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Date:   Mon, 17 Apr 2023 18:40:06 -0700
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Subject: [RFC PATCH v3 06/37] fuse-bpf: Add data structures for fuse-bpf
From:   Daniel Rosenberg <drosen@google.com>
To:     Miklos Szeredi <miklos@szeredi.hu>, bpf@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>
Cc:     Amir Goldstein <amir73il@gmail.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Joanne Koong <joannelkoong@gmail.com>,
        Mykola Lysenko <mykolal@fb.com>, kernel-team@android.com,
        Daniel Rosenberg <drosen@google.com>
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Precedence: bulk

These structures will be used to interact between the fuse bpf calls and
normal userspace calls

Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
 include/linux/bpf_fuse.h | 84 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 include/linux/bpf_fuse.h

diff --git a/include/linux/bpf_fuse.h b/include/linux/bpf_fuse.h
new file mode 100644
index 000000000000..ce8b1b347496
--- /dev/null
+++ b/include/linux/bpf_fuse.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2022 Google LLC.
+ */
+
+#ifndef _BPF_FUSE_H
+#define _BPF_FUSE_H
+
+#include <linux/types.h>
+#include <linux/fuse.h>
+
+struct fuse_buffer {
+	void *data;
+	unsigned size;
+	unsigned alloc_size;
+	unsigned max_size;
+	int flags;
+};
+
+/* These flags are used internally to track information about the fuse buffers.
+ * Fuse sets some of the flags in init. The helper functions sets others, depending on what
+ * was requested by the bpf program.
+ */
+// Flags set by FUSE
+#define BPF_FUSE_IMMUTABLE	(1 << 0) // Buffer may not be written to
+#define BPF_FUSE_VARIABLE_SIZE	(1 << 1) // Buffer length may be changed (growth requires alloc)
+#define BPF_FUSE_MUST_ALLOCATE	(1 << 2) // Buffer must be re allocated before allowing writes
+
+// Flags set by helper function
+#define BPF_FUSE_MODIFIED	(1 << 3) // The helper function allowed writes to the buffer
+#define BPF_FUSE_ALLOCATED	(1 << 4) // The helper function allocated the buffer
+
+/*
+ * BPF Fuse Args
+ *
+ * Used to translate between bpf program parameters and their userspace equivalent calls.
+ * Variable sized arguments are held in fuse_buffers. To access these, bpf programs must
+ * use kfuncs to access them as dynptrs.
+ *
+ */
+
+#define FUSE_MAX_ARGS_IN 3
+#define FUSE_MAX_ARGS_OUT 2
+
+struct bpf_fuse_arg {
+	union {
+		void *value;
+		struct fuse_buffer *buffer;
+	};
+	unsigned size;
+	bool is_buffer;
+};
+
+struct bpf_fuse_meta_info {
+	uint64_t nodeid;
+	uint32_t opcode;
+	uint32_t error_in;
+};
+
+struct bpf_fuse_args {
+	struct bpf_fuse_meta_info info;
+	uint32_t in_numargs;
+	uint32_t out_numargs;
+	uint32_t flags;
+	struct bpf_fuse_arg in_args[FUSE_MAX_ARGS_IN];
+	struct bpf_fuse_arg out_args[FUSE_MAX_ARGS_OUT];
+};
+
+// Mirrors for struct fuse_args flags
+#define FUSE_BPF_FORCE (1 << 0)
+#define FUSE_BPF_OUT_ARGVAR (1 << 6)
+#define FUSE_BPF_IS_LOOKUP (1 << 11)
+
+static inline void *bpf_fuse_arg_value(const struct bpf_fuse_arg *arg)
+{
+	return arg->is_buffer ? arg->buffer : arg->value;
+}
+
+static inline unsigned bpf_fuse_arg_size(const struct bpf_fuse_arg *arg)
+{
+	return arg->is_buffer ? arg->buffer->size : arg->size;
+}
+
+#endif /* _BPF_FUSE_H */
-- 
2.40.0.634.g4ca3ef3211-goog