Merge tag 'mm-nonmm-stable-2024-09-21-07-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:
 "Many singleton patches - please see the various changelogs for
  details.

  Quite a lot of nilfs2 work this time around.

  Notable patch series in this pull request are:

   - "mul_u64_u64_div_u64: new implementation" by Nicolas Pitre, with
     assistance from Uwe Kleine-König. Reimplement mul_u64_u64_div_u64()
     to provide (much) more accurate results. The current implementation
     was causing Uwe some issues in the PWM drivers.

   - "xz: Updates to license, filters, and compression options" from
     Lasse Collin. Miscellaneous maintenance and kinor feature work to
     the xz decompressor.

   - "Fix some GDB command error and add some GDB commands" from
     Kuan-Ying Lee. Fixes and enhancements to the gdb scripts.

   - "treewide: add missing MODULE_DESCRIPTION() macros" from Jeff
     Johnson. Adds lots of MODULE_DESCRIPTIONs, thus fixing lots of
     warnings about this.

   - "nilfs2: add support for some common ioctls" from Ryusuke Konishi.
     Adds various commonly-available ioctls to nilfs2.

   - "This series fixes a number of formatting issues in kernel doc
     comments" from Ryusuke Konishi does that.

   - "nilfs2: prevent unexpected ENOENT propagation" from Ryusuke
     Konishi. Fix issues where -ENOENT was being unintentionally and
     inappropriately returned to userspace.

   - "nilfs2: assorted cleanups" from Huang Xiaojia.

   - "nilfs2: fix potential issues with empty b-tree nodes" from Ryusuke
     Konishi fixes some issues which can occur on corrupted nilfs2
     filesystems.

   - "scripts/decode_stacktrace.sh: improve error reporting and
     usability" from Luca Ceresoli does those things"

* tag 'mm-nonmm-stable-2024-09-21-07-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (103 commits)
  list: test: increase coverage of list_test_list_replace*()
  list: test: fix tests for list_cut_position()
  proc: use __auto_type more
  treewide: correct the typo 'retun'
  ocfs2: cleanup return value and mlog in ocfs2_global_read_info()
  nilfs2: remove duplicate 'unlikely()' usage
  nilfs2: fix potential oob read in nilfs_btree_check_delete()
  nilfs2: determine empty node blocks as corrupted
  nilfs2: fix potential null-ptr-deref in nilfs_btree_insert()
  user_namespace: use kmemdup_array() instead of kmemdup() for multiple allocation
  tools/mm: rm thp_swap_allocator_test when make clean
  squashfs: fix percpu address space issues in decompressor_multi_percpu.c
  lib: glob.c: added null check for character class
  nilfs2: refactor nilfs_segctor_thread()
  nilfs2: use kthread_create and kthread_stop for the log writer thread
  nilfs2: remove sc_timer_task
  nilfs2: do not repair reserved inode bitmap in nilfs_new_inode()
  nilfs2: eliminate the shared counter and spinlock for i_generation
  nilfs2: separate inode type information from i_state field
  nilfs2: use the BITS_PER_LONG macro
  ...

10 files changed, 418 insertions, 54 deletions

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 207325eaf1d1..dae2089e7bc6 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -530,14 +530,17 @@ quiet_cmd_fit = FIT     $@
 
 # XZ
 # ---------------------------------------------------------------------------
-# Use xzkern to compress the kernel image and xzmisc to compress other things.
+# Use xzkern or xzkern_with_size to compress the kernel image and xzmisc to
+# compress other things.
 #
 # xzkern uses a big LZMA2 dictionary since it doesn't increase memory usage
 # of the kernel decompressor. A BCJ filter is used if it is available for
-# the target architecture. xzkern also appends uncompressed size of the data
-# using size_append. The .xz format has the size information available at
-# the end of the file too, but it's in more complex format and it's good to
-# avoid changing the part of the boot code that reads the uncompressed size.
+# the target architecture.
+#
+# xzkern_with_size also appends uncompressed size of the data using
+# size_append. The .xz format has the size information available at the end
+# of the file too, but it's in more complex format and it's good to avoid
+# changing the part of the boot code that reads the uncompressed size.
 # Note that the bytes added by size_append will make the xz tool think that
 # the file is corrupt. This is expected.
 #
diff --git a/scripts/decode_stacktrace.sh b/scripts/decode_stacktrace.sh
index a0f50a5b4f7c..826836d264c6 100755
--- a/scripts/decode_stacktrace.sh
+++ b/scripts/decode_stacktrace.sh
@@ -1,11 +1,13 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # SPDX-License-Identifier: GPL-2.0
 # (c) 2014, Sasha Levin <sasha.levin@oracle.com>
 #set -x
 
 usage() {
 	echo "Usage:"
-	echo "	$0 -r <release> | <vmlinux> [<base path>|auto] [<modules path>]"
+	echo "	$0 -r <release>"
+	echo "	$0 [<vmlinux> [<base_path>|auto [<modules_path>]]]"
+	echo "	$0 -h"
 }
 
