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, 404 insertions, 0 deletions

diff --git a/drivers/tee/optee/supp.c b/drivers/tee/optee/supp.c
new file mode 100644
index 000000000..06747e90c
--- /dev/null
+++ b/drivers/tee/optee/supp.c
@@ -0,0 +1,404 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, Linaro Limited
+ */
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include "optee_private.h"
+
+struct optee_supp_req {
+	struct list_head link;
+
+	int id;
+
+	bool in_queue;
+	bool processed;
+
+	u32 func;
+	u32 ret;
+	size_t num_params;
+	struct tee_param *param;
+
+	struct completion c;
+};
+
+/* It is temporary request used for revoked pending request in supp->idr. */
+#define INVALID_REQ_PTR ((struct optee_supp_req *)ERR_PTR(-EBADF))
+
+void optee_supp_init(struct optee_supp *supp)
+{
+	memset(supp, 0, sizeof(*supp));
+	mutex_init(&supp->mutex);
+	init_completion(&supp->reqs_c);
+	idr_init(&supp->idr);
+	INIT_LIST_HEAD(&supp->reqs);
+	supp->req_id = -1;
+}
+
+void optee_supp_uninit(struct optee_supp *supp)
+{
+	mutex_destroy(&supp->mutex);
+	idr_destroy(&supp->idr);
+}
+
+void optee_supp_release(struct optee_supp *supp)
+{
+	int id;
+	struct optee_supp_req *req;
+
+	mutex_lock(&supp->mutex);
+
+	/* Abort all request */
+	idr_for_each_entry(&supp->idr, req, id) {
+		idr_remove(&supp->idr, id);
+		/* Skip if request was already marked invalid */
+		if (IS_ERR(req))
+			continue;
+
+		/* For queued requests where supplicant has not seen it */
+		if (req->in_queue) {
+			list_del(&req->link);
+			req->in_queue = false;
+		}
+
+		req->processed = true;
+		req->ret = TEEC_ERROR_COMMUNICATION;
+		complete(&req->c);
+	}
+
+	supp->ctx = NULL;
+	supp->req_id = -1;
+
+	mutex_unlock(&supp->mutex);
+}
+
+/**
+ * optee_supp_thrd_req() - request service from supplicant
+ * @ctx:	context doing the request
+ * @func:	function requested
+ * @num_params:	number of elements in @param array
+ * @param:	parameters for function
+ *
+ * Returns result of operation to be passed to secure world
+ */
+u32 optee_supp_thrd_req(struct tee_context *ctx, u32 func, size_t num_params,
+			struct tee_param *param)
+
+{
+	struct optee *optee = tee_get_drvdata(ctx->teedev);
+	struct optee_supp *supp = &optee->supp;
+	struct optee_supp_req *req;
+	u32 ret;
+
+	/*
+	 * Return in case there is no supplicant available and
+	 * non-blocking request.
+	 */
+	if (!supp->ctx && ctx->supp_nowait)
+		return TEEC_ERROR_COMMUNICATION;
+
+	req = kzalloc_obj(*req);
+	if (!req)
+		return TEEC_ERROR_OUT_OF_MEMORY;
+
+	init_completion(&req->c);
+	req->func = func;
+	req->num_params = num_params;
+	req->param = param;
+
+	/* Insert the request in the request list */
+	mutex_lock(&supp->mutex);
+	req->id = idr_alloc(&supp->idr, req, 1, 0, GFP_KERNEL);
+	if (req->id < 0) {
+		mutex_unlock(&supp->mutex);
+		kfree(req);
+		return TEEC_ERROR_OUT_OF_MEMORY;
+	}
+
+	list_add_tail(&req->link, &supp->reqs);
+	req->in_queue = true;
+	req->processed = false;
+	mutex_unlock(&supp->mutex);
+
+	/* Tell an eventual waiter there's a new request */
+	complete(&supp->reqs_c);
+
+	/*
+	 * Wait for supplicant to process and return result, once we've
+	 * returned from wait_for_completion(&req->c) successfully we have
+	 * exclusive access again. Allow the wait to be killable such that
+	 * the wait doesn't turn into an indefinite state if the supplicant
+	 * gets hung for some reason.
