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, 325 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/sp-dev.c b/drivers/crypto/ccp/sp-dev.c
new file mode 100644
index 000000000..f204aa5df
--- /dev/null
+++ b/drivers/crypto/ccp/sp-dev.c
@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Secure Processor driver
+ *
+ * Copyright (C) 2017-2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@amd.com>
+ * Author: Gary R Hook <gary.hook@amd.com>
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/spinlock_types.h>
+#include <linux/types.h>
+#include <linux/ccp.h>
+
+#include "sev-dev.h"
+#include "ccp-dev.h"
+#include "sp-dev.h"
+
+MODULE_AUTHOR("Tom Lendacky <thomas.lendacky@amd.com>");
+MODULE_AUTHOR("Gary R Hook <gary.hook@amd.com>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.1.0");
+MODULE_DESCRIPTION("AMD Secure Processor driver");
+
+/* List of SPs, SP count, read-write access lock, and access functions
+ *
+ * Lock structure: get sp_unit_lock for reading whenever we need to
+ * examine the SP list.
+ */
+static DEFINE_RWLOCK(sp_unit_lock);
+static LIST_HEAD(sp_units);
+
+/* Ever-increasing value to produce unique unit numbers */
+static atomic_t sp_ordinal;
+
+static void sp_add_device(struct sp_device *sp)
+{
+	unsigned long flags;
+
+	write_lock_irqsave(&sp_unit_lock, flags);
+
+	list_add_tail(&sp->entry, &sp_units);
+
+	write_unlock_irqrestore(&sp_unit_lock, flags);
+}
+
+static void sp_del_device(struct sp_device *sp)
+{
+	unsigned long flags;
+
+	write_lock_irqsave(&sp_unit_lock, flags);
+
+	list_del(&sp->entry);
+
+	write_unlock_irqrestore(&sp_unit_lock, flags);
+}
+
+static irqreturn_t sp_irq_handler(int irq, void *data)
+{
+	struct sp_device *sp = data;
+
+	if (sp->ccp_irq_handler)
+		sp->ccp_irq_handler(irq, sp->ccp_irq_data);
+
+	if (sp->psp_irq_handler)
+		sp->psp_irq_handler(irq, sp->psp_irq_data);
+
+	return IRQ_HANDLED;
+}
+
+int sp_request_ccp_irq(struct sp_device *sp, irq_handler_t handler,
+		       const char *name, void *data)
+{
+	int ret;
+
+	if ((sp->psp_irq == sp->ccp_irq) && sp->dev_vdata->psp_vdata) {
+		/* Need a common routine to manage all interrupts */
+		sp->ccp_irq_data = data;
+		sp->ccp_irq_handler = handler;
+
+		if (!sp->irq_registered) {
+			ret = request_irq(sp->ccp_irq, sp_irq_handler, 0,
+					  sp->name, sp);
+			if (ret)
+				return ret;
+
+			sp->irq_registered = true;
+		}
+	} else {
+		/* Each sub-device can manage it's own interrupt */
+		ret = request_irq(sp->ccp_irq, handler, 0, name, data);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+int sp_request_psp_irq(struct sp_device *sp, irq_handler_t handler,
+		       const char *name, void *data)
+{
+	int ret;
+
+	if ((sp->psp_irq == sp->ccp_irq) && sp->dev_vdata->ccp_vdata) {
+		/* Need a common routine to manage all interrupts */
+		sp->psp_irq_data = data;
+		sp->psp_irq_handler = handler;
+
+		if (!sp->irq_registered) {
+			ret = request_irq(sp->psp_irq, sp_irq_handler, 0,
+					  sp->name, sp);
+			if (ret)
+				return ret;
+
+			sp->irq_registered = true;
+		}
+	} else {
+		/* Each sub-device can manage it's own interrupt */
+		ret = request_irq(sp->psp_irq, handler, 0, name, data);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+void sp_free_ccp_irq(struct sp_device *sp, void *data)
+{
+	if ((sp->psp_irq == sp->ccp_irq) && sp->dev_vdata->psp_vdata) {