 # Try to find a Rust demangler
@@ -32,7 +34,10 @@ READELF=${UTIL_PREFIX}readelf${UTIL_SUFFIX}
 ADDR2LINE=${UTIL_PREFIX}addr2line${UTIL_SUFFIX}
 NM=${UTIL_PREFIX}nm${UTIL_SUFFIX}
 
-if [[ $1 == "-r" ]] ; then
+if [[ $1 == "-h" ]] ; then
+	usage
+	exit 0
+elif [[ $1 == "-r" ]] ; then
 	vmlinux=""
 	basepath="auto"
 	modpath=""
@@ -89,31 +94,32 @@ find_module() {
 		fi
 	fi
 
-	if [[ "$modpath" != "" ]] ; then
-		for fn in $(find "$modpath" -name "${module//_/[-_]}.ko*") ; do
-			if ${READELF} -WS "$fn" | grep -qwF .debug_line ; then
-				echo $fn
-				return
-			fi
-		done
-		return 1
-	fi
-
-	modpath=$(dirname "$vmlinux")
-	find_module && return
-
-	if [[ $release == "" ]] ; then
+	if [ -z $release ] ; then
 		release=$(gdb -ex 'print init_uts_ns.name.release' -ex 'quit' -quiet -batch "$vmlinux" 2>/dev/null | sed -n 's/\$1 = "\(.*\)".*/\1/p')
 	fi
+	if [ -n "${release}" ] ; then
+		release_dirs="/usr/lib/debug/lib/modules/$release /lib/modules/$release"
+	fi
 
-	for dn in {/usr/lib/debug,}/lib/modules/$release ; do
-		if [ -e "$dn" ] ; then
-			modpath="$dn"
-			find_module && return
+	found_without_debug_info=false
+	for dir in "$modpath" "$(dirname "$vmlinux")" ${release_dirs}; do
+		if [ -n "${dir}" ] && [ -e "${dir}" ]; then
+			for fn in $(find "$dir" -name "${module//_/[-_]}.ko*") ; do
+				if ${READELF} -WS "$fn" | grep -qwF .debug_line ; then
+					echo $fn
+					return
+				fi
+				found_without_debug_info=true
+			done
 		fi
 	done
 
-	modpath=""
+	if [[ ${found_without_debug_info} == true ]]; then
+		echo "WARNING! No debugging info in module ${module}, rebuild with DEBUG_KERNEL and DEBUG_INFO" >&2
+	else
+		echo "WARNING! Cannot find .ko for module ${module}, please pass a valid module path" >&2
+	fi
+
 	return 1
 }
 
@@ -131,7 +137,6 @@ parse_symbol() {
 	else
 		local objfile=$(find_module)
 		if [[ $objfile == "" ]] ; then
-			echo "WARNING! Modules path isn't set, but is needed to parse this symbol" >&2
 			return
 		fi
 		if [[ $aarray_support == true ]]; then
diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py
new file mode 100644
index 000000000000..56730b3fde0b
--- /dev/null
+++ b/scripts/gdb/linux/kasan.py
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright 2024 Canonical Ltd.
+#
+# Authors:
+#  Kuan-Ying Lee <kuan-ying.lee@canonical.com>
+#
+
+import gdb
+from linux import constants, mm
+
+def help():
+    t = """Usage: lx-kasan_mem_to_shadow [Hex memory addr]
+    Example:
+        lx-kasan_mem_to_shadow 0xffff000008eca008\n"""
+    gdb.write("Unrecognized command\n")
+    raise gdb.GdbError(t)
+
+class KasanMemToShadow(gdb.Command):
+    """Translate memory address to kasan shadow address"""
+
+    p_ops = None
+
+    def __init__(self):
+        if constants.LX_CONFIG_KASAN_GENERIC or constants.LX_CONFIG_KASAN_SW_TAGS:
+            super(KasanMemToShadow, self).__init__("lx-kasan_mem_to_shadow", gdb.COMMAND_SUPPORT)
+
+    def invoke(self, args, from_tty):
+        if not constants.LX_CONFIG_KASAN_GENERIC or constants.LX_CONFIG_KASAN_SW_TAGS:
+            raise gdb.GdbError('CONFIG_KASAN_GENERIC or CONFIG_KASAN_SW_TAGS is not set')
+
+        argv = gdb.string_to_argv(args)
+        if len(argv) == 1:
+            if self.p_ops is None:
+                self.p_ops = mm.page_ops().ops
+            addr = int(argv[0], 16)
+            shadow_addr = self.kasan_mem_to_shadow(addr)
+            gdb.write('shadow addr: 0x%x\n' % shadow_addr)
+        else:
+            help()
+    def kasan_mem_to_shadow(self, addr):
+        return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.KASAN_SHADOW_OFFSET
+
+KasanMemToShadow()
diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
index 43c687e7a69d..65dd1bd12964 100644
--- a/scripts/gdb/linux/proc.py
+++ b/scripts/gdb/linux/proc.py
@@ -18,6 +18,7 @@ from linux import utils
 from linux import tasks
 from linux import lists
 from linux import vfs
+from linux import rbtree
 from struct import *
 
