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/scsi_logging.c b/drivers/scsi/scsi_logging.c
new file mode 100644
index 000000000..3cd0d3074
--- /dev/null
+++ b/drivers/scsi/scsi_logging.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * scsi_logging.c
+ *
+ * Copyright (C) 2014 SUSE Linux Products GmbH
+ * Copyright (C) 2014 Hannes Reinecke <hare@suse.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/atomic.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_dbg.h>
+
+static char *scsi_log_reserve_buffer(size_t *len)
+{
+	*len = 128;
+	return kmalloc(*len, GFP_ATOMIC);
+}
+
+static void scsi_log_release_buffer(char *bufptr)
+{
+	kfree(bufptr);
+}
+
+static inline const char *scmd_name(struct scsi_cmnd *scmd)
+{
+	const struct request *rq = scsi_cmd_to_rq(scmd);
+
+	if (!rq->q || !rq->q->disk)
+		return NULL;
+	return rq->q->disk->disk_name;
+}
+
+static size_t sdev_format_header(char *logbuf, size_t logbuf_len,
+				 const char *name, int tag)
+{
+	size_t off = 0;
+
+	if (name)
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "[%s] ", name);
+
+	if (WARN_ON(off >= logbuf_len))
+		return off;
+
+	if (tag >= 0)
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "tag#%d ", tag);
+	return off;
+}
+
+void sdev_prefix_printk(const char *level, const struct scsi_device *sdev,
+			const char *name, const char *fmt, ...)
+{
+	va_list args;
+	char *logbuf;
+	size_t off = 0, logbuf_len;
+
+	if (!sdev)
+		return;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+
+	if (name)
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "[%s] ", name);
+	if (!WARN_ON(off >= logbuf_len)) {
+		va_start(args, fmt);
+		off += vscnprintf(logbuf + off, logbuf_len - off, fmt, args);
+		va_end(args);
+	}
+	dev_printk(level, &sdev->sdev_gendev, "%s", logbuf);
+	scsi_log_release_buffer(logbuf);
+}
+EXPORT_SYMBOL(sdev_prefix_printk);
+
+void scmd_printk(const char *level, struct scsi_cmnd *scmd, const char *fmt,
+		 ...)
+{
+	va_list args;
+	char *logbuf;
+	size_t off = 0, logbuf_len;
+
+	if (!scmd)
+		return;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+	off = sdev_format_header(logbuf, logbuf_len, scmd_name(scmd),
+				 scsi_cmd_to_rq(scmd)->tag);
+	if (off < logbuf_len) {
+		va_start(args, fmt);
+		off += vscnprintf(logbuf + off, logbuf_len - off, fmt, args);
+		va_end(args);
+	}
+	dev_printk(level, &scmd->device->sdev_gendev, "%s", logbuf);
+	scsi_log_release_buffer(logbuf);
+}
+EXPORT_SYMBOL(scmd_printk);
+
+static size_t scsi_format_opcode_name(char *buffer, size_t buf_len,
+				      const unsigned char *cdbp)
+{
+	int sa, cdb0;
+	const char *cdb_name = NULL, *sa_name = NULL;
+	size_t off;
+
+	cdb0 = cdbp[0];
+	if (cdb0 == VARIABLE_LENGTH_CMD) {
+		int len = scsi_varlen_cdb_length(cdbp);
+
+		if (len < 10) {
+			off = scnprintf(buffer, buf_len,
+					"short variable length command, len=%d",
+					len);
+			return off;
+		}
+		sa = (cdbp[8] << 8) + cdbp[9];
+	} else
+		sa = cdbp[1] & 0x1f;
+
+	if (!scsi_opcode_sa_name(cdb0, sa, &cdb_name, &sa_name)) {
+		if (cdb_name)
+			off = scnprintf(buffer, buf_len, "%s", cdb_name);
+		else {
+			off = scnprintf(buffer, buf_len, "opcode=0x%x", cdb0);
