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, 408 insertions, 0 deletions

diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
new file mode 100644
index 000000000..ad384969e
--- /dev/null
+++ b/include/trace/events/xen.h
@@ -0,0 +1,408 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM xen
+
+#if !defined(_TRACE_XEN_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_XEN_H
+
+#include <linux/tracepoint.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/trace_types.h>
+
+struct multicall_entry;
+
+/* Multicalls */
+TRACE_EVENT(xen_mc_batch,
+	    TP_PROTO(unsigned long flags),
+	    TP_ARGS(flags),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, flags)
+		    ),
+	    TP_fast_assign(__entry->flags = flags),
+	    TP_printk("start batch lazy flags %lx", __entry->flags)
+	);
+
+TRACE_EVENT(xen_mc_issue,
+	    TP_PROTO(bool flush, unsigned long flags),
+	    TP_ARGS(flush, flags),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, flags)
+		    __field(bool, flush)
+		    ),
+	    TP_fast_assign(__entry->flush = flush;
+			   __entry->flags = flags;
+		    ),
+	    TP_printk("flush: %s, flags %lx",
+		      __entry->flush ? "yes" : "no", __entry->flags)
+	);
+
+TRACE_DEFINE_SIZEOF(ulong);
+
+TRACE_EVENT(xen_mc_entry,
+	    TP_PROTO(struct multicall_entry *mc, unsigned nargs),
+	    TP_ARGS(mc, nargs),
+	    TP_STRUCT__entry(
+		    __field(unsigned int, op)
+		    __field(unsigned int, nargs)
+		    __array(unsigned long, args, 6)
+		    ),
+	    TP_fast_assign(__entry->op = mc->op;
+			   __entry->nargs = nargs;
+			   memcpy(__entry->args, mc->args, sizeof(ulong) * nargs);
+			   memset(__entry->args + nargs, 0, sizeof(ulong) * (6 - nargs));
+		    ),
+	    TP_printk("op %u%s args [%lx, %lx, %lx, %lx, %lx, %lx]",
+		      __entry->op, xen_hypercall_name(__entry->op),
+		      __entry->args[0], __entry->args[1], __entry->args[2],
+		      __entry->args[3], __entry->args[4], __entry->args[5])
+	);
+
+TRACE_EVENT(xen_mc_entry_alloc,
+	    TP_PROTO(size_t args),
+	    TP_ARGS(args),
+	    TP_STRUCT__entry(
+		    __field(size_t, args)
+		    ),
+	    TP_fast_assign(__entry->args = args),
+	    TP_printk("alloc entry %zu arg bytes", __entry->args)
+	);
+
+TRACE_EVENT(xen_mc_callback,
+	    TP_PROTO(xen_mc_callback_fn_t fn, void *data),
+	    TP_ARGS(fn, data),
+	    TP_STRUCT__entry(
+		    /*
+		     * Use field_struct to avoid is_signed_type()
+		     * comparison of a function pointer.
+		     */
+		    __field_struct(xen_mc_callback_fn_t, fn)
+		    __field(void *, data)
+		    ),
+	    TP_fast_assign(
+		    __entry->fn = fn;
+		    __entry->data = data;
+		    ),
+	    TP_printk("callback %ps, data %p",
+		      __entry->fn, __entry->data)
+	);
+
+TRACE_EVENT(xen_mc_flush_reason,
+	    TP_PROTO(enum xen_mc_flush_reason reason),
+	    TP_ARGS(reason),
+	    TP_STRUCT__entry(
+		    __field(enum xen_mc_flush_reason, reason)
+		    ),
+	    TP_fast_assign(__entry->reason = reason),
+	    TP_printk("flush reason %s",
+		      (__entry->reason == XEN_MC_FL_NONE) ? "NONE" :
+		      (__entry->reason == XEN_MC_FL_BATCH) ? "BATCH" :
+		      (__entry->reason == XEN_MC_FL_ARGS) ? "ARGS" :
+		      (__entry->reason == XEN_MC_FL_CALLBACK) ? "CALLBACK" : "??")
