[PATCH bpf-next v6 3/9] 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_prog_load_log_attr_init(): initialize the 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          | 19 ++++++++++++++++-
 include/linux/bpf_verifier.h | 11 ++++++++++
 kernel/bpf/log.c             | 40 ++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c         |  9 +++++++-
 kernel/bpf/verifier.c        | 19 ++++++-----------
 5 files changed, 83 insertions(+), 15 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5936f8e2996f..3a525a7e8747 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2867,8 +2867,25 @@ int bpf_get_file_flag(int flags);
 int bpf_check_uarg_tail_zero(bpfptr_t uaddr, size_t expected_size,
 			     size_t actual_size);
 
+struct bpf_attrs {
+	const void *attr;
+	bpfptr_t uattr;
+	u32 size;
+};
+
+static inline void bpf_attrs_init(struct bpf_attrs *attrs, const void *attr, bpfptr_t uattr,
+				  u32 size)
+{
+	memset(attrs, 0, sizeof(*attrs));
+	attrs->attr = attr;
+	attrs->uattr = uattr;
+	attrs->size = 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 *log_attr);
 
 #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 130bcbd66f60..4c9632c40059 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -631,6 +631,17 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 	return log && log->level;
 }
 
+struct bpf_log_attr {
+	u64 log_buf;
+	u32 log_size;
+	u32 log_level;
+	struct bpf_attrs *attrs;
+	u32 offsetof_log_true_size;
+};
+
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
+int bpf_log_attr_finalize(struct bpf_log_attr *log_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..457b724c4176 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -863,3 +863,43 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
 	}
 	print_verifier_state(env, vstate, frameno, false);
 }
+
+static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
+			     u32 log_size, u32 log_level, int offsetof_log_true_size)
+{
+	memset(log_attr, 0, sizeof(*log_attr));
+	log_attr->log_buf = log_buf;
+	log_attr->log_size = log_size;
+	log_attr->log_level = log_level;
+	log_attr->attrs = attrs;
+	log_attr->offsetof_log_true_size = offsetof_log_true_size;
+	return 0;
+}
+
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+{
+	const union bpf_attr *attr = attrs->attr;
+
+	return bpf_log_attr_init(log_attr, attrs, attr->log_buf, attr->log_size, attr->log_level,
+				 offsetof(union bpf_attr, log_true_size));
+}
+
+int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
+{
+	u32 log_true_size, off;
+	size_t size;
+	int err;
+
+	if (!log)
+		return 0;
+
+	err = bpf_vlog_finalize(log, &log_true_size);
+
+	size = sizeof(log_true_size);
+	off = log_attr->offsetof_log_true_size;
+	if (log_attr->attrs && log_attr->attrs->size >= off + size &&
+	    copy_to_bpfptr_offset(log_attr->attrs->uattr, off, &log_true_size, size))
+		err = -EFAULT;
+
+	return err;
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 27fc73a29b0f..645cc0c0cd3f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2871,6 +2871,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	struct bpf_prog *prog, *dst_prog = NULL;
 	struct btf *attach_btf = NULL;
 	struct bpf_token *token = NULL;
+	struct bpf_log_attr log_attr;
+	struct bpf_attrs attrs;
 	bool bpf_cap;
 	int err;
 	char license[128];
@@ -3082,8 +3084,13 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	if (err)
 		goto free_prog_sec;
 
+	bpf_attrs_init(&attrs, attr, uattr, uattr_size);
+	err = bpf_prog_load_log_attr_init(&log_attr, &attrs);
+	if (err < 0)
+		goto free_used_maps;
+
 	/* run eBPF verifier */
-	err = bpf_check(&prog, attr, uattr, uattr_size);
+	err = bpf_check(&prog, attr, uattr, &log_attr);
 	if (err < 0)
 		goto free_used_maps;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9de0ec0c3ed9..768b6f92c335 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -25161,12 +25161,12 @@ 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 *log_attr)
 {
 	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);
@@ -25213,9 +25213,9 @@ 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, log_attr->log_level,
+			    u64_to_user_ptr(log_attr->log_buf),
+			    log_attr->log_size);
 	if (ret)
 		goto err_unlock;
 
@@ -25365,17 +25365,10 @@ 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(log_attr, &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