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, 335 insertions, 0 deletions

diff --git a/drivers/tee/optee/protmem.c b/drivers/tee/optee/protmem.c
new file mode 100644
index 000000000..be3abf6e8
--- /dev/null
+++ b/drivers/tee/optee/protmem.c
@@ -0,0 +1,335 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2025, Linaro Limited
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/errno.h>
+#include <linux/genalloc.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/tee_core.h>
+#include <linux/types.h>
+#include "optee_private.h"
+
+struct optee_protmem_dyn_pool {
+	struct tee_protmem_pool pool;
+	struct gen_pool *gen_pool;
+	struct optee *optee;
+	size_t page_count;
+	u32 *mem_attrs;
+	u_int mem_attr_count;
+	refcount_t refcount;
+	u32 use_case;
+	struct tee_shm *protmem;
+	/* Protects when initializing and tearing down this struct */
+	struct mutex mutex;
+};
+
+static struct optee_protmem_dyn_pool *
+to_protmem_dyn_pool(struct tee_protmem_pool *pool)
+{
+	return container_of(pool, struct optee_protmem_dyn_pool, pool);
+}
+
+static int init_dyn_protmem(struct optee_protmem_dyn_pool *rp)
+{
+	int rc;
+
+	rp->protmem = tee_shm_alloc_dma_mem(rp->optee->ctx, rp->page_count);
+	if (IS_ERR(rp->protmem)) {
+		rc = PTR_ERR(rp->protmem);
+		goto err_null_protmem;
+	}
+
+	/*
+	 * TODO unmap the memory range since the physical memory will
+	 * become inaccesible after the lend_protmem() call.
+	 *
+	 * If the platform supports a hypervisor at EL2, it will unmap the
+	 * intermediate physical memory for us and stop cache pre-fetch of
+	 * the memory.
+	 */
+	rc = rp->optee->ops->lend_protmem(rp->optee, rp->protmem,
+					  rp->mem_attrs,
+					  rp->mem_attr_count, rp->use_case);
+	if (rc)
+		goto err_put_shm;
+	rp->protmem->flags |= TEE_SHM_DYNAMIC;
+
+	rp->gen_pool = gen_pool_create(PAGE_SHIFT, -1);
+	if (!rp->gen_pool) {
+		rc = -ENOMEM;
+		goto err_reclaim;
+	}
+
+	rc = gen_pool_add(rp->gen_pool, rp->protmem->paddr,
+			  rp->protmem->size, -1);
+	if (rc)
+		goto err_free_pool;
+
+	refcount_set(&rp->refcount, 1);
+	return 0;
+
+err_free_pool:
+	gen_pool_destroy(rp->gen_pool);
+	rp->gen_pool = NULL;
+err_reclaim:
+	rp->optee->ops->reclaim_protmem(rp->optee, rp->protmem);
+err_put_shm:
+	tee_shm_put(rp->protmem);
+err_null_protmem:
+	rp->protmem = NULL;
+	return rc;
+}
+
+static int get_dyn_protmem(struct optee_protmem_dyn_pool *rp)
+{
+	int rc = 0;
+
+	if (!refcount_inc_not_zero(&rp->refcount)) {
+		mutex_lock(&rp->mutex);
+		if (rp->gen_pool) {
+			/*
+			 * Another thread has already initialized the pool
+			 * before us, or the pool was just about to be torn
+			 * down. Either way we only need to increase the
+			 * refcount and we're done.
