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, 338 insertions, 0 deletions

diff --git a/drivers/interconnect/imx/imx.c b/drivers/interconnect/imx/imx.c
new file mode 100644
index 000000000..9511f80cf
--- /dev/null
+++ b/drivers/interconnect/imx/imx.c
@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Interconnect framework driver for i.MX SoC
+ *
+ * Copyright (c) 2019, BayLibre
+ * Copyright (c) 2019-2020, NXP
+ * Author: Alexandre Bailon <abailon@baylibre.com>
+ * Author: Leonard Crestez <leonard.crestez@nxp.com>
+ */
+
+#include <linux/device.h>
+#include <linux/interconnect-provider.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_qos.h>
+
+#include "imx.h"
+
+/* private icc_node data */
+struct imx_icc_node {
+	const struct imx_icc_node_desc *desc;
+	const struct imx_icc_noc_setting *setting;
+	struct device *qos_dev;
+	struct dev_pm_qos_request qos_req;
+	struct imx_icc_provider *imx_provider;
+};
+
+static int imx_icc_get_bw(struct icc_node *node, u32 *avg, u32 *peak)
+{
+	*avg = 0;
+	*peak = 0;
+
+	return 0;
+}
+
+static int imx_icc_node_set(struct icc_node *node)
+{
+	struct device *dev = node->provider->dev;
+	struct imx_icc_node *node_data = node->data;
+	void __iomem *base;
+	u32 prio;
+	u64 freq;
+
+	if (node_data->setting && node->peak_bw) {
+		base = node_data->setting->reg + node_data->imx_provider->noc_base;
+		if (node_data->setting->mode == IMX_NOC_MODE_FIXED) {
+			prio = node_data->setting->prio_level;
+			prio = PRIORITY_COMP_MARK | (prio << 8) | prio;
+			writel(prio, base + IMX_NOC_PRIO_REG);
+			writel(node_data->setting->mode, base + IMX_NOC_MODE_REG);
+			writel(node_data->setting->ext_control, base + IMX_NOC_EXT_CTL_REG);
+			dev_dbg(dev, "%s: mode: 0x%x, prio: 0x%x, ext_control: 0x%x\n",
+				node_data->desc->name, node_data->setting->mode, prio,
+				node_data->setting->ext_control);
+		} else if (node_data->setting->mode == IMX_NOC_MODE_UNCONFIGURED) {
+			dev_dbg(dev, "%s: mode not unconfigured\n", node_data->desc->name);
+		} else {
+			dev_info(dev, "%s: mode: %d not supported\n",
+				 node_data->desc->name, node_data->setting->mode);
+			return -EOPNOTSUPP;
+		}
+	}
+
+	if (!node_data->qos_dev)
+		return 0;
+
+	freq = (node->avg_bw + node->peak_bw) * node_data->desc->adj->bw_mul;
+	do_div(freq, node_data->desc->adj->bw_div);
+	dev_dbg(dev, "node %s device %s avg_bw %ukBps peak_bw %ukBps min_freq %llukHz\n",
+		node->name, dev_name(node_data->qos_dev),
+		node->avg_bw, node->peak_bw, freq);
+
+	if (freq > S32_MAX) {
+		dev_err(dev, "%s can't request more than S32_MAX freq\n",
+				node->name);
+		return -ERANGE;
+	}
+
+	dev_pm_qos_update_request(&node_data->qos_req, freq);
+
+	return 0;
+}
+
+static int imx_icc_set(struct icc_node *src, struct icc_node *dst)
+{
+	int ret;
+
+	ret = imx_icc_node_set(src);
+	if (ret)
+		return ret;
+
+	return imx_icc_node_set(dst);
+}
+
+/* imx_icc_node_destroy() - Destroy an imx icc_node, including private data */
+static void imx_icc_node_destroy(struct icc_node *node)
+{
+	struct imx_icc_node *node_data = node->data;
+	int ret;
+
+	if (dev_pm_qos_request_active(&node_data->qos_req)) {