+		/* Using common routine to manage all interrupts */
+		if (!sp->psp_irq_handler) {
+			/* Nothing else using it, so free it */
+			free_irq(sp->ccp_irq, sp);
+
+			sp->irq_registered = false;
+		}
+
+		sp->ccp_irq_handler = NULL;
+		sp->ccp_irq_data = NULL;
+	} else {
+		/* Each sub-device can manage it's own interrupt */
+		free_irq(sp->ccp_irq, data);
+	}
+}
+
+void sp_free_psp_irq(struct sp_device *sp, void *data)
+{
+	if ((sp->psp_irq == sp->ccp_irq) && sp->dev_vdata->ccp_vdata) {
+		/* Using common routine to manage all interrupts */
+		if (!sp->ccp_irq_handler) {
+			/* Nothing else using it, so free it */
+			free_irq(sp->psp_irq, sp);
+
+			sp->irq_registered = false;
+		}
+
+		sp->psp_irq_handler = NULL;
+		sp->psp_irq_data = NULL;
+	} else {
+		/* Each sub-device can manage it's own interrupt */
+		free_irq(sp->psp_irq, data);
+	}
+}
+
+/**
+ * sp_alloc_struct - allocate and initialize the sp_device struct
+ *
+ * @dev: device struct of the SP
+ */
+struct sp_device *sp_alloc_struct(struct device *dev)
+{
+	struct sp_device *sp;
+
+	sp = devm_kzalloc(dev, sizeof(*sp), GFP_KERNEL);
+	if (!sp)
+		return NULL;
+
+	sp->dev = dev;
+	sp->ord = atomic_inc_return(&sp_ordinal);
+	snprintf(sp->name, SP_MAX_NAME_LEN, "sp-%u", sp->ord);
+
+	return sp;
+}
+
+int sp_init(struct sp_device *sp)
+{
+	sp_add_device(sp);
+
+	if (sp->dev_vdata->ccp_vdata)
+		ccp_dev_init(sp);
+
+	if (sp->dev_vdata->psp_vdata)
+		psp_dev_init(sp);
+	return 0;
+}
+
+void sp_destroy(struct sp_device *sp)
+{
+	if (sp->dev_vdata->ccp_vdata)
+		ccp_dev_destroy(sp);
+
+	if (sp->dev_vdata->psp_vdata)
+		psp_dev_destroy(sp);
+
+	sp_del_device(sp);
+}
+
+int sp_suspend(struct sp_device *sp)
+{
+	if (sp->dev_vdata->ccp_vdata) {
+		ccp_dev_suspend(sp);
+	}
+
+	return 0;
+}
+
+int sp_resume(struct sp_device *sp)
+{
+	if (sp->dev_vdata->ccp_vdata) {
+		ccp_dev_resume(sp);
+	}
+
+	return 0;
+}
+
+int sp_restore(struct sp_device *sp)
+{
+	if (sp->psp_data) {
+		int ret = psp_restore(sp);
+
+		if (ret)
+			return ret;
+	}
+
+	return sp_resume(sp);
+}
+
+struct sp_device *sp_get_psp_master_device(void)
+{
+	struct sp_device *i, *ret = NULL;
+	unsigned long flags;
+
+	write_lock_irqsave(&sp_unit_lock, flags);
+	if (list_empty(&sp_units))
+		goto unlock;
+
+	list_for_each_entry(i, &sp_units, entry) {
+		if (i->psp_data && i->get_psp_master_device) {
+			ret = i->get_psp_master_device();
+			break;
+		}
+	}
+
+unlock:
+	write_unlock_irqrestore(&sp_unit_lock, flags);
+	return ret;
+}
+
+static int __init sp_mod_init(void)
+{
+#ifdef CONFIG_X86
+	static bool initialized;
+	int ret;
+
+	if (initialized)
+		return 0;
+
+	ret = sp_pci_init();
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_CRYPTO_DEV_SP_PSP
+	psp_pci_init();
+#endif
+
+	initialized = true;
+
+	return 0;
+#endif
+
+#ifdef CONFIG_ARM64
+	int ret;
+
+	ret = sp_platform_init();
+	if (ret)
+		return ret;
+
+	return 0;
+#endif
+
+	return -ENODEV;
+}
+
+#if IS_BUILTIN(CONFIG_KVM_AMD) && IS_ENABLED(CONFIG_KVM_AMD_SEV)
+int __init sev_module_init(void)
+{
+	return sp_mod_init();
+}
+#endif
+
+static void __exit sp_mod_exit(void)
+{
+#ifdef CONFIG_X86
+
+#ifdef CONFIG_CRYPTO_DEV_SP_PSP
+	psp_pci_exit();
+#endif
+
+	sp_pci_exit();
+#endif
+
+#ifdef CONFIG_ARM64
+	sp_platform_exit();
+#endif
+}
+
+module_init(sp_mod_init);
+module_exit(sp_mod_exit);