+	);
+
+TRACE_EVENT(xen_mc_flush,
+	    TP_PROTO(unsigned mcidx, unsigned argidx, unsigned cbidx),
+	    TP_ARGS(mcidx, argidx, cbidx),
+	    TP_STRUCT__entry(
+		    __field(unsigned, mcidx)
+		    __field(unsigned, argidx)
+		    __field(unsigned, cbidx)
+		    ),
+	    TP_fast_assign(__entry->mcidx = mcidx;
+			   __entry->argidx = argidx;
+			   __entry->cbidx = cbidx),
+	    TP_printk("flushing %u hypercalls, %u arg bytes, %u callbacks",
+		      __entry->mcidx, __entry->argidx, __entry->cbidx)
+	);
+
+TRACE_EVENT(xen_mc_extend_args,
+	    TP_PROTO(unsigned long op, size_t args, enum xen_mc_extend_args res),
+	    TP_ARGS(op, args, res),
+	    TP_STRUCT__entry(
+		    __field(unsigned int, op)
+		    __field(size_t, args)
+		    __field(enum xen_mc_extend_args, res)
+		    ),
+	    TP_fast_assign(__entry->op = op;
+			   __entry->args = args;
+			   __entry->res = res),
+	    TP_printk("extending op %u%s by %zu bytes res %s",
+		      __entry->op, xen_hypercall_name(__entry->op),
+		      __entry->args,
+		      __entry->res == XEN_MC_XE_OK ? "OK" :
+		      __entry->res == XEN_MC_XE_BAD_OP ? "BAD_OP" :
+		      __entry->res == XEN_MC_XE_NO_SPACE ? "NO_SPACE" : "???")
+	);
+
+/* mmu */
+TRACE_DEFINE_SIZEOF(pteval_t);
+
+TRACE_EVENT(xen_mmu_set_pte,
+	    TP_PROTO(pte_t *ptep, pte_t pteval),
+	    TP_ARGS(ptep, pteval),
+	    TP_STRUCT__entry(
+		    __field(pte_t *, ptep)
+		    __field(pteval_t, pteval)
+		    ),
+	    TP_fast_assign(__entry->ptep = ptep;
+			   __entry->pteval = pteval.pte),
+	    TP_printk("ptep %p pteval %0*llx (raw %0*llx)",
+		      __entry->ptep,
+		      (int)sizeof(pteval_t) * 2, (unsigned long long)pte_val(native_make_pte(__entry->pteval)),
+		      (int)sizeof(pteval_t) * 2, (unsigned long long)__entry->pteval)
+	);
+
+TRACE_DEFINE_SIZEOF(pmdval_t);
+
+TRACE_EVENT(xen_mmu_set_pmd,
+	    TP_PROTO(pmd_t *pmdp, pmd_t pmdval),
+	    TP_ARGS(pmdp, pmdval),
+	    TP_STRUCT__entry(
+		    __field(pmd_t *, pmdp)
+		    __field(pmdval_t, pmdval)
+		    ),
+	    TP_fast_assign(__entry->pmdp = pmdp;
+			   __entry->pmdval = pmdval.pmd),
+	    TP_printk("pmdp %p pmdval %0*llx (raw %0*llx)",
+		      __entry->pmdp,
+		      (int)sizeof(pmdval_t) * 2, (unsigned long long)pmd_val(native_make_pmd(__entry->pmdval)),
+		      (int)sizeof(pmdval_t) * 2, (unsigned long long)__entry->pmdval)
+	);
+
+TRACE_DEFINE_SIZEOF(pudval_t);
+
+TRACE_EVENT(xen_mmu_set_pud,
+	    TP_PROTO(pud_t *pudp, pud_t pudval),
+	    TP_ARGS(pudp, pudval),
+	    TP_STRUCT__entry(
+		    __field(pud_t *, pudp)
+		    __field(pudval_t, pudval)
+		    ),
+	    TP_fast_assign(__entry->pudp = pudp;
+			   __entry->pudval = native_pud_val(pudval)),
+	    TP_printk("pudp %p pudval %0*llx (raw %0*llx)",
+		      __entry->pudp,
+		      (int)sizeof(pudval_t) * 2, (unsigned long long)pud_val(native_make_pud(__entry->pudval)),
+		      (int)sizeof(pudval_t) * 2, (unsigned long long)__entry->pudval)
+	);
+
+TRACE_DEFINE_SIZEOF(p4dval_t);
+
+TRACE_EVENT(xen_mmu_set_p4d,
+	    TP_PROTO(p4d_t *p4dp, p4d_t *user_p4dp, p4d_t p4dval),
+	    TP_ARGS(p4dp, user_p4dp, p4dval),
+	    TP_STRUCT__entry(
+		    __field(p4d_t *, p4dp)
+		    __field(p4d_t *, user_p4dp)
+		    __field(p4dval_t, p4dval)
+		    ),
+	    TP_fast_assign(__entry->p4dp = p4dp;
+			   __entry->user_p4dp = user_p4dp;
+			   __entry->p4dval = p4d_val(p4dval)),
