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, 438 insertions, 0 deletions

diff --git a/drivers/scsi/ps3rom.c b/drivers/scsi/ps3rom.c
new file mode 100644
index 000000000..a9c727d22
--- /dev/null
+++ b/drivers/scsi/ps3rom.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PS3 BD/DVD/CD-ROM Storage Driver
+ *
+ * Copyright (C) 2007 Sony Computer Entertainment Inc.
+ * Copyright 2007 Sony Corp.
+ */
+
+#include <linux/cdrom.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_eh.h>
+
+#include <asm/lv1call.h>
+#include <asm/ps3stor.h>
+
+
+#define DEVICE_NAME			"ps3rom"
+
+#define BOUNCE_SIZE			(64*1024)
+
+#define PS3ROM_MAX_SECTORS		(BOUNCE_SIZE >> 9)
+
+
+struct ps3rom_private {
+	struct ps3_storage_device *dev;
+	struct scsi_cmnd *curr_cmd;
+};
+
+
+#define LV1_STORAGE_SEND_ATAPI_COMMAND	(1)
+
+struct lv1_atapi_cmnd_block {
+	u8	pkt[32];	/* packet command block           */
+	u32	pktlen;		/* should be 12 for ATAPI 8020    */
+	u32	blocks;
+	u32	block_size;
+	u32	proto;		/* transfer mode                  */
+	u32	in_out;		/* transfer direction             */
+	u64	buffer;		/* parameter except command block */
+	u32	arglen;		/* length above                   */
+};
+
+enum lv1_atapi_proto {
+	NON_DATA_PROTO     = 0,
+	PIO_DATA_IN_PROTO  = 1,
+	PIO_DATA_OUT_PROTO = 2,
+	DMA_PROTO = 3
+};
+
+enum lv1_atapi_in_out {
+	DIR_WRITE = 0,		/* memory -> device */
+	DIR_READ = 1		/* device -> memory */
+};
+
+
+static int ps3rom_sdev_configure(struct scsi_device *scsi_dev,
+				 struct queue_limits *lim)
+{
+	struct ps3rom_private *priv = shost_priv(scsi_dev->host);
+	struct ps3_storage_device *dev = priv->dev;
+
+	dev_dbg(&dev->sbd.core, "%s:%u: id %u, lun %llu, channel %u\n", __func__,
+		__LINE__, scsi_dev->id, scsi_dev->lun, scsi_dev->channel);
+
+	/*
+	 * ATAPI SFF8020 devices use MODE_SENSE_10,
+	 * so we can prohibit MODE_SENSE_6
+	 */
+	scsi_dev->use_10_for_ms = 1;
+
+	/* we don't support {READ,WRITE}_6 */
+	scsi_dev->use_10_for_rw = 1;
+
+	return 0;
+}
+
+static int ps3rom_atapi_request(struct ps3_storage_device *dev,
+				struct scsi_cmnd *cmd)
+{
+	struct lv1_atapi_cmnd_block atapi_cmnd;
+	unsigned char opcode = cmd->cmnd[0];
+	int res;
+	u64 lpar;
+
+	dev_dbg(&dev->sbd.core, "%s:%u: send ATAPI command 0x%02x\n", __func__,
+		__LINE__, opcode);
+
+	memset(&atapi_cmnd, 0, sizeof(struct lv1_atapi_cmnd_block));
+	memcpy(&atapi_cmnd.pkt, cmd->cmnd, 12);
+	atapi_cmnd.pktlen = 12;
+	atapi_cmnd.block_size = 1; /* transfer size is block_size * blocks */
+	atapi_cmnd.blocks = atapi_cmnd.arglen = scsi_bufflen(cmd);
+	atapi_cmnd.buffer = dev->bounce_lpar;
+
+	switch (cmd->sc_data_direction) {
+	case DMA_FROM_DEVICE:
+		if (scsi_bufflen(cmd) >= CD_FRAMESIZE)
+			atapi_cmnd.proto = DMA_PROTO;
+		else
+			atapi_cmnd.proto = PIO_DATA_IN_PROTO;
