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, 337 insertions, 0 deletions

diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
new file mode 100644
index 000000000..a6e5a44c9
--- /dev/null
+++ b/include/trace/events/mmflags.h
@@ -0,0 +1,337 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/node.h>
+#include <linux/mmzone.h>
+#include <linux/compaction.h>
+/*
+ * The order of these masks is important. Matching masks will be seen
+ * first and the left over flags will end up showing by themselves.
+ *
+ * For example, if we have GFP_KERNEL before GFP_USER we wil get:
+ *
+ *  GFP_KERNEL|GFP_HARDWALL
+ *
+ * Thus most bits set go first.
+ */
+
+/* These define the values that are enums (the bits) */
+#define TRACE_GFP_FLAGS_GENERAL			\
+	TRACE_GFP_EM(DMA)			\
+	TRACE_GFP_EM(HIGHMEM)			\
+	TRACE_GFP_EM(DMA32)			\
+	TRACE_GFP_EM(MOVABLE)			\
+	TRACE_GFP_EM(RECLAIMABLE)		\
+	TRACE_GFP_EM(HIGH)			\
+	TRACE_GFP_EM(IO)			\
+	TRACE_GFP_EM(FS)			\
+	TRACE_GFP_EM(ZERO)			\
+	TRACE_GFP_EM(DIRECT_RECLAIM)		\
+	TRACE_GFP_EM(KSWAPD_RECLAIM)		\
+	TRACE_GFP_EM(WRITE)			\
+	TRACE_GFP_EM(NOWARN)			\
+	TRACE_GFP_EM(RETRY_MAYFAIL)		\
+	TRACE_GFP_EM(NOFAIL)			\
+	TRACE_GFP_EM(NORETRY)			\
+	TRACE_GFP_EM(MEMALLOC)			\
+	TRACE_GFP_EM(COMP)			\
+	TRACE_GFP_EM(NOMEMALLOC)		\
+	TRACE_GFP_EM(HARDWALL)			\
+	TRACE_GFP_EM(THISNODE)			\
+	TRACE_GFP_EM(ACCOUNT)			\
+	TRACE_GFP_EM(ZEROTAGS)
+
+#ifdef CONFIG_KASAN_HW_TAGS
+# define TRACE_GFP_FLAGS_KASAN			\
+	TRACE_GFP_EM(SKIP_ZERO)			\
+	TRACE_GFP_EM(SKIP_KASAN)
+#else
+# define TRACE_GFP_FLAGS_KASAN
+#endif
+
+#ifdef CONFIG_LOCKDEP
+# define TRACE_GFP_FLAGS_LOCKDEP		\
+	TRACE_GFP_EM(NOLOCKDEP)
+#else
+# define TRACE_GFP_FLAGS_LOCKDEP
+#endif
+
+#ifdef CONFIG_SLAB_OBJ_EXT
+# define TRACE_GFP_FLAGS_SLAB			\
+	TRACE_GFP_EM(NO_OBJ_EXT)
+#else
+# define TRACE_GFP_FLAGS_SLAB
+#endif
+
+#define TRACE_GFP_FLAGS				\
+	TRACE_GFP_FLAGS_GENERAL			\
+	TRACE_GFP_FLAGS_KASAN			\
+	TRACE_GFP_FLAGS_LOCKDEP			\
+	TRACE_GFP_FLAGS_SLAB
+
+#undef TRACE_GFP_EM
+#define TRACE_GFP_EM(a) TRACE_DEFINE_ENUM(___GFP_##a##_BIT);
+
+TRACE_GFP_FLAGS
+
+/* Just in case these are ever used */
+TRACE_DEFINE_ENUM(___GFP_UNUSED_BIT);
+TRACE_DEFINE_ENUM(___GFP_LAST_BIT);
+
+#define gfpflag_string(flag) {(__force unsigned long)flag, #flag}
+
+/*
+ * For the values that match the bits, use the TRACE_GFP_FLAGS
+ * which will allow any updates to be included automatically.
