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, 48 insertions, 0 deletions

diff --git a/drivers/phy/starfive/Kconfig b/drivers/phy/starfive/Kconfig
new file mode 100644
index 000000000..d0cdd7cb4
--- /dev/null
+++ b/drivers/phy/starfive/Kconfig
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Phy drivers for StarFive platforms
+#
+
+if ARCH_STARFIVE || COMPILE_TEST
+
+config PHY_STARFIVE_JH7110_DPHY_RX
+	tristate "StarFive JH7110 D-PHY RX support"
+	depends on HAS_IOMEM
+	select GENERIC_PHY
+	select GENERIC_PHY_MIPI_DPHY
+	help
+	  Choose this option if you have a StarFive D-PHY in your
+	  system. If M is selected, the module will be called
+	  phy-jh7110-dphy-rx.ko.
+
+config PHY_STARFIVE_JH7110_DPHY_TX
+	tristate "StarFive JH7110 D-PHY TX Support"
+	depends on HAS_IOMEM
+	select GENERIC_PHY
+	select GENERIC_PHY_MIPI_DPHY
+	help
+	  Choose this option if you have a StarFive D-PHY TX in your
+	  system. If M is selected, the module will be called
+	  phy-jh7110-dphy-tx.ko.
+
+config PHY_STARFIVE_JH7110_PCIE
+	tristate "Starfive JH7110 PCIE 2.0/USB 3.0 PHY support"
+	depends on HAS_IOMEM
+	select GENERIC_PHY
+	help
+	  Enable this to support the StarFive PCIe 2.0 PHY,
+	  or used as USB 3.0 PHY.
+	  If M is selected, the module will be called
+	  phy-jh7110-pcie.ko.
+
+config PHY_STARFIVE_JH7110_USB
+	tristate "Starfive JH7110 USB 2.0 PHY support"
+	depends on USB_SUPPORT
+	select GENERIC_PHY
+	help
+	  Enable this to support the StarFive USB 2.0 PHY,
+	  used with the Cadence USB controller.
+	  If M is selected, the module will be called
+	  phy-jh7110-usb.ko.
+
+endif # ARCH_STARFIVE || COMPILE_TEST