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, 455 insertions, 0 deletions

diff --git a/drivers/mtd/ssfdc.c b/drivers/mtd/ssfdc.c
new file mode 100644
index 000000000..4a5225699
--- /dev/null
+++ b/drivers/mtd/ssfdc.c
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Linux driver for SSFDC Flash Translation Layer (Read only)
+ * © 2005 Eptar srl
+ * Author: Claudio Lanconelli <lanconelli.claudio@eptar.com>
+ *
+ * Based on NTFL and MTDBLOCK_RO drivers
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/hdreg.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/rawnand.h>
+#include <linux/mtd/blktrans.h>
+
+struct ssfdcr_record {
+	struct mtd_blktrans_dev mbd;
+	unsigned char heads;
+	unsigned char sectors;
+	unsigned short cylinders;
+	int cis_block;			/* block n. containing CIS/IDI */
+	int erase_size;			/* phys_block_size */
+	unsigned short *logic_block_map; /* all zones (max 8192 phys blocks on
+					    the 128MiB) */
+	int map_len;			/* n. phys_blocks on the card */
+};
+
+#define SSFDCR_MAJOR		257
+#define SSFDCR_PARTN_BITS	3
+
+#define SECTOR_SIZE		512
+#define SECTOR_SHIFT		9
+#define OOB_SIZE		16
+
+#define MAX_LOGIC_BLK_PER_ZONE	1000
+#define MAX_PHYS_BLK_PER_ZONE	1024
+
+#define KiB(x)	( (x) * 1024L )
+#define MiB(x)	( KiB(x) * 1024L )
+
+/** CHS Table
+		1MiB	2MiB	4MiB	8MiB	16MiB	32MiB	64MiB	128MiB
+NCylinder	125	125	250	250	500	500	500	500
+NHead		4	4	4	4	4	8	8	16
+NSector		4	8	8	16	16	16	32	32
+SumSector	2,000	4,000	8,000	16,000	32,000	64,000	128,000	256,000
+SectorSize	512	512	512	512	512	512	512	512
+**/
+
+typedef struct {
+	unsigned long size;
+	unsigned short cyl;
+	unsigned char head;
+	unsigned char sec;
+} chs_entry_t;
+
+/* Must be ordered by size */
+static const chs_entry_t chs_table[] = {
+	{ MiB(  1), 125,  4,  4 },
+	{ MiB(  2), 125,  4,  8 },
+	{ MiB(  4), 250,  4,  8 },
+	{ MiB(  8), 250,  4, 16 },
+	{ MiB( 16), 500,  4, 16 },
+	{ MiB( 32), 500,  8, 16 },
+	{ MiB( 64), 500,  8, 32 },
+	{ MiB(128), 500, 16, 32 },
+	{ 0 },
+};
+
+static int get_chs(unsigned long size, unsigned short *cyl, unsigned char *head,
+			unsigned char *sec)
+{
+	int k;
+	int found = 0;
+
+	k = 0;
+	while (chs_table[k].size > 0 && size > chs_table[k].size)
+		k++;
+
+	if (chs_table[k].size > 0) {
+		if (cyl)
+			*cyl = chs_table[k].cyl;
+		if (head)
+			*head = chs_table[k].head;
+		if (sec)
+			*sec = chs_table[k].sec;
+		found = 1;
+	}
+
+	return found;
+}
+
+/* These bytes are the signature for the CIS/IDI sector */
+static const uint8_t cis_numbers[] = {
+	0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
+};
+
+/* Read and check for a valid CIS sector */
+static int get_valid_cis_sector(struct mtd_info *mtd)
+{
+	int ret, k, cis_sector;
+	size_t retlen;
+	loff_t offset;
+	uint8_t *sect_buf;
+
+	cis_sector = -1;
+
+	sect_buf = kmalloc(SECTOR_SIZE, GFP_KERNEL);
+	if (!sect_buf)
+		goto out;
+
+	/*
+	 * Look for CIS/IDI sector on the first GOOD block (give up after 4 bad
+	 * blocks). If the first good block doesn't contain CIS number the flash