+	    TP_printk("p4dp %p user_p4dp %p p4dval %0*llx (raw %0*llx)",
+		      __entry->p4dp, __entry->user_p4dp,
+		      (int)sizeof(p4dval_t) * 2, (unsigned long long)pgd_val(native_make_pgd(__entry->p4dval)),
+		      (int)sizeof(p4dval_t) * 2, (unsigned long long)__entry->p4dval)
+	);
+
+DECLARE_EVENT_CLASS(xen_mmu_ptep_modify_prot,
+	    TP_PROTO(struct mm_struct *mm, unsigned long addr,
+		     pte_t *ptep, pte_t pteval),
+	    TP_ARGS(mm, addr, ptep, pteval),
+	    TP_STRUCT__entry(
+		    __field(struct mm_struct *, mm)
+		    __field(unsigned long, addr)
+		    __field(pte_t *, ptep)
+		    __field(pteval_t, pteval)
+		    ),
+	    TP_fast_assign(__entry->mm = mm;
+			   __entry->addr = addr;
+			   __entry->ptep = ptep;
+			   __entry->pteval = pteval.pte),
+	    TP_printk("mm %p addr %lx ptep %p pteval %0*llx (raw %0*llx)",
+		      __entry->mm, __entry->addr, __entry->ptep,
+		      (int)sizeof(pteval_t) * 2, (unsigned long long)pte_val(native_make_pte(__entry->pteval)),
+		      (int)sizeof(pteval_t) * 2, (unsigned long long)__entry->pteval)
+	);
+#define DEFINE_XEN_MMU_PTEP_MODIFY_PROT(name)				\
+	DEFINE_EVENT(xen_mmu_ptep_modify_prot, name,			\
+		     TP_PROTO(struct mm_struct *mm, unsigned long addr,	\
+			      pte_t *ptep, pte_t pteval),		\
+		     TP_ARGS(mm, addr, ptep, pteval))
+
+DEFINE_XEN_MMU_PTEP_MODIFY_PROT(xen_mmu_ptep_modify_prot_start);
+DEFINE_XEN_MMU_PTEP_MODIFY_PROT(xen_mmu_ptep_modify_prot_commit);
+
+TRACE_EVENT(xen_mmu_alloc_ptpage,
+	    TP_PROTO(struct mm_struct *mm, unsigned long pfn, unsigned level, bool pinned),
+	    TP_ARGS(mm, pfn, level, pinned),
+	    TP_STRUCT__entry(
+		    __field(struct mm_struct *, mm)
+		    __field(unsigned long, pfn)
+		    __field(unsigned, level)
+		    __field(bool, pinned)
+		    ),
+	    TP_fast_assign(__entry->mm = mm;
+			   __entry->pfn = pfn;
+			   __entry->level = level;
+			   __entry->pinned = pinned),
+	    TP_printk("mm %p  pfn %lx  level %d  %spinned",
+		      __entry->mm, __entry->pfn, __entry->level,
+		      __entry->pinned ? "" : "un")
+	);
+
+TRACE_EVENT(xen_mmu_release_ptpage,
+	    TP_PROTO(unsigned long pfn, unsigned level, bool pinned),
+	    TP_ARGS(pfn, level, pinned),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, pfn)
+		    __field(unsigned, level)
+		    __field(bool, pinned)
+		    ),
+	    TP_fast_assign(__entry->pfn = pfn;
+			   __entry->level = level;
+			   __entry->pinned = pinned),
+	    TP_printk("pfn %lx  level %d  %spinned",
+		      __entry->pfn, __entry->level,
+		      __entry->pinned ? "" : "un")
+	);
+
+DECLARE_EVENT_CLASS(xen_mmu_pgd,
+	    TP_PROTO(struct mm_struct *mm, pgd_t *pgd),
+	    TP_ARGS(mm, pgd),
+	    TP_STRUCT__entry(
+		    __field(struct mm_struct *, mm)
+		    __field(pgd_t *, pgd)
+		    ),
+	    TP_fast_assign(__entry->mm = mm;
+			   __entry->pgd = pgd),
+	    TP_printk("mm %p pgd %p", __entry->mm, __entry->pgd)
+	);
+#define DEFINE_XEN_MMU_PGD_EVENT(name)				\
+	DEFINE_EVENT(xen_mmu_pgd, name,				\
+		TP_PROTO(struct mm_struct *mm, pgd_t *pgd),	\
+		     TP_ARGS(mm, pgd))
+
+DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_pin);
+DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_unpin);
+
+TRACE_EVENT(xen_mmu_flush_tlb_one_user,
+	    TP_PROTO(unsigned long addr),
+	    TP_ARGS(addr),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, addr)
+		    ),
+	    TP_fast_assign(__entry->addr = addr),
