BACKPORT: ANDROID: fuse-bpf v1

Bug: 202785178
Test: test_fuse passes on linux, feature works on cuttlefish
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Change-Id: I987684b799b07391ccde350e98fde7976f5601aa

kernel/bpf/Makefile

@@ -36,3 +36,6 @@ obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
 obj-${CONFIG_BPF_LSM} += bpf_lsm.o
 endif
 obj-$(CONFIG_BPF_PRELOAD) += preload/
+ifeq ($(CONFIG_FUSE_BPF),y)
+obj-$(CONFIG_BPF_SYSCALL) += bpf_fuse.o
+endif

kernel/bpf/bpf_fuse.c

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2021 Google LLC
+
+#include <linux/filter.h>
+#include <linux/fuse.h>
+
+static const struct bpf_func_proto *
+fuse_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_trace_printk:
+			return bpf_get_trace_printk_proto();
+
+	case BPF_FUNC_get_current_uid_gid:
+			return &bpf_get_current_uid_gid_proto;
+
+	case BPF_FUNC_get_current_pid_tgid:
+			return &bpf_get_current_pid_tgid_proto;
+
+	case BPF_FUNC_map_lookup_elem:
+		return &bpf_map_lookup_elem_proto;
+
+	case BPF_FUNC_map_update_elem:
+		return &bpf_map_update_elem_proto;
+
+	default:
+		pr_debug("Invalid fuse bpf func %d\n", func_id);
+		return NULL;
+	}
+}
+
+static bool fuse_prog_is_valid_access(int off, int size,
+				enum bpf_access_type type,
+				const struct bpf_prog *prog,
+				struct bpf_insn_access_aux *info)
+{
+	int i;
+
+	if (off < 0 || off > offsetofend(struct fuse_args, out_args))
+		return false;
+
+	/* TODO This is garbage. Do it properly */
+	for (i = 0; i < 5; i++) {
+		if (off == offsetof(struct fuse_args, in_args[i].value)) {
+			info->reg_type = PTR_TO_RDONLY_BUF;
+			info->ctx_field_size = 256;
+			if (type != BPF_READ)
+				return false;
+			return true;
+		}
+	}
+	for (i = 0; i < 3; i++) {
+		if (off == offsetof(struct fuse_args, out_args[i].value)) {
+			info->reg_type = PTR_TO_RDWR_BUF;
+			info->ctx_field_size = 256;
+			return true;
+		}
+	}
+	if (type != BPF_READ)
+		return false;
+
+	return true;
+}
+
+const struct bpf_verifier_ops fuse_verifier_ops = {
+	.get_func_proto  = fuse_prog_func_proto,
+	.is_valid_access = fuse_prog_is_valid_access,
+};
+
+const struct bpf_prog_ops fuse_prog_ops = {
+};
+

kernel/bpf/btf.c

@@ -3,6 +3,7 @@
 
 #include <uapi/linux/btf.h>
 #include <uapi/linux/bpf.h>
+#include <uapi/linux/fuse.h>
 #include <uapi/linux/bpf_perf_event.h>
 #include <uapi/linux/types.h>
 #include <linux/seq_file.h>