+			if (WARN_ON(off >= buf_len))
+				return off;
+			if (cdb0 >= VENDOR_SPECIFIC_CDB)
+				off += scnprintf(buffer + off, buf_len - off,
+						 " (vendor)");
+			else if (cdb0 >= 0x60 && cdb0 < 0x7e)
+				off += scnprintf(buffer + off, buf_len - off,
+						 " (reserved)");
+		}
+	} else {
+		if (sa_name)
+			off = scnprintf(buffer, buf_len, "%s", sa_name);
+		else if (cdb_name)
+			off = scnprintf(buffer, buf_len, "%s, sa=0x%x",
+					cdb_name, sa);
+		else
+			off = scnprintf(buffer, buf_len,
+					"opcode=0x%x, sa=0x%x", cdb0, sa);
+	}
+	WARN_ON(off >= buf_len);
+	return off;
+}
+
+size_t __scsi_format_command(char *logbuf, size_t logbuf_len,
+			     const unsigned char *cdb, size_t cdb_len)
+{
+	int len, k;
+	size_t off;
+
+	off = scsi_format_opcode_name(logbuf, logbuf_len, cdb);
+	if (off >= logbuf_len)
+		return off;
+	len = scsi_command_size(cdb);
+	if (cdb_len < len)
+		len = cdb_len;
+	/* print out all bytes in cdb */
+	for (k = 0; k < len; ++k) {
+		if (off > logbuf_len - 3)
+			break;
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 " %02x", cdb[k]);
+	}
+	return off;
+}
+EXPORT_SYMBOL(__scsi_format_command);
+
+void scsi_print_command(struct scsi_cmnd *cmd)
+{
+	int k;
+	char *logbuf;
+	size_t off, logbuf_len;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+
+	off = sdev_format_header(logbuf, logbuf_len,
+				 scmd_name(cmd), scsi_cmd_to_rq(cmd)->tag);
+	if (off >= logbuf_len)
+		goto out_printk;
+	off += scnprintf(logbuf + off, logbuf_len - off, "CDB: ");
+	if (WARN_ON(off >= logbuf_len))
+		goto out_printk;
+
+	off += scsi_format_opcode_name(logbuf + off, logbuf_len - off,
+				       cmd->cmnd);
+	if (off >= logbuf_len)
+		goto out_printk;
+
+	/* print out all bytes in cdb */
+	if (cmd->cmd_len > 16) {
+		/* Print opcode in one line and use separate lines for CDB */
+		off += scnprintf(logbuf + off, logbuf_len - off, "\n");
+		dev_printk(KERN_INFO, &cmd->device->sdev_gendev, "%s", logbuf);
+		for (k = 0; k < cmd->cmd_len; k += 16) {
+			size_t linelen = min(cmd->cmd_len - k, 16);
+
+			off = sdev_format_header(logbuf, logbuf_len,
+						 scmd_name(cmd),
+						 scsi_cmd_to_rq(cmd)->tag);
+			if (!WARN_ON(off > logbuf_len - 58)) {
+				off += scnprintf(logbuf + off, logbuf_len - off,
+						 "CDB[%02x]: ", k);
+				hex_dump_to_buffer(&cmd->cmnd[k], linelen,
+						   16, 1, logbuf + off,
+						   logbuf_len - off, false);
+			}
+			dev_printk(KERN_INFO, &cmd->device->sdev_gendev, "%s",
+				   logbuf);
+		}
+		goto out;
+	}
+	if (!WARN_ON(off > logbuf_len - 49)) {
+		off += scnprintf(logbuf + off, logbuf_len - off, " ");
+		hex_dump_to_buffer(cmd->cmnd, cmd->cmd_len, 16, 1,
+				   logbuf + off, logbuf_len - off,
+				   false);
+	}
+out_printk:
+	dev_printk(KERN_INFO, &cmd->device->sdev_gendev, "%s", logbuf);
+out:
+	scsi_log_release_buffer(logbuf);
+}
+EXPORT_SYMBOL(scsi_print_command);
+
+static size_t
+scsi_format_extd_sense(char *buffer, size_t buf_len,
+		       unsigned char asc, unsigned char ascq)
+{
+	size_t off = 0;
+	const char *extd_sense_fmt = NULL;
+	const char *extd_sense_str = scsi_extd_sense_format(asc, ascq,