+	 */
+	if (wait_for_completion_killable(&req->c)) {
+		mutex_lock(&supp->mutex);
+		if (req->in_queue) {
+			/* Supplicant has not seen this request yet. */
+			idr_remove(&supp->idr, req->id);
+			list_del(&req->link);
+			req->in_queue = false;
+
+			ret = TEEC_ERROR_COMMUNICATION;
+		} else if (req->processed) {
+			/*
+			 * Supplicant has processed this request. Ignore the
+			 * kill signal for now and submit the result. req is not
+			 * in supp->reqs (removed by supp_pop_entry()) nor in
+			 * supp->idr (removed by supp_pop_req()).
+			 */
+			ret = req->ret;
+		} else {
+			/*
+			 * Supplicant is in the middle of processing this
+			 * request. Replace req with INVALID_REQ_PTR so that
+			 * the ID remains busy, causing optee_supp_send() to
+			 * fail on the next call to supp_pop_req() with this ID.
+			 */
+			idr_replace(&supp->idr, INVALID_REQ_PTR, req->id);
+			ret = TEEC_ERROR_COMMUNICATION;
+		}
+
+		mutex_unlock(&supp->mutex);
+	} else {
+		ret = req->ret;
+	}
+
+	kfree(req);
+
+	return ret;
+}
+
+static struct optee_supp_req  *supp_pop_entry(struct optee_supp *supp,
+					      int num_params)
+{
+	struct optee_supp_req *req;
+
+	if (supp->req_id != -1) {
+		/*
+		 * Supplicant should not mix synchronous and asnynchronous
+		 * requests.
+		 */
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (list_empty(&supp->reqs))
+		return NULL;
+
+	req = list_first_entry(&supp->reqs, struct optee_supp_req, link);
+
+	if (num_params < req->num_params) {
+		/* Not enough room for parameters */
+		return ERR_PTR(-EINVAL);
+	}
+
+	list_del(&req->link);
+	req->in_queue = false;
+
+	return req;
+}
+
+static int supp_check_recv_params(size_t num_params, struct tee_param *params,
+				  size_t *num_meta)
+{
+	size_t n;
+
+	if (!num_params)
+		return -EINVAL;
+
+	/*
+	 * If there's memrefs we need to decrease those as they where
+	 * increased earlier and we'll even refuse to accept any below.
+	 */
+	for (n = 0; n < num_params; n++)
+		if (tee_param_is_memref(params + n) && params[n].u.memref.shm)
+			tee_shm_put(params[n].u.memref.shm);
+
+	/*
+	 * We only expect parameters as TEE_IOCTL_PARAM_ATTR_TYPE_NONE with
+	 * or without the TEE_IOCTL_PARAM_ATTR_META bit set.
+	 */
+	for (n = 0; n < num_params; n++)
+		if (params[n].attr &&
+		    params[n].attr != TEE_IOCTL_PARAM_ATTR_META)
+			return -EINVAL;
+
+	/* At most we'll need one meta parameter so no need to check for more */
+	if (params->attr == TEE_IOCTL_PARAM_ATTR_META)
+		*num_meta = 1;
+	else
+		*num_meta = 0;
+
+	return 0;
+}
+
+/**
+ * optee_supp_recv() - receive request for supplicant
+ * @ctx:	context receiving the request
+ * @func:	requested function in supplicant
+ * @num_params:	number of elements allocated in @param, updated with number
+ *		used elements
+ * @param:	space for parameters for @func
+ *
+ * Returns 0 on success or <0 on failure
+ */
+int optee_supp_recv(struct tee_context *ctx, u32 *func, u32 *num_params,
+		    struct tee_param *param)
+{
+	struct tee_device *teedev = ctx->teedev;
+	struct optee *optee = tee_get_drvdata(teedev);
+	struct optee_supp *supp = &optee->supp;
+	struct optee_supp_req *req = NULL;
+	size_t num_meta;
+	int rc;
+
+	rc = supp_check_recv_params(*num_params, param, &num_meta);
+	if (rc)
+		return rc;
+
+	while (true) {
+		mutex_lock(&supp->mutex);
+		req = supp_pop_entry(supp, *num_params - num_meta);
+		if (req)
+			break; /* Keep mutex held. */
+		mutex_unlock(&supp->mutex);
+
+		/*
+		 * If we didn't get a request we'll block in
+		 * wait_for_completion() to avoid needless spinning.