+	 * is not SSFDC formatted
+	 */
+	for (k = 0, offset = 0; k < 4; k++, offset += mtd->erasesize) {
+		if (mtd_block_isbad(mtd, offset)) {
+			ret = mtd_read(mtd, offset, SECTOR_SIZE, &retlen,
+				       sect_buf);
+
+			/* CIS pattern match on the sector buffer */
+			if (ret < 0 || retlen != SECTOR_SIZE) {
+				printk(KERN_WARNING
+					"SSFDC_RO:can't read CIS/IDI sector\n");
+			} else if (!memcmp(sect_buf, cis_numbers,
+					sizeof(cis_numbers))) {
+				/* Found */
+				cis_sector = (int)(offset >> SECTOR_SHIFT);
+			} else {
+				pr_debug("SSFDC_RO: CIS/IDI sector not found"
+					" on %s (mtd%d)\n", mtd->name,
+					mtd->index);
+			}
+			break;
+		}
+	}
+
+	kfree(sect_buf);
+ out:
+	return cis_sector;
+}
+
+/* Read physical sector (wrapper to MTD_READ) */
+static int read_physical_sector(struct mtd_info *mtd, uint8_t *sect_buf,
+				int sect_no)
+{
+	int ret;
+	size_t retlen;
+	loff_t offset = (loff_t)sect_no << SECTOR_SHIFT;
+
+	ret = mtd_read(mtd, offset, SECTOR_SIZE, &retlen, sect_buf);
+	if (ret < 0 || retlen != SECTOR_SIZE)
+		return -1;
+
+	return 0;
+}
+
+/* Read redundancy area (wrapper to MTD_READ_OOB */
+static int read_raw_oob(struct mtd_info *mtd, loff_t offs, uint8_t *buf)
+{
+	struct mtd_oob_ops ops = { };
+	int ret;
+
+	ops.mode = MTD_OPS_RAW;
+	ops.ooboffs = 0;
+	ops.ooblen = OOB_SIZE;
+	ops.oobbuf = buf;
+	ops.datbuf = NULL;
+
+	ret = mtd_read_oob(mtd, offs, &ops);
+	if (ret < 0 || ops.oobretlen != OOB_SIZE)
+		return -1;
+
+	return 0;
+}
+
+/* Parity calculator on a word of n bit size */
+static int get_parity(int number, int size)
+{
+ 	int k;
+	int parity;
+
+	parity = 1;
+	for (k = 0; k < size; k++) {
+		parity += (number >> k);
+		parity &= 1;
+	}
+	return parity;
+}
+
+/* Read and validate the logical block address field stored in the OOB */
+static int get_logical_address(uint8_t *oob_buf)
+{
+	int block_address, parity;
+	int offset[2] = {6, 11}; /* offset of the 2 address fields within OOB */
+	int j;
+	int ok = 0;
+
+	/*
+	 * Look for the first valid logical address
+	 * Valid address has fixed pattern on most significant bits and
+	 * parity check
+	 */
+	for (j = 0; j < ARRAY_SIZE(offset); j++) {
+		block_address = ((int)oob_buf[offset[j]] << 8) |
+			oob_buf[offset[j]+1];
+
+		/* Check for the signature bits in the address field (MSBits) */
+		if ((block_address & ~0x7FF) == 0x1000) {
+			parity = block_address & 0x01;
+			block_address &= 0x7FF;
+			block_address >>= 1;
+
+			if (get_parity(block_address, 10) != parity) {
+				pr_debug("SSFDC_RO: logical address field%d"
+					"parity error(0x%04X)\n", j+1,
+					block_address);
+			} else {
+				ok = 1;
+				break;
+			}
+		}
+	}
+
+	if (!ok)
+		block_address = -2;
+
+	pr_debug("SSFDC_RO: get_logical_address() %d\n",
+		block_address);
+
+	return block_address;
+}
+
+/* Build the logic block map */
+static int build_logical_block_map(struct ssfdcr_record *ssfdc)
+{
+	unsigned long offset;
+	uint8_t oob_buf[OOB_SIZE];
+	int ret, block_address, phys_block;