+							    &extd_sense_fmt);
+
+	if (extd_sense_str) {
+		off = scnprintf(buffer, buf_len, "Add. Sense: %s",
+				extd_sense_str);
+		if (extd_sense_fmt)
+			off += scnprintf(buffer + off, buf_len - off,
+					 "(%s%x)", extd_sense_fmt, ascq);
+	} else {
+		if (asc >= 0x80)
+			off = scnprintf(buffer, buf_len, "<<vendor>>");
+		off += scnprintf(buffer + off, buf_len - off,
+				 "ASC=0x%x ", asc);
+		if (ascq >= 0x80)
+			off += scnprintf(buffer + off, buf_len - off,
+					 "<<vendor>>");
+		off += scnprintf(buffer + off, buf_len - off,
+				 "ASCQ=0x%x ", ascq);
+	}
+	return off;
+}
+
+static size_t
+scsi_format_sense_hdr(char *buffer, size_t buf_len,
+		      const struct scsi_sense_hdr *sshdr)
+{
+	const char *sense_txt;
+	size_t off;
+
+	off = scnprintf(buffer, buf_len, "Sense Key : ");
+	sense_txt = scsi_sense_key_string(sshdr->sense_key);
+	if (sense_txt)
+		off += scnprintf(buffer + off, buf_len - off,
+				 "%s ", sense_txt);
+	else
+		off += scnprintf(buffer + off, buf_len - off,
+				 "0x%x ", sshdr->sense_key);
+	off += scnprintf(buffer + off, buf_len - off,
+		scsi_sense_is_deferred(sshdr) ? "[deferred] " : "[current] ");
+
+	if (sshdr->response_code >= 0x72)
+		off += scnprintf(buffer + off, buf_len - off, "[descriptor] ");
+	return off;
+}
+
+static void
+scsi_log_dump_sense(const struct scsi_device *sdev, const char *name, int tag,
+		    const unsigned char *sense_buffer, int sense_len)
+{
+	char *logbuf;
+	size_t logbuf_len;
+	int i;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+
+	for (i = 0; i < sense_len; i += 16) {
+		int len = min(sense_len - i, 16);
+		size_t off;
+
+		off = sdev_format_header(logbuf, logbuf_len,
+					 name, tag);
+		hex_dump_to_buffer(&sense_buffer[i], len, 16, 1,
+				   logbuf + off, logbuf_len - off,
+				   false);
+		dev_printk(KERN_INFO, &sdev->sdev_gendev, "%s", logbuf);
+	}
+	scsi_log_release_buffer(logbuf);
+}
+
+static void
+scsi_log_print_sense_hdr(const struct scsi_device *sdev, const char *name,
+			 int tag, const struct scsi_sense_hdr *sshdr)
+{
+	char *logbuf;
+	size_t off, logbuf_len;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+	off = sdev_format_header(logbuf, logbuf_len, name, tag);
+	off += scsi_format_sense_hdr(logbuf + off, logbuf_len - off, sshdr);
+	dev_printk(KERN_INFO, &sdev->sdev_gendev, "%s", logbuf);
+	scsi_log_release_buffer(logbuf);
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+	off = sdev_format_header(logbuf, logbuf_len, name, tag);
+	off += scsi_format_extd_sense(logbuf + off, logbuf_len - off,
+				      sshdr->asc, sshdr->ascq);
+	dev_printk(KERN_INFO, &sdev->sdev_gendev, "%s", logbuf);
+	scsi_log_release_buffer(logbuf);
+}
+
+static void
+scsi_log_print_sense(const struct scsi_device *sdev, const char *name, int tag,
+		     const unsigned char *sense_buffer, int sense_len)
+{
+	struct scsi_sense_hdr sshdr;
+
+	if (scsi_normalize_sense(sense_buffer, sense_len, &sshdr))
+		scsi_log_print_sense_hdr(sdev, name, tag, &sshdr);
+	else
+		scsi_log_dump_sense(sdev, name, tag, sense_buffer, sense_len);
+}
+
+/*
+ * Print normalized SCSI sense header with a prefix.
