[RFC PATCH bpf-next v3 03/10] bpf: Refactor reporting log_true_size for prog_load

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

In the next commit, it will be able to report logs via extended common
attributes, which will report 'log_true_size' via the extended common
attributes meanwhile.

Therefore, refactor the way of 'log_true_size' reporting in order to
report 'log_true_size' via the extended common attributes easily.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf.h   |  2 +-
 kernel/bpf/syscall.c  | 24 ++++++++++++++++++++----
 kernel/bpf/verifier.c | 12 ++----------
 3 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a98c833461347..4f595439943d7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2738,7 +2738,7 @@ 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);
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr, bpfptr_t uattr);
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8d97d67e6abaa..2bdc0b43ec832 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2841,7 +2841,7 @@ static int bpf_prog_verify_signature(struct bpf_prog *prog, union bpf_attr *attr
 /* 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)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog, *dst_prog = NULL;
@@ -3059,7 +3059,7 @@ 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);
 	if (err < 0)
 		goto free_used_maps;
 
@@ -6092,12 +6092,25 @@ static int prog_stream_read(union bpf_attr *attr)
 	return ret;
 }
 
+static int copy_prog_load_log_true_size(union bpf_attr *attr, bpfptr_t uattr, unsigned int size)
+{
+	if (!attr->log_true_size)
+		return 0;
+
+	if (size >= offsetofend(union bpf_attr, log_true_size) &&
+	    copy_to_bpfptr_offset(uattr, offsetof(union bpf_attr, log_true_size),
+				  &attr->log_true_size, sizeof(attr->log_true_size)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		     bpfptr_t uattr_common, unsigned int size_common)
 {
 	struct bpf_common_attr common_attrs;
 	union bpf_attr attr;
-	int err;
+	int err, ret;
 
 	err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size);
 	if (err)
@@ -6145,7 +6158,10 @@ 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);
+		attr.log_true_size = 0;
+		err = bpf_prog_load(&attr, uattr);
+		ret = copy_prog_load_log_true_size(&attr, uattr, size);
+		err = ret ? ret : err;
 		break;
 	case BPF_OBJ_PIN:
 		err = bpf_obj_pin(&attr);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e892df386eed7..d5089f026f578 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -24499,12 +24499,11 @@ 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)
 {
 	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);
@@ -24700,17 +24699,10 @@ 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_vlog_finalize(&env->log, &attr->log_true_size);
 	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;
 
-- 
2.51.0