[PATCH bpf-next v9 6/9] bpf: Add syscall common attributes support for btf_load

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

BPF_BTF_LOAD can now provide log parameters through both union bpf_attr
and bpf_common_attr. Apply the same conflict and precedence rules as
prog_load:

- if both are provided and btf_log_buf/btf_log_size/btf_log_level match,
  use them;
- if only one side provides a log buffer, use that one;
- if both provide log buffers but differ, return -EINVAL.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf_verifier.h |  3 ++-
 kernel/bpf/log.c             | 18 ++++++++++++++++--
 kernel/bpf/syscall.c         |  3 ++-
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index b6e33ee82f63..1144657bbc2f 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -641,7 +641,8 @@ int bpf_prog_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *a
 				bpfptr_t uattr, u32 size, struct bpf_common_attr *attr_common,
 				bpfptr_t uattr_common, u32 size_common);
 int bpf_btf_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *attr,
-			       bpfptr_t uattr, u32 size);
+			       bpfptr_t uattr, u32 size, struct bpf_common_attr *attr_common,
+			       bpfptr_t uattr_common, u32 size_common);
 int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct bpf_verifier_log *log);
 
 #define BPF_MAX_SUBPROGS 256
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 8ad88e4aa12c..db2716586f85 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -901,9 +901,23 @@ int bpf_prog_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *a
 }
 
 int bpf_btf_load_log_attr_init(struct bpf_log_attr *attr_log, union bpf_attr *attr,
-			       bpfptr_t uattr, u32 size)
+			       bpfptr_t uattr, u32 size, struct bpf_common_attr *attr_common,
+			       bpfptr_t uattr_common, u32 size_common)
 {
-	bpf_log_attr_init(attr_log, offsetof(union bpf_attr, btf_log_true_size), uattr, size);
+	if (bpf_log_attrs_diff(attr_common, attr->btf_log_buf, attr->btf_log_size,
+			       attr->btf_log_level))
+		return -EINVAL;
+
+	if (!attr->btf_log_buf && attr_common->log_buf) {
+		attr->btf_log_buf = attr_common->log_buf;
+		attr->btf_log_size = attr_common->log_size;
+		attr->btf_log_level = attr_common->log_level;
+		bpf_log_attr_init(attr_log, offsetof(struct bpf_common_attr, log_true_size),
+				  uattr_common, size_common);
+	} else {
+		bpf_log_attr_init(attr_log, offsetof(union bpf_attr, btf_log_true_size), uattr,
+				  size);
+	}
 	return 0;
 }
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b6e4ec641dc1..4a8933c1dd38 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6279,7 +6279,8 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
 		err = bpf_raw_tracepoint_open(&attr);
 		break;
 	case BPF_BTF_LOAD:
-		err = bpf_btf_load_log_attr_init(&attr_log, &attr, uattr, size);
+		err = bpf_btf_load_log_attr_init(&attr_log, &attr, uattr, size, &attr_common,
+						 uattr_common, size_common);
 		err = err ?: bpf_btf_load(&attr, uattr, &attr_log);
 		break;
 	case BPF_BTF_GET_FD_BY_ID:
-- 
2.52.0