Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 943 insertions, 0 deletions

diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
new file mode 100755
index 000000000..b52a8489d
--- /dev/null
+++ b/scripts/livepatch/klp-build
@@ -0,0 +1,943 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Build a livepatch module
+
+# shellcheck disable=SC1090,SC2155,SC2164
+
+if (( BASH_VERSINFO[0]  < 4 || \
+     (BASH_VERSINFO[0] == 4 && BASH_VERSINFO[1] < 4) )); then
+		echo "error: this script requires bash 4.4+" >&2
+	exit 1
+fi
+
+set -o errtrace
+set -o pipefail
+set -o nounset
+
+# Allow doing 'cmd | mapfile -t array' instead of 'mapfile -t array < <(cmd)'.
+# This helps keep execution in pipes so pipefail+ERR trap can catch errors.
+shopt -s lastpipe
+
+unset DEBUG_CLONE DIFF_CHECKSUM SKIP_CLEANUP VERBOSE XTRACE
+
+REPLACE=1
+SHORT_CIRCUIT=0
+JOBS="$(getconf _NPROCESSORS_ONLN)"
+shopt -o xtrace | grep -q 'on' && XTRACE=1
+
+# Avoid removing the previous $TMP_DIR until args have been fully processed.
+KEEP_TMP=1
+
+SCRIPT="$(basename "$0")"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+FIX_PATCH_LINES="$SCRIPT_DIR/fix-patch-lines"
+
+OBJTOOL="$PWD/tools/objtool/objtool"
+CONFIG="$PWD/.config"
+TMP_DIR="$PWD/klp-tmp"
+
+ORIG_DIR="$TMP_DIR/1-orig"
+PATCHED_DIR="$TMP_DIR/2-patched"
+ORIG_CSUM_DIR="$TMP_DIR/3-checksum-orig"
+PATCHED_CSUM_DIR="$TMP_DIR/3-checksum-patched"
+DIFF_DIR="$TMP_DIR/4-diff"
+KMOD_DIR="$TMP_DIR/5-kmod"
+
+STASH_DIR="$TMP_DIR/stash"
+TIMESTAMP="$TMP_DIR/timestamp"
+PATCH_TMP_DIR="$TMP_DIR/tmp"
+
+KLP_DIFF_LOG="$DIFF_DIR/diff.log"
+
+# Terminal output colors
+read -r COLOR_RESET COLOR_BOLD COLOR_ERROR COLOR_WARN <<< ""
+if [[ -t 1 && -t 2 ]]; then
+	COLOR_RESET="\033[0m"
+	COLOR_BOLD="\033[1m"
+	COLOR_ERROR="\033[0;31m"
+	COLOR_WARN="\033[0;33m"
+fi
+
+grep0() {
+	# shellcheck disable=SC2317
+	command grep "$@" || true
+}
+
+# Because pipefail is enabled, the grep0 helper should be used instead of
+# grep, otherwise a failed match can propagate to an error.
+grep() {
+	echo "error: $SCRIPT: use grep0 or 'command grep' instead of bare grep" >&2
+	exit 1
+}
+
+status() {
+	echo -e "${COLOR_BOLD}$*${COLOR_RESET}"
+}
+
+warn() {
+	echo -e "${COLOR_WARN}warning${COLOR_RESET}: $SCRIPT: $*" >&2
+}
+
+die() {
+	echo -e "${COLOR_ERROR}error${COLOR_RESET}: $SCRIPT: $*" >&2
+	exit 1
+}
+
+declare -a STASHED_FILES
+
+stash_file() {
+	local file="$1"
+	local rel_file="${file#"$PWD"/}"
+
+	[[ ! -e "$file" ]] && die "no file to stash: $file"
+
+	mkdir -p "$STASH_DIR/$(dirname "$rel_file")"
+	cp -f "$file" "$STASH_DIR/$rel_file"
+
+	STASHED_FILES+=("$rel_file")
+}
+
+restore_files() {
+	local file
+
+	for file in "${STASHED_FILES[@]}"; do
+		mv -f "$STASH_DIR/$file" "$PWD/$file" || warn "can't restore file: $file"
+	done
+
+	STASHED_FILES=()
+}
+
+cleanup() {
+	set +o nounset
+	revert_patches
+	restore_files
+	[[ "$KEEP_TMP" -eq 0 ]] && rm -rf "$TMP_DIR"
+	return 0
+}
+
+trap_err() {
+	die "line ${BASH_LINENO[0]}: '$BASH_COMMAND'"
+}
+
+trap cleanup  EXIT INT TERM HUP
+trap trap_err ERR
+
+__usage() {
+	cat <<EOF
+Usage: $SCRIPT [OPTIONS] PATCH_FILE(s)
+Generate a livepatch module.
