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, 234 insertions, 0 deletions

diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
new file mode 100755
index 000000000..531c0e0e8
--- /dev/null
+++ b/tools/perf/check-headers.sh
@@ -0,0 +1,234 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+YELLOW='\033[0;33m'
+NC='\033[0m' # No Color
+
+declare -a FILES=(
+  "include/uapi/linux/const.h"
+  "include/uapi/linux/bits.h"
+  "include/uapi/linux/fscrypt.h"
+  "include/uapi/linux/genetlink.h"
+  "include/uapi/linux/if_addr.h"
+  "include/uapi/linux/in.h"
+  "include/uapi/linux/kcmp.h"
+  "include/uapi/linux/kvm.h"
+  "include/uapi/linux/neighbour.h"
+  "include/uapi/linux/netfilter.h"
+  "include/uapi/linux/netfilter_arp.h"
+  "include/uapi/linux/perf_event.h"
+  "include/uapi/linux/rtnetlink.h"
+  "include/uapi/linux/seccomp.h"
+  "include/uapi/linux/stat.h"
+  "include/linux/bits.h"
+  "include/vdso/bits.h"
+  "include/linux/cfi_types.h"
+  "include/linux/const.h"
+  "include/vdso/const.h"
+  "include/vdso/unaligned.h"
+  "include/linux/gfp_types.h"
+  "include/linux/hash.h"
+  "include/linux/list-sort.h"
+  "include/uapi/linux/hw_breakpoint.h"
+  "arch/x86/include/asm/cpufeatures.h"
+  "arch/x86/include/asm/inat_types.h"
+  "arch/x86/include/asm/emulate_prefix.h"
+  "arch/x86/include/asm/msr-index.h"
+  "arch/x86/lib/x86-opcode-map.txt"
+  "arch/x86/tools/gen-insn-attr-x86.awk"
+  "arch/arm/include/uapi/asm/perf_regs.h"
+  "arch/arm64/include/uapi/asm/perf_regs.h"
+  "arch/loongarch/include/uapi/asm/perf_regs.h"
+  "arch/mips/include/uapi/asm/perf_regs.h"
+  "arch/powerpc/include/uapi/asm/perf_regs.h"
+  "arch/s390/include/uapi/asm/perf_regs.h"
+  "arch/x86/include/uapi/asm/perf_regs.h"
+  "arch/x86/include/uapi/asm/kvm.h"
+  "arch/x86/include/uapi/asm/svm.h"
+  "arch/x86/include/uapi/asm/unistd.h"
+  "arch/x86/include/uapi/asm/vmx.h"
+  "arch/powerpc/include/uapi/asm/kvm.h"
+  "arch/s390/include/uapi/asm/kvm.h"
+  "arch/s390/include/uapi/asm/sie.h"
+  "arch/arm64/include/uapi/asm/kvm.h"
+  "arch/alpha/include/uapi/asm/errno.h"
+  "arch/mips/include/asm/errno.h"
+  "arch/mips/include/uapi/asm/errno.h"
+  "arch/parisc/include/uapi/asm/errno.h"
+  "arch/powerpc/include/uapi/asm/errno.h"
+  "arch/sparc/include/uapi/asm/errno.h"
+  "arch/x86/include/uapi/asm/errno.h"
+  "include/asm-generic/bitops/arch_hweight.h"
+  "include/asm-generic/bitops/const_hweight.h"
+  "include/asm-generic/bitops/__fls.h"
+  "include/asm-generic/bitops/fls.h"
+  "include/asm-generic/bitops/fls64.h"
+  "include/linux/coresight-pmu.h"
+  "include/uapi/asm-generic/errno.h"
+  "include/uapi/asm-generic/errno-base.h"
+  "include/uapi/asm-generic/ioctls.h"
+  "include/uapi/asm-generic/mman-common.h"
+  "include/uapi/asm-generic/unistd.h"
+  "scripts/syscall.tbl"
+)
+
+declare -a SYNC_CHECK_FILES=(
+  "arch/x86/include/asm/inat.h"
+  "arch/x86/include/asm/insn.h"
+  "arch/x86/lib/inat.c"
+  "arch/x86/lib/insn.c"
+)
+
+# These copies are under tools/perf/trace/beauty/ as they are not used to in
+# building object files only by scripts in tools/perf/trace/beauty/ to generate
+# tables that then gets included in .c files for things like id->string syscall
+# tables (and the reverse lookup as well: string -> id)
+
+declare -a BEAUTY_FILES=(
+  "arch/x86/include/asm/irq_vectors.h"
+  "arch/x86/include/uapi/asm/prctl.h"
+  "include/uapi/drm/drm.h"
+  "include/uapi/drm/i915_drm.h"
+  "include/linux/socket.h"
+  "include/uapi/linux/fadvise.h"
+  "include/uapi/linux/fcntl.h"
+  "include/uapi/linux/fs.h"
+  "include/uapi/linux/mount.h"
+  "include/uapi/linux/prctl.h"
+  "include/uapi/linux/sched.h"
+  "include/uapi/linux/stat.h"
+  "include/uapi/linux/usbdevice_fs.h"
+  "include/uapi/linux/vhost.h"
+  "include/uapi/sound/asound.h"
+)
+
+declare -a FAILURES
+
+check_2 () {
+  tools_file=$1
+  orig_file=$2
+
+  shift
+  shift
+
+  cmd="diff $* $tools_file $orig_file > /dev/null"
+
+  if [ -f "$orig_file" ] && ! eval "$cmd"
+  then
+    FAILURES+=(
+      "$tools_file $orig_file"
+    )
+  fi
+}
+
+check () {
+  file=$1
+
+  shift
+
+  check_2 "tools/$file" "$file" "$@"
+}
+
+beauty_check () {
+  file=$1
+
+  shift
+
+  check_2 "tools/perf/trace/beauty/$file" "$file" "$@"
+}
+
+check_ignore_some_hunks () {
+  orig_file="$1"
+  tools_file="tools/$orig_file"
+  hunks_to_ignore="tools/perf/check-header_ignore_hunks/$orig_file"
+
+  if [ ! -f "$hunks_to_ignore" ]; then
+    echo "$hunks_to_ignore not found. Skipping $orig_file check."