+	struct mtd_info *mtd = ssfdc->mbd.mtd;
+
+	pr_debug("SSFDC_RO: build_block_map() nblks=%d (%luK)\n",
+	      ssfdc->map_len,
+	      (unsigned long)ssfdc->map_len * ssfdc->erase_size / 1024);
+
+	/* Scan every physical block, skip CIS block */
+	for (phys_block = ssfdc->cis_block + 1; phys_block < ssfdc->map_len;
+			phys_block++) {
+		offset = (unsigned long)phys_block * ssfdc->erase_size;
+		if (mtd_block_isbad(mtd, offset))
+			continue;	/* skip bad blocks */
+
+		ret = read_raw_oob(mtd, offset, oob_buf);
+		if (ret < 0) {
+			pr_debug("SSFDC_RO: mtd read_oob() failed at %lu\n",
+				offset);
+			return -1;
+		}
+		block_address = get_logical_address(oob_buf);
+
+		/* Skip invalid addresses */
+		if (block_address >= 0 &&
+				block_address < MAX_LOGIC_BLK_PER_ZONE) {
+			int zone_index;
+
+			zone_index = phys_block / MAX_PHYS_BLK_PER_ZONE;
+			block_address += zone_index * MAX_LOGIC_BLK_PER_ZONE;
+			ssfdc->logic_block_map[block_address] =
+				(unsigned short)phys_block;
+
+			pr_debug("SSFDC_RO: build_block_map() phys_block=%d,"
+				"logic_block_addr=%d, zone=%d\n",
+				phys_block, block_address, zone_index);
+		}
+	}
+	return 0;
+}
+
+static void ssfdcr_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+	struct ssfdcr_record *ssfdc;
+	int cis_sector;
+
+	/* Check for small page NAND flash */
+	if (!mtd_type_is_nand(mtd) || mtd->oobsize != OOB_SIZE ||
+	    mtd->size > UINT_MAX)
+		return;
+
+	/* Check for SSDFC format by reading CIS/IDI sector */
+	cis_sector = get_valid_cis_sector(mtd);
+	if (cis_sector == -1)
+		return;
+
+	ssfdc = kzalloc_obj(*ssfdc);
+	if (!ssfdc)
+		return;
+
+	ssfdc->mbd.mtd = mtd;
+	ssfdc->mbd.devnum = -1;
+	ssfdc->mbd.tr = tr;
+	ssfdc->mbd.readonly = 1;
+
+	ssfdc->cis_block = cis_sector / (mtd->erasesize >> SECTOR_SHIFT);
+	ssfdc->erase_size = mtd->erasesize;
+	ssfdc->map_len = (u32)mtd->size / mtd->erasesize;
+
+	pr_debug("SSFDC_RO: cis_block=%d,erase_size=%d,map_len=%d,n_zones=%d\n",
+		ssfdc->cis_block, ssfdc->erase_size, ssfdc->map_len,
+		DIV_ROUND_UP(ssfdc->map_len, MAX_PHYS_BLK_PER_ZONE));
+
+	/* Set geometry */
+	ssfdc->heads = 16;
+	ssfdc->sectors = 32;
+	get_chs(mtd->size, NULL, &ssfdc->heads, &ssfdc->sectors);
+	ssfdc->cylinders = (unsigned short)(((u32)mtd->size >> SECTOR_SHIFT) /
+			((long)ssfdc->sectors * (long)ssfdc->heads));
+
+	pr_debug("SSFDC_RO: using C:%d H:%d S:%d == %ld sects\n",
+		ssfdc->cylinders, ssfdc->heads , ssfdc->sectors,
+		(long)ssfdc->cylinders * (long)ssfdc->heads *
+		(long)ssfdc->sectors);
+
+	ssfdc->mbd.size = (long)ssfdc->heads * (long)ssfdc->cylinders *
+				(long)ssfdc->sectors;
+
+	/* Allocate logical block map */
+	ssfdc->logic_block_map =
+		kmalloc_array(ssfdc->map_len,
+			      sizeof(ssfdc->logic_block_map[0]), GFP_KERNEL);
+	if (!ssfdc->logic_block_map)
+		goto out_free_ssfdc;
+	memset(ssfdc->logic_block_map, 0xff, sizeof(ssfdc->logic_block_map[0]) *
+		ssfdc->map_len);
+
+	/* Build logical block map */
+	if (build_logical_block_map(ssfdc) < 0)
+		goto out_err;
