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, 442 insertions, 0 deletions

diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
new file mode 100644
index 000000000..b282e3a86
--- /dev/null
+++ b/include/trace/events/kvm.h
@@ -0,0 +1,442 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#if !defined(_TRACE_KVM_MAIN_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_KVM_MAIN_H
+
+#include <linux/tracepoint.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM kvm
+
+#define ERSN(x) { KVM_EXIT_##x, "KVM_EXIT_" #x }
+
+#define kvm_trace_exit_reason						\
+	ERSN(UNKNOWN), ERSN(EXCEPTION), ERSN(IO), ERSN(HYPERCALL),	\
+	ERSN(DEBUG), ERSN(HLT), ERSN(MMIO), ERSN(IRQ_WINDOW_OPEN),	\
+	ERSN(SHUTDOWN), ERSN(FAIL_ENTRY), ERSN(INTR), ERSN(SET_TPR),	\
+	ERSN(TPR_ACCESS), ERSN(S390_SIEIC), ERSN(S390_RESET), ERSN(DCR),\
+	ERSN(NMI), ERSN(INTERNAL_ERROR), ERSN(OSI), ERSN(PAPR_HCALL),	\
+	ERSN(S390_UCONTROL), ERSN(WATCHDOG), ERSN(S390_TSCH), ERSN(EPR),\
+	ERSN(SYSTEM_EVENT), ERSN(S390_STSI), ERSN(IOAPIC_EOI),          \
+	ERSN(HYPERV), ERSN(ARM_NISV), ERSN(X86_RDMSR), ERSN(X86_WRMSR)
+
+TRACE_EVENT(kvm_userspace_exit,
+	    TP_PROTO(__u32 reason, int errno),
+	    TP_ARGS(reason, errno),
+
+	TP_STRUCT__entry(
+		__field(	__u32,		reason		)
+		__field(	int,		errno		)
+	),
+
+	TP_fast_assign(
+		__entry->reason		= reason;
+		__entry->errno		= errno;
+	),
+
+	TP_printk("reason %s (%d)",
+		  __entry->errno < 0 ?
+		  (__entry->errno == -EINTR ? "restart" : "error") :
+		  __print_symbolic(__entry->reason, kvm_trace_exit_reason),
+		  __entry->errno < 0 ? -__entry->errno : __entry->reason)
+);
+
+TRACE_EVENT(kvm_vcpu_wakeup,
+	    TP_PROTO(__u64 ns, bool waited, bool valid),
+	    TP_ARGS(ns, waited, valid),
+
+	TP_STRUCT__entry(
+		__field(	__u64,		ns		)
+		__field(	bool,		waited		)
+		__field(	bool,		valid		)
+	),
+
+	TP_fast_assign(
+		__entry->ns		= ns;
+		__entry->waited		= waited;
+		__entry->valid		= valid;
+	),
+
+	TP_printk("%s time %lld ns, polling %s",
+		  __entry->waited ? "wait" : "poll",
+		  __entry->ns,
+		  __entry->valid ? "valid" : "invalid")
+);
+
+#if defined(CONFIG_HAVE_KVM_IRQCHIP)
+TRACE_EVENT(kvm_set_irq,
+	TP_PROTO(unsigned int gsi, int level, int irq_source_id),
+	TP_ARGS(gsi, level, irq_source_id),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	gsi		)
+		__field(	int,		level		)
+		__field(	int,		irq_source_id	)
+	),
+
+	TP_fast_assign(
+		__entry->gsi		= gsi;
+		__entry->level		= level;
+		__entry->irq_source_id	= irq_source_id;
+	),
+
+	TP_printk("gsi %u level %d source %d",
+		  __entry->gsi, __entry->level, __entry->irq_source_id)
+);
+
+#ifdef CONFIG_KVM_IOAPIC
+
+#define kvm_irqchips						\
+	{KVM_IRQCHIP_PIC_MASTER,	"PIC master"},		\
+	{KVM_IRQCHIP_PIC_SLAVE,		"PIC slave"},		\
+	{KVM_IRQCHIP_IOAPIC,		"IOAPIC"}
+
+#endif /* CONFIG_KVM_IOAPIC */
+
+#ifdef kvm_irqchips
+#define kvm_ack_irq_string "irqchip %s pin %u"
+#define kvm_ack_irq_parm  __print_symbolic(__entry->irqchip, kvm_irqchips), __entry->pin
+#else
+#define kvm_ack_irq_string "irqchip %d pin %u"
+#define kvm_ack_irq_parm  __entry->irqchip, __entry->pin
+#endif
+
+TRACE_EVENT(kvm_ack_irq,
+	TP_PROTO(unsigned int irqchip, unsigned int pin),
+	TP_ARGS(irqchip, pin),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	irqchip		)
+		__field(	unsigned int,	pin		)
+	),
+
+	TP_fast_assign(
+		__entry->irqchip	= irqchip;
+		__entry->pin		= pin;
+	),
+
+	TP_printk(kvm_ack_irq_string, kvm_ack_irq_parm)
+);
+
+#endif /* defined(CONFIG_HAVE_KVM_IRQCHIP) */