+
+Options:
+   -f, --show-first-changed	Show address of first changed instruction
+   -j, --jobs=<jobs>		Build jobs to run simultaneously [default: $JOBS]
+   -o, --output=<file.ko>	Output file [default: livepatch-<patch-name>.ko]
+       --no-replace		Disable livepatch atomic replace
+   -v, --verbose		Pass V=1 to kernel/module builds
+
+Advanced Options:
+   -d, --debug			Show symbol/reloc cloning decisions
+   -S, --short-circuit=STEP	Start at build step (requires prior --keep-tmp)
+				   1|orig		Build original kernel (default)
+				   2|patched		Build patched kernel
+				   3|checksum		Generate checksums
+				   4|diff		Diff objects
+				   5|kmod		Build patch module
+   -T, --keep-tmp		Preserve tmp dir on exit
+
+EOF
+}
+
+usage() {
+	__usage >&2
+}
+
+process_args() {
+	local keep_tmp=0
+	local short
+	local long
+	local args
+	local patch
+
+	short="hfj:o:vdS:T"
+	long="help,show-first-changed,jobs:,output:,no-replace,verbose,debug,short-circuit:,keep-tmp"
+
+	args=$(getopt --options "$short" --longoptions "$long" -- "$@") || {
+		echo; usage; exit
+	}
+	eval set -- "$args"
+
+	while true; do
+		case "$1" in
+			-h | --help)
+				usage
+				exit 0
+				;;
+			-f | --show-first-changed)
+				DIFF_CHECKSUM=1
+				shift
+				;;
+			-j | --jobs)
+				JOBS="$2"
+				shift 2
+				;;
+			-o | --output)
+				[[ "$2" != *.ko ]] && die "output filename should end with .ko"
+				OUTFILE="$2"
+				NAME="$(basename "$OUTFILE")"
+				NAME="${NAME%.ko}"
+				NAME="$(module_name_string "$NAME")"
+				shift 2
+				;;
+			--no-replace)
+				REPLACE=0
+				shift
+				;;
+			-v | --verbose)
+				VERBOSE=1
+				shift
+				;;
+			-d | --debug)
+				DEBUG_CLONE=1
+				keep_tmp=1
+				shift
+				;;
+			-S | --short-circuit)
+				[[ ! -d "$TMP_DIR" ]] && die "--short-circuit requires preserved klp-tmp dir"
+				keep_tmp=1
+				case "$2" in
+					1 | orig)		SHORT_CIRCUIT=1; ;;
+					2 | patched)		SHORT_CIRCUIT=2; ;;
+					3 | checksum)		SHORT_CIRCUIT=3; ;;
+					4 | diff)		SHORT_CIRCUIT=4; ;;
+					5 | kmod)		SHORT_CIRCUIT=5; ;;
+					*)		die "invalid short-circuit step '$2'" ;;
+				esac
+				shift 2
+				;;
+			-T | --keep-tmp)
+				keep_tmp=1
+				shift
+				;;
+			--)
+				shift
+				break
+				;;
+			*)
+				usage
+				exit 1
+				;;
+		esac
+	done
+
+	if [[ $# -eq 0 ]] && (( SHORT_CIRCUIT <= 2 )); then
+		usage
+		exit 1
+	fi
+
+	KEEP_TMP="$keep_tmp"
+	PATCHES=("$@")
+
+	for patch in "${PATCHES[@]}"; do
+		[[ -f "$patch" ]] || die "$patch doesn't exist"
+	done
+}
+
+# temporarily disable xtrace for especially verbose code
+xtrace_save() {
+	[[ -v XTRACE ]] && set +x
+	return 0
+}
+
+xtrace_restore() {
+	[[ -v XTRACE ]] && set -x
+	return 0
+}
+
+validate_config() {
+	xtrace_save "reading .config"
+	source "$CONFIG" || die "no .config file in $(dirname "$CONFIG")"
+	xtrace_restore
+
+	[[ -v CONFIG_LIVEPATCH ]] ||			\
+		die "CONFIG_LIVEPATCH not enabled"
+
+	[[ -v CONFIG_KLP_BUILD ]] ||			\
+		die "CONFIG_KLP_BUILD not enabled"
+
+	[[ -v CONFIG_GCC_PLUGIN_LATENT_ENTROPY ]] &&	\
+		die "kernel option 'CONFIG_GCC_PLUGIN_LATENT_ENTROPY' not supported"
+
+	[[ -v CONFIG_GCC_PLUGIN_RANDSTRUCT ]] &&	\