+ */
+#undef TRACE_GFP_EM
+#define TRACE_GFP_EM(a) gfpflag_string(__GFP_##a),
+
+#define __def_gfpflag_names			\
+	gfpflag_string(GFP_TRANSHUGE),		\
+	gfpflag_string(GFP_TRANSHUGE_LIGHT),	\
+	gfpflag_string(GFP_HIGHUSER_MOVABLE),	\
+	gfpflag_string(GFP_HIGHUSER),		\
+	gfpflag_string(GFP_USER),		\
+	gfpflag_string(GFP_KERNEL_ACCOUNT),	\
+	gfpflag_string(GFP_KERNEL),		\
+	gfpflag_string(GFP_NOFS),		\
+	gfpflag_string(GFP_ATOMIC),		\
+	gfpflag_string(GFP_NOIO),		\
+	gfpflag_string(GFP_NOWAIT),		\
+	gfpflag_string(GFP_DMA),		\
+	gfpflag_string(GFP_DMA32),		\
+	gfpflag_string(__GFP_RECLAIM),		\
+	TRACE_GFP_FLAGS				\
+	{ 0, NULL }
+
+#define show_gfp_flags(flags)						\
+	(flags) ? __print_flags(flags, "|", __def_gfpflag_names		\
+	) : "none"
+
+#ifdef CONFIG_MMU
+#define IF_HAVE_PG_MLOCK(_name) ,{1UL << PG_##_name, __stringify(_name)}
+#else
+#define IF_HAVE_PG_MLOCK(_name)
+#endif
+
+#ifdef CONFIG_MEMORY_FAILURE
+#define IF_HAVE_PG_HWPOISON(_name) ,{1UL << PG_##_name, __stringify(_name)}
+#else
+#define IF_HAVE_PG_HWPOISON(_name)
+#endif
+
+#if defined(CONFIG_PAGE_IDLE_FLAG) && defined(CONFIG_64BIT)
+#define IF_HAVE_PG_IDLE(_name) ,{1UL << PG_##_name, __stringify(_name)}
+#else
+#define IF_HAVE_PG_IDLE(_name)
+#endif
+
+#ifdef CONFIG_ARCH_USES_PG_ARCH_2
+#define IF_HAVE_PG_ARCH_2(_name) ,{1UL << PG_##_name, __stringify(_name)}
+#else
+#define IF_HAVE_PG_ARCH_2(_name)
+#endif
+
+#ifdef CONFIG_ARCH_USES_PG_ARCH_3
+#define IF_HAVE_PG_ARCH_3(_name) ,{1UL << PG_##_name, __stringify(_name)}
+#else
+#define IF_HAVE_PG_ARCH_3(_name)
+#endif
+
+#define DEF_PAGEFLAG_NAME(_name) { 1UL <<  PG_##_name, __stringify(_name) }
+
+#define __def_pageflag_names						\
+	DEF_PAGEFLAG_NAME(locked),					\
+	DEF_PAGEFLAG_NAME(waiters),					\
+	DEF_PAGEFLAG_NAME(referenced),					\
+	DEF_PAGEFLAG_NAME(uptodate),					\
+	DEF_PAGEFLAG_NAME(dirty),					\
+	DEF_PAGEFLAG_NAME(lru),						\
+	DEF_PAGEFLAG_NAME(active),					\
+	DEF_PAGEFLAG_NAME(workingset),					\
+	DEF_PAGEFLAG_NAME(owner_priv_1),				\
+	DEF_PAGEFLAG_NAME(owner_2),					\
+	DEF_PAGEFLAG_NAME(arch_1),					\
+	DEF_PAGEFLAG_NAME(reserved),					\
+	DEF_PAGEFLAG_NAME(private),					\
+	DEF_PAGEFLAG_NAME(private_2),					\
+	DEF_PAGEFLAG_NAME(writeback),					\
+	DEF_PAGEFLAG_NAME(head),					\
+	DEF_PAGEFLAG_NAME(reclaim),					\
+	DEF_PAGEFLAG_NAME(swapbacked),					\
+	DEF_PAGEFLAG_NAME(unevictable),					\
+	DEF_PAGEFLAG_NAME(dropbehind)					\
+IF_HAVE_PG_MLOCK(mlocked)						\
+IF_HAVE_PG_HWPOISON(hwpoison)						\
+IF_HAVE_PG_IDLE(idle)							\
+IF_HAVE_PG_IDLE(young)							\
