[PATCH bpf-next v9 4/9] bpf: Add syscall common attributes support for prog_load

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

BPF_PROG_LOAD can now provide log parameters through both union bpf_attr
and struct bpf_common_attr. Define clear conflict and precedence rules:

- if both are provided and log_buf/log_size/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             | 24 ++++++++++++++++++++++--
 kernel/bpf/syscall.c         |  3 ++-
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c805b85b6f7a..0d106fddbbc5 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -638,7 +638,8 @@ struct bpf_log_attr {
 };
 
 int bpf_prog_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 ff579fcba36f..345005ba98dd 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -873,10 +873,30 @@ static void bpf_log_attr_init(struct bpf_log_attr *attr_log, int offsetof_true_s
 	attr_log->uattr = uattr;
 }
 
+static bool bpf_log_attrs_diff(struct bpf_common_attr *common, u64 log_buf, u32 log_size,
+			       u32 log_level)
+{
+	return log_buf && common->log_buf && (log_buf != common->log_buf ||
+					      log_size != common->log_size ||
+					      log_level != common->log_level);
+}
+
 int bpf_prog_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, log_true_size), uattr, size);
+	if (bpf_log_attrs_diff(attr_common, attr->log_buf, attr->log_size, attr->log_level))
+		return -EINVAL;
+
+	if (!attr->log_buf && attr_common->log_buf) {
+		attr->log_buf = attr_common->log_buf;
+		attr->log_size = attr_common->log_size;
+		attr->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, log_true_size), uattr, size);
+	}
 	return 0;
 }
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e81199361241..7125ea445c6c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -6232,7 +6232,8 @@ 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_log_attr_init(&attr_log, &attr, uattr, size);
+		err = bpf_prog_load_log_attr_init(&attr_log, &attr, uattr, size, &attr_common,
+						  uattr_common, size_common);
 		err = err ?: bpf_prog_load(&attr, uattr, &attr_log);
 		break;
 	case BPF_OBJ_PIN:
-- 
2.52.0