+		die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported"
+
+	[[ -v CONFIG_LD_DEAD_CODE_DATA_ELIMINATION ]] &&		\
+		die "kernel option 'CONFIG_LD_DEAD_CODE_DATA_ELIMINATION' not supported"
+
+	[[ -v CONFIG_AS_IS_LLVM ]] &&				\
+		[[ "$CONFIG_AS_VERSION" -lt 200000 ]] &&	\
+		die "Clang assembler version < 20 not supported"
+
+	[[ -x "$OBJTOOL" ]] && "$OBJTOOL" klp 2>&1 | command grep -q "not implemented" && \
+		die "objtool not built with KLP support; install xxhash-devel/libxxhash-dev (version >= 0.8) and recompile"
+
+	return 0
+}
+
+# Only allow alphanumerics and '_' and '-' in the module name.  Everything else
+# is replaced with '-'.  Also truncate to 55 chars so the full name + NUL
+# terminator fits in the kernel's 56-byte module name array.
+module_name_string() {
+	echo "${1//[^a-zA-Z0-9_-]/-}" | cut -c 1-55
+}
+
+# If the module name wasn't specified on the cmdline with --output, give it a
+# name based on the patch name.
+set_module_name() {
+	[[ -v NAME ]] && return 0
+
+	if [[ "${#PATCHES[@]}" -eq 1 ]]; then
+		NAME="$(basename "${PATCHES[0]}")"
+		NAME="${NAME%.*}"
+	else
+		NAME="patch"
+	fi
+
+	NAME="livepatch-$NAME"
+	NAME="$(module_name_string "$NAME")"
+
+	OUTFILE="$NAME.ko"
+}
+
+# Hardcode the value printed by the localversion script to prevent patch
+# application from appending it with '+' due to a dirty working tree.
+set_kernelversion() {
+	local file="$PWD/scripts/setlocalversion"
+	local kernelrelease
+
+	stash_file "$file"
+
+	if [[ -n "$(make -s listnewconfig 2>/dev/null)" ]]; then
+		die ".config mismatch, check your .config or run 'make olddefconfig'"
+	fi
+	make syncconfig &>/dev/null || die "make syncconfig failed"
+
+	kernelrelease="$(make -s kernelrelease)"
+	[[ -z "$kernelrelease" ]] && die "failed to get kernel version"
+
+	sed -i "2i echo $kernelrelease; exit 0" scripts/setlocalversion
+}
+
+get_patch_input_files() {
+	local patch="$1"
+
+	grep0 -E '^--- ' "$patch"				\
+		| grep0 -v -e '/dev/null' -e '1969-12-31' -e '1970-01-01' \
+		| gawk '{print $2}'				\
+		| sed 's|^[^/]*/||'				\
+		| sort -u
+}
+
+get_patch_output_files() {
+	local patch="$1"
+
+	grep0 -E '^\+\+\+ ' "$patch"				\
+		| grep0 -v -e '/dev/null' -e '1969-12-31' -e '1970-01-01' \
+		| gawk '{print $2}'				\
+		| sed 's|^[^/]*/||'				\
+		| sort -u
+}
+
+get_patch_files() {
+	local patch="$1"
+
+	{ get_patch_input_files "$patch"; get_patch_output_files "$patch"; } \
+		| sort -u
+}
+
+check_unsupported_patches() {
+	local patch
+
+	for patch in "${PATCHES[@]}"; do
+		local files=()
+
+		get_patch_files "$patch" | mapfile -t files
+
+		for file in "${files[@]}"; do
+			case "$file" in
+				lib/*|*/vdso/*|*/realmode/rm/*|*.S)
+					die "${patch}: unsupported patch to $file"
+					;;
+			esac
+		done
+	done
+}
+
+apply_patch() {
+	local patch="$1"
+	shift
+	local extra_args=("$@")
+	local drift_regex="with fuzz|offset [0-9]+ line"
+	local output
+	local status
+
+	[[ ! -f "$patch" ]] && die "$patch doesn't exist"
+	status=0
+	output=$(patch -p1 --dry-run --no-backup-if-mismatch -r /dev/null "${extra_args[@]}" < "$patch" 2>&1) || status=$?