+		ret = dev_pm_qos_remove_request(&node_data->qos_req);
+		if (ret)
+			dev_warn(node->provider->dev,
+				 "failed to remove qos request for %s\n",
+				 dev_name(node_data->qos_dev));
+	}
+
+	put_device(node_data->qos_dev);
+	icc_node_del(node);
+	icc_node_destroy(node->id);
+}
+
+static int imx_icc_node_init_qos(struct icc_provider *provider,
+				 struct icc_node *node)
+{
+	struct imx_icc_node *node_data = node->data;
+	const struct imx_icc_node_adj_desc *adj = node_data->desc->adj;
+	struct device *dev = provider->dev;
+	struct device_node *dn = NULL;
+	struct platform_device *pdev;
+
+	if (adj->main_noc) {
+		node_data->qos_dev = dev;
+		dev_dbg(dev, "icc node %s[%d] is main noc itself\n",
+			node->name, node->id);
+	} else {
+		dn = of_parse_phandle(dev->of_node, adj->phandle_name, 0);
+		if (!dn) {
+			dev_warn(dev, "Failed to parse %s\n",
+				 adj->phandle_name);
+			return -ENODEV;
+		}
+		/* Allow scaling to be disabled on a per-node basis */
+		if (!of_device_is_available(dn)) {
+			dev_warn(dev, "Missing property %s, skip scaling %s\n",
+				 adj->phandle_name, node->name);
+			of_node_put(dn);
+			return 0;
+		}
+
+		pdev = of_find_device_by_node(dn);
+		of_node_put(dn);
+		if (!pdev) {
+			dev_warn(dev, "node %s[%d] missing device for %pOF\n",
+				 node->name, node->id, dn);
+			return -EPROBE_DEFER;
+		}
+		node_data->qos_dev = &pdev->dev;
+		dev_dbg(dev, "node %s[%d] has device node %pOF\n",
+			node->name, node->id, dn);
+	}
+
+	return dev_pm_qos_add_request(node_data->qos_dev,
+				      &node_data->qos_req,
+				      DEV_PM_QOS_MIN_FREQUENCY, 0);
+}
+
+static struct icc_node *imx_icc_node_add(struct imx_icc_provider *imx_provider,
+					 const struct imx_icc_node_desc *node_desc,
+					 const struct imx_icc_noc_setting *setting)
+{
+	struct icc_provider *provider = &imx_provider->provider;
+	struct device *dev = provider->dev;
+	struct imx_icc_node *node_data;
+	struct icc_node *node;
+	int ret;
+
+	node = icc_node_create(node_desc->id);
+	if (IS_ERR(node)) {
+		dev_err(dev, "failed to create node %d\n", node_desc->id);
+		return node;
+	}
+
+	if (node->data) {
+		dev_err(dev, "already created node %s id=%d\n",
+			node_desc->name, node_desc->id);
+		return ERR_PTR(-EEXIST);
+	}
+
+	node_data = devm_kzalloc(dev, sizeof(*node_data), GFP_KERNEL);
+	if (!node_data) {
+		icc_node_destroy(node->id);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	node->name = node_desc->name;
+	node->data = node_data;
+	node_data->desc = node_desc;
+	node_data->setting = setting;
+	node_data->imx_provider = imx_provider;
+	icc_node_add(node, provider);
+
+	if (node_desc->adj) {
+		ret = imx_icc_node_init_qos(provider, node);
+		if (ret < 0) {
+			imx_icc_node_destroy(node);
+			return ERR_PTR(ret);
+		}
+	}
+
+	return node;
+}
+
+static void imx_icc_unregister_nodes(struct icc_provider *provider)
+{
+	struct icc_node *node, *tmp;
+
+	list_for_each_entry_safe(node, tmp, &provider->nodes, node_list)
+		imx_icc_node_destroy(node);
+}
+
+static int imx_icc_register_nodes(struct imx_icc_provider *imx_provider,
+				  const struct imx_icc_node_desc *descs,
+				  int count,
+				  const struct imx_icc_noc_setting *settings)
