linux-kernel - [PATCH RFC v2 5/5] lib/Kconfig.debug: introduce CONFIG_NO_AUTO

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250416-noautoinline-v2-5-e69a2717530f@uniontech.com>
Date: Wed, 16 Apr 2025 17:44:51 +0800
From: Chen Linxuan via B4 Relay <devnull+chenlinxuan.uniontech.com@...nel.org>
To: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Yishai Hadas <yishaih@...dia.com>, Jason Gunthorpe <jgg@...pe.ca>, 
 Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>, 
 Kevin Tian <kevin.tian@...el.com>, 
 Alex Williamson <alex.williamson@...hat.com>, 
 Peter Huewe <peterhuewe@....de>, Jarkko Sakkinen <jarkko@...nel.org>, 
 Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
 linux-integrity@...r.kernel.org, linux-kbuild@...r.kernel.org, 
 llvm@...ts.linux.dev, Winston Wen <wentao@...ontech.com>, 
 Chen Linxuan <chenlinxuan@...ontech.com>, 
 Changbin Du <changbin.du@...el.com>
Subject: [PATCH RFC v2 5/5] lib/Kconfig.debug: introduce
 CONFIG_NO_AUTO_INLINE

From: Winston Wen <wentao@...ontech.com>

Add a new kernel hacking option CONFIG_NO_AUTO_INLINE that prevents the
compiler from auto-inlining functions not explicitly marked with the
'inline' keyword.

This enhancement improves function tracer capabilities as it can only
trace functions that haven't been inlined by the compiler.

Previous discussions:

Link: https://lore.kernel.org/all/20181028130945.23581-3-changbin.du@gmail.com/

This patch is modified from commit 917fad29febd ("kernel hacking: add a
config option to disable compiler auto-inlining") which can be founded
in linux-next-history:

Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next-history.git/commit/?id=917fad29febd

Unlike the original implementation, this patch:

1. Make it depends on CC_IS_GCC,
   as Clang 18.1.3 break test_bitmap_const_eval() in lib/test_bitmap.c

2. Make it depends on X86 and LOONGARCH,
   as I haven't test other architectures

3. Removes unnecessary cc-option checks per commit 7d73c3e9c514
   ("Makefile: remove stale cc-option checks").

4. Update help information.

Cc: Changbin Du <changbin.du@...il.com>
Co-developed-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Winston Wen <wentao@...ontech.com>
---
 Makefile          |  6 ++++++
 lib/Kconfig.debug | 15 +++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Makefile b/Makefile
index c91afd55099ea6bc7ed89bc3ef9cf58a498596d4..52da2c27f94167d2d2892a67c065e5df15efbde0 100644
--- a/Makefile
+++ b/Makefile
@@ -1071,6 +1071,12 @@ endif
 # Ensure compilers do not transform certain loops into calls to wcslen()
 KBUILD_CFLAGS += -fno-builtin-wcslen
 
+ifdef CONFIG_NO_AUTO_INLINE
+KBUILD_CFLAGS   += -fno-inline-functions \