+
+
+
+#define KVM_TRACE_MMIO_READ_UNSATISFIED 0
+#define KVM_TRACE_MMIO_READ 1
+#define KVM_TRACE_MMIO_WRITE 2
+
+#define kvm_trace_symbol_mmio \
+	{ KVM_TRACE_MMIO_READ_UNSATISFIED, "unsatisfied-read" }, \
+	{ KVM_TRACE_MMIO_READ, "read" }, \
+	{ KVM_TRACE_MMIO_WRITE, "write" }
+
+TRACE_EVENT(kvm_mmio,
+	TP_PROTO(int type, int len, u64 gpa, void *val),
+	TP_ARGS(type, len, gpa, val),
+
+	TP_STRUCT__entry(
+		__field(	u32,	type		)
+		__field(	u32,	len		)
+		__field(	u64,	gpa		)
+		__field(	u64,	val		)
+	),
+
+	TP_fast_assign(
+		__entry->type		= type;
+		__entry->len		= len;
+		__entry->gpa		= gpa;
+		__entry->val		= 0;
+		if (val)
+			memcpy(&__entry->val, val,
+			       min_t(u32, sizeof(__entry->val), len));
+	),
+
+	TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx",
+		  __print_symbolic(__entry->type, kvm_trace_symbol_mmio),
+		  __entry->len, __entry->gpa, __entry->val)
+);
+
+#define kvm_fpu_load_symbol	\
+	{0, "unload"},		\
+	{1, "load"}
+
+TRACE_EVENT(kvm_fpu,
+	TP_PROTO(int load),
+	TP_ARGS(load),
+
+	TP_STRUCT__entry(
+		__field(	u32,	        load		)
+	),
+
+	TP_fast_assign(
+		__entry->load		= load;
+	),
+
+	TP_printk("%s", __print_symbolic(__entry->load, kvm_fpu_load_symbol))
+);
+
+#ifdef CONFIG_KVM_ASYNC_PF
+DECLARE_EVENT_CLASS(kvm_async_get_page_class,
+
+	TP_PROTO(u64 gva, u64 gfn),
+
+	TP_ARGS(gva, gfn),
+
+	TP_STRUCT__entry(
+		__field(__u64, gva)
+		__field(u64, gfn)
+	),
+
+	TP_fast_assign(
+		__entry->gva = gva;
+		__entry->gfn = gfn;
+	),
+
+	TP_printk("gva = %#llx, gfn = %#llx", __entry->gva, __entry->gfn)
+);
+
+DEFINE_EVENT(kvm_async_get_page_class, kvm_try_async_get_page,
+
+	TP_PROTO(u64 gva, u64 gfn),
+
+	TP_ARGS(gva, gfn)
+);
+
+DEFINE_EVENT(kvm_async_get_page_class, kvm_async_pf_repeated_fault,
+
+	TP_PROTO(u64 gva, u64 gfn),
+
+	TP_ARGS(gva, gfn)
+);
+
+DECLARE_EVENT_CLASS(kvm_async_pf_nopresent_ready,
+
+	TP_PROTO(u64 token, u64 gva),
+
+	TP_ARGS(token, gva),
+
+	TP_STRUCT__entry(
+		__field(__u64, token)
+		__field(__u64, gva)
+	),
+
+	TP_fast_assign(
+		__entry->token = token;
+		__entry->gva = gva;
+	),
+
+	TP_printk("token %#llx gva %#llx", __entry->token, __entry->gva)
+
+);
+
+DEFINE_EVENT(kvm_async_pf_nopresent_ready, kvm_async_pf_not_present,
+
+	TP_PROTO(u64 token, u64 gva),
+
+	TP_ARGS(token, gva)
+);
+
+DEFINE_EVENT(kvm_async_pf_nopresent_ready, kvm_async_pf_ready,
+
+	TP_PROTO(u64 token, u64 gva),
+
+	TP_ARGS(token, gva)
+);
+
+TRACE_EVENT(
+	kvm_async_pf_completed,
+	TP_PROTO(unsigned long address, u64 gva),
+	TP_ARGS(address, gva),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, address)
+		__field(u64, gva)
+		),
+
+	TP_fast_assign(
+		__entry->address = address;
+		__entry->gva = gva;
+		),
+
+	TP_printk("gva %#llx address %#lx",  __entry->gva,
+		  __entry->address)
+);
+
+#endif
+
+TRACE_EVENT(kvm_halt_poll_ns,
+	TP_PROTO(bool grow, unsigned int vcpu_id, unsigned int new,
+		 unsigned int old),
+	TP_ARGS(grow, vcpu_id, new, old),
+
+	TP_STRUCT__entry(
+		__field(bool, grow)
+		__field(unsigned int, vcpu_id)
+		__field(unsigned int, new)
+		__field(unsigned int, old)
+	),
+
+	TP_fast_assign(
+		__entry->grow           = grow;
+		__entry->vcpu_id        = vcpu_id;
+		__entry->new            = new;
+		__entry->old            = old;
+	),
+
+	TP_printk("vcpu %u: halt_poll_ns %u (%s %u)",
+			__entry->vcpu_id,
+			__entry->new,
+			__entry->grow ? "grow" : "shrink",
+			__entry->old)
+);
+
+#define trace_kvm_halt_poll_ns_grow(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(true, vcpu_id, new, old)