 
@@ -172,8 +173,7 @@ values of that process namespace"""
         gdb.write("{:^18} {:^15} {:>9} {} {} options\n".format(
                   "mount", "super_block", "devname", "pathname", "fstype"))
 
-        for mnt in lists.list_for_each_entry(namespace['list'],
-                                             mount_ptr_type, "mnt_list"):
+        for mnt in rbtree.rb_inorder_for_each_entry(namespace['mounts'], mount_ptr_type, "mnt_node"):
             devname = mnt['mnt_devname'].string()
             devname = devname if devname else "none"
 
diff --git a/scripts/gdb/linux/rbtree.py b/scripts/gdb/linux/rbtree.py
index fe462855eefd..fcbcc5f4153c 100644
--- a/scripts/gdb/linux/rbtree.py
+++ b/scripts/gdb/linux/rbtree.py
@@ -9,6 +9,18 @@ from linux import utils
 rb_root_type = utils.CachedType("struct rb_root")
 rb_node_type = utils.CachedType("struct rb_node")
 
+def rb_inorder_for_each(root):
+    def inorder(node):
+        if node:
+            yield from inorder(node['rb_left'])
+            yield node
+            yield from inorder(node['rb_right'])
+
+    yield from inorder(root['rb_node'])
+
+def rb_inorder_for_each_entry(root, gdbtype, member):
+    for node in rb_inorder_for_each(root):
+        yield utils.container_of(node, gdbtype, member)
 
 def rb_first(root):
     if root.type == rb_root_type.get_type():
diff --git a/scripts/gdb/linux/stackdepot.py b/scripts/gdb/linux/stackdepot.py
index bb3a0f843931..37313a5a51a0 100644
--- a/scripts/gdb/linux/stackdepot.py
+++ b/scripts/gdb/linux/stackdepot.py
@@ -13,6 +13,13 @@ if constants.LX_CONFIG_STACKDEPOT:
     stack_record_type = utils.CachedType('struct stack_record')
     DEPOT_STACK_ALIGN = 4
 
+def help():
+    t = """Usage: lx-stack_depot_lookup [Hex handle value]
+    Example:
+        lx-stack_depot_lookup 0x00c80300\n"""
+    gdb.write("Unrecognized command\n")
+    raise gdb.GdbError(t)
+
 def stack_depot_fetch(handle):
     global DEPOT_STACK_ALIGN
     global stack_record_type
@@ -57,3 +64,23 @@ def stack_depot_print(handle):
                 gdb.execute("x /i 0x%x" % (int(entries[i])))
             except Exception as e:
                 gdb.write("%s\n" % e)
+
+class StackDepotLookup(gdb.Command):
+    """Search backtrace by handle"""
+
+    def __init__(self):
+        if constants.LX_CONFIG_STACKDEPOT:
+            super(StackDepotLookup, self).__init__("lx-stack_depot_lookup", gdb.COMMAND_SUPPORT)
+
+    def invoke(self, args, from_tty):
+        if not constants.LX_CONFIG_STACKDEPOT:
+            raise gdb.GdbError('CONFIG_STACKDEPOT is not set')
+
+        argv = gdb.string_to_argv(args)
+        if len(argv) == 1:
+            handle = int(argv[0], 16)
+            stack_depot_print(gdb.Value(handle).cast(utils.get_uint_type()))
+        else:
+            help()
+
+StackDepotLookup()
diff --git a/scripts/gdb/linux/timerlist.py b/scripts/gdb/linux/timerlist.py
index 64bc87191003..98445671fe83 100644
--- a/scripts/gdb/linux/timerlist.py
+++ b/scripts/gdb/linux/timerlist.py
@@ -87,21 +87,22 @@ def print_cpu(hrtimer_bases, cpu, max_clock_bases):
             text += "\n"
 