+			 */
+			refcount_inc(&rp->refcount);
+		} else {
+			rc = init_dyn_protmem(rp);
+		}
+		mutex_unlock(&rp->mutex);
+	}
+
+	return rc;
+}
+
+static void release_dyn_protmem(struct optee_protmem_dyn_pool *rp)
+{
+	gen_pool_destroy(rp->gen_pool);
+	rp->gen_pool = NULL;
+
+	rp->optee->ops->reclaim_protmem(rp->optee, rp->protmem);
+	rp->protmem->flags &= ~TEE_SHM_DYNAMIC;
+
+	WARN(refcount_read(&rp->protmem->refcount) != 1, "Unexpected refcount");
+	tee_shm_put(rp->protmem);
+	rp->protmem = NULL;
+}
+
+static void put_dyn_protmem(struct optee_protmem_dyn_pool *rp)
+{
+	if (refcount_dec_and_test(&rp->refcount)) {
+		mutex_lock(&rp->mutex);
+		if (rp->gen_pool)
+			release_dyn_protmem(rp);
+		mutex_unlock(&rp->mutex);
+	}
+}
+
+static int protmem_pool_op_dyn_alloc(struct tee_protmem_pool *pool,
+				     struct sg_table *sgt, size_t size,
+				     size_t *offs)
+{
+	struct optee_protmem_dyn_pool *rp = to_protmem_dyn_pool(pool);
+	size_t sz = ALIGN(size, PAGE_SIZE);
+	phys_addr_t pa;
+	int rc;
+
+	rc = get_dyn_protmem(rp);
+	if (rc)
+		return rc;
+
+	pa = gen_pool_alloc(rp->gen_pool, sz);
+	if (!pa) {
+		rc = -ENOMEM;
+		goto err_put;
+	}
+
+	rc = sg_alloc_table(sgt, 1, GFP_KERNEL);
+	if (rc)
+		goto err_free;
+
+	sg_set_page(sgt->sgl, phys_to_page(pa), size, 0);
+	*offs = pa - rp->protmem->paddr;
+
+	return 0;
+err_free:
+	gen_pool_free(rp->gen_pool, pa, size);
+err_put:
+	put_dyn_protmem(rp);
+
+	return rc;
+}
+
+static void protmem_pool_op_dyn_free(struct tee_protmem_pool *pool,
+				     struct sg_table *sgt)
+{
+	struct optee_protmem_dyn_pool *rp = to_protmem_dyn_pool(pool);
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sgtable_sg(sgt, sg, i)
+		gen_pool_free(rp->gen_pool, sg_phys(sg), sg->length);
+	sg_free_table(sgt);
+	put_dyn_protmem(rp);
+}
+
+static int protmem_pool_op_dyn_update_shm(struct tee_protmem_pool *pool,
+					  struct sg_table *sgt, size_t offs,
+					  struct tee_shm *shm,
+					  struct tee_shm **parent_shm)
+{
+	struct optee_protmem_dyn_pool *rp = to_protmem_dyn_pool(pool);
+
+	*parent_shm = rp->protmem;
+
+	return 0;
+}
+
+static void pool_op_dyn_destroy_pool(struct tee_protmem_pool *pool)
+{
+	struct optee_protmem_dyn_pool *rp = to_protmem_dyn_pool(pool);
+
+	mutex_destroy(&rp->mutex);
+	kfree(rp);
+}
+
+static struct tee_protmem_pool_ops protmem_pool_ops_dyn = {
+	.alloc = protmem_pool_op_dyn_alloc,
+	.free = protmem_pool_op_dyn_free,
+	.update_shm = protmem_pool_op_dyn_update_shm,
+	.destroy_pool = pool_op_dyn_destroy_pool,
+};
+
+static int get_protmem_config(struct optee *optee, u32 use_case,
+			      size_t *min_size, u_int *pa_width,
+			      u32 *mem_attrs, u_int *ma_count)
+{
+	struct tee_param params[2] = {
+		[0] = {
+			.attr = TEE_IOCTL_PARAM_ATTR_TYPE_VALUE_INOUT,
+			.u.value.a = use_case,
+		},
+		[1] = {
