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, 411 insertions, 0 deletions

diff --git a/drivers/block/z2ram.c b/drivers/block/z2ram.c
new file mode 100644
index 000000000..b216cba1c
--- /dev/null
+++ b/drivers/block/z2ram.c
@@ -0,0 +1,411 @@
+/*
+** z2ram - Amiga pseudo-driver to access 16bit-RAM in ZorroII space
+**         as a block device, to be used as a RAM disk or swap space
+** 
+** Copyright (C) 1994 by Ingo Wilken (Ingo.Wilken@informatik.uni-oldenburg.de)
+**
+** ++Geert: support for zorro_unused_z2ram, better range checking
+** ++roman: translate accesses via an array
+** ++Milan: support for ChipRAM usage
+** ++yambo: converted to 2.0 kernel
+** ++yambo: modularized and support added for 3 minor devices including:
+**          MAJOR  MINOR  DESCRIPTION
+**          -----  -----  ----------------------------------------------
+**          37     0       Use Zorro II and Chip ram
+**          37     1       Use only Zorro II ram
+**          37     2       Use only Chip ram
+**          37     4-7     Use memory list entry 1-4 (first is 0)
+** ++jskov: support for 1-4th memory list entry.
+**
+** Permission to use, copy, modify, and distribute this software and its
+** documentation for any purpose and without fee is hereby granted, provided
+** that the above copyright notice appear in all copies and that both that
+** copyright notice and this permission notice appear in supporting
+** documentation.  This software is provided "as is" without express or
+** implied warranty.
+*/
+
+#define DEVICE_NAME "Z2RAM"
+
+#include <linux/major.h>
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/blk-mq.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/pgtable.h>
+
+#include <asm/setup.h>
+#include <asm/amigahw.h>
+
+#include <linux/zorro.h>
+
+#define Z2MINOR_COMBINED      (0)
+#define Z2MINOR_Z2ONLY        (1)
+#define Z2MINOR_CHIPONLY      (2)
+#define Z2MINOR_MEMLIST1      (4)
+#define Z2MINOR_MEMLIST2      (5)
+#define Z2MINOR_MEMLIST3      (6)
+#define Z2MINOR_MEMLIST4      (7)
+#define Z2MINOR_COUNT         (8)	/* Move this down when adding a new minor */
+
+#define Z2RAM_CHUNK1024       ( Z2RAM_CHUNKSIZE >> 10 )
+
+static DEFINE_MUTEX(z2ram_mutex);
+static u_long *z2ram_map = NULL;
+static u_long z2ram_size = 0;
+static int z2_count = 0;
+static int chip_count = 0;
+static int list_count = 0;
+static int current_device = -1;
+
+static DEFINE_SPINLOCK(z2ram_lock);
+
+static struct gendisk *z2ram_gendisk[Z2MINOR_COUNT];
+
+static blk_status_t z2_queue_rq(struct blk_mq_hw_ctx *hctx,
+				const struct blk_mq_queue_data *bd)
+{
+	struct request *req = bd->rq;
+	unsigned long start = blk_rq_pos(req) << 9;
+	unsigned long len = blk_rq_cur_bytes(req);
+
+	blk_mq_start_request(req);
+
+	if (start + len > z2ram_size) {
+		pr_err(DEVICE_NAME ": bad access: block=%llu, "
+		       "count=%u\n",
+		       (unsigned long long)blk_rq_pos(req),
+		       blk_rq_cur_sectors(req));
+		return BLK_STS_IOERR;
+	}
+
+	spin_lock_irq(&z2ram_lock);
+
+	while (len) {
+		unsigned long addr = start & Z2RAM_CHUNKMASK;
+		unsigned long size = Z2RAM_CHUNKSIZE - addr;
+		void *buffer = bio_data(req->bio);
+
+		if (len < size)
+			size = len;
+		addr += z2ram_map[start >> Z2RAM_CHUNKSHIFT];
+		if (rq_data_dir(req) == READ)
