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, 242 insertions, 0 deletions

diff --git a/drivers/scsi/sim710.c b/drivers/scsi/sim710.c
new file mode 100644
index 000000000..408f37003
--- /dev/null
+++ b/drivers/scsi/sim710.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * sim710.c - Copyright (C) 1999 Richard Hirst <richard@sleepie.demon.co.uk>
+ *
+ *----------------------------------------------------------------------------
+ *----------------------------------------------------------------------------
+ *
+ * MCA card detection code by Trent McNair. (now deleted)
+ * Fixes to not explicitly nul bss data from Xavier Bestel.
+ * Some multiboard fixes from Rolf Eike Beer.
+ * Auto probing of EISA config space from Trevor Hemsley.
+ *
+ * Rewritten to use 53c700.c by James.Bottomley@SteelEye.com
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#include <linux/blkdev.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/eisa.h>
+#include <linux/interrupt.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_transport.h>
+#include <scsi/scsi_transport_spi.h>
+
+#include "53c700.h"
+
+
+/* Must be enough for EISA */
+#define MAX_SLOTS 8
+static __u8 __initdata id_array[MAX_SLOTS] = { [0 ... MAX_SLOTS-1] = 7 };
+
+static char *sim710;		/* command line passed by insmod */
+
+MODULE_AUTHOR("Richard Hirst");
+MODULE_DESCRIPTION("Simple NCR53C710 driver");
+MODULE_LICENSE("GPL");
+
+module_param(sim710, charp, 0);
+
+#ifdef MODULE
+#define ARG_SEP ' '
+#else
+#define ARG_SEP ','
+#endif
+
+static __init int
+param_setup(char *str)
+{
+	char *pos = str, *next;
+	int slot = -1;
+
+	while(pos != NULL && (next = strchr(pos, ':')) != NULL) {
+		int val = (int)simple_strtoul(++next, NULL, 0);
+
+		if(!strncmp(pos, "slot:", 5))
+			slot = val;
+		else if(!strncmp(pos, "id:", 3)) {
+			if(slot == -1) {
+				printk(KERN_WARNING "sim710: Must specify slot for id parameter\n");
+			} else if(slot >= MAX_SLOTS) {
+				printk(KERN_WARNING "sim710: Illegal slot %d for id %d\n", slot, val);
+			} else {
+				id_array[slot] = val;
+			}
+		}
+		if((pos = strchr(pos, ARG_SEP)) != NULL)
+			pos++;
+	}
+	return 1;
+}
+__setup("sim710=", param_setup);
+
+static struct scsi_host_template sim710_driver_template = {
+	.name			= "LSI (Symbios) 710 EISA",
+	.proc_name		= "sim710",
+	.this_id		= 7,
+	.module			= THIS_MODULE,
+};
+
+static int sim710_probe_common(struct device *dev, unsigned long base_addr,
+			       int irq, int clock, int differential,
+			       int scsi_id)
+{
+	struct Scsi_Host * host = NULL;
+	struct NCR_700_Host_Parameters *hostdata =
+		kzalloc_obj(struct NCR_700_Host_Parameters);
+
+	printk(KERN_NOTICE "sim710: %s\n", dev_name(dev));
+	printk(KERN_NOTICE "sim710: irq = %d, clock = %d, base = 0x%lx, scsi_id = %d\n",
+	       irq, clock, base_addr, scsi_id);
+
+	if(hostdata == NULL) {
+		printk(KERN_ERR "sim710: Failed to allocate host data\n");
+		goto out;
+	}
+
+	if(request_region(base_addr, 64, "sim710") == NULL) {
+		printk(KERN_ERR "sim710: Failed to reserve IO region 0x%lx\n",
+		       base_addr);
+		goto out_free;
+	}
+
+	/* Fill in the three required pieces of hostdata */
+	hostdata->base = ioport_map(base_addr, 64);
+	hostdata->differential = differential;