+IF_HAVE_PG_ARCH_2(arch_2)						\
+IF_HAVE_PG_ARCH_3(arch_3)
+
+#define show_page_flags(flags)						\
+	(flags) ? __print_flags(flags, "|",				\
+	__def_pageflag_names						\
+	) : "none"
+
+#if defined(CONFIG_PPC64)
+#define __VM_ARCH_SPECIFIC_1 {VM_SAO,     "sao"           }
+#elif defined(CONFIG_PARISC)
+#define __VM_ARCH_SPECIFIC_1 {VM_GROWSUP,	"growsup"	}
+#elif !defined(CONFIG_MMU)
+#define __VM_ARCH_SPECIFIC_1 {VM_MAPPED_COPY,"mappedcopy"	}
+#else
+#define __VM_ARCH_SPECIFIC_1 {VM_ARCH_1,	"arch_1"	}
+#endif
+
+#ifdef CONFIG_MEM_SOFT_DIRTY
+#define IF_HAVE_VM_SOFTDIRTY(flag,name) {flag, name },
+#else
+#define IF_HAVE_VM_SOFTDIRTY(flag,name)
+#endif
+
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
+# define IF_HAVE_UFFD_MINOR(flag, name) {flag, name},
+#else
+# define IF_HAVE_UFFD_MINOR(flag, name)
+#endif
+
+#if defined(CONFIG_64BIT) || defined(CONFIG_PPC32)
+# define IF_HAVE_VM_DROPPABLE(flag, name) {flag, name},
+#else
+# define IF_HAVE_VM_DROPPABLE(flag, name)
+#endif
+
+#define __def_vmaflag_names						\
+	{VM_READ,			"read"		},		\
+	{VM_WRITE,			"write"		},		\
+	{VM_EXEC,			"exec"		},		\
+	{VM_SHARED,			"shared"	},		\
+	{VM_MAYREAD,			"mayread"	},		\
+	{VM_MAYWRITE,			"maywrite"	},		\
+	{VM_MAYEXEC,			"mayexec"	},		\
+	{VM_MAYSHARE,			"mayshare"	},		\
+	{VM_GROWSDOWN,			"growsdown"	},		\
+	{VM_UFFD_MISSING,		"uffd_missing"	},		\
+IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR,	"uffd_minor"	)		\
+	{VM_PFNMAP,			"pfnmap"	},		\
+	{VM_MAYBE_GUARD,		"maybe_guard"	},		\
+	{VM_UFFD_WP,			"uffd_wp"	},		\
+	{VM_LOCKED,			"locked"	},		\
+	{VM_IO,				"io"		},		\
+	{VM_SEQ_READ,			"seqread"	},		\
+	{VM_RAND_READ,			"randread"	},		\
+	{VM_DONTCOPY,			"dontcopy"	},		\
+	{VM_DONTEXPAND,			"dontexpand"	},		\
+	{VM_LOCKONFAULT,		"lockonfault"	},		\
+	{VM_ACCOUNT,			"account"	},		\
+	{VM_NORESERVE,			"noreserve"	},		\
+	{VM_HUGETLB,			"hugetlb"	},		\
+	{VM_SYNC,			"sync"		},		\
+	__VM_ARCH_SPECIFIC_1				,		\
+	{VM_WIPEONFORK,			"wipeonfork"	},		\
+	{VM_DONTDUMP,			"dontdump"	},		\
+IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY,	"softdirty"	)		\
+	{VM_MIXEDMAP,			"mixedmap"	},		\
+	{VM_HUGEPAGE,			"hugepage"	},		\
+	{VM_NOHUGEPAGE,			"nohugepage"	},		\
+IF_HAVE_VM_DROPPABLE(VM_DROPPABLE,	"droppable"	)		\
+	{VM_MERGEABLE,			"mergeable"	}		\
+
+#define show_vma_flags(flags)						\
+	(flags) ? __print_flags(flags, "|",				\
+	__def_vmaflag_names						\
+	) : "none"
+
+#ifdef CONFIG_COMPACTION
+#define COMPACTION_STATUS					\
+	EM( COMPACT_SKIPPED,		"skipped")		\
