_trim_cap(sk, skb, 1, reason);
 }
 
+struct bpf_prog *bpf_prog_select_jit(struct bpf_prog *fp, int *err);
+struct bpf_prog *__bpf_prog_select_runtime(struct bpf_prog *fp, bool jit_attempted, int *err);
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err);
 void bpf_prog_free(struct bpf_prog *fp);
 
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 229c74f3d6ae..00be578a438d 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2505,18 +2505,18 @@ static bool bpf_prog_select_interpreter(struct bpf_prog *fp)
 	return select_interpreter;
 }
 
-/**
- *	bpf_prog_select_runtime - select exec runtime for BPF program
- *	@fp: bpf_prog populated with BPF program
- *	@err: pointer to error variable
- *
- * Try to JIT eBPF program, if JIT is not available, use interpreter.
- * The BPF program will be executed via bpf_prog_run() function.
- *
- * Return: the &fp argument along with &err set to 0 for success or
- * a negative errno code on failure
- */
-struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
+struct bpf_prog *bpf_prog_select_jit(struct bpf_prog *fp, int *err)
+{
+	*err = bpf_prog_alloc_jited_linfo(fp);
+	if (*err)
+		return fp;
+
+	fp = bpf_int_jit_compile(fp);
+	bpf_prog_jit_attempt_done(fp);
+	return fp;
+}
+
+struct bpf_prog *__bpf_prog_select_runtime(struct bpf_prog *fp, bool jit_attempted, int *err)
 {
 	/* In case of BPF to BPF calls, verifier did all the prep
 	 * work with regards to JITing, etc.
@@ -2540,12 +2540,11 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 	 * be JITed, but falls back to the interpreter.
 	 */
 	if (!bpf_prog_is_offloaded(fp->aux)) {
-		*err = bpf_prog_alloc_jited_linfo(fp);
-		if (*err)
-			return fp;
-
-		fp = bpf_int_jit_compile(fp);
-		bpf_prog_jit_attempt_done(fp);
+		if (!jit_attempted) {
+			fp = bpf_prog_select_jit(fp, err);
+			if (*err)
+				return fp;
+		}
 		if (!fp->jited && jit_needed) {
 			*err = -ENOTSUPP;
 			return fp;
@@ -2570,6 +2569,22 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 
 	return fp;
 }
+
+/**
+ *	bpf_prog_select_runtime - select exec runtime for BPF program
+ *	@fp: bpf_prog populated with BPF program
+ *	@err: pointer to error variable
+ *
+ * Try to JIT eBPF program, if JIT is not available, use interpreter.
+ * The BPF program will be executed via bpf_prog_run() function.
+ *
+ * Return: the &fp argument along with &err set to 0 for success or
+ * a negative errno code on failure
+ */
+struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
+{
+	return __bpf_prog_select_runtime(fp, false, err);
+}
 EXPORT_SYMBOL_GPL(bpf_prog_select_runtime);
 
 static unsigned int __bpf_prog_ret1(const void *ctx,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 274039e36465..d6982107ba80 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3090,7 +3090,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	if (err < 0)
 		goto free_used_maps;
 
-	prog = bpf_prog_select_runtime(prog, &err);
+	prog = __bpf_prog_select_runtime(prog, true, &err);
 	if (err < 0)
 		goto free_used_maps;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index fc4ccd1de569..ab2bc0850770 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -26086,6 +26086,11 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 		convert_pseudo_ld_imm64(env);
 	}
 
+	/* constants blinding in the JIT may increase prog->len */
+	len = env->prog->len;
+	if (env->subprog_cnt == 1)
+		env->prog = bpf_prog_select_jit(env->prog, &ret);
+
 	adjust_btf_func(env);
 
 err_release_maps:
@@ -26111,7 +26116,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 err_unlock:
 	if (!is_priv)
 		mutex_unlock(&bpf_verifier_lock);
-	clear_insn_aux_data(env, 0, env->prog->len);
+	clear_insn_aux_data(env, 0, len);
 	vfree(env->insn_aux_data);
 err_free_env:
 	bpf_stack_liveness_free(env);
-- 
2.47.3