+	hostdata->clock = clock;
+	hostdata->chip710 = 1;
+	hostdata->burst_length = 8;
+
+	/* and register the chip */
+	if((host = NCR_700_detect(&sim710_driver_template, hostdata, dev))
+	   == NULL) {
+		printk(KERN_ERR "sim710: No host detected; card configuration problem?\n");
+		goto out_release;
+	}
+	host->this_id = scsi_id;
+	host->base = base_addr;
+	host->irq = irq;
+	if (request_irq(irq, NCR_700_intr, IRQF_SHARED, "sim710", host)) {
+		printk(KERN_ERR "sim710: request_irq failed\n");
+		goto out_put_host;
+	}
+
+	dev_set_drvdata(dev, host);
+	scsi_scan_host(host);
+
+	return 0;
+
+ out_put_host:
+	scsi_host_put(host);
+ out_release:
+	ioport_unmap(hostdata->base);
+	release_region(base_addr, 64);
+ out_free:
+	kfree(hostdata);
+ out:
+	return -ENODEV;
+}
+
+static int sim710_device_remove(struct device *dev)
+{
+	struct Scsi_Host *host = dev_get_drvdata(dev);
+	struct NCR_700_Host_Parameters *hostdata =
+		(struct NCR_700_Host_Parameters *)host->hostdata[0];
+
+	scsi_remove_host(host);
+	NCR_700_release(host);
+	ioport_unmap(hostdata->base);
+	kfree(hostdata);
+	free_irq(host->irq, host);
+	release_region(host->base, 64);
+	return 0;
+}
+
+#ifdef CONFIG_EISA
+static struct eisa_device_id sim710_eisa_ids[] = {
+	{ "CPQ4410" },
+	{ "CPQ4411" },
+	{ "HWP0C80" },
+	{ "" }
+};
+MODULE_DEVICE_TABLE(eisa, sim710_eisa_ids);
+
+static int sim710_eisa_probe(struct device *dev)
+{
+	struct eisa_device *edev = to_eisa_device(dev);
+	unsigned long io_addr = edev->base_addr;
+	char eisa_cpq_irqs[] = { 11, 14, 15, 10, 9, 0 };
+	char eisa_hwp_irqs[] = { 3, 4, 5, 7, 12, 10, 11, 0};
+	char *eisa_irqs;
+	unsigned char irq_index;
+	unsigned char irq, differential = 0, scsi_id = 7;
+
+	if(strcmp(edev->id.sig, "HWP0C80") == 0) {
+		__u8 val;
+		eisa_irqs =  eisa_hwp_irqs;
+		irq_index = (inb(io_addr + 0xc85) & 0x7) - 1;
+
+		val = inb(io_addr + 0x4);
+		scsi_id = ffs(val) - 1;
+
+		if(scsi_id > 7 || (val & ~(1<<scsi_id)) != 0) {
+			printk(KERN_ERR "sim710.c, EISA card %s has incorrect scsi_id, setting to 7\n", dev_name(dev));
+			scsi_id = 7;
+		}
+	} else {
+		eisa_irqs = eisa_cpq_irqs;
+		irq_index = inb(io_addr + 0xc88) & 0x07;
+	}
+
+	if(irq_index >= strlen(eisa_irqs)) {
+		printk("sim710.c: irq nasty\n");
+		return -ENODEV;
+	}
+
+	irq = eisa_irqs[irq_index];
+		
+	return sim710_probe_common(dev, io_addr, irq, 50,
+				   differential, scsi_id);
+}
+
+static struct eisa_driver sim710_eisa_driver = {
+	.id_table		= sim710_eisa_ids,
+	.driver = {
+		.name		= "sim710",
+		.probe		= sim710_eisa_probe,
+		.remove		= sim710_device_remove,
+	},
+};
+#endif /* CONFIG_EISA */
+
+static int __init sim710_init(void)
+{
+#ifdef MODULE
+	if (sim710)
+		param_setup(sim710);
+#endif
+
+#ifdef CONFIG_EISA
+	/*
+	 * FIXME: We'd really like to return -ENODEV if no devices have actually
+	 * been found.  However eisa_driver_register() only reports problems
+	 * with kobject_register() so simply return success for now.
+	 */
+	eisa_driver_register(&sim710_eisa_driver);
+#endif
+	return 0;
+}
+
+static void __exit sim710_exit(void)
+{
+#ifdef CONFIG_EISA
+	eisa_driver_unregister(&sim710_eisa_driver);
+#endif
+}
+
+module_init(sim710_init);
+module_exit(sim710_exit);