+{
+	struct icc_provider *provider = &imx_provider->provider;
+	struct icc_onecell_data *provider_data = provider->data;
+	int ret;
+	int i;
+
+	for (i = 0; i < count; i++) {
+		struct icc_node *node;
+		const struct imx_icc_node_desc *node_desc = &descs[i];
+		size_t j;
+
+		node = imx_icc_node_add(imx_provider, node_desc,
+					settings ? &settings[node_desc->id] : NULL);
+		if (IS_ERR(node)) {
+			ret = dev_err_probe(provider->dev, PTR_ERR(node),
+					    "failed to add %s\n", node_desc->name);
+			goto err;
+		}
+		provider_data->nodes[node->id] = node;
+
+		for (j = 0; j < node_desc->num_links; j++) {
+			ret = icc_link_create(node, node_desc->links[j]);
+			if (ret) {
+				dev_err(provider->dev, "failed to link node %d to %d: %d\n",
+					node->id, node_desc->links[j], ret);
+				goto err;
+			}
+		}
+	}
+
+	return 0;
+
+err:
+	imx_icc_unregister_nodes(provider);
+
+	return ret;
+}
+
+static int get_max_node_id(struct imx_icc_node_desc *nodes, int nodes_count)
+{
+	int i, ret = 0;
+
+	for (i = 0; i < nodes_count; ++i)
+		if (nodes[i].id > ret)
+			ret = nodes[i].id;
+
+	return ret;
+}
+
+int imx_icc_register(struct platform_device *pdev,
+		     struct imx_icc_node_desc *nodes, int nodes_count,
+		     struct imx_icc_noc_setting *settings)
+{
+	struct device *dev = &pdev->dev;
+	struct icc_onecell_data *data;
+	struct imx_icc_provider *imx_provider;
+	struct icc_provider *provider;
+	int num_nodes;
+	int ret;
+
+	/* icc_onecell_data is indexed by node_id, unlike nodes param */
+	num_nodes = get_max_node_id(nodes, nodes_count) + 1;
+	data = devm_kzalloc(dev, struct_size(data, nodes, num_nodes),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	data->num_nodes = num_nodes;
+
+	imx_provider = devm_kzalloc(dev, sizeof(*imx_provider), GFP_KERNEL);
+	if (!imx_provider)
+		return -ENOMEM;
+	provider = &imx_provider->provider;
+	provider->set = imx_icc_set;
+	provider->get_bw = imx_icc_get_bw;
+	provider->aggregate = icc_std_aggregate;
+	provider->xlate = of_icc_xlate_onecell;
+	provider->data = data;
+	provider->dev = dev->parent;
+
+	icc_provider_init(provider);
+
+	platform_set_drvdata(pdev, imx_provider);
+
+	if (settings) {
+		imx_provider->noc_base = devm_of_iomap(dev, provider->dev->of_node, 0, NULL);
+		if (IS_ERR(imx_provider->noc_base)) {
+			ret = PTR_ERR(imx_provider->noc_base);
+			dev_err(dev, "Error mapping NoC: %d\n", ret);
+			return ret;
+		}
+	}
+
+	ret = imx_icc_register_nodes(imx_provider, nodes, nodes_count, settings);
+	if (ret)
+		return ret;
+
+	ret = icc_provider_register(provider);
+	if (ret)
+		goto err_unregister_nodes;
+
+	return 0;
+
+err_unregister_nodes:
+	imx_icc_unregister_nodes(&imx_provider->provider);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(imx_icc_register);
+
+void imx_icc_unregister(struct platform_device *pdev)
+{
+	struct imx_icc_provider *imx_provider = platform_get_drvdata(pdev);
+
+	icc_provider_deregister(&imx_provider->provider);
+	imx_icc_unregister_nodes(&imx_provider->provider);
+}
+EXPORT_SYMBOL_GPL(imx_icc_unregister);
+
+MODULE_DESCRIPTION("Interconnect framework driver for i.MX SoC");
+MODULE_LICENSE("GPL v2");