+	if [[ "$status" -ne 0 ]]; then
+		echo "$output" >&2
+		die "$patch did not apply"
+	elif [[ "$output" =~ $drift_regex ]]; then
+		[[ -v VERBOSE ]] && echo "$output" >&2
+		warn "${patch} applied with fuzz"
+	fi
+
+	APPLIED_PATCHES+=("$patch")
+	patch -p1 --no-backup-if-mismatch -r /dev/null "${extra_args[@]}" --silent < "$patch"
+}
+
+revert_patch() {
+	local patch="$1"
+	local tmp=()
+
+	patch -p1 -R --force --no-backup-if-mismatch -r /dev/null &> /dev/null < "$patch" || true
+
+	for p in "${APPLIED_PATCHES[@]}"; do
+		[[ "$p" == "$patch" ]] && continue
+		tmp+=("$p")
+	done
+
+	APPLIED_PATCHES=("${tmp[@]}")
+}
+
+apply_patches() {
+	local extra_args=("$@")
+	local patch
+
+	for patch in "${PATCHES[@]}"; do
+		apply_patch "$patch" "${extra_args[@]}"
+	done
+}
+
+revert_patches() {
+	local patches=("${APPLIED_PATCHES[@]}")
+
+	for (( i=${#patches[@]}-1 ; i>=0 ; i-- )) ; do
+		revert_patch "${patches[$i]}"
+	done
+
+	APPLIED_PATCHES=()
+}
+
+validate_patches() {
+	check_unsupported_patches
+	apply_patches
+	revert_patches
+}
+
+do_init() {
+	# We're not yet smart enough to handle anything other than in-tree
+	# builds in pwd.
+	[[ ! "$PWD" -ef "$SCRIPT_DIR/../.." ]] && die "please run from the kernel root directory"
+
+	if (( SHORT_CIRCUIT >= 2 )); then
+		[[ -f "$ORIG_DIR/.complete" ]] || die "-S $SHORT_CIRCUIT requires completed $ORIG_DIR"
+	fi
+	if (( SHORT_CIRCUIT >= 3 )); then
+		[[ -f "$PATCHED_DIR/.complete" ]] || die "-S $SHORT_CIRCUIT requires completed $PATCHED_DIR"
+	fi
+	if (( SHORT_CIRCUIT >= 4 )); then
+		[[ -f "$ORIG_CSUM_DIR/.complete" ]] || die "-S $SHORT_CIRCUIT requires completed $ORIG_CSUM_DIR"
+		[[ -f "$PATCHED_CSUM_DIR/.complete" ]] || die "-S $SHORT_CIRCUIT requires completed $PATCHED_CSUM_DIR"
+	fi
+	if (( SHORT_CIRCUIT >= 5 )); then
+		[[ -f "$DIFF_DIR/.complete" ]] || die "-S $SHORT_CIRCUIT requires completed $DIFF_DIR"
+	fi
+
+	(( SHORT_CIRCUIT <= 1 )) && rm -rf "$TMP_DIR"
+	mkdir -p "$TMP_DIR"
+
+	APPLIED_PATCHES=()
+
+	[[ -x "$FIX_PATCH_LINES" ]] || die "can't find fix-patch-lines"
+	command -v recountdiff &>/dev/null || die "recountdiff not found (install patchutils)"
+
+	validate_config
+	set_module_name
+	set_kernelversion
+}
+
+# Refresh the patch hunk headers, specifically the line numbers and counts.