         if constants.LX_CONFIG_TICK_ONESHOT:
-            fmts = [("  .{}      : {}", 'nohz_mode'),
-                    ("  .{}      : {} nsecs", 'last_tick'),
-                    ("  .{}   : {}", 'tick_stopped'),
-                    ("  .{}   : {}", 'idle_jiffies'),
-                    ("  .{}     : {}", 'idle_calls'),
-                    ("  .{}    : {}", 'idle_sleeps'),
-                    ("  .{} : {} nsecs", 'idle_entrytime'),
-                    ("  .{}  : {} nsecs", 'idle_waketime'),
-                    ("  .{}  : {} nsecs", 'idle_exittime'),
-                    ("  .{} : {} nsecs", 'idle_sleeptime'),
-                    ("  .{}: {} nsecs", 'iowait_sleeptime'),
-                    ("  .{}   : {}", 'last_jiffies'),
-                    ("  .{}     : {}", 'next_timer'),
-                    ("  .{}   : {} nsecs", 'idle_expires')]
-            text += "\n".join([s.format(f, ts[f]) for s, f in fmts])
+            TS_FLAG_STOPPED = 1 << 1
+            TS_FLAG_NOHZ = 1 << 4
+            text += f"  .{'nohz':15s}: {int(bool(ts['flags'] & TS_FLAG_NOHZ))}\n"
+            text += f"  .{'last_tick':15s}: {ts['last_tick']}\n"
+            text += f"  .{'tick_stopped':15s}: {int(bool(ts['flags'] & TS_FLAG_STOPPED))}\n"
+            text += f"  .{'idle_jiffies':15s}: {ts['idle_jiffies']}\n"
+            text += f"  .{'idle_calls':15s}: {ts['idle_calls']}\n"
+            text += f"  .{'idle_sleeps':15s}: {ts['idle_sleeps']}\n"
+            text += f"  .{'idle_entrytime':15s}: {ts['idle_entrytime']} nsecs\n"
+            text += f"  .{'idle_waketime':15s}: {ts['idle_waketime']} nsecs\n"
+            text += f"  .{'idle_exittime':15s}: {ts['idle_exittime']} nsecs\n"
+            text += f"  .{'idle_sleeptime':15s}: {ts['idle_sleeptime']} nsecs\n"
+            text += f"  .{'iowait_sleeptime':15s}: {ts['iowait_sleeptime']} nsecs\n"
+            text += f"  .{'last_jiffies':15s}: {ts['last_jiffies']}\n"
+            text += f"  .{'next_timer':15s}: {ts['next_timer']}\n"
+            text += f"  .{'idle_expires':15s}: {ts['idle_expires']} nsecs\n"
             text += "\njiffies: {}\n".format(jiffies)
 
