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, 263 insertions, 0 deletions

diff --git a/drivers/scsi/nsp32_debug.c b/drivers/scsi/nsp32_debug.c
new file mode 100644
index 000000000..4f1d4bf9c
--- /dev/null
+++ b/drivers/scsi/nsp32_debug.c
@@ -0,0 +1,263 @@
+/*
+ * Workbit NinjaSCSI-32Bi/UDE PCI/CardBus SCSI Host Bus Adapter driver
+ * Debug routine
+ *
+ * This software may be used and distributed according to the terms of
+ * the GNU General Public License.
+ */
+
+/*
+ * Show the command data of a command
+ */
+static const char unknown[] = "UNKNOWN";
+
+static const char * group_0_commands[] = {
+/* 00-03 */ "Test Unit Ready", "Rezero Unit", unknown, "Request Sense",
+/* 04-07 */ "Format Unit", "Read Block Limits", unknown, "Reassign Blocks",
+/* 08-0d */ "Read (6)", unknown, "Write (6)", "Seek (6)", unknown, unknown,
+/* 0e-12 */ unknown, "Read Reverse", "Write Filemarks", "Space", "Inquiry",  
+/* 13-16 */ unknown, "Recover Buffered Data", "Mode Select", "Reserve",
+/* 17-1b */ "Release", "Copy", "Erase", "Mode Sense", "Start/Stop Unit",
+/* 1c-1d */ "Receive Diagnostic", "Send Diagnostic", 
+/* 1e-1f */ "Prevent/Allow Medium Removal", unknown,
+};
+
+
+static const char *group_1_commands[] = {
+/* 20-22 */  unknown, unknown, unknown,
+/* 23-28 */ unknown, unknown, "Read Capacity", unknown, unknown, "Read (10)",
+/* 29-2d */ unknown, "Write (10)", "Seek (10)", unknown, unknown,
+/* 2e-31 */ "Write Verify","Verify", "Search High", "Search Equal",
+/* 32-34 */ "Search Low", "Set Limits", "Prefetch or Read Position", 
+/* 35-37 */ "Synchronize Cache","Lock/Unlock Cache", "Read Defect Data",
+/* 38-3c */ "Medium Scan", "Compare","Copy Verify", "Write Buffer", "Read Buffer",
+/* 3d-3f */ "Update Block", "Read Long",  "Write Long",
+};
+
+
+static const char *group_2_commands[] = {
+/* 40-41 */ "Change Definition", "Write Same", 
+/* 42-48 */ "Read Sub-Ch(cd)", "Read TOC", "Read Header(cd)", "Play Audio(cd)", unknown, "Play Audio MSF(cd)", "Play Audio Track/Index(cd)", 
+/* 49-4f */ "Play Track Relative(10)(cd)", unknown, "Pause/Resume(cd)", "Log Select", "Log Sense", unknown, unknown,
+/* 50-55 */ unknown, unknown, unknown, unknown, unknown, "Mode Select (10)",
+/* 56-5b */ unknown, unknown, unknown, unknown, "Mode Sense (10)", unknown,
+/* 5c-5f */ unknown, unknown, unknown,
+};
+
+#define group(opcode) (((opcode) >> 5) & 7)
+
+#define RESERVED_GROUP  0
+#define VENDOR_GROUP    1
+#define NOTEXT_GROUP    2
+
+static const char **commands[] = {
+    group_0_commands, group_1_commands, group_2_commands, 
+    (const char **) RESERVED_GROUP, (const char **) RESERVED_GROUP, 
+    (const char **) NOTEXT_GROUP, (const char **) VENDOR_GROUP, 