+refresh_patch() {
+	local patch="$1"
+	local tmpdir="$PATCH_TMP_DIR"
+	local input_files=()
+	local output_files=()
+
+	rm -rf "$tmpdir"
+	mkdir -p "$tmpdir/a"
+	mkdir -p "$tmpdir/b"
+
+	# Get all source files affected by the patch
+	get_patch_input_files "$patch" | mapfile -t input_files
+	get_patch_output_files "$patch" | mapfile -t output_files
+
+	# Copy orig source files to 'a'
+	echo "${input_files[@]}" | xargs cp --parents --target-directory="$tmpdir/a"
+
+	# Copy patched source files to 'b'
+	apply_patch "$patch" "--silent"
+	echo "${output_files[@]}" | xargs cp --parents --target-directory="$tmpdir/b"
+	revert_patch "$patch"
+
+	# Diff 'a' and 'b' to make a clean patch
+	( cd "$tmpdir" && diff -Nupr a b > "$patch" ) || true
+}
+
+# Copy the patches to a temporary directory, fix their lines so as not to
+# affect the __LINE__ macro for otherwise unchanged functions further down the
+# file, and update $PATCHES to point to the fixed patches.
+fix_patches() {
+	local idx
+	local i
+
+	rm -f "$TMP_DIR"/*.patch
+
+	idx=0001
+	for i in "${!PATCHES[@]}"; do
+		local old_patch="${PATCHES[$i]}"
+		local tmp_patch="$TMP_DIR/tmp.patch"
+		local patch="${PATCHES[$i]}"
+		local new_patch
+
+		new_patch="$TMP_DIR/$idx-fixed-$(basename "$patch")"
+
+		cp -f "$old_patch" "$tmp_patch"
+		refresh_patch "$tmp_patch"
+		"$FIX_PATCH_LINES" "$tmp_patch" | recountdiff > "$new_patch"
+
+		PATCHES[i]="$new_patch"
+
+		rm -f "$tmp_patch"
+		idx=$(printf "%04d" $(( 10#$idx + 1 )))
+	done
+}
+
+clean_kernel() {
+	local cmd=()
+
+	cmd=("make")
+	cmd+=("--silent")
+	cmd+=("-j$JOBS")
+	cmd+=("clean")
+
+	"${cmd[@]}"
+}
+
+build_kernel() {
+	local build="$1"
+	local log="$TMP_DIR/build.log"
+	local cmd=()
+
+	cmd=("make")
+
+	# When a patch to a kernel module references a newly created unexported
+	# symbol which lives in vmlinux or another kernel module, the patched
+	# kernel build fails with the following error:
+	#
+	#   ERROR: modpost: "klp_string" [fs/xfs/xfs.ko] undefined!
+	#
+	# The undefined symbols are working as designed in that case.  They get
+	# resolved later when the livepatch module build link pulls all the
+	# disparate objects together into the same kernel module.
+	#
+	# It would be good to have a way to tell modpost to skip checking for
+	# undefined symbols altogether.  For now, just convert the error to a
+	# warning with KBUILD_MODPOST_WARN, and grep out the warning to avoid
+	# confusing the user.
+	#
+	cmd+=("KBUILD_MODPOST_WARN=1")
+
+	cmd+=("KLP_SYMIDS=1")
+
+	if [[ -v VERBOSE ]]; then
+		cmd+=("V=1")
+	else
+		cmd+=("-s")
+	fi
+	cmd+=("-j$JOBS")
+	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
+	cmd+=("vmlinux")
+	cmd+=("modules")
+
+	"${cmd[@]}"							\
+		1> >(tee -a "$log")					\
+		2> >(tee -a "$log" | grep0 -v "modpost.*undefined!" >&2) \
+		|| die "$build kernel build failed"
+}
+
+find_objects() {
+	local opts=("$@")
+
+	# Find root-level vmlinux.o and non-root-level .ko files,
+	# excluding klp-tmp/ and hidden directories.
