[PATCH bpf-next v10 3/8] bpf: Refactor reporting log_true_size for prog_load

[Leon Hwang <leon.hwang@linux.dev>]

The next commit will add support for reporting logs via extended common
attributes, including 'log_true_size'.

To prepare for that, refactor the 'log_true_size' reporting logic by
introducing a new struct bpf_log_attr to encapsulate log-related behavior:

 * bpf_log_attr_init(): initialize log fields, which will support
   extended common attributes in the next commit.
 * bpf_log_attr_finalize(): handle log finalization and write back
   'log_true_size' to userspace.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf.h          |  4 +++-
 include/linux/bpf_verifier.h | 11 +++++++++++
 kernel/bpf/log.c             | 25 +++++++++++++++++++++++++
 kernel/bpf/syscall.c         | 13 ++++++++++---
 kernel/bpf/verifier.c        | 17 ++++-------------
 5 files changed, 53 insertions(+), 17 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cd9b96434904..d4dbcc7ad156 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2913,7 +2913,9 @@ int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
 			     size_t actual_size);
 
 /* verify correctness of eBPF program */
-int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size);
+struct bpf_log_attr;
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr,
+	      struct bpf_log_attr *attr_log);
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index ef8e45a362d9..dbd9bdb955b3 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -635,6 +635,17 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 	return log && log->level;
 }
 
+struct bpf_log_attr {
+	char __user *log_buf;
+	u32 log_size;
+	u32 log_level;
+	u32 __user *log_true_size;
+};
+
+int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32 log_size, u32 log_level,
+		      u32 __user *log_true_size);
+int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log);
+
 #define BPF_MAX_SUBPROGS 256
 
 struct bpf_subprog_arg_info {
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index a0c3b35de2ce..e31747b84fe2 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -863,3 +863,28 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
 	}
 	print_verifier_state(env, vstate, frameno, false);
 }
+
+int bpf_log_attr_init(struct bpf_log_attr *log, u64 log_buf, u32 log_size, u32 log_level,
+		      u32 __user *log_true_size)
+{
+	memset(log, 0, sizeof(*log));
+	log->log_buf = u64_to_user_ptr(log_buf);
+	log->log_size = log_size;
+	log->log_level = log_level;
+	log->log_true_size = log_true_size;
+	return 0;
+}
+
+int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log)
+{
+	u32 log_true_size;
+	int err;
+
+	err = bpf_vlog_finalize(log, &log_true_size);
+
+	if (attr->log_true_size && copy_to_user(attr->log_true_size, &log_true_size,
+						sizeof(log_true_size)))
+		return -EFAULT;
+
+	return err;
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0e231c0b1d04..e86674811996 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2867,7 +2867,7 @@ static int bpf_prog_mark_insn_arrays_ready(struct bpf_prog *prog)
 /* last field in 'union bpf_attr' used by this command */
 #define BPF_PROG_LOAD_LAST_FIELD keyring_id
 
-static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_attr *attr_log)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog, *dst_prog = NULL;
@@ -3085,7 +3085,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 		goto free_prog_sec;
 
 	/* run eBPF verifier */
-	err = bpf_check(&prog, attr, uattr, uattr_size);
+	err = bpf_check(&prog, attr, uattr, attr_log);
 	if (err < 0)
 		goto free_used_maps;
 
@@ -6189,7 +6189,10 @@ static int prog_assoc_struct_ops(union bpf_attr *attr)
 static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		     bpfptr_t uattr_common, unsigned int size_common)
 {
+	bool from_user = !bpfptr_is_kernel(uattr);
 	struct bpf_common_attr attr_common;
+	u32 __user *log_true_size = NULL;
+	struct bpf_log_attr attr_log;
 	union bpf_attr attr;
 	int err;
 
@@ -6241,7 +6244,11 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = map_freeze(&attr);
 		break;
 	case BPF_PROG_LOAD:
-		err = bpf_prog_load(&attr, uattr, size);
+		if (from_user && size >= offsetofend(union bpf_attr, log_true_size))
+			log_true_size = uattr.user + offsetof(union bpf_attr, log_true_size);
+		err = bpf_log_attr_init(&attr_log, attr.log_buf, attr.log_size, attr.log_level,
+					log_true_size);
+		err = err ?: bpf_prog_load(&attr, uattr, &attr_log);
 		break;
 	case BPF_OBJ_PIN:
 		err = bpf_obj_pin(&attr);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index edf5342b982f..f1447b1878fd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -25840,12 +25840,12 @@ static int compute_scc(struct bpf_verifier_env *env)
 	return err;
 }
 
-int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
+int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
+	      struct bpf_log_attr *attr_log)
 {
 	u64 start_time = ktime_get_ns();
 	struct bpf_verifier_env *env;
 	int i, len, ret = -EINVAL, err;
-	u32 log_true_size;
 	bool is_priv;
 
 	BTF_TYPE_EMIT(enum bpf_features);
@@ -25892,9 +25892,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	/* user could have requested verbose verifier output
 	 * and supplied buffer to store the verification trace
 	 */
-	ret = bpf_vlog_init(&env->log, attr->log_level,
-			    (char __user *) (unsigned long) attr->log_buf,
-			    attr->log_size);
+	ret = bpf_vlog_init(&env->log, attr_log->log_level, attr_log->log_buf, attr_log->log_size);
 	if (ret)
 		goto err_unlock;
 
@@ -26044,17 +26042,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	env->prog->aux->verified_insns = env->insn_processed;
 
 	/* preserve original error even if log finalization is successful */
-	err = bpf_vlog_finalize(&env->log, &log_true_size);
+	err = bpf_log_attr_finalize(attr_log, &env->log);
 	if (err)
 		ret = err;
 
-	if (uattr_size >= offsetofend(union bpf_attr, log_true_size) &&
-	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
-				  &log_true_size, sizeof(log_true_size))) {
-		ret = -EFAULT;
-		goto err_release_maps;
-	}
-
 	if (ret)
 		goto err_release_maps;
 
-- 
2.52.0