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, 356 insertions, 0 deletions

diff --git a/drivers/tty/ipwireless/main.c b/drivers/tty/ipwireless/main.c
new file mode 100644
index 000000000..a28758232
--- /dev/null
+++ b/drivers/tty/ipwireless/main.c
@@ -0,0 +1,356 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IPWireless 3G PCMCIA Network Driver
+ *
+ * Original code
+ *   by Stephen Blackheath <stephen@blacksapphire.com>,
+ *      Ben Martel <benm@symmetric.co.nz>
+ *
+ * Copyrighted as follows:
+ *   Copyright (C) 2004 by Symmetric Systems Ltd (NZ)
+ *
+ * Various driver changes and rewrites, port to new kernels
+ *   Copyright (C) 2006-2007 Jiri Kosina
+ *
+ * Misc code cleanups and updates
+ *   Copyright (C) 2007 David Sterba
+ */
+
+#include "hardware.h"
+#include "network.h"
+#include "main.h"
+#include "tty.h"
+
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include <pcmcia/cisreg.h>
+#include <pcmcia/device_id.h>
+#include <pcmcia/ss.h>
+#include <pcmcia/ds.h>
+
+static const struct pcmcia_device_id ipw_ids[] = {
+	PCMCIA_DEVICE_MANF_CARD(0x02f2, 0x0100),
+	PCMCIA_DEVICE_MANF_CARD(0x02f2, 0x0200),
+	PCMCIA_DEVICE_NULL
+};
+MODULE_DEVICE_TABLE(pcmcia, ipw_ids);
+
+static void ipwireless_detach(struct pcmcia_device *link);
+
+/*
+ * Module params
+ */
+/* Debug mode: more verbose, print sent/recv bytes */
+int ipwireless_debug;
+int ipwireless_loopback;
+int ipwireless_out_queue = 10;
+
+module_param_named(debug, ipwireless_debug, int, 0);
+module_param_named(loopback, ipwireless_loopback, int, 0);
+module_param_named(out_queue, ipwireless_out_queue, int, 0);
+MODULE_PARM_DESC(debug, "switch on debug messages [0]");
+MODULE_PARM_DESC(loopback,
+		"debug: enable ras_raw channel [0]");
+MODULE_PARM_DESC(out_queue, "debug: set size of outgoing PPP queue [10]");
+
+/* Executes in process context. */
+static void signalled_reboot_work(struct work_struct *work_reboot)
+{
+	struct ipw_dev *ipw = container_of(work_reboot, struct ipw_dev,
+			work_reboot);
+	struct pcmcia_device *link = ipw->link;
+	pcmcia_reset_card(link->socket);
+}
+
+static void signalled_reboot_callback(void *callback_data)
+{
+	struct ipw_dev *ipw = (struct ipw_dev *) callback_data;
+
+	/* Delegate to process context. */
+	schedule_work(&ipw->work_reboot);
+}
+
+static int ipwireless_probe(struct pcmcia_device *p_dev, void *priv_data)
+{
+	struct ipw_dev *ipw = priv_data;
+	int ret;
+
+	p_dev->resource[0]->flags &= ~IO_DATA_PATH_WIDTH;
+	p_dev->resource[0]->flags |= IO_DATA_PATH_WIDTH_AUTO;
+
+	/* 0x40 causes it to generate level mode interrupts. */
+	/* 0x04 enables IREQ pin. */
+	p_dev->config_index |= 0x44;
+	p_dev->io_lines = 16;
+	ret = pcmcia_request_io(p_dev);
+	if (ret)
+		return ret;
+
+	if (!request_region(p_dev->resource[0]->start,
+			    resource_size(p_dev->resource[0]),
+			    IPWIRELESS_PCCARD_NAME)) {
+		ret = -EBUSY;
+		goto exit;
+	}
+
+	p_dev->resource[2]->flags |=
+		WIN_DATA_WIDTH_16 | WIN_MEMORY_TYPE_CM | WIN_ENABLE;
+