+	find "$PWD" -mindepth 1 \
+		    \( -path "$TMP_DIR" -o -name ".*" -o -regex "$PWD/[^/][^/]*\.ko" \) -prune -o \
+		    -type f "${opts[@]}"				\
+		    \( -name "*.ko" -o -path "$PWD/vmlinux.o" \)	\
+		    -printf '%P\n'
+}
+
+# Copy all .o archives to $ORIG_DIR
+copy_orig_objects() {
+	local files=()
+
+	rm -rf "$ORIG_DIR"
+	mkdir -p "$ORIG_DIR"
+
+	find_objects | mapfile -t files
+
+	xtrace_save "copying original objects"
+	for _file in "${files[@]}"; do
+		local rel_file="${_file/.ko/.o}"
+		local file="$PWD/$rel_file"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local orig_dir="$(dirname "$orig_file")"
+
+		[[ ! -f "$file" ]] && die "missing $(basename "$file") for $_file"
+
+		mkdir -p "$orig_dir"
+		cp -f "$file" "$orig_dir"
+	done
+	xtrace_restore
+
+	cp -f "$PWD/vmlinux" "$ORIG_DIR" || die "missing vmlinux"
+
+	mv -f "$TMP_DIR/build.log" "$ORIG_DIR"
+	touch "$TIMESTAMP"
+	touch "$ORIG_DIR/.complete"
+}
+
+# Copy all changed objects to $PATCHED_DIR
+copy_patched_objects() {
+	local files=()
+	local opts=()
+	local found=0
+
+	rm -rf "$PATCHED_DIR"
+	mkdir -p "$PATCHED_DIR"
+
+	# Note this doesn't work with some configs, thus the 'cmp' below.
+	opts=("-newer")
+	opts+=("$TIMESTAMP")
+
+	find_objects "${opts[@]}" | mapfile -t files
+
+	xtrace_save "copying changed objects"
+	for _file in "${files[@]}"; do
+		local rel_file="${_file/.ko/.o}"
+		local file="$PWD/$rel_file"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local patched_file="$PATCHED_DIR/$rel_file"
+		local patched_dir="$(dirname "$patched_file")"
+
+		[[ ! -f "$file" ]] && die "missing $(basename "$file") for $_file"
+
+		cmp -s "$orig_file" "$file" && continue
+
+		mkdir -p "$patched_dir"
+		cp -f "$file" "$patched_dir"
+		found=1
+	done
+	xtrace_restore
+
+	(( found == 0 )) && die "no changes detected"
+
+	mv -f "$TMP_DIR/build.log" "$PATCHED_DIR"
+	touch "$PATCHED_DIR/.complete"
+}
+
+# Copy .o files to a separate directory and run "objtool klp checksum" on each
+# copy.  The checksums are written to a .discard.sym_checksum section.
+#
+# If match_dir is given, only process files which also exist there.
+generate_checksums() {
+	local src_dir="$1"
+	local dest_dir="$2"
+	local match_dir="${3:-}"
+	local files=()
+	local file
+
+	rm -rf "$dest_dir"
+	mkdir -p "$dest_dir"
+
+	find "$src_dir" -type f -name "*.o" | mapfile -t files
+	for file in "${files[@]}"; do
+		local rel="${file#"$src_dir"/}"
+		local dest="$dest_dir/$rel"
+
+		[[ -n "$match_dir" && ! -f "$match_dir/$rel" ]] && continue
+
+		mkdir -p "$(dirname "$dest")"
+		cp -f "$file" "$dest"
+		"$OBJTOOL" klp checksum "$dest"
+	done
+
+	[[ -f "$src_dir/vmlinux" ]] && cp -f "$src_dir/vmlinux" "$dest_dir"
+
+	touch "$dest_dir/.complete"
+}
+
+# Diff changed objects, writing output object to $DIFF_DIR
+diff_objects() {
+	local log="$KLP_DIFF_LOG"
+	local files=()
+	local opts=()
+
+	rm -rf "$DIFF_DIR"
+	mkdir -p "$DIFF_DIR"
+
+	find "$PATCHED_CSUM_DIR" -type f -name "*.o" | mapfile -t files
+	[[ ${#files[@]} -eq 0 ]] && die "no changes detected"
+
