rust: export generated symbols

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5J75G
CVE: NA

Reference: https://lore.kernel.org/rust-for-linux/CANiq72nDcJLSB3pLhkdqGdLitfmqqCUVVfkY5EjP9AcwVv9B4A@mail.gmail.com/T/#t

--------------------------------

All symbols are reexported reusing the `EXPORT_SYMBOL_GPL` macro
from C. The lists of symbols are generated on the fly.

There are three main sets of symbols to distinguish:

  - The ones from the `core` and `alloc` crates (from the Rust
    standard library). The code is licensed as Apache/MIT.

  - The ones from our abstractions in the `kernel` crate.

  - The helpers (already exported since they are not generated).

We export everything as GPL. This ensures we do not mistakenly
expose GPL kernel symbols/features as non-GPL, even indirectly.
Co-developed-by: NAlex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: NAlex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: NWedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: NWedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: NMiguel Ojeda <ojeda@kernel.org>
Signed-off-by: NWeilong Chen <chenweilong@huawei.com>

rust/exports.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A hack to export Rust symbols for loadable modules without having to redo
+ * the entire `include/linux/export.h` logic in Rust.
+ *
+ * This requires the Rust's new/future `v0` mangling scheme because the default
+ * one ("legacy") uses invalid characters for C identifiers (thus we cannot use
+ * the `EXPORT_SYMBOL_*` macros).
+ *
+ * All symbols are exported as GPL-only to guarantee no GPL-only feature is
+ * accidentally exposed.
+ */
+
+#include <linux/module.h>
+
+#define EXPORT_SYMBOL_RUST_GPL(sym) extern int sym; EXPORT_SYMBOL_GPL(sym);
+
+#include "exports_core_generated.h"
+#include "exports_alloc_generated.h"
+#include "exports_kernel_generated.h"