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, 36 insertions, 0 deletions

diff --git a/drivers/scsi/lpfc/Makefile b/drivers/scsi/lpfc/Makefile
new file mode 100644
index 000000000..bbd1faf41
--- /dev/null
+++ b/drivers/scsi/lpfc/Makefile
@@ -0,0 +1,36 @@
+#/*******************************************************************
+# * This file is part of the Emulex Linux Device Driver for         *
+# * Fibre Channel Host Bus Adapters.                                *
+# * Copyright (C) 2017-2018 Broadcom. All Rights Reserved. The term *
+# * “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.     *
+# * Copyright (C) 2004-2012 Emulex.  All rights reserved.           *
+# * EMULEX and SLI are trademarks of Emulex.                        *
+# * www.broadcom.com                                                *
+# *                                                                 *
+# * This program is free software; you can redistribute it and/or   *
+# * modify it under the terms of version 2 of the GNU General       *
+# * Public License as published by the Free Software Foundation.    *
+# * This program is distributed in the hope that it will be useful. *
+# * ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND          *
+# * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,  *
+# * FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT, ARE      *
+# * DISCLAIMED, EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD *
+# * TO BE LEGALLY INVALID.  See the GNU General Public License for  *
+# * more details, a copy of which can be found in the file COPYING  *
+# * included with this package.                                     *
+# *******************************************************************/
+######################################################################
+
+ccflags-$(GCOV) := -fprofile-arcs -ftest-coverage
+ccflags-$(GCOV) += -O0
+
+ifdef WARNINGS_BECOME_ERRORS
+ccflags-y += -Werror
+endif
+
+obj-$(CONFIG_SCSI_LPFC) := lpfc.o
+
+lpfc-objs := lpfc_mem.o lpfc_sli.o lpfc_ct.o lpfc_els.o \
+	lpfc_hbadisc.o	lpfc_init.o lpfc_mbox.o lpfc_nportdisc.o   \
+	lpfc_scsi.o lpfc_attr.o lpfc_vport.o lpfc_debugfs.o lpfc_bsg.o \
+	lpfc_nvme.o lpfc_nvmet.o lpfc_vmid.o