+	    TP_printk("addr %lx", __entry->addr)
+	);
+
+TRACE_EVENT(xen_mmu_flush_tlb_multi,
+	    TP_PROTO(const struct cpumask *cpus, struct mm_struct *mm,
+		     unsigned long addr, unsigned long end),
+	    TP_ARGS(cpus, mm, addr, end),
+	    TP_STRUCT__entry(
+		    __field(unsigned, ncpus)
+		    __field(struct mm_struct *, mm)
+		    __field(unsigned long, addr)
+		    __field(unsigned long, end)
+		    ),
+	    TP_fast_assign(__entry->ncpus = cpumask_weight(cpus);
+			   __entry->mm = mm;
+			   __entry->addr = addr,
+			   __entry->end = end),
+	    TP_printk("ncpus %d mm %p addr %lx, end %lx",
+		      __entry->ncpus, __entry->mm, __entry->addr, __entry->end)
+	);
+
+TRACE_EVENT(xen_mmu_write_cr3,
+	    TP_PROTO(bool kernel, unsigned long cr3),
+	    TP_ARGS(kernel, cr3),
+	    TP_STRUCT__entry(
+		    __field(bool, kernel)
+		    __field(unsigned long, cr3)
+		    ),
+	    TP_fast_assign(__entry->kernel = kernel;
+			   __entry->cr3 = cr3),
+	    TP_printk("%s cr3 %lx",
+		      __entry->kernel ? "kernel" : "user", __entry->cr3)
+	);
+
+
+/* CPU */
+TRACE_EVENT(xen_cpu_write_ldt_entry,
+	    TP_PROTO(struct desc_struct *dt, int entrynum, u64 desc),
+	    TP_ARGS(dt, entrynum, desc),
+	    TP_STRUCT__entry(
+		    __field(struct desc_struct *, dt)
+		    __field(int, entrynum)
+		    __field(u64, desc)
+		    ),
+	    TP_fast_assign(__entry->dt = dt;
+			   __entry->entrynum = entrynum;
+			   __entry->desc = desc;
+		    ),
+	    TP_printk("dt %p  entrynum %d  entry %016llx",
+		      __entry->dt, __entry->entrynum,
+		      (unsigned long long)__entry->desc)
+	);
+
+TRACE_EVENT(xen_cpu_write_idt_entry,
+	    TP_PROTO(gate_desc *dt, int entrynum, const gate_desc *ent),
+	    TP_ARGS(dt, entrynum, ent),
+	    TP_STRUCT__entry(
+		    __field(gate_desc *, dt)
+		    __field(int, entrynum)
+		    ),
+	    TP_fast_assign(__entry->dt = dt;
+			   __entry->entrynum = entrynum;
+		    ),
+	    TP_printk("dt %p  entrynum %d",
+		      __entry->dt, __entry->entrynum)
+	);
+
+TRACE_EVENT(xen_cpu_load_idt,
+	    TP_PROTO(const struct desc_ptr *desc),
+	    TP_ARGS(desc),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, addr)
+		    ),
+	    TP_fast_assign(__entry->addr = desc->address),
+	    TP_printk("addr %lx", __entry->addr)
+	);
+
+TRACE_EVENT(xen_cpu_write_gdt_entry,
+	    TP_PROTO(struct desc_struct *dt, int entrynum, const void *desc, int type),
+	    TP_ARGS(dt, entrynum, desc, type),
+	    TP_STRUCT__entry(
+		    __field(u64, desc)
+		    __field(struct desc_struct *, dt)
+		    __field(int, entrynum)
+		    __field(int, type)
+		    ),
+	    TP_fast_assign(__entry->dt = dt;
+			   __entry->entrynum = entrynum;
+			   __entry->desc = *(u64 *)desc;
+			   __entry->type = type;
+		    ),
+	    TP_printk("dt %p  entrynum %d  type %d  desc %016llx",
+		      __entry->dt, __entry->entrynum, __entry->type,
+		      (unsigned long long)__entry->desc)
+	);
+
+TRACE_EVENT(xen_cpu_set_ldt,
+	    TP_PROTO(const void *addr, unsigned entries),
+	    TP_ARGS(addr, entries),
+	    TP_STRUCT__entry(
+		    __field(const void *, addr)
+		    __field(unsigned, entries)
+		    ),
+	    TP_fast_assign(__entry->addr = addr;
+			   __entry->entries = entries),
+	    TP_printk("addr %p  entries %u",
+		      __entry->addr, __entry->entries)
+	);
+
+#endif /*  _TRACE_XEN_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>