+	ret = pcmcia_request_window(p_dev, p_dev->resource[2], 0);
+	if (ret != 0)
+		goto exit1;
+
+	ret = pcmcia_map_mem_page(p_dev, p_dev->resource[2], p_dev->card_addr);
+	if (ret != 0)
+		goto exit1;
+
+	ipw->is_v2_card = resource_size(p_dev->resource[2]) == 0x100;
+
+	ipw->common_memory = ioremap(p_dev->resource[2]->start,
+				resource_size(p_dev->resource[2]));
+	if (!ipw->common_memory) {
+		ret = -ENOMEM;
+		goto exit1;
+	}
+	if (!request_mem_region(p_dev->resource[2]->start,
+				resource_size(p_dev->resource[2]),
+				IPWIRELESS_PCCARD_NAME)) {
+		ret = -EBUSY;
+		goto exit2;
+	}
+
+	p_dev->resource[3]->flags |= WIN_DATA_WIDTH_16 | WIN_MEMORY_TYPE_AM |
+					WIN_ENABLE;
+	p_dev->resource[3]->end = 0; /* this used to be 0x1000 */
+	ret = pcmcia_request_window(p_dev, p_dev->resource[3], 0);
+	if (ret != 0)
+		goto exit3;
+
+	ret = pcmcia_map_mem_page(p_dev, p_dev->resource[3], 0);
+	if (ret != 0)
+		goto exit3;
+
+	ipw->attr_memory = ioremap(p_dev->resource[3]->start,
+				resource_size(p_dev->resource[3]));
+	if (!ipw->attr_memory) {
+		ret = -ENOMEM;
+		goto exit3;
+	}
+	if (!request_mem_region(p_dev->resource[3]->start,
+				resource_size(p_dev->resource[3]),
+				IPWIRELESS_PCCARD_NAME)) {
+		ret = -EBUSY;
+		goto exit4;
+	}
+
+	return 0;
+
+exit4:
+	iounmap(ipw->attr_memory);
+exit3:
+	release_mem_region(p_dev->resource[2]->start,
+			resource_size(p_dev->resource[2]));
+exit2:
+	iounmap(ipw->common_memory);
+exit1:
+	release_region(p_dev->resource[0]->start,
+		       resource_size(p_dev->resource[0]));
+exit:
+	pcmcia_disable_device(p_dev);
+	return ret;
+}
+
+static int config_ipwireless(struct ipw_dev *ipw)
+{
+	struct pcmcia_device *link = ipw->link;
+	int ret = 0;
+
+	ipw->is_v2_card = 0;
+	link->config_flags |= CONF_AUTO_SET_IO | CONF_AUTO_SET_IOMEM |
+		CONF_ENABLE_IRQ;
+
+	ret = pcmcia_loop_config(link, ipwireless_probe, ipw);
+	if (ret != 0)
+		return ret;
+
+	INIT_WORK(&ipw->work_reboot, signalled_reboot_work);
+
+	ipwireless_init_hardware_v1(ipw->hardware, link->resource[0]->start,
+				    ipw->attr_memory, ipw->common_memory,
+				    ipw->is_v2_card, signalled_reboot_callback,
+				    ipw);
+
+	ret = pcmcia_request_irq(link, ipwireless_interrupt);
+	if (ret != 0)
+		goto exit;
+
+	printk(KERN_INFO IPWIRELESS_PCCARD_NAME ": Card type %s\n",
+			ipw->is_v2_card ? "V2/V3" : "V1");
+	printk(KERN_INFO IPWIRELESS_PCCARD_NAME
+		": I/O ports %pR, irq %d\n", link->resource[0],
+			(unsigned int) link->irq);
+	if (ipw->attr_memory && ipw->common_memory)
+		printk(KERN_INFO IPWIRELESS_PCCARD_NAME
+			": attr memory %pR, common memory %pR\n",
+			link->resource[3],
+			link->resource[2]);
+
+	ipw->network = ipwireless_network_create(ipw->hardware);
+	if (!ipw->network)
+		goto exit;
+
+	ipw->tty = ipwireless_tty_create(ipw->hardware, ipw->network);
+	if (!ipw->tty)
+		goto exit;
+
+	ipwireless_init_hardware_v2_v3(ipw->hardware);
+
+	/*
+	 * Do the RequestConfiguration last, because it enables interrupts.
+	 * Then we don't get any interrupts before we're ready for them.
