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, 145 insertions, 0 deletions

diff --git a/drivers/scsi/imm.h b/drivers/scsi/imm.h
new file mode 100644
index 000000000..398fa5b15
--- /dev/null
+++ b/drivers/scsi/imm.h
@@ -0,0 +1,145 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*  Driver for the Iomega MatchMaker parallel port SCSI HBA embedded in 
+ * the Iomega ZIP Plus drive
+ * 
+ * (c) 1998     David Campbell
+ *
+ * Please note that I live in Perth, Western Australia. GMT+0800
+ */
+
+#ifndef _IMM_H
+#define _IMM_H
+
+#define   IMM_VERSION   "2.05 (for Linux 2.4.0)"
+
+/* 
+ * 10 Apr 1998 (Good Friday) - Received EN144302 by email from Iomega.
+ * Scarry thing is the level of support from one of their managers.
+ * The onus is now on us (the developers) to shut up and start coding.
+ *                                              11Apr98 [ 0.10 ]
+ *
+ * --- SNIP ---
+ *
+ * It manages to find the drive which is a good start. Writing data during
+ * data phase is known to be broken (due to requirements of two byte writes).
+ * Removing "Phase" debug messages.
+ *
+ * PS: Took four hours of coding after I bought a drive.
+ *      ANZAC Day (Aus "War Veterans Holiday")  25Apr98 [ 0.14 ]
+ *
+ * Ten minutes later after a few fixes.... (LITERALLY!!!)
+ * Have mounted disk, copied file, dismounted disk, remount disk, diff file
+ *                    -----  It actually works!!! -----
+ *                                              25Apr98 [ 0.15 ]
+ *
+ * Twenty minutes of mucking around, rearanged the IEEE negotiate mechanism.
+ * Now have byte mode working (only EPP and ECP to go now... :=)
+ *                                              26Apr98 [ 0.16 ]
+ *
+ * Thirty minutes of further coding results in EPP working on my machine.
+ *                                              27Apr98 [ 0.17 ]
+ *
+ * Due to work commitments and inability to get a "true" ECP mode functioning
+ * I have decided to code the parport support into imm.
+ *                                              09Jun98 [ 0.18 ]
+ *
+ * Driver is now out of beta testing.
+ * Support for parport has been added.
+ * Now distributed with the ppa driver.
+ *                                              12Jun98 [ 2.00 ]
+ *
+ * Err.. It appears that imm-2.00 was broken....
+ *                                              18Jun98 [ 2.01 ]
+ *
+ * Patch applied to sync this against the Linux 2.1.x kernel code
+ * Included qboot_zip.sh
+ *                                              21Jun98 [ 2.02 ]
+ *
+ * Other clean ups include the follow changes:
+ *    CONFIG_SCSI_PPA_HAVE_PEDANTIC => CONFIG_SCSI_IZIP_EPP16
+ *    added CONFIG_SCSI_IZIP_SLOW_CTR option
+ *                                                      [2.03]
+ *  Fix kernel panic on scsi timeout.		20Aug00 [2.04]
+ *
+ *  Avoid io_request_lock problems.
+ *  John Cavan <johncavan@home.com>		16Nov00 [2.05]
+ */
+/* ------ END OF USER CONFIGURABLE PARAMETERS ----- */
+
+#include  <linux/stddef.h>
+#include  <linux/module.h>
+#include  <linux/kernel.h>
+#include  <linux/ioport.h>
+#include  <linux/delay.h>
+#include  <linux/proc_fs.h>
+#include  <linux/stat.h>
+#include  <linux/blkdev.h>
+#include  <linux/sched.h>
+#include  <linux/interrupt.h>
+
+#include  <asm/io.h>
+#include  <scsi/scsi_host.h>
+/* batteries not included :-) */
+
+/*
+ * modes in which the driver can operate 
+ */
+#define   IMM_AUTODETECT        0	/* Autodetect mode                */
+#define   IMM_NIBBLE            1	/* work in standard 4 bit mode    */
+#define   IMM_PS2               2	/* PS/2 byte mode         */
+#define   IMM_EPP_8             3	/* EPP mode, 8 bit                */
+#define   IMM_EPP_16            4	/* EPP mode, 16 bit               */
+#define   IMM_EPP_32            5	/* EPP mode, 32 bit               */
+#define   IMM_UNKNOWN           6	/* Just in case...                */
+
+static char *IMM_MODE_STRING[] =
+{
+	[IMM_AUTODETECT] = "Autodetect",
+	[IMM_NIBBLE]	 = "SPP",
+	[IMM_PS2]	 = "PS/2",
+	[IMM_EPP_8]	 = "EPP 8 bit",
+	[IMM_EPP_16]	 = "EPP 16 bit",
+	[IMM_EPP_32]	 = "EPP 32 bit",
+	[IMM_UNKNOWN]	 = "Unknown",
+};
+
+/* other options */
+#define IMM_BURST_SIZE	512	/* data burst size */
+#define IMM_SELECT_TMO  500	/* 500 how long to wait for target ? */
+#define IMM_SPIN_TMO    5000	/* 50000 imm_wait loop limiter */
+#define IMM_DEBUG	0	/* debugging option */
+#define IN_EPP_MODE(x) (x == IMM_EPP_8 || x == IMM_EPP_16 || x == IMM_EPP_32)
+
+/* args to imm_connect */
+#define CONNECT_EPP_MAYBE 1
+#define CONNECT_NORMAL  0
+
+#define r_dtr(x)        (unsigned char)inb((x))
+#define r_str(x)        (unsigned char)inb((x)+1)
+#define r_ctr(x)        (unsigned char)inb((x)+2)
+#define r_epp(x)        (unsigned char)inb((x)+4)
+#define r_fifo(x)       (unsigned char)inb((x))   /* x must be base_hi */
+					/* On PCI is: base+0x400 != base_hi */
+#define r_ecr(x)        (unsigned char)inb((x)+2) /* x must be base_hi */
+
+#define w_dtr(x,y)      outb(y, (x))
+#define w_str(x,y)      outb(y, (x)+1)
+#define w_epp(x,y)      outb(y, (x)+4)
+#define w_fifo(x,y)     outb(y, (x))     /* x must be base_hi */
+#define w_ecr(x,y)      outb(y, (x)+0x2) /* x must be base_hi */
+
+#ifdef CONFIG_SCSI_IZIP_SLOW_CTR
+#define w_ctr(x,y)      outb_p(y, (x)+2)
+#else
+#define w_ctr(x,y)      outb(y, (x)+2)
+#endif
+
+static inline struct scsi_pointer *imm_scsi_pointer(struct scsi_cmnd *cmd)
+{
+	return scsi_cmd_priv(cmd);
+}
+
+static int imm_engine(imm_struct *, struct scsi_cmnd *);
+
+#endif				/* _IMM_H */