+	EM( COMPACT_DEFERRED,		"deferred")		\
+	EM( COMPACT_CONTINUE,		"continue")		\
+	EM( COMPACT_SUCCESS,		"success")		\
+	EM( COMPACT_PARTIAL_SKIPPED,	"partial_skipped")	\
+	EM( COMPACT_COMPLETE,		"complete")		\
+	EM( COMPACT_NO_SUITABLE_PAGE,	"no_suitable_page")	\
+	EM( COMPACT_NOT_SUITABLE_ZONE,	"not_suitable_zone")	\
+	EMe(COMPACT_CONTENDED,		"contended")
+
+/* High-level compaction status feedback */
+#define COMPACTION_FAILED	1
+#define COMPACTION_WITHDRAWN	2
+#define COMPACTION_PROGRESS	3
+
+#define compact_result_to_feedback(result)	\
+({						\
+	enum compact_result __result = result;	\
+	(__result == COMPACT_COMPLETE) ? COMPACTION_FAILED : \
+		(__result == COMPACT_SUCCESS) ? COMPACTION_PROGRESS : COMPACTION_WITHDRAWN; \
+})
+
+#define COMPACTION_FEEDBACK		\
+	EM(COMPACTION_FAILED,		"failed")	\
+	EM(COMPACTION_WITHDRAWN,	"withdrawn")	\
+	EMe(COMPACTION_PROGRESS,	"progress")
+
+#define COMPACTION_PRIORITY						\
+	EM(COMPACT_PRIO_SYNC_FULL,	"COMPACT_PRIO_SYNC_FULL")	\
+	EM(COMPACT_PRIO_SYNC_LIGHT,	"COMPACT_PRIO_SYNC_LIGHT")	\
+	EMe(COMPACT_PRIO_ASYNC,		"COMPACT_PRIO_ASYNC")
+#else
+#define COMPACTION_STATUS
+#define COMPACTION_PRIORITY
+#define COMPACTION_FEEDBACK
+#endif
+
+#ifdef CONFIG_ZONE_DMA
+#define IFDEF_ZONE_DMA(X) X
+#else
+#define IFDEF_ZONE_DMA(X)
+#endif
+
+#ifdef CONFIG_ZONE_DMA32
+#define IFDEF_ZONE_DMA32(X) X
+#else
+#define IFDEF_ZONE_DMA32(X)
+#endif
+
+#ifdef CONFIG_HIGHMEM
+#define IFDEF_ZONE_HIGHMEM(X) X
+#else
+#define IFDEF_ZONE_HIGHMEM(X)
+#endif
+
+#define ZONE_TYPE						\
+	IFDEF_ZONE_DMA(		EM (ZONE_DMA,	 "DMA"))	\
+	IFDEF_ZONE_DMA32(	EM (ZONE_DMA32,	 "DMA32"))	\
+				EM (ZONE_NORMAL, "Normal")	\
+	IFDEF_ZONE_HIGHMEM(	EM (ZONE_HIGHMEM,"HighMem"))	\
+				EMe(ZONE_MOVABLE,"Movable")
+
+#define LRU_NAMES		\
+		EM (LRU_INACTIVE_ANON, "inactive_anon") \
+		EM (LRU_ACTIVE_ANON, "active_anon") \
+		EM (LRU_INACTIVE_FILE, "inactive_file") \
+		EM (LRU_ACTIVE_FILE, "active_file") \
+		EMe(LRU_UNEVICTABLE, "unevictable")
+
+/*
+ * First define the enums in the above macros to be exported to userspace
+ * via TRACE_DEFINE_ENUM().
+ */
+#undef EM
+#undef EMe
+#define EM(a, b)	TRACE_DEFINE_ENUM(a);
+#define EMe(a, b)	TRACE_DEFINE_ENUM(a);
+
+COMPACTION_STATUS
+COMPACTION_PRIORITY
+/* COMPACTION_FEEDBACK are defines not enums. Not needed here. */
+ZONE_TYPE
+LRU_NAMES
+
+/*
+ * Now redefine the EM() and EMe() macros to map the enums to the strings
+ * that will be printed in the output.
+ */
+#undef EM
+#undef EMe
+#define EM(a, b)	{a, b},
+#define EMe(a, b)	{a, b}