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, 146 insertions, 0 deletions

diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
new file mode 100644
index 000000000..8d7e5caef
--- /dev/null
+++ b/include/acpi/ghes.h
@@ -0,0 +1,146 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef GHES_H
+#define GHES_H
+
+#include <acpi/apei.h>
+#include <acpi/hed.h>
+
+/*
+ * One struct ghes is created for each generic hardware error source.
+ * It provides the context for APEI hardware error timer/IRQ/SCI/NMI
+ * handler.
+ *
+ * estatus: memory buffer for error status block, allocated during
+ * HEST parsing.
+ */
+#define GHES_EXITING		0x0002
+
+struct ghes {
+	union {
+		struct acpi_hest_generic *generic;
+		struct acpi_hest_generic_v2 *generic_v2;
+	};
+	struct acpi_hest_generic_status *estatus;
+	unsigned int estatus_length;
+	unsigned long flags;
+	union {
+		struct list_head list;
+		struct timer_list timer;
+		unsigned int irq;
+	};
+	struct device *dev;
+	struct list_head elist;
+	void __iomem *error_status_vaddr;
+};
+
+struct ghes_estatus_node {
+	struct llist_node llnode;
+	struct acpi_hest_generic *generic;
+	struct ghes *ghes;
+};
+
+struct ghes_estatus_cache {
+	u32 estatus_len;
+	atomic_t count;
+	struct acpi_hest_generic *generic;
+	unsigned long long time_in;
+	struct rcu_head rcu;
+};
+
+enum {
+	GHES_SEV_NO = 0x0,
+	GHES_SEV_CORRECTED = 0x1,
+	GHES_SEV_RECOVERABLE = 0x2,
+	GHES_SEV_PANIC = 0x3,
+};
+
+#ifdef CONFIG_ACPI_APEI_GHES
+/**
+ * ghes_register_vendor_record_notifier - register a notifier for vendor
+ * records that the kernel would otherwise ignore.
+ * @nb: pointer to the notifier_block structure of the event handler.
+ *
+ * return 0 : SUCCESS, non-zero : FAIL
+ */
+int ghes_register_vendor_record_notifier(struct notifier_block *nb);
+
+/**
+ * ghes_unregister_vendor_record_notifier - unregister the previously
+ * registered vendor record notifier.
+ * @nb: pointer to the notifier_block structure of the vendor record handler.
+ */
+void ghes_unregister_vendor_record_notifier(struct notifier_block *nb);
+
+/**
+ * devm_ghes_register_vendor_record_notifier - device-managed vendor
+ * record notifier registration.
+ * @dev: device that owns the notifier lifetime
+ * @nb: pointer to the notifier_block structure of the vendor record handler
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int devm_ghes_register_vendor_record_notifier(struct device *dev,
+					      struct notifier_block *nb);
+
+struct list_head *ghes_get_devices(void);
+
+void ghes_estatus_pool_region_free(unsigned long addr, u32 size);
+#else
+static inline struct list_head *ghes_get_devices(void) { return NULL; }
+
+static inline void ghes_estatus_pool_region_free(unsigned long addr, u32 size) { return; }
+#endif
+
+int ghes_estatus_pool_init(unsigned int num_ghes);
+
+static inline int acpi_hest_get_version(struct acpi_hest_generic_data *gdata)
+{
+	return gdata->revision >> 8;
+}
+
+static inline void *acpi_hest_get_payload(struct acpi_hest_generic_data *gdata)
+{
+	if (acpi_hest_get_version(gdata) >= 3)
+		return (void *)(((struct acpi_hest_generic_data_v300 *)(gdata)) + 1);
+
+	return gdata + 1;
+}
+
+static inline int acpi_hest_get_error_length(struct acpi_hest_generic_data *gdata)
+{
+	return ((struct acpi_hest_generic_data *)(gdata))->error_data_length;
+}
+
+static inline int acpi_hest_get_size(struct acpi_hest_generic_data *gdata)
+{
+	if (acpi_hest_get_version(gdata) >= 3)
+		return sizeof(struct acpi_hest_generic_data_v300);
+
+	return sizeof(struct acpi_hest_generic_data);
+}
+
+static inline int acpi_hest_get_record_size(struct acpi_hest_generic_data *gdata)
+{
+	return (acpi_hest_get_size(gdata) + acpi_hest_get_error_length(gdata));
+}
+
+static inline void *acpi_hest_get_next(struct acpi_hest_generic_data *gdata)
+{
+	return (void *)(gdata) + acpi_hest_get_record_size(gdata);
+}
+
+#define apei_estatus_for_each_section(estatus, section)			\
+	for (section = (struct acpi_hest_generic_data *)(estatus + 1);	\
+	     (void *)section - (void *)(estatus + 1) < estatus->data_length; \
+	     section = acpi_hest_get_next(section))
+
+#ifdef CONFIG_ACPI_APEI_SEA
+int ghes_notify_sea(void);
+#else
+static inline int ghes_notify_sea(void) { return -ENOENT; }
+#endif
+
+struct notifier_block;
+extern void ghes_register_report_chain(struct notifier_block *nb);
+extern void ghes_unregister_report_chain(struct notifier_block *nb);
+#endif /* GHES_H */