+		atapi_cmnd.in_out = DIR_READ;
+		break;
+
+	case DMA_TO_DEVICE:
+		if (scsi_bufflen(cmd) >= CD_FRAMESIZE)
+			atapi_cmnd.proto = DMA_PROTO;
+		else
+			atapi_cmnd.proto = PIO_DATA_OUT_PROTO;
+		atapi_cmnd.in_out = DIR_WRITE;
+		scsi_sg_copy_to_buffer(cmd, dev->bounce_buf, dev->bounce_size);
+		break;
+
+	default:
+		atapi_cmnd.proto = NON_DATA_PROTO;
+		break;
+	}
+
+	lpar = ps3_mm_phys_to_lpar(__pa(&atapi_cmnd));
+	res = lv1_storage_send_device_command(dev->sbd.dev_id,
+					      LV1_STORAGE_SEND_ATAPI_COMMAND,
+					      lpar, sizeof(atapi_cmnd),
+					      atapi_cmnd.buffer,
+					      atapi_cmnd.arglen, &dev->tag);
+	if (res == LV1_DENIED_BY_POLICY) {
+		dev_dbg(&dev->sbd.core,
+			"%s:%u: ATAPI command 0x%02x denied by policy\n",
+			__func__, __LINE__, opcode);
+		return DID_ERROR << 16;
+	}
+
+	if (res) {
+		dev_err(&dev->sbd.core,
+			"%s:%u: ATAPI command 0x%02x failed %d\n", __func__,
+			__LINE__, opcode, res);
+		return DID_ERROR << 16;
+	}
+
+	return 0;
+}
+
+static inline unsigned int srb10_lba(const struct scsi_cmnd *cmd)
+{
+	return cmd->cmnd[2] << 24 | cmd->cmnd[3] << 16 | cmd->cmnd[4] << 8 |
+	       cmd->cmnd[5];
+}
+
+static inline unsigned int srb10_len(const struct scsi_cmnd *cmd)
+{
+	return cmd->cmnd[7] << 8 | cmd->cmnd[8];
+}
+
+static int ps3rom_read_request(struct ps3_storage_device *dev,
+			       struct scsi_cmnd *cmd, u32 start_sector,
+			       u32 sectors)
+{
+	int res;
+
+	dev_dbg(&dev->sbd.core, "%s:%u: read %u sectors starting at %u\n",
+		__func__, __LINE__, sectors, start_sector);
+
+	res = lv1_storage_read(dev->sbd.dev_id,
+			       dev->regions[dev->region_idx].id, start_sector,
+			       sectors, 0, dev->bounce_lpar, &dev->tag);
+	if (res) {
+		dev_err(&dev->sbd.core, "%s:%u: read failed %d\n", __func__,
+			__LINE__, res);
+		return DID_ERROR << 16;
+	}
+
+	return 0;
+}
+
+static int ps3rom_write_request(struct ps3_storage_device *dev,
+				struct scsi_cmnd *cmd, u32 start_sector,
+				u32 sectors)
+{
+	int res;
+
+	dev_dbg(&dev->sbd.core, "%s:%u: write %u sectors starting at %u\n",
+		__func__, __LINE__, sectors, start_sector);
+
+	scsi_sg_copy_to_buffer(cmd, dev->bounce_buf, dev->bounce_size);
+
+	res = lv1_storage_write(dev->sbd.dev_id,
+				dev->regions[dev->region_idx].id, start_sector,
+				sectors, 0, dev->bounce_lpar, &dev->tag);
+	if (res) {
+		dev_err(&dev->sbd.core, "%s:%u: write failed %d\n", __func__,
+			__LINE__, res);
+		return DID_ERROR << 16;
+	}
+
+	return 0;
+}
+
+static enum scsi_qc_status ps3rom_queuecommand_lck(struct scsi_cmnd *cmd)
+{
+	struct ps3rom_private *priv = shost_priv(cmd->device->host);
+	struct ps3_storage_device *dev = priv->dev;
+	unsigned char opcode;
+	int res;
+
+	priv->curr_cmd = cmd;
+
+	opcode = cmd->cmnd[0];
+	/*