+			memcpy(buffer, (char *)addr, size);
+		else
+			memcpy((char *)addr, buffer, size);
+		start += size;
+		len -= size;
+	}
+
+	spin_unlock_irq(&z2ram_lock);
+	blk_mq_end_request(req, BLK_STS_OK);
+	return BLK_STS_OK;
+}
+
+static void get_z2ram(void)
+{
+	int i;
+
+	for (i = 0; i < Z2RAM_SIZE / Z2RAM_CHUNKSIZE; i++) {
+		if (test_bit(i, zorro_unused_z2ram)) {
+			z2_count++;
+			z2ram_map[z2ram_size++] =
+			    (unsigned long)ZTWO_VADDR(Z2RAM_START) +
+			    (i << Z2RAM_CHUNKSHIFT);
+			clear_bit(i, zorro_unused_z2ram);
+		}
+	}
+
+	return;
+}
+
+static void get_chipram(void)
+{
+
+	while (amiga_chip_avail() > (Z2RAM_CHUNKSIZE * 4)) {
+		chip_count++;
+		z2ram_map[z2ram_size] =
+		    (u_long) amiga_chip_alloc(Z2RAM_CHUNKSIZE, "z2ram");
+
+		if (z2ram_map[z2ram_size] == 0) {
+			break;
+		}
+
+		z2ram_size++;
+	}
+
+	return;
+}
+
+static int z2_open(struct gendisk *disk, blk_mode_t mode)
+{
+	int device = disk->first_minor;
+	int max_z2_map = (Z2RAM_SIZE / Z2RAM_CHUNKSIZE) * sizeof(z2ram_map[0]);
+	int max_chip_map = (amiga_chip_size / Z2RAM_CHUNKSIZE) *
+	    sizeof(z2ram_map[0]);
+	int rc = -ENOMEM;
+
+	mutex_lock(&z2ram_mutex);
+	if (current_device != -1 && current_device != device) {
+		rc = -EBUSY;
+		goto err_out;
+	}
+
+	if (current_device == -1) {
+		z2_count = 0;
+		chip_count = 0;
+		list_count = 0;
+		z2ram_size = 0;
+
+		/* Use a specific list entry. */
+		if (device >= Z2MINOR_MEMLIST1 && device <= Z2MINOR_MEMLIST4) {
+			int index = device - Z2MINOR_MEMLIST1 + 1;
+			unsigned long size, paddr, vaddr;
+
+			if (index >= m68k_realnum_memory) {
+				printk(KERN_ERR DEVICE_NAME
+				       ": no such entry in z2ram_map\n");
+				goto err_out;
+			}
+
+			paddr = m68k_memory[index].addr;
+			size = m68k_memory[index].size & ~(Z2RAM_CHUNKSIZE - 1);
+
+#ifdef __powerpc__
+			/* FIXME: ioremap doesn't build correct memory tables. */
+			{
+				vfree(vmalloc(size));
+			}
+
+			vaddr = (unsigned long)ioremap_wt(paddr, size);
+
+#else
+			vaddr =
+			    (unsigned long)z_remap_nocache_nonser(paddr, size);
+#endif
+			z2ram_map =
+			    kmalloc_objs(z2ram_map[0], size / Z2RAM_CHUNKSIZE);
+			if (z2ram_map == NULL) {
+				printk(KERN_ERR DEVICE_NAME
+				       ": cannot get mem for z2ram_map\n");
+				goto err_out;
+			}
+
+			while (size) {
+				z2ram_map[z2ram_size++] = vaddr;
+				size -= Z2RAM_CHUNKSIZE;
+				vaddr += Z2RAM_CHUNKSIZE;
+				list_count++;
+			}
+
+			if (z2ram_size != 0)
+				printk(KERN_INFO DEVICE_NAME
+				       ": using %iK List Entry %d Memory\n",
+				       list_count * Z2RAM_CHUNK1024, index);
+		} else
+			switch (device) {
+			case Z2MINOR_COMBINED:
+
+				z2ram_map =
+				    kmalloc(max_z2_map + max_chip_map,
+					    GFP_KERNEL);
+				if (z2ram_map == NULL) {
+					printk(KERN_ERR DEVICE_NAME
+					       ": cannot get mem for z2ram_map\n");
+					goto err_out;
+				}
+
+				get_z2ram();
+				get_chipram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK Zorro II RAM and %iK Chip RAM (Total %dK)\n",
+					       z2_count * Z2RAM_CHUNK1024,
+					       chip_count * Z2RAM_CHUNK1024,
+					       (z2_count +
+						chip_count) * Z2RAM_CHUNK1024);
+
+				break;
+
+			case Z2MINOR_Z2ONLY:
+				z2ram_map = kmalloc(max_z2_map, GFP_KERNEL);
+				if (!z2ram_map)
+					goto err_out;