+			.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT,
+		},
+	};
+	struct optee_shm_arg_entry *entry;
+	struct tee_shm *shm_param = NULL;
+	struct optee_msg_arg *msg_arg;
+	struct tee_shm *shm;
+	u_int offs;
+	int rc;
+
+	if (mem_attrs && *ma_count) {
+		params[1].u.memref.size = *ma_count * sizeof(*mem_attrs);
+		shm_param = tee_shm_alloc_priv_buf(optee->ctx,
+						   params[1].u.memref.size);
+		if (IS_ERR(shm_param))
+			return PTR_ERR(shm_param);
+		params[1].u.memref.shm = shm_param;
+	}
+
+	msg_arg = optee_get_msg_arg(optee->ctx, ARRAY_SIZE(params), &entry,
+				    &shm, &offs);
+	if (IS_ERR(msg_arg)) {
+		rc = PTR_ERR(msg_arg);
+		goto out_free_shm;
+	}
+	msg_arg->cmd = OPTEE_MSG_CMD_GET_PROTMEM_CONFIG;
+
+	rc = optee->ops->to_msg_param(optee, msg_arg->params,
+				      ARRAY_SIZE(params), params);
+	if (rc)
+		goto out_free_msg;
+
+	rc = optee->ops->do_call_with_arg(optee->ctx, shm, offs, false);
+	if (rc)
+		goto out_free_msg;
+	if (msg_arg->ret && msg_arg->ret != TEEC_ERROR_SHORT_BUFFER) {
+		rc = -EINVAL;
+		goto out_free_msg;
+	}
+
+	rc = optee->ops->from_msg_param(optee, params, ARRAY_SIZE(params),
+					msg_arg->params);
+	if (rc)
+		goto out_free_msg;
+
+	if (!msg_arg->ret && mem_attrs &&
+	    *ma_count < params[1].u.memref.size / sizeof(*mem_attrs)) {
+		rc = -EINVAL;
+		goto out_free_msg;
+	}
+
+	*min_size = params[0].u.value.a;
+	*pa_width = params[0].u.value.c;
+	*ma_count = params[1].u.memref.size / sizeof(*mem_attrs);
+
+	if (msg_arg->ret == TEEC_ERROR_SHORT_BUFFER) {
+		rc = -ENOSPC;
+		goto out_free_msg;
+	}
+
+	if (mem_attrs)
+		memcpy(mem_attrs, tee_shm_get_va(shm_param, 0),
+		       params[1].u.memref.size);
+
+out_free_msg:
+	optee_free_msg_arg(optee->ctx, entry, offs);
+out_free_shm:
+	if (shm_param)
+		tee_shm_free(shm_param);
+	return rc;
+}
+
+struct tee_protmem_pool *optee_protmem_alloc_dyn_pool(struct optee *optee,
+						      enum tee_dma_heap_id id)
+{
+	struct optee_protmem_dyn_pool *rp;
+	size_t min_size;
+	u_int pa_width;
+	int rc;
+
+	rp = kzalloc_obj(*rp);
+	if (!rp)
+		return ERR_PTR(-ENOMEM);
+	rp->use_case = id;
+
+	rc = get_protmem_config(optee, id, &min_size, &pa_width, NULL,
+				&rp->mem_attr_count);
+	if (rc) {
+		if (rc != -ENOSPC)
+			goto err;
+		rp->mem_attrs = kcalloc(rp->mem_attr_count,
+					sizeof(*rp->mem_attrs), GFP_KERNEL);
+		if (!rp->mem_attrs) {
+			rc = -ENOMEM;
+			goto err;
+		}
+		rc = get_protmem_config(optee, id, &min_size, &pa_width,
+					rp->mem_attrs, &rp->mem_attr_count);
+		if (rc)
+			goto err_kfree_eps;
+	}
+
+	rc = optee_set_dma_mask(optee, pa_width);
+	if (rc)
+		goto err_kfree_eps;
+
+	rp->pool.ops = &protmem_pool_ops_dyn;
+	rp->optee = optee;
+	rp->page_count = min_size / PAGE_SIZE;
+	mutex_init(&rp->mutex);
+
+	return &rp->pool;
+
+err_kfree_eps:
+	kfree(rp->mem_attrs);
+err:
+	kfree(rp);
+	return ERR_PTR(rc);
+}