+	[[ -v DEBUG_CLONE ]] && opts=("--debug")
+
+	# Diff all changed objects
+	for file in "${files[@]}"; do
+		local rel_file="${file#"$PATCHED_CSUM_DIR"/}"
+		local orig_file="$rel_file"
+		local patched_file="$PATCHED_CSUM_DIR/$rel_file"
+		local out_file="$DIFF_DIR/$rel_file"
+		local filter=()
+		local cmd=()
+
+		mkdir -p "$(dirname "$out_file")"
+
+		cmd=("$OBJTOOL")
+		cmd+=("klp")
+		cmd+=("diff")
+		(( ${#opts[@]} > 0 )) && cmd+=("${opts[@]}")
+		cmd+=("$orig_file")
+		cmd+=("$patched_file")
+		cmd+=("$out_file")
+
+		if [[ -v DIFF_CHECKSUM ]]; then
+			filter=("grep0")
+			filter+=("-Ev")
+			filter+=("DEBUG: .*checksum: ")
+		else
+			filter=("cat")
+		fi
+
+		(
+			cd "$ORIG_CSUM_DIR"
+			[[ -v VERBOSE ]] && echo "cd $ORIG_CSUM_DIR && ${cmd[*]}"
+			"${cmd[@]}"							\
+				1> >(tee -a "$log")					\
+				2> >(tee -a "$log" | "${filter[@]}" >&2) ||		\
+				die "objtool klp diff failed"
+		)
+	done
+
+	touch "$DIFF_DIR/.complete"
+}
+
+# For each changed object, run "objtool klp checksum" with --debug-checksum to
+# get the per-instruction checksums, and then diff those to find the first
+# changed instruction for each function.
+diff_checksums() {
+	local orig_log="$ORIG_DIR/checksum.log"
+	local patched_log="$PATCHED_DIR/checksum.log"
+	local -A funcs
+	local cmd=()
+	local line
+	local file
+	local func
+
+	gawk '/\.o: changed function: / {
+		sub(/:$/, "", $1)
+		print $1, $NF
+	}' "$KLP_DIFF_LOG" | mapfile -t lines
+
+	for line in "${lines[@]}"; do
+		read -r file func <<< "$line"
+		if [[ ! -v funcs["$file"] ]]; then
+			funcs["$file"]="$func"
+		else
+			funcs["$file"]+=" $func"
+		fi
+	done
+
+	cmd=("$OBJTOOL")
+	cmd+=("klp" "checksum")
+	cmd+=("--dry-run")
+
+	for file in "${!funcs[@]}"; do
+		local opt="--debug-checksum=${funcs[$file]// /,}"
+
+		(
+			cd "$ORIG_DIR"
+			"${cmd[@]}" "$opt" "$file" &> "$orig_log" || \
+				( cat "$orig_log" >&2; die "objtool klp checksum failed" )
+
+			cd "$PATCHED_DIR"
+			"${cmd[@]}" "$opt" "$file" &> "$patched_log" ||	\
+				( cat "$patched_log" >&2; die "objtool klp checksum failed" )
+		)
+
+		for func in ${funcs[$file]}; do
+			local -a orig patched
+			paste <(grep0 -E "^DEBUG: .*checksum: $func " "$orig_log") \
+			      <(grep0 -E "^DEBUG: .*checksum: $func " "$patched_log") |
+			while IFS= read -r line; do
+				read -ra orig <<< "${line%%$'\t'*}"
+				read -ra patched <<< "${line#*$'\t'}"
+
+				if [[ ${#patched[@]} -eq 0 ]]; then
+					printf "%s: %s: %s (removed)\n" "${orig[1]%:}" "${orig[3]}" "${orig[-2]}"
+					break
+				elif [[ ${#orig[@]} -eq 0 ]]; then
+					printf "%s: %s: %s (added)\n" "${patched[1]%:}" "${patched[3]}" "${patched[-2]}"
+					break
+				fi
+
+				[[ "${orig[-1]}" == "${patched[-1]}" ]] && continue
+
+				printf "%s: %s: %s" "${orig[1]%:}" "${orig[3]}" "${orig[-2]}"
+				[[ "${orig[-2]}" != "${patched[-2]}" ]] && \
+					printf " (patched: %s)" "${patched[-2]}"
+				printf "\n"
+				break
+			done || true
+		done
+	done
+}
+
+# Build and post-process livepatch module in $KMOD_DIR
+build_patch_module() {