         text += "\n"
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index fc53cdf286f1..d4eeed4506fd 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -49,3 +49,4 @@ else:
     import linux.page_owner
     import linux.slab
     import linux.vmalloc
+    import linux.kasan
diff --git a/scripts/macro_checker.py b/scripts/macro_checker.py
new file mode 100755
index 000000000000..ba550982e98f
--- /dev/null
+++ b/scripts/macro_checker.py
@@ -0,0 +1,131 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: GPL-2.0
+# Author: Julian Sun <sunjunchao2870@gmail.com>
+
+""" Find macro definitions with unused parameters. """
+
+import argparse
+import os
+import re
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument("path", type=str, help="The file or dir path that needs check")
+parser.add_argument("-v", "--verbose", action="store_true",
+                    help="Check conditional macros, but may lead to more false positives")
+args = parser.parse_args()
+
+macro_pattern = r"#define\s+(\w+)\(([^)]*)\)"
+# below vars were used to reduce false positives
+fp_patterns = [r"\s*do\s*\{\s*\}\s*while\s*\(\s*0\s*\)",
+               r"\(?0\)?", r"\(?1\)?"]
+correct_macros = []
+cond_compile_mark = "#if"
+cond_compile_end = "#endif"
+
+def check_macro(macro_line, report):
+    match = re.match(macro_pattern, macro_line)
+    if match:
+        macro_def = re.sub(macro_pattern, '', macro_line)
+        identifier = match.group(1)
+        content = match.group(2)
+        arguments = [item.strip() for item in content.split(',') if item.strip()]
+
+        macro_def = macro_def.strip()
+        if not macro_def:
+            return
+        # used to reduce false positives, like #define endfor_nexthops(rt) }
+        if len(macro_def) == 1:
+            return
+
+        for fp_pattern in fp_patterns:
+            if (re.match(fp_pattern, macro_def)):
+                return
+
+        for arg in arguments:
+            # used to reduce false positives
+            if "..." in arg:
+                return
+        for arg in arguments:
+            if not arg in macro_def and report == False:
+                return
+            # if there is a correct macro with the same name, do not report it.
+            if not arg in macro_def and identifier not in correct_macros:
+                print(f"Argument {arg} is not used in function-line macro {identifier}")
+                return
+
+        correct_macros.append(identifier)
+
+
+# remove comment and whitespace
+def macro_strip(macro):
+    comment_pattern1 = r"\/\/*"
+    comment_pattern2 = r"\/\**\*\/"
+
+    macro = macro.strip()
+    macro = re.sub(comment_pattern1, '', macro)
+    macro = re.sub(comment_pattern2, '', macro)
+
+    return macro
+
+def file_check_macro(file_path, report):
+    # number of conditional compiling
+    cond_compile = 0
+    # only check .c and .h file
+    if not file_path.endswith(".c") and not file_path.endswith(".h"):
+        return
+
+    with open(file_path, "r") as f:
+        while True:
+            line = f.readline()
+            if not line:
+                break
+            line = line.strip()
+            if line.startswith(cond_compile_mark):
+                cond_compile += 1
+                continue
+            if line.startswith(cond_compile_end):
+                cond_compile -= 1
+                continue
+
+            macro = re.match(macro_pattern, line)
+            if macro:
+                macro = macro_strip(macro.string)
+                while macro[-1] == '\\':
+                    macro = macro[0:-1]
+                    macro = macro.strip()
+                    macro += f.readline()
+                    macro = macro_strip(macro)
+                if not args.verbose:
+                    if file_path.endswith(".c")  and cond_compile != 0:
+                        continue
+                    # 1 is for #ifdef xxx at the beginning of the header file
+                    if file_path.endswith(".h") and cond_compile != 1:
+                        continue
+                check_macro(macro, report)
+
+def get_correct_macros(path):
+    file_check_macro(path, False)
+
+def dir_check_macro(dir_path):
+
+    for dentry in os.listdir(dir_path):
+        path = os.path.join(dir_path, dentry)
+        if os.path.isdir(path):
+            dir_check_macro(path)
+        elif os.path.isfile(path):
+            get_correct_macros(path)
+            file_check_macro(path, True)
+
+
+def main():
+    if os.path.isfile(args.path):
+        get_correct_macros(args.path)
+        file_check_macro(args.path, True)
+    elif os.path.isdir(args.path):
+        dir_check_macro(args.path)
+    else:
+        print(f"{args.path} doesn't exit or is neither a file nor a dir")
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/scripts/xz_wrap.sh b/scripts/xz_wrap.sh
index d06baf626abe..f19369687030 100755
--- a/scripts/xz_wrap.sh
+++ b/scripts/xz_wrap.sh
@@ -1,22 +1,162 @@
 #!/bin/sh
+# SPDX-License-Identifier: 0BSD
 #
 # This is a wrapper for xz to compress the kernel image using appropriate
 # compression options depending on the architecture.
 #
 # Author: Lasse Collin <lasse.collin@tukaani.org>
+
+# This has specialized settings for the following archs. However,
+# XZ-compressed kernel isn't currently supported on every listed arch.
 #
-# This file has been put into the public domain.
-# You can do whatever you want with this file.
-#
+#   Arch        Align   Notes
+#   arm          2/4    ARM and ARM-Thumb2
+#   arm64         4
+#   csky          2
+#   loongarch     4
+#   mips         2/4    MicroMIPS is 2-byte aligned
+#   parisc        4
+#   powerpc       4     Uses its own wrapper for compressors instead of this.
+#   riscv        2/4
+#   s390          2
+#   sh            2
+#   sparc         4
+#   x86           1
+
+# A few archs use 2-byte or 4-byte aligned instructions depending on
+# the kernel config. This function is used to check if the relevant
+# config option is set to "y".
+is_enabled()
+{
+	grep -q "^$1=y$" include/config/auto.conf
+}
+
+# XZ_VERSION is needed to disable features that aren't available in
+# old XZ Utils versions.
+XZ_VERSION=$($XZ --robot --version) || exit
+XZ_VERSION=$(printf '%s\n' "$XZ_VERSION" | sed -n 's/^XZ_VERSION=//p')
 
