From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- scripts/extract-vmlinux | 65 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100755 scripts/extract-vmlinux (limited to 'scripts/extract-vmlinux') diff --git a/scripts/extract-vmlinux b/scripts/extract-vmlinux new file mode 100755 index 000000000..266df9bc7 --- /dev/null +++ b/scripts/extract-vmlinux @@ -0,0 +1,65 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-only +# ---------------------------------------------------------------------- +# extract-vmlinux - Extract uncompressed vmlinux from a kernel image +# +# Inspired from extract-ikconfig +# (c) 2009,2010 Dick Streefland +# +# (c) 2011 Corentin Chary +# +# ---------------------------------------------------------------------- + +me=${0##*/} + +check_vmlinux() +{ + if file "$1" | grep -q 'Linux kernel.*boot executable' || + readelf -h "$1" > /dev/null 2>&1 + then + cat "$1" + echo "$me: Extracted vmlinux using '$2' from offset $3" >&2 + exit 0 + fi +} + +try_decompress() +{ + # The obscure use of the "tr" filter is to work around older versions of + # "grep" that report the byte offset of the line instead of the pattern. + + # Try to find the header ($1) and decompress from here + for pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"` + do + pos=${pos%%:*} + tail -c+$pos "$img" | $3 > $tmp 2> /dev/null + check_vmlinux $tmp "$3" $pos + done +} + +# Check invocation: +img=$1 +if [ $# -ne 1 -o ! -s "$img" ] +then + echo "Usage: $me " >&2 + exit 2 +fi + +# Prepare temp files: +tmp=$(mktemp /tmp/vmlinux-XXX) +trap "rm -f $tmp" 0 + +# That didn't work, so retry after decompression. +try_decompress '\037\213\010' xy gunzip +try_decompress '\3757zXZ\000' abcde unxz +try_decompress 'BZh' xy bunzip2 +try_decompress '\135\0\0\0' xxx unlzma +try_decompress '\211\114\132' xy 'lzop -d' +try_decompress '\002!L\030' xxx 'lz4 -d' +try_decompress '(\265/\375' xxx unzstd + +# Finally check for uncompressed images or objects: +check_vmlinux "$img" cat 0 + +# Bail out: +echo "$me: Cannot find vmlinux." >&2 -- cgit v1.3.1