+ */
+void
+scsi_print_sense_hdr(const struct scsi_device *sdev, const char *name,
+		     const struct scsi_sense_hdr *sshdr)
+{
+	scsi_log_print_sense_hdr(sdev, name, -1, sshdr);
+}
+EXPORT_SYMBOL(scsi_print_sense_hdr);
+
+/* Normalize and print sense buffer with name prefix */
+void __scsi_print_sense(const struct scsi_device *sdev, const char *name,
+			const unsigned char *sense_buffer, int sense_len)
+{
+	scsi_log_print_sense(sdev, name, -1, sense_buffer, sense_len);
+}
+EXPORT_SYMBOL(__scsi_print_sense);
+
+/* Normalize and print sense buffer in SCSI command */
+void scsi_print_sense(struct scsi_cmnd *cmd)
+{
+	scsi_log_print_sense(cmd->device, scmd_name(cmd),
+			     scsi_cmd_to_rq(cmd)->tag, cmd->sense_buffer,
+			     SCSI_SENSE_BUFFERSIZE);
+}
+EXPORT_SYMBOL(scsi_print_sense);
+
+void scsi_print_result(struct scsi_cmnd *cmd, const char *msg, int disposition)
+{
+	char *logbuf;
+	size_t off, logbuf_len;
+	const char *mlret_string = scsi_mlreturn_string(disposition);
+	const char *hb_string = scsi_hostbyte_string(cmd->result);
+	unsigned long cmd_age = (jiffies - cmd->jiffies_at_alloc) / HZ;
+
+	logbuf = scsi_log_reserve_buffer(&logbuf_len);
+	if (!logbuf)
+		return;
+
+	off = sdev_format_header(logbuf, logbuf_len, scmd_name(cmd),
+				 scsi_cmd_to_rq(cmd)->tag);
+
+	if (off >= logbuf_len)
+		goto out_printk;
+
+	if (msg) {
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "%s: ", msg);
+		if (WARN_ON(off >= logbuf_len))
+			goto out_printk;
+	}
+	if (mlret_string)
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "%s ", mlret_string);
+	else
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "UNKNOWN(0x%02x) ", disposition);
+	if (WARN_ON(off >= logbuf_len))
+		goto out_printk;
+
+	off += scnprintf(logbuf + off, logbuf_len - off, "Result: ");
+	if (WARN_ON(off >= logbuf_len))
+		goto out_printk;
+
+	if (hb_string)
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "hostbyte=%s ", hb_string);
+	else
+		off += scnprintf(logbuf + off, logbuf_len - off,
+				 "hostbyte=0x%02x ", host_byte(cmd->result));
+	if (WARN_ON(off >= logbuf_len))
+		goto out_printk;
+
+	off += scnprintf(logbuf + off, logbuf_len - off,
+			 "driverbyte=DRIVER_OK ");
+
+	off += scnprintf(logbuf + off, logbuf_len - off,
+			 "cmd_age=%lus", cmd_age);
+
+out_printk:
+	dev_printk(KERN_INFO, &cmd->device->sdev_gendev, "%s", logbuf);
+	scsi_log_release_buffer(logbuf);
+}
+EXPORT_SYMBOL(scsi_print_result);