+# Assume that no BCJ filter is available.
 BCJ=
-LZMA2OPTS=
 
+# Set the instruction alignment to 1, 2, or 4 bytes.
+#
+# Set the BCJ filter if one is available.
+# It must match the #ifdef usage in lib/decompress_unxz.c.
 case $SRCARCH in
-	x86)            BCJ=--x86 ;;
-	powerpc)        BCJ=--powerpc ;;
-	arm)            BCJ=--arm ;;
-	sparc)          BCJ=--sparc ;;
+	arm)
+		if is_enabled CONFIG_THUMB2_KERNEL; then
+			ALIGN=2
+			BCJ=--armthumb
+		else
+			ALIGN=4
+			BCJ=--arm
+		fi
+		;;
+
+	arm64)
+		ALIGN=4
+
+		# ARM64 filter was added in XZ Utils 5.4.0.
+		if [ "$XZ_VERSION" -ge 50040002 ]; then
+			BCJ=--arm64
+		else
+			echo "$0: Upgrading to xz >= 5.4.0" \
+				"would enable the ARM64 filter" \
+				"for better compression" >&2
+		fi
+		;;
+
+	csky)
+		ALIGN=2
+		;;
+
+	loongarch)
+		ALIGN=4
+		;;
+
+	mips)
+		if is_enabled CONFIG_CPU_MICROMIPS; then
+			ALIGN=2
+		else
+			ALIGN=4
+		fi
+		;;
+
+	parisc)
+		ALIGN=4
+		;;
+
+	powerpc)
+		ALIGN=4
+
+		# The filter is only for big endian instruction encoding.
+		if is_enabled CONFIG_CPU_BIG_ENDIAN; then
+			BCJ=--powerpc
+		fi
+		;;
+
+	riscv)
+		if is_enabled CONFIG_RISCV_ISA_C; then
+			ALIGN=2
+		else
+			ALIGN=4
+		fi
+
+		# RISC-V filter was added in XZ Utils 5.6.0.
+		if [ "$XZ_VERSION" -ge 50060002 ]; then
+			BCJ=--riscv
+		else
+			echo "$0: Upgrading to xz >= 5.6.0" \
+				"would enable the RISC-V filter" \
+				"for better compression" >&2
+		fi
+		;;
+
+	s390)
+		ALIGN=2
+		;;
+
+	sh)
+		ALIGN=2
+		;;
+
+	sparc)
+		ALIGN=4
+		BCJ=--sparc
+		;;
+
+	x86)
+		ALIGN=1
+		BCJ=--x86
+		;;
+
+	*)
+		echo "$0: Arch-specific tuning is missing for '$SRCARCH'" >&2
+
+		# Guess 2-byte-aligned instructions. Guessing too low
+		# should hurt less than guessing too high.
+		ALIGN=2
+		;;
+esac
+
+# Select the LZMA2 options matching the instruction alignment.
+case $ALIGN in
+	1)  LZMA2OPTS= ;;
+	2)  LZMA2OPTS=lp=1 ;;
+	4)  LZMA2OPTS=lp=2,lc=2 ;;
+	*)  echo "$0: ALIGN wrong or missing" >&2; exit 1 ;;
 esac
 
-exec $XZ --check=crc32 $BCJ --lzma2=$LZMA2OPTS,dict=32MiB
+# Use single-threaded mode because it compresses a little better
+# (and uses less RAM) than multithreaded mode.
+#
+# For the best compression, the dictionary size shouldn't be
+# smaller than the uncompressed kernel. 128 MiB dictionary
+# needs less than 1400 MiB of RAM in single-threaded mode.
+#
+# On the archs that use this script to compress the kernel,
+# decompression in the preboot code is done in single-call mode.
+# Thus the dictionary size doesn't affect the memory requirements
+# of the preboot decompressor at all.
+exec $XZ --check=crc32 --threads=1 $BCJ --lzma2=$LZMA2OPTS,dict=128MiB