+
+	/* Register device + partitions */
+	if (add_mtd_blktrans_dev(&ssfdc->mbd))
+		goto out_err;
+
+	printk(KERN_INFO "SSFDC_RO: Found ssfdc%c on mtd%d (%s)\n",
+		ssfdc->mbd.devnum + 'a', mtd->index, mtd->name);
+	return;
+
+out_err:
+	kfree(ssfdc->logic_block_map);
+out_free_ssfdc:
+	kfree(ssfdc);
+}
+
+static void ssfdcr_remove_dev(struct mtd_blktrans_dev *dev)
+{
+	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
+
+	pr_debug("SSFDC_RO: remove_dev (i=%d)\n", dev->devnum);
+
+	del_mtd_blktrans_dev(dev);
+	kfree(ssfdc->logic_block_map);
+}
+
+static int ssfdcr_readsect(struct mtd_blktrans_dev *dev,
+				unsigned long logic_sect_no, char *buf)
+{
+	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
+	int sectors_per_block, offset, block_address;
+
+	sectors_per_block = ssfdc->erase_size >> SECTOR_SHIFT;
+	offset = (int)(logic_sect_no % sectors_per_block);
+	block_address = (int)(logic_sect_no / sectors_per_block);
+
+	pr_debug("SSFDC_RO: ssfdcr_readsect(%lu) sec_per_blk=%d, ofst=%d,"
+		" block_addr=%d\n", logic_sect_no, sectors_per_block, offset,
+		block_address);
+
+	BUG_ON(block_address >= ssfdc->map_len);
+
+	block_address = ssfdc->logic_block_map[block_address];
+
+	pr_debug("SSFDC_RO: ssfdcr_readsect() phys_block_addr=%d\n",
+		block_address);
+
+	if (block_address < 0xffff) {
+		unsigned long sect_no;
+
+		sect_no = (unsigned long)block_address * sectors_per_block +
+				offset;
+
+		pr_debug("SSFDC_RO: ssfdcr_readsect() phys_sect_no=%lu\n",
+			sect_no);
+
+		if (read_physical_sector(ssfdc->mbd.mtd, buf, sect_no) < 0)
+			return -EIO;
+	} else {
+		memset(buf, 0xff, SECTOR_SIZE);
+	}
+
+	return 0;
+}
+
+static int ssfdcr_getgeo(struct mtd_blktrans_dev *dev,  struct hd_geometry *geo)
+{
+	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
+
+	pr_debug("SSFDC_RO: ssfdcr_getgeo() C=%d, H=%d, S=%d\n",
+			ssfdc->cylinders, ssfdc->heads, ssfdc->sectors);
+
+	geo->heads = ssfdc->heads;
+	geo->sectors = ssfdc->sectors;
+	geo->cylinders = ssfdc->cylinders;
+
+	return 0;
+}
+
+/****************************************************************************
+ *
+ * Module stuff
+ *
+ ****************************************************************************/
+
+static struct mtd_blktrans_ops ssfdcr_tr = {
+	.name		= "ssfdc",
+	.major		= SSFDCR_MAJOR,
+	.part_bits	= SSFDCR_PARTN_BITS,
+	.blksize	= SECTOR_SIZE,
+	.getgeo		= ssfdcr_getgeo,
+	.readsect	= ssfdcr_readsect,
+	.add_mtd	= ssfdcr_add_mtd,
+	.remove_dev	= ssfdcr_remove_dev,
+	.owner		= THIS_MODULE,
+};
+
+static int __init init_ssfdcr(void)
+{
+	printk(KERN_INFO "SSFDC read-only Flash Translation layer\n");
+
+	return register_mtd_blktrans(&ssfdcr_tr);
+}
+
+static void __exit cleanup_ssfdcr(void)
+{
+	deregister_mtd_blktrans(&ssfdcr_tr);
+}
+
+module_init(init_ssfdcr);
+module_exit(cleanup_ssfdcr);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Claudio Lanconelli <lanconelli.claudio@eptar.com>");
+MODULE_DESCRIPTION("Flash Translation Layer for read-only SSFDC SmartMedia card");