+
+				get_z2ram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK of Zorro II RAM\n",
+					       z2_count * Z2RAM_CHUNK1024);
+
+				break;
+
+			case Z2MINOR_CHIPONLY:
+				z2ram_map = kmalloc(max_chip_map, GFP_KERNEL);
+				if (!z2ram_map)
+					goto err_out;
+
+				get_chipram();
+
+				if (z2ram_size != 0)
+					printk(KERN_INFO DEVICE_NAME
+					       ": using %iK Chip RAM\n",
+					       chip_count * Z2RAM_CHUNK1024);
+
+				break;
+
+			default:
+				rc = -ENODEV;
+				goto err_out;
+
+				break;
+			}
+
+		if (z2ram_size == 0) {
+			printk(KERN_NOTICE DEVICE_NAME
+			       ": no unused ZII/Chip RAM found\n");
+			goto err_out_kfree;
+		}
+
+		current_device = device;
+		z2ram_size <<= Z2RAM_CHUNKSHIFT;
+		set_capacity(z2ram_gendisk[device], z2ram_size >> 9);
+	}
+
+	mutex_unlock(&z2ram_mutex);
+	return 0;
+
+err_out_kfree:
+	kfree(z2ram_map);
+err_out:
+	mutex_unlock(&z2ram_mutex);
+	return rc;
+}
+
+static void z2_release(struct gendisk *disk)
+{
+	mutex_lock(&z2ram_mutex);
+	if (current_device == -1) {
+		mutex_unlock(&z2ram_mutex);
+		return;
+	}
+	mutex_unlock(&z2ram_mutex);
+	/*
+	 * FIXME: unmap memory
+	 */
+}
+
+static const struct block_device_operations z2_fops = {
+	.owner = THIS_MODULE,
+	.open = z2_open,
+	.release = z2_release,
+};
+
+static struct blk_mq_tag_set tag_set;
+
+static const struct blk_mq_ops z2_mq_ops = {
+	.queue_rq = z2_queue_rq,
+};
+
+static int z2ram_register_disk(int minor)
+{
+	struct gendisk *disk;
+	int err;
+
+	disk = blk_mq_alloc_disk(&tag_set, NULL, NULL);
+	if (IS_ERR(disk))
+		return PTR_ERR(disk);
+
+	disk->major = Z2RAM_MAJOR;
+	disk->first_minor = minor;
+	disk->minors = 1;
+	disk->flags |= GENHD_FL_NO_PART;
+	disk->fops = &z2_fops;
+	if (minor)
+		sprintf(disk->disk_name, "z2ram%d", minor);
+	else
+		sprintf(disk->disk_name, "z2ram");
+
+	z2ram_gendisk[minor] = disk;
+	err = add_disk(disk);
+	if (err)
+		put_disk(disk);
+	return err;
+}
+
+static int __init z2_init(void)
+{
+	int ret, i;
+
+	if (!MACH_IS_AMIGA)
+		return -ENODEV;
+
+	if (register_blkdev(Z2RAM_MAJOR, DEVICE_NAME))
+		return -EBUSY;
+
+	tag_set.ops = &z2_mq_ops;
+	tag_set.nr_hw_queues = 1;
+	tag_set.nr_maps = 1;
+	tag_set.queue_depth = 16;
+	tag_set.numa_node = NUMA_NO_NODE;
+	ret = blk_mq_alloc_tag_set(&tag_set);
+	if (ret)
+		goto out_unregister_blkdev;
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		ret = z2ram_register_disk(i);
+		if (ret && i == 0)
+			goto out_free_tagset;
+	}
+
+	return 0;
+
+out_free_tagset:
+	blk_mq_free_tag_set(&tag_set);
+out_unregister_blkdev:
+	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
+	return ret;
+}
+
+static void __exit z2_exit(void)
+{
+	int i, j;
+
+	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		del_gendisk(z2ram_gendisk[i]);
+		put_disk(z2ram_gendisk[i]);
+	}
+	blk_mq_free_tag_set(&tag_set);
+
+	if (current_device != -1) {
+		i = 0;
+
+		for (j = 0; j < z2_count; j++) {
+			set_bit(i++, zorro_unused_z2ram);
+		}
+
+		for (j = 0; j < chip_count; j++) {
+			if (z2ram_map[i]) {
+				amiga_chip_free((void *)z2ram_map[i++]);
+			}
+		}
+
+		if (z2ram_map != NULL) {
+			kfree(z2ram_map);
+		}
+	}
+
+	return;
+}
+
+module_init(z2_init);
+module_exit(z2_exit);
+MODULE_DESCRIPTION("Amiga Zorro II ramdisk driver");
+MODULE_LICENSE("GPL");