+    FAILURES+=(
+      "$tools_file $orig_file"
+    )
+    return
+  fi
+
+  cmd="diff -u \"$tools_file\" \"$orig_file\" | grep -vf \"$hunks_to_ignore\" | wc -l | grep -qw 0"
+
+  if [ -f "$orig_file" ] && ! eval "$cmd"
+  then
+    FAILURES+=(
+      "$tools_file $orig_file"
+    )
+  fi
+}
+
+
+# Check if we have the kernel headers (tools/perf/../../include), else
+# we're probably on a detached tarball, so no point in trying to check
+# differences.
+if ! [ -d ../../include ]
+then
+  echo -e "${YELLOW}Warning${NC}: Skipped check-headers due to missing ../../include"
+  exit 0
+fi
+
+cd ../..
+
+# simple diff check
+for i in "${FILES[@]}"
+do
+  check "$i" -B
+done
+
+for i in "${SYNC_CHECK_FILES[@]}"
+do
+  check "$i" '-I "^.*\/\*.*__ignore_sync_check__.*\*\/.*$"'
+done
+
+# diff with extra ignore lines
+check arch/x86/lib/memcpy_64.S        '-I "^EXPORT_SYMBOL" -I "^#include <asm/export.h>" -I"^SYM_FUNC_START\(_LOCAL\)*(memcpy_\(erms\|orig\))" -I"^#include <linux/cfi_types.h>"'
+check arch/x86/lib/memset_64.S        '-I "^EXPORT_SYMBOL" -I "^#include <asm/export.h>" -I"^SYM_FUNC_START\(_LOCAL\)*(memset_\(erms\|orig\))"'
+check arch/x86/include/asm/amd/ibs.h  '-I "^#include .*/msr-index.h"'
+check include/linux/unaligned.h '-I "^#include <linux/unaligned/packed_struct.h>" -I "^#include <asm/byteorder.h>" -I "^#pragma GCC diagnostic"'
+check include/uapi/asm-generic/mman.h '-I "^#include <\(uapi/\)*asm-generic/mman-common\(-tools\)*.h>"'
+check include/uapi/linux/mman.h       '-I "^#include <\(uapi/\)*asm/mman.h>"'
+check include/linux/build_bug.h       '-I "^#\(ifndef\|endif\)\( \/\/\)* static_assert$"'
+check include/linux/ctype.h	      '-I "isdigit("'
+check lib/ctype.c		      '-I "^EXPORT_SYMBOL" -I "^#include <linux/export.h>" -B'
+
+# diff non-symmetric files
+check_2 tools/perf/arch/x86/entry/syscalls/syscall_32.tbl arch/x86/entry/syscalls/syscall_32.tbl
+check_2 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
+check_2 tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl
+check_2 tools/perf/arch/arm/entry/syscalls/syscall.tbl arch/arm/tools/syscall.tbl
+check_2 tools/perf/arch/sh/entry/syscalls/syscall.tbl arch/sh/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/sparc/entry/syscalls/syscall.tbl arch/sparc/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/xtensa/entry/syscalls/syscall.tbl arch/xtensa/kernel/syscalls/syscall.tbl
+check_2 tools/perf/arch/alpha/entry/syscalls/syscall.tbl arch/alpha/entry/syscalls/syscall.tbl
+check_2 tools/perf/arch/parisc/entry/syscalls/syscall.tbl arch/parisc/entry/syscalls/syscall.tbl
+check_2 tools/perf/arch/arm64/entry/syscalls/syscall_32.tbl arch/arm64/entry/syscalls/syscall_32.tbl
+check_2 tools/perf/arch/arm64/entry/syscalls/syscall_64.tbl arch/arm64/entry/syscalls/syscall_64.tbl
+
+for i in "${BEAUTY_FILES[@]}"
+do
+  beauty_check "$i" -B
+done
+
+# check duplicated library files
+check_2 tools/perf/util/hashmap.h tools/lib/bpf/hashmap.h
+check_2 tools/perf/util/hashmap.c tools/lib/bpf/hashmap.c
+
+# Files with larger differences
+
+check_ignore_some_hunks lib/list_sort.c
+
+cd tools/perf || exit
+
+if [ ${#FAILURES[@]} -gt 0 ]
+then
+  echo -e "${YELLOW}Warning${NC}: Kernel ABI header differences:"
+  for i in "${FAILURES[@]}"
+  do
+    echo "  diff -u $i"
+  done
+fi