+	 * While we can submit READ/WRITE SCSI commands as ATAPI commands,
+	 * it's recommended for various reasons (performance, error handling,
+	 * ...) to use lv1_storage_{read,write}() instead
+	 */
+	switch (opcode) {
+	case READ_10:
+		res = ps3rom_read_request(dev, cmd, srb10_lba(cmd),
+					  srb10_len(cmd));
+		break;
+
+	case WRITE_10:
+		res = ps3rom_write_request(dev, cmd, srb10_lba(cmd),
+					   srb10_len(cmd));
+		break;
+
+	default:
+		res = ps3rom_atapi_request(dev, cmd);
+		break;
+	}
+
+	if (res) {
+		scsi_build_sense(cmd, 0, ILLEGAL_REQUEST, 0, 0);
+		cmd->result = res;
+		priv->curr_cmd = NULL;
+		scsi_done(cmd);
+	}
+
+	return 0;
+}
+
+static DEF_SCSI_QCMD(ps3rom_queuecommand)
+
+static int decode_lv1_status(u64 status, unsigned char *sense_key,
+			     unsigned char *asc, unsigned char *ascq)
+{
+	if (((status >> 24) & 0xff) != SAM_STAT_CHECK_CONDITION)
+		return -1;
+
+	*sense_key = (status >> 16) & 0xff;
+	*asc       = (status >>  8) & 0xff;
+	*ascq      =  status        & 0xff;
+	return 0;
+}
+
+static irqreturn_t ps3rom_interrupt(int irq, void *data)
+{
+	struct ps3_storage_device *dev = data;
+	struct Scsi_Host *host;
+	struct ps3rom_private *priv;
+	struct scsi_cmnd *cmd;
+	int res;
+	u64 tag, status;
+	unsigned char sense_key, asc, ascq;
+
+	res = lv1_storage_get_async_status(dev->sbd.dev_id, &tag, &status);
+	/*
+	 * status = -1 may mean that ATAPI transport completed OK, but
+	 * ATAPI command itself resulted CHECK CONDITION
+	 * so, upper layer should issue REQUEST_SENSE to check the sense data
+	 */
+
+	if (tag != dev->tag)
+		dev_err(&dev->sbd.core,
+			"%s:%u: tag mismatch, got %llx, expected %llx\n",
+			__func__, __LINE__, tag, dev->tag);
+
+	if (res) {
+		dev_err(&dev->sbd.core, "%s:%u: res=%d status=0x%llx\n",
+			__func__, __LINE__, res, status);
+		return IRQ_HANDLED;
+	}
+
+	host = ps3_system_bus_get_drvdata(&dev->sbd);
+	priv = shost_priv(host);
+	cmd = priv->curr_cmd;
+
+	if (!status) {
+		/* OK, completed */
+		if (cmd->sc_data_direction == DMA_FROM_DEVICE) {
+			int len;
+
+			len = scsi_sg_copy_from_buffer(cmd,
+						       dev->bounce_buf,
+						       dev->bounce_size);
+
+			scsi_set_resid(cmd, scsi_bufflen(cmd) - len);
+		}
+		cmd->result = DID_OK << 16;
+		goto done;
+	}
+
+	if (cmd->cmnd[0] == REQUEST_SENSE) {
+		/* SCSI spec says request sense should never get error */
+		dev_err(&dev->sbd.core, "%s:%u: end error without autosense\n",
+			__func__, __LINE__);
+		cmd->result = DID_ERROR << 16 | SAM_STAT_CHECK_CONDITION;
+		goto done;
+	}
+
+	if (decode_lv1_status(status, &sense_key, &asc, &ascq)) {
+		cmd->result = DID_ERROR << 16;
+		goto done;
+	}
+
+	scsi_build_sense(cmd, 0, sense_key, asc, ascq);
+
+done:
+	priv->curr_cmd = NULL;
+	scsi_done(cmd);
+	return IRQ_HANDLED;
+}
+