+#define trace_kvm_halt_poll_ns_shrink(vcpu_id, new, old) \
+	trace_kvm_halt_poll_ns(false, vcpu_id, new, old)
+
+TRACE_EVENT(kvm_dirty_ring_push,
+	TP_PROTO(struct kvm_dirty_ring *ring, u32 slot, u64 offset),
+	TP_ARGS(ring, slot, offset),
+
+	TP_STRUCT__entry(
+		__field(int, index)
+		__field(u32, dirty_index)
+		__field(u32, reset_index)
+		__field(u32, slot)
+		__field(u64, offset)
+	),
+
+	TP_fast_assign(
+		__entry->index          = ring->index;
+		__entry->dirty_index    = ring->dirty_index;
+		__entry->reset_index    = ring->reset_index;
+		__entry->slot           = slot;
+		__entry->offset         = offset;
+	),
+
+	TP_printk("ring %d: dirty 0x%x reset 0x%x "
+		  "slot %u offset 0x%llx (used %u)",
+		  __entry->index, __entry->dirty_index,
+		  __entry->reset_index,  __entry->slot, __entry->offset,
+		  __entry->dirty_index - __entry->reset_index)
+);
+
+TRACE_EVENT(kvm_dirty_ring_reset,
+	TP_PROTO(struct kvm_dirty_ring *ring),
+	TP_ARGS(ring),
+
+	TP_STRUCT__entry(
+		__field(int, index)
+		__field(u32, dirty_index)
+		__field(u32, reset_index)
+	),
+
+	TP_fast_assign(
+		__entry->index          = ring->index;
+		__entry->dirty_index    = ring->dirty_index;
+		__entry->reset_index    = ring->reset_index;
+	),
+
+	TP_printk("ring %d: dirty 0x%x reset 0x%x (used %u)",
+		  __entry->index, __entry->dirty_index, __entry->reset_index,
+		  __entry->dirty_index - __entry->reset_index)
+);
+
+TRACE_EVENT(kvm_dirty_ring_exit,
+	TP_PROTO(struct kvm_vcpu *vcpu),
+	TP_ARGS(vcpu),
+
+	TP_STRUCT__entry(
+	    __field(int, vcpu_id)
+	),
+
+	TP_fast_assign(
+	    __entry->vcpu_id = vcpu->vcpu_id;
+	),
+
+	TP_printk("vcpu %d", __entry->vcpu_id)
+);
+
+#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+/*
+ * @start:	Starting address of guest memory range
+ * @end:	End address of guest memory range
+ * @attr:	The value of the attribute being set.
+ */
+TRACE_EVENT(kvm_vm_set_mem_attributes,
+	TP_PROTO(gfn_t start, gfn_t end, unsigned long attr),
+	TP_ARGS(start, end, attr),
+
+	TP_STRUCT__entry(
+		__field(gfn_t,		start)
+		__field(gfn_t,		end)
+		__field(unsigned long,	attr)
+	),
+
+	TP_fast_assign(
+		__entry->start		= start;
+		__entry->end		= end;
+		__entry->attr		= attr;
+	),
+
+	TP_printk("%#016llx -- %#016llx [0x%lx]",
+		  __entry->start, __entry->end, __entry->attr)
+);
+#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+
+TRACE_EVENT(kvm_unmap_hva_range,
+	TP_PROTO(unsigned long start, unsigned long end),
+	TP_ARGS(start, end),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	start		)
+		__field(	unsigned long,	end		)
+	),
+
+	TP_fast_assign(
+		__entry->start		= start;
+		__entry->end		= end;
+	),
+
+	TP_printk("mmu notifier unmap range: %#016lx -- %#016lx",
+		  __entry->start, __entry->end)
+);
+
+TRACE_EVENT(kvm_age_hva,
+	TP_PROTO(unsigned long start, unsigned long end),
+	TP_ARGS(start, end),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	start		)
+		__field(	unsigned long,	end		)
+	),
+
+	TP_fast_assign(
+		__entry->start		= start;
+		__entry->end		= end;
+	),
+
+	TP_printk("mmu notifier age hva: %#016lx -- %#016lx",
+		  __entry->start, __entry->end)
+);
+
+TRACE_EVENT(kvm_test_age_hva,
+	TP_PROTO(unsigned long hva),
+	TP_ARGS(hva),
+
+	TP_STRUCT__entry(
+		__field(	unsigned long,	hva		)
+	),
+
+	TP_fast_assign(
+		__entry->hva		= hva;
+	),
+
+	TP_printk("mmu notifier test age hva: %#016lx", __entry->hva)
+);
+
+#endif /* _TRACE_KVM_MAIN_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>