+		 *
+		 * This is where supplicant will be hanging most of
+		 * the time, let's make this interruptable so we
+		 * can easily restart supplicant if needed.
+		 */
+		if (wait_for_completion_interruptible(&supp->reqs_c))
+			return -ERESTARTSYS;
+	}
+
+	/* supp->mutex held and req != NULL. */
+
+	if (IS_ERR(req)) {
+		mutex_unlock(&supp->mutex);
+		return PTR_ERR(req);
+	}
+
+	if (num_meta) {
+		/*
+		 * tee-supplicant support meta parameters -> requsts can be
+		 * processed asynchronously.
+		 */
+		param->attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INOUT |
+			      TEE_IOCTL_PARAM_ATTR_META;
+		param->u.value.a = req->id;
+		param->u.value.b = 0;
+		param->u.value.c = 0;
+	} else {
+		supp->req_id = req->id;
+	}
+
+	*func = req->func;
+	*num_params = req->num_params + num_meta;
+	memcpy(param + num_meta, req->param,
+	       sizeof(struct tee_param) * req->num_params);
+
+	mutex_unlock(&supp->mutex);
+	return 0;
+}
+
+static struct optee_supp_req *supp_pop_req(struct optee_supp *supp,
+					   size_t num_params,
+					   struct tee_param *param,
+					   size_t *num_meta)
+{
+	struct optee_supp_req *req;
+	int id;
+	size_t nm;
+	const u32 attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INOUT |
+			 TEE_IOCTL_PARAM_ATTR_META;
+
+	if (!num_params)
+		return ERR_PTR(-EINVAL);
+
+	if (supp->req_id == -1) {
+		if (param->attr != attr)
+			return ERR_PTR(-EINVAL);
+		id = param->u.value.a;
+		nm = 1;
+	} else {
+		id = supp->req_id;
+		nm = 0;
+	}
+
+	req = idr_find(&supp->idr, id);
+	if (!req)
+		return ERR_PTR(-ENOENT);
+
+	/* optee_supp_thrd_req() already returned to optee. */
+	if (IS_ERR(req))
+		goto failed_req;
+
+	if ((num_params - nm) != req->num_params)
+		return ERR_PTR(-EINVAL);
+
+	*num_meta = nm;
+failed_req:
+	idr_remove(&supp->idr, id);
+	supp->req_id = -1;
+
+	return req;
+}
+
+/**
+ * optee_supp_send() - send result of request from supplicant
+ * @ctx:	context sending result
+ * @ret:	return value of request
+ * @num_params:	number of parameters returned
+ * @param:	returned parameters
+ *
+ * Returns 0 on success or <0 on failure.
+ */
+int optee_supp_send(struct tee_context *ctx, u32 ret, u32 num_params,
+		    struct tee_param *param)
+{
+	struct tee_device *teedev = ctx->teedev;
+	struct optee *optee = tee_get_drvdata(teedev);
+	struct optee_supp *supp = &optee->supp;
+	struct optee_supp_req *req;
+	size_t n;
+	size_t num_meta;
+
+	mutex_lock(&supp->mutex);
+	req = supp_pop_req(supp, num_params, param, &num_meta);
+	if (IS_ERR(req)) {
+		mutex_unlock(&supp->mutex);
+		/* Something is wrong, let supplicant handel it. */
+		return PTR_ERR(req);
+	}
+
+	/* Update out and in/out parameters */
+	for (n = 0; n < req->num_params; n++) {
+		struct tee_param *p = req->param + n;
+
+		switch (p->attr & TEE_IOCTL_PARAM_ATTR_TYPE_MASK) {
+		case TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_OUTPUT:
+		case TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INOUT:
+			p->u.value.a = param[n + num_meta].u.value.a;
+			p->u.value.b = param[n + num_meta].u.value.b;
+			p->u.value.c = param[n + num_meta].u.value.c;
+			break;
+		case TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT:
+		case TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT:
+			p->u.memref.size = param[n + num_meta].u.memref.size;
+			break;
+		default:
+			break;
+		}
+	}
+	req->ret = ret;
+	req->processed = true;
+	/* Let the requesting thread continue */
+	complete(&req->c);
+	mutex_unlock(&supp->mutex);
+
+	return 0;
+}