+static const struct scsi_host_template ps3rom_host_template = {
+	.name =			DEVICE_NAME,
+	.sdev_configure =	ps3rom_sdev_configure,
+	.queuecommand =		ps3rom_queuecommand,
+	.can_queue =		1,
+	.this_id =		7,
+	.sg_tablesize =		SG_ALL,
+	.emulated =             1,		/* only sg driver uses this */
+	.max_sectors =		PS3ROM_MAX_SECTORS,
+	.module =		THIS_MODULE,
+};
+
+
+static int ps3rom_probe(struct ps3_system_bus_device *_dev)
+{
+	struct ps3_storage_device *dev = to_ps3_storage_device(&_dev->core);
+	int error;
+	struct Scsi_Host *host;
+	struct ps3rom_private *priv;
+
+	if (dev->blk_size != CD_FRAMESIZE) {
+		dev_err(&dev->sbd.core,
+			"%s:%u: cannot handle block size %llu\n", __func__,
+			__LINE__, dev->blk_size);
+		return -EINVAL;
+	}
+
+	dev->bounce_size = BOUNCE_SIZE;
+	dev->bounce_buf = kmalloc(BOUNCE_SIZE, GFP_DMA);
+	if (!dev->bounce_buf)
+		return -ENOMEM;
+
+	error = ps3stor_setup(dev, ps3rom_interrupt);
+	if (error)
+		goto fail_free_bounce;
+
+	host = scsi_host_alloc(&ps3rom_host_template,
+			       sizeof(struct ps3rom_private));
+	if (!host) {
+		dev_err(&dev->sbd.core, "%s:%u: scsi_host_alloc failed\n",
+			__func__, __LINE__);
+		error = -ENOMEM;
+		goto fail_teardown;
+	}
+
+	priv = shost_priv(host);
+	ps3_system_bus_set_drvdata(&dev->sbd, host);
+	priv->dev = dev;
+
+	/* One device/LUN per SCSI bus */
+	host->max_id = 1;
+	host->max_lun = 1;
+
+	error = scsi_add_host(host, &dev->sbd.core);
+	if (error) {
+		dev_err(&dev->sbd.core, "%s:%u: scsi_host_alloc failed %d\n",
+			__func__, __LINE__, error);
+		error = -ENODEV;
+		goto fail_host_put;
+	}
+
+	scsi_scan_host(host);
+	return 0;
+
+fail_host_put:
+	scsi_host_put(host);
+	ps3_system_bus_set_drvdata(&dev->sbd, NULL);
+fail_teardown:
+	ps3stor_teardown(dev);
+fail_free_bounce:
+	kfree(dev->bounce_buf);
+	return error;
+}
+
+static void ps3rom_remove(struct ps3_system_bus_device *_dev)
+{
+	struct ps3_storage_device *dev = to_ps3_storage_device(&_dev->core);
+	struct Scsi_Host *host = ps3_system_bus_get_drvdata(&dev->sbd);
+
+	scsi_remove_host(host);
+	ps3stor_teardown(dev);
+	scsi_host_put(host);
+	ps3_system_bus_set_drvdata(&dev->sbd, NULL);
+	kfree(dev->bounce_buf);
+}
+
+static struct ps3_system_bus_driver ps3rom = {
+	.match_id	= PS3_MATCH_ID_STOR_ROM,
+	.core.name	= DEVICE_NAME,
+	.core.owner	= THIS_MODULE,
+	.probe		= ps3rom_probe,
+	.remove		= ps3rom_remove
+};
+
+
+static int __init ps3rom_init(void)
+{
+	return ps3_system_bus_driver_register(&ps3rom);
+}
+
+static void __exit ps3rom_exit(void)
+{
+	ps3_system_bus_driver_unregister(&ps3rom);
+}
+
+module_init(ps3rom_init);
+module_exit(ps3rom_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("PS3 BD/DVD/CD-ROM Storage Driver");
+MODULE_AUTHOR("Sony Corporation");
+MODULE_ALIAS(PS3_MODULE_ALIAS_STOR_ROM);