+    (const char **) VENDOR_GROUP
+};
+
+static const char reserved[] = "RESERVED";
+static const char vendor[] = "VENDOR SPECIFIC";
+
+static void print_opcodek(unsigned char opcode)
+{
+	const char **table = commands[ group(opcode) ];
+
+	switch ((unsigned long) table) {
+	case RESERVED_GROUP:
+		printk("%s[%02x] ", reserved, opcode); 
+		break;
+	case NOTEXT_GROUP:
+		printk("%s(notext)[%02x] ", unknown, opcode); 
+		break;
+	case VENDOR_GROUP:
+		printk("%s[%02x] ", vendor, opcode); 
+		break;
+	default:
+		if (table[opcode & 0x1f] != unknown)
+			printk("%s[%02x] ", table[opcode & 0x1f], opcode);
+		else
+			printk("%s[%02x] ", unknown, opcode);
+		break;
+	}
+}
+
+static void print_commandk (unsigned char *command)
+{
+	int i,s;
+//	printk(KERN_DEBUG);
+	print_opcodek(command[0]);
+	/*printk(KERN_DEBUG "%s ", __func__);*/
+	if ((command[0] >> 5) == 6 ||
+	    (command[0] >> 5) == 7 ) {
+		s = 12; /* vender specific */
+	} else {
+		s = COMMAND_SIZE(command[0]);
+	}
+
+	for ( i = 1; i < s; ++i) {
+		printk("%02x ", command[i]);
+	}
+
+	switch (s) {
+	case 6:
+		printk("LBA=%d len=%d",
+		       (((unsigned int)command[1] & 0x0f) << 16) |
+		       ( (unsigned int)command[2]         <<  8) |
+		       ( (unsigned int)command[3]              ),
+		       (unsigned int)command[4]
+			);
+		break;
+	case 10:
+		printk("LBA=%d len=%d",
+		       ((unsigned int)command[2] << 24) |
+		       ((unsigned int)command[3] << 16) |
+		       ((unsigned int)command[4] <<  8) |
+		       ((unsigned int)command[5]      ),
+		       ((unsigned int)command[7] <<  8) |
+		       ((unsigned int)command[8]      )
+		       );
+		break;
+	case 12:
+		printk("LBA=%d len=%d",
+		       ((unsigned int)command[2] << 24) |
+		       ((unsigned int)command[3] << 16) |
+		       ((unsigned int)command[4] <<  8) |
+		       ((unsigned int)command[5]      ),
+		       ((unsigned int)command[6] << 24) |
+		       ((unsigned int)command[7] << 16) |
+		       ((unsigned int)command[8] <<  8) |
+		       ((unsigned int)command[9]      )
+		       );
+		break;
+	default:
+		break;
+	}
+	printk("\n");
+}
+
+static void show_command(struct scsi_cmnd *SCpnt)
+{
+	print_commandk(SCpnt->cmnd);
+}
+
+static void show_busphase(unsigned char stat)
+{
+	switch(stat) {
+	case BUSPHASE_COMMAND:
+		printk( "BUSPHASE_COMMAND\n");
+		break;
+	case BUSPHASE_MESSAGE_IN:
+		printk( "BUSPHASE_MESSAGE_IN\n");
+		break;
+	case BUSPHASE_MESSAGE_OUT:
+		printk( "BUSPHASE_MESSAGE_OUT\n");
+		break;
+	case BUSPHASE_DATA_IN:
+		printk( "BUSPHASE_DATA_IN\n");
+		break;
+	case BUSPHASE_DATA_OUT:
+		printk( "BUSPHASE_DATA_OUT\n");
+		break;
+	case BUSPHASE_STATUS:
+		printk( "BUSPHASE_STATUS\n");
+		break;
+	case BUSPHASE_SELECT:
+		printk( "BUSPHASE_SELECT\n");
+		break;
+	default:
+		printk( "BUSPHASE_other: 0x%x\n", stat);
+		break;
+	}
+}
+
+static void show_autophase(unsigned short i)
+{
+	printk("auto: 0x%x,", i);
+
+	if(i & COMMAND_PHASE) {
+		printk(" cmd");
+	}
+	if(i & DATA_IN_PHASE) {
+		printk(" din");
+	}
+	if(i & DATA_OUT_PHASE) {
+		printk(" dout");
+	}
+	if(i & MSGOUT_PHASE) {
+		printk(" mout");
+	}
+	if(i & STATUS_PHASE) {
+		printk(" stat");
+	}
+	if(i & ILLEGAL_PHASE) {
+		printk(" ill");
+	}
+	if(i & BUS_FREE_OCCUER) {
+		printk(" bfree-o");
+	}
+	if(i & MSG_IN_OCCUER) {
+		printk(" min-o");
+	}
+	if(i & MSG_OUT_OCCUER) {
+		printk(" mout-o");
+	}
+	if(i & SELECTION_TIMEOUT) {
+		printk(" sel");
+	}
+	if(i & MSGIN_00_VALID) {
+		printk(" m0");
+	}
+	if(i & MSGIN_02_VALID) {
+		printk(" m2");
+	}
+	if(i & MSGIN_03_VALID) {
+		printk(" m3");
+	}
+	if(i & MSGIN_04_VALID) {
+		printk(" m4");
+	}
+	if(i & AUTOSCSI_BUSY) {
+		printk(" busy");
+	}
+
+	printk("\n");
+}
+
+static void nsp32_print_register(int base)
+{
+	if (!(NSP32_DEBUG_MASK & NSP32_SPECIAL_PRINT_REGISTER))
+		return;
+
+	printk("Phase=0x%x, ", nsp32_read1(base, SCSI_BUS_MONITOR));
+	printk("OldPhase=0x%x, ", nsp32_index_read1(base, OLD_SCSI_PHASE));
+	printk("syncreg=0x%x, ", nsp32_read1(base, SYNC_REG));
+	printk("ackwidth=0x%x, ", nsp32_read1(base, ACK_WIDTH));
+	printk("sgtpaddr=0x%lx, ", nsp32_read4(base, SGT_ADR));
+	printk("scsioutlatch=0x%x, ", nsp32_read1(base, SCSI_OUT_LATCH_TARGET_ID));
+	printk("msgout=0x%lx, ", nsp32_read4(base, SCSI_MSG_OUT));
+	printk("miscrd=0x%x, ", nsp32_index_read2(base, MISC_WR));
+	printk("seltimeout=0x%x, ", nsp32_read2(base, SEL_TIME_OUT));
+	printk("sreqrate=0x%x, ", nsp32_read1(base, SREQ_SMPL_RATE));
+	printk("transStatus=0x%x, ", nsp32_read2(base, TRANSFER_STATUS));
+	printk("reselectid=0x%x, ", nsp32_read2(base, COMMAND_CONTROL));
+	printk("arbit=0x%x, ", nsp32_read1(base, ARBIT_STATUS));
+	printk("BmStart=0x%lx, ", nsp32_read4(base, BM_START_ADR));
+	printk("BmCount=0x%lx, ", nsp32_read4(base, BM_CNT));
+	printk("SackCnt=0x%lx, ", nsp32_read4(base, SACK_CNT));
+	printk("SReqCnt=0x%lx, ", nsp32_read4(base, SREQ_CNT));
+	printk("SavedSackCnt=0x%lx, ", nsp32_read4(base, SAVED_SACK_CNT));
+	printk("ScsiBusControl=0x%x, ", nsp32_read1(base, SCSI_BUS_CONTROL));
+	printk("FifoRestCnt=0x%x, ", nsp32_read2(base, FIFO_REST_CNT));
+	printk("CdbIn=0x%x, ", nsp32_read1(base, SCSI_CSB_IN));
+	printk("\n");
+
+	if (0) {
+		printk("execph=0x%x, ", nsp32_read2(base, SCSI_EXECUTE_PHASE));
+		printk("IrqStatus=0x%x, ", nsp32_read2(base, IRQ_STATUS));
+		printk("\n");
+	}
+}
+
+/* end */