[RFC PATCH v4 02/36] fuse-bpf: Add data structures for fuse-bpf

Daniel Rosenberg
2024-03-29T01:54:05Z

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 */
--
2.44.0.478.gd926399ef9-goog