kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 195 insertions, 0 deletions

diff --git a/drivers/tee/optee/device.c b/drivers/tee/optee/device.c
new file mode 100644
index 000000000..f751d743a
--- /dev/null
+++ b/drivers/tee/optee/device.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/tee_core.h>
+#include <linux/uuid.h>
+#include "optee_private.h"
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	return (ver->impl_id == TEE_IMPL_ID_OPTEE);
+}
+
+static int get_devices(struct tee_context *ctx, u32 session,
+		       struct tee_shm *device_shm, u32 *shm_size,
+		       u32 func)
+{
+	int ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg;
+	struct tee_param param[4];
+
+	memset(&inv_arg, 0, sizeof(inv_arg));
+	memset(&param, 0, sizeof(param));
+
+	inv_arg.func = func;
+	inv_arg.session = session;
+	inv_arg.num_params = 4;
+
+	/* Fill invoke cmd params */
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = device_shm;
+	param[0].u.memref.size = *shm_size;
+	param[0].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(ctx, &inv_arg, param);
+	if ((ret < 0) || ((inv_arg.ret != TEEC_SUCCESS) &&
+			  (inv_arg.ret != TEEC_ERROR_SHORT_BUFFER))) {
+		/*
+		 * TEE_ERROR_STORAGE_NOT_AVAILABLE is returned when getting
+		 * the list of device TAs that depends on RPMB but a usable
+		 * RPMB device isn't found.
+		 */
+		if (inv_arg.ret == TEE_ERROR_STORAGE_NOT_AVAILABLE)
+			return -ENODEV;
+		pr_err("PTA_CMD_GET_DEVICES invoke function err: %x\n",
+		       inv_arg.ret);
+		return -EINVAL;
+	}
+
+	*shm_size = param[0].u.memref.size;
+
+	return 0;
+}
+
+static void optee_release_device(struct device *dev)
+{
+	struct tee_client_device *optee_device = to_tee_client_device(dev);
+
+	kfree(optee_device);
+}
+
+static ssize_t need_supplicant_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	return 0;
+}
+
+static DEVICE_ATTR_RO(need_supplicant);
+
+static int optee_register_device(const uuid_t *device_uuid, u32 func)
+{
+	struct tee_client_device *optee_device = NULL;
+	int rc;
+
+	optee_device = kzalloc_obj(*optee_device);
+	if (!optee_device)
+		return -ENOMEM;
+
+	optee_device->dev.bus = &tee_bus_type;
+	optee_device->dev.release = optee_release_device;
+	if (dev_set_name(&optee_device->dev, "optee-ta-%pUb", device_uuid)) {
+		kfree(optee_device);
+		return -ENOMEM;
+	}
+	uuid_copy(&optee_device->id.uuid, device_uuid);
+
+	rc = device_register(&optee_device->dev);
+	if (rc) {
+		pr_err("device registration failed, err: %d\n", rc);
+		put_device(&optee_device->dev);
+		return rc;
+	}
+
+	if (func == PTA_CMD_GET_DEVICES_SUPP)
+		device_create_file(&optee_device->dev,
+				   &dev_attr_need_supplicant);
+
+	return 0;
+}
+
+static int __optee_enumerate_devices(u32 func)
+{
+	const uuid_t pta_uuid =
+		UUID_INIT(0x7011a688, 0xddde, 0x4053,
+			  0xa5, 0xa9, 0x7b, 0x3c, 0x4d, 0xdf, 0x13, 0xb8);
+	struct tee_ioctl_open_session_arg sess_arg;
+	struct tee_shm *device_shm = NULL;
+	const uuid_t *device_uuid = NULL;
+	struct tee_context *ctx = NULL;
+	u32 shm_size = 0, idx, num_devices = 0;
+	int rc;
+
+	memset(&sess_arg, 0, sizeof(sess_arg));
+
+	/* Open context with OP-TEE driver */
+	ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, NULL);
+	if (IS_ERR(ctx))
+		return -ENODEV;
+
+	/* Open session with device enumeration pseudo TA */
+	export_uuid(sess_arg.uuid, &pta_uuid);
+	sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
+	sess_arg.num_params = 0;
+
+	rc = tee_client_open_session(ctx, &sess_arg, NULL);
+	if ((rc < 0) || (sess_arg.ret != TEEC_SUCCESS)) {
+		/* Device enumeration pseudo TA not found */
+		rc = 0;
+		goto out_ctx;
+	}
+
+	rc = get_devices(ctx, sess_arg.session, NULL, &shm_size, func);
+	if (rc < 0 || !shm_size)
+		goto out_sess;
+
+	device_shm = tee_shm_alloc_kernel_buf(ctx, shm_size);
+	if (IS_ERR(device_shm)) {
+		pr_err("tee_shm_alloc_kernel_buf failed\n");
+		rc = PTR_ERR(device_shm);
+		goto out_sess;
+	}
+
+	rc = get_devices(ctx, sess_arg.session, device_shm, &shm_size, func);
+	if (rc < 0)
+		goto out_shm;
+
+	device_uuid = tee_shm_get_va(device_shm, 0);
+	if (IS_ERR(device_uuid)) {
+		pr_err("tee_shm_get_va failed\n");
+		rc = PTR_ERR(device_uuid);
+		goto out_shm;
+	}
+
+	num_devices = shm_size / sizeof(uuid_t);
+
+	for (idx = 0; idx < num_devices; idx++) {
+		rc = optee_register_device(&device_uuid[idx], func);
+		if (rc)
+			goto out_shm;
+	}
+
+out_shm:
+	tee_shm_free(device_shm);
+out_sess:
+	tee_client_close_session(ctx, sess_arg.session);
+out_ctx:
+	tee_client_close_context(ctx);
+
+	return rc;
+}
+
+int optee_enumerate_devices(u32 func)
+{
+	return  __optee_enumerate_devices(func);
+}
+
+static int __optee_unregister_device(struct device *dev, void *data)
+{
+	if (!strncmp(dev_name(dev), "optee-ta", strlen("optee-ta")))
+		device_unregister(dev);
+
+	return 0;
+}
+
+void optee_unregister_devices(void)
+{
+	bus_for_each_dev(&tee_bus_type, NULL, NULL,
+			 __optee_unregister_device);
+}