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, 125 insertions, 0 deletions

diff --git a/include/pcmcia/soc_common.h b/include/pcmcia/soc_common.h
new file mode 100644
index 000000000..d4f18f467
--- /dev/null
+++ b/include/pcmcia/soc_common.h
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <pcmcia/ss.h>
+
+struct module;
+struct cpufreq_freqs;
+
+struct soc_pcmcia_regulator {
+	struct regulator	*reg;
+	bool			on;
+};
+
+struct pcmcia_state {
+  unsigned detect: 1,
+            ready: 1,
+             bvd1: 1,
+             bvd2: 1,
+           wrprot: 1,
+            vs_3v: 1,
+            vs_Xv: 1;
+};
+
+/*
+ * This structure encapsulates per-socket state which we might need to
+ * use when responding to a Card Services query of some kind.
+ */
+struct soc_pcmcia_socket {
+	struct pcmcia_socket	socket;
+
+	/*
+	 * Info from low level handler
+	 */
+	unsigned int		nr;
+	struct clk		*clk;
+
+	/*
+	 * Core PCMCIA state
+	 */
+	const struct pcmcia_low_level *ops;
+
+	unsigned int		status;
+	socket_state_t		cs_state;
+
+	unsigned short		spd_io[MAX_IO_WIN];
+	unsigned short		spd_mem[MAX_WIN];
+	unsigned short		spd_attr[MAX_WIN];
+
+	struct resource		res_skt;
+	struct resource		res_io;
+	struct resource		res_io_io;
+	struct resource		res_mem;
+	struct resource		res_attr;
+
+	struct {
+		int		gpio;
+		struct gpio_desc *desc;
+		unsigned int	irq;
+		const char	*name;
+	} stat[6];
+#define SOC_STAT_CD		0	/* Card detect */
+#define SOC_STAT_BVD1		1	/* BATDEAD / IOSTSCHG */
+#define SOC_STAT_BVD2		2	/* BATWARN / IOSPKR */
+#define SOC_STAT_RDY		3	/* Ready / Interrupt */
+#define SOC_STAT_VS1		4	/* Voltage sense 1 */
+#define SOC_STAT_VS2		5	/* Voltage sense 2 */
+
+	struct gpio_desc	*gpio_reset;
+	struct gpio_desc	*gpio_bus_enable;
+	struct soc_pcmcia_regulator vcc;
+	struct soc_pcmcia_regulator vpp;
+
+	unsigned int		irq_state;
+
+#ifdef CONFIG_CPU_FREQ
+	struct notifier_block	cpufreq_nb;
+#endif
+	struct timer_list	poll_timer;
+	struct list_head	node;
+	void *driver_data;
+};
+
+
+struct pcmcia_low_level {
+	struct module *owner;
+
+	/* first socket in system */
+	int first;
+	/* nr of sockets */
+	int nr;
+
+	int (*hw_init)(struct soc_pcmcia_socket *);
+	void (*hw_shutdown)(struct soc_pcmcia_socket *);
+
+	void (*socket_state)(struct soc_pcmcia_socket *, struct pcmcia_state *);
+	int (*configure_socket)(struct soc_pcmcia_socket *, const socket_state_t *);
+
+	/*
+	 * Enable card status IRQs on (re-)initialisation.  This can
+	 * be called at initialisation, power management event, or
+	 * pcmcia event.
+	 */
+	void (*socket_init)(struct soc_pcmcia_socket *);
+
+	/*
+	 * Disable card status IRQs and PCMCIA bus on suspend.
+	 */
+	void (*socket_suspend)(struct soc_pcmcia_socket *);
+
+	/*
+	 * Hardware specific timing routines.
+	 * If provided, the get_timing routine overrides the SOC default.
+	 */
+	unsigned int (*get_timing)(struct soc_pcmcia_socket *, unsigned int, unsigned int);
+	int (*set_timing)(struct soc_pcmcia_socket *);
+	int (*show_timing)(struct soc_pcmcia_socket *, char *);
+
+#ifdef CONFIG_CPU_FREQ
+	/*
+	 * CPUFREQ support.
+	 */
+	int (*frequency_change)(struct soc_pcmcia_socket *, unsigned long, struct cpufreq_freqs *);
+#endif
+};
+
+
+