+	 */
+	ret = pcmcia_enable_device(link);
+	if (ret != 0)
+		goto exit;
+
+	return 0;
+
+exit:
+	if (ipw->common_memory) {
+		release_mem_region(link->resource[2]->start,
+				resource_size(link->resource[2]));
+		iounmap(ipw->common_memory);
+	}
+	if (ipw->attr_memory) {
+		release_mem_region(link->resource[3]->start,
+				resource_size(link->resource[3]));
+		iounmap(ipw->attr_memory);
+	}
+	pcmcia_disable_device(link);
+	return -1;
+}
+
+static void release_ipwireless(struct ipw_dev *ipw)
+{
+	release_region(ipw->link->resource[0]->start,
+		       resource_size(ipw->link->resource[0]));
+	if (ipw->common_memory) {
+		release_mem_region(ipw->link->resource[2]->start,
+				resource_size(ipw->link->resource[2]));
+		iounmap(ipw->common_memory);
+	}
+	if (ipw->attr_memory) {
+		release_mem_region(ipw->link->resource[3]->start,
+				resource_size(ipw->link->resource[3]));
+		iounmap(ipw->attr_memory);
+	}
+	pcmcia_disable_device(ipw->link);
+}
+
+/*
+ * ipwireless_attach() creates an "instance" of the driver, allocating
+ * local data structures for one device (one interface).  The device
+ * is registered with Card Services.
+ *
+ * The pcmcia_device structure is initialized, but we don't actually
+ * configure the card at this point -- we wait until we receive a
+ * card insertion event.
+ */
+static int ipwireless_attach(struct pcmcia_device *link)
+{
+	struct ipw_dev *ipw;
+	int ret;
+
+	ipw = kzalloc_obj(struct ipw_dev);
+	if (!ipw)
+		return -ENOMEM;
+
+	ipw->link = link;
+	link->priv = ipw;
+
+	ipw->hardware = ipwireless_hardware_create();
+	if (!ipw->hardware) {
+		kfree(ipw);
+		return -ENOMEM;
+	}
+	/* RegisterClient will call config_ipwireless */
+
+	ret = config_ipwireless(ipw);
+
+	if (ret != 0) {
+		ipwireless_detach(link);
+		return ret;
+	}
+
+	return 0;
+}
+
+/*
+ * This deletes a driver "instance".  The device is de-registered with
+ * Card Services.  If it has been released, all local data structures
+ * are freed.  Otherwise, the structures will be freed when the device
+ * is released.
+ */
+static void ipwireless_detach(struct pcmcia_device *link)
+{
+	struct ipw_dev *ipw = link->priv;
+
+	release_ipwireless(ipw);
+
+	if (ipw->tty != NULL)
+		ipwireless_tty_free(ipw->tty);
+	if (ipw->network != NULL)
+		ipwireless_network_free(ipw->network);
+	if (ipw->hardware != NULL)
+		ipwireless_hardware_free(ipw->hardware);
+	kfree(ipw);
+}
+
+static struct pcmcia_driver me = {
+	.owner		= THIS_MODULE,
+	.probe          = ipwireless_attach,
+	.remove         = ipwireless_detach,
+	.name		= IPWIRELESS_PCCARD_NAME,
+	.id_table       = ipw_ids
+};
+
+/*
+ * Module insertion : initialisation of the module.
+ * Register the card with cardmgr...
+ */
+static int __init init_ipwireless(void)
+{
+	int ret;
+
+	ret = ipwireless_tty_init();
+	if (ret != 0)
+		return ret;
+
+	ret = pcmcia_register_driver(&me);
+	if (ret != 0)
+		ipwireless_tty_release();
+
+	return ret;
+}
+
+/*
+ * Module removal
+ */
+static void __exit exit_ipwireless(void)
+{
+	pcmcia_unregister_driver(&me);
+	ipwireless_tty_release();
+}
+
+module_init(init_ipwireless);
+module_exit(exit_ipwireless);
+
+MODULE_AUTHOR(IPWIRELESS_PCMCIA_AUTHOR);
+MODULE_DESCRIPTION(IPWIRELESS_PCCARD_NAME " " IPWIRELESS_PCMCIA_VERSION);
+MODULE_LICENSE("GPL");