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, 77 insertions, 0 deletions

diff --git a/include/dt-bindings/pinctrl/dra.h b/include/dt-bindings/pinctrl/dra.h
new file mode 100644
index 000000000..252cdfd0d
--- /dev/null
+++ b/include/dt-bindings/pinctrl/dra.h
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * This header provides constants for DRA pinctrl bindings.
+ *
+ * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com/
+ * Author: Rajendra Nayak <rnayak@ti.com>
+ */
+
+#ifndef _DT_BINDINGS_PINCTRL_DRA_H
+#define _DT_BINDINGS_PINCTRL_DRA_H
+
+/* DRA7 mux mode options for each pin. See TRM for options */
+#define MUX_MODE0	0x0
+#define MUX_MODE1	0x1
+#define MUX_MODE2	0x2
+#define MUX_MODE3	0x3
+#define MUX_MODE4	0x4
+#define MUX_MODE5	0x5
+#define MUX_MODE6	0x6
+#define MUX_MODE7	0x7
+#define MUX_MODE8	0x8
+#define MUX_MODE9	0x9
+#define MUX_MODE10	0xa
+#define MUX_MODE11	0xb
+#define MUX_MODE12	0xc
+#define MUX_MODE13	0xd
+#define MUX_MODE14	0xe
+#define MUX_MODE15	0xf
+
+/* Certain pins need virtual mode, but note: they may glitch */
+#define MUX_VIRTUAL_MODE0	(MODE_SELECT | (0x0 << 4))
+#define MUX_VIRTUAL_MODE1	(MODE_SELECT | (0x1 << 4))
+#define MUX_VIRTUAL_MODE2	(MODE_SELECT | (0x2 << 4))
+#define MUX_VIRTUAL_MODE3	(MODE_SELECT | (0x3 << 4))
+#define MUX_VIRTUAL_MODE4	(MODE_SELECT | (0x4 << 4))
+#define MUX_VIRTUAL_MODE5	(MODE_SELECT | (0x5 << 4))
+#define MUX_VIRTUAL_MODE6	(MODE_SELECT | (0x6 << 4))
+#define MUX_VIRTUAL_MODE7	(MODE_SELECT | (0x7 << 4))
+#define MUX_VIRTUAL_MODE8	(MODE_SELECT | (0x8 << 4))
+#define MUX_VIRTUAL_MODE9	(MODE_SELECT | (0x9 << 4))
+#define MUX_VIRTUAL_MODE10	(MODE_SELECT | (0xa << 4))
+#define MUX_VIRTUAL_MODE11	(MODE_SELECT | (0xb << 4))
+#define MUX_VIRTUAL_MODE12	(MODE_SELECT | (0xc << 4))
+#define MUX_VIRTUAL_MODE13	(MODE_SELECT | (0xd << 4))
+#define MUX_VIRTUAL_MODE14	(MODE_SELECT | (0xe << 4))
+#define MUX_VIRTUAL_MODE15	(MODE_SELECT | (0xf << 4))
+
+#define MODE_SELECT		(1 << 8)
+
+#define PULL_ENA		(0 << 16)
+#define PULL_DIS		(1 << 16)
+#define PULL_UP			(1 << 17)
+#define INPUT_EN		(1 << 18)
+#define SLEWCONTROL		(1 << 19)
+#define WAKEUP_EN		(1 << 24)
+#define WAKEUP_EVENT		(1 << 25)
+
+/* Active pin states */
+#define PIN_OUTPUT		(0 | PULL_DIS)
+#define PIN_OUTPUT_PULLUP	(PULL_UP)
+#define PIN_OUTPUT_PULLDOWN	(0)
+#define PIN_INPUT		(INPUT_EN | PULL_DIS)
+#define PIN_INPUT_SLEW		(INPUT_EN | SLEWCONTROL)
+#define PIN_INPUT_PULLUP	(PULL_ENA | INPUT_EN | PULL_UP)
+#define PIN_INPUT_PULLDOWN	(PULL_ENA | INPUT_EN)
+
+/*
+ * Macro to allow using the absolute physical address instead of the
+ * padconf registers instead of the offset from padconf base.
+ */
+#define DRA7XX_CORE_IOPAD(pa, val)	(((pa) & 0xffff) - 0x3400) (val)
+
+/* DRA7 IODELAY configuration parameters */
+#define A_DELAY_PS(val)			((val) & 0xffff)
+#define G_DELAY_PS(val)			((val) & 0xffff)
+#endif
+