+	local makefile="$KMOD_DIR/Kbuild"
+	local log="$KMOD_DIR/build.log"
+	local kmod_file
+	local cflags=()
+	local files=()
+	local cmd=()
+
+	rm -rf "$KMOD_DIR"
+	mkdir -p "$KMOD_DIR"
+
+	cp -f "$SCRIPT_DIR/init.c" "$KMOD_DIR"
+
+	echo "obj-m := $NAME.o" > "$makefile"
+	echo -n "$NAME-y := init.o" >> "$makefile"
+
+	find "$DIFF_DIR" -type f -name "*.o" | mapfile -t files
+	[[ ${#files[@]} -eq 0 ]] && die "no changes detected"
+
+	for file in "${files[@]}"; do
+		local rel_file="${file#"$DIFF_DIR"/}"
+		local orig_file="$ORIG_DIR/$rel_file"
+		local orig_dir="$(dirname "$orig_file")"
+		local kmod_file="$KMOD_DIR/$rel_file"
+		local kmod_dir="$(dirname "$kmod_file")"
+		local cmd_file="$kmod_dir/.$(basename "$file").cmd"
+
+		mkdir -p "$kmod_dir"
+		cp -f "$file" "$kmod_dir"
+
+		# Tell kbuild this is a prebuilt object
+		cp -f "$file" "${kmod_file}_shipped"
+
+		# Make modpost happy
+		touch "$cmd_file"
+
+		echo -n " $rel_file" >> "$makefile"
+	done
+
+	echo >> "$makefile"
+
+	cflags=("-ffunction-sections")
+	cflags+=("-fdata-sections")
+	[[ $REPLACE -eq 0 ]] && cflags+=("-DKLP_NO_REPLACE")
+
+	cmd=("make")
+	if [[ -v VERBOSE ]]; then
+		cmd+=("V=1")
+	else
+		cmd+=("-s")
+	fi
+	cmd+=("-j$JOBS")
+	cmd+=("--directory=.")
+	cmd+=("M=$KMOD_DIR")
+	cmd+=("KCFLAGS=${cflags[*]}")
+
+	# Build a "normal" kernel module with init.c and the diffed objects
+	"${cmd[@]}"							\
+		1> >(tee -a "$log")					\
+		2> >(tee -a "$log" >&2)
+
+	kmod_file="$KMOD_DIR/$NAME.ko"
+
+	# Save off the intermediate binary for debugging
+	cp -f "$kmod_file" "$kmod_file.orig"
+
+	# Work around issue where slight .config change makes corrupt BTF
+	objcopy --remove-section=.BTF "$kmod_file"
+
+	# Fix (and work around) linker wreckage for klp syms / relocs
+	"$OBJTOOL" klp post-link "$kmod_file" || die "objtool klp post-link failed"
+
+	cp -f "$kmod_file" "$OUTFILE"
+}
+
+
+################################################################################
+
+process_args "$@"
+do_init
+
+if (( SHORT_CIRCUIT <= 2 )); then
+	status "Validating patch(es)"
+	validate_patches
+fi
+
+if (( SHORT_CIRCUIT <= 1 )); then
+	status "Building original kernel"
+	clean_kernel
+	build_kernel "original"
+	status "Copying original object files"
+	copy_orig_objects
+fi
+
+if (( SHORT_CIRCUIT <= 2 )); then
+	status "Fixing patch(es)"
+	fix_patches
+	apply_patches "--silent"
+	status "Building patched kernel"
+	build_kernel "patched"
+	revert_patches
+	status "Copying patched object files"
+	copy_patched_objects
+fi
+
+if (( SHORT_CIRCUIT <= 3 )); then
+	status "Generating original checksums"
+	generate_checksums "$ORIG_DIR" "$ORIG_CSUM_DIR" "$PATCHED_DIR"
+	status "Generating patched checksums"
+	generate_checksums "$PATCHED_DIR" "$PATCHED_CSUM_DIR"
+fi
+
+if (( SHORT_CIRCUIT <= 4 )); then
+	status "Diffing objects"
+	diff_objects
+	if [[ -v DIFF_CHECKSUM ]]; then
+		status "Finding first changed instructions"
+		diff_checksums
+	fi
+fi
+
+if (( SHORT_CIRCUIT <= 5 )); then
+	status "Building patch module: $OUTFILE"
+	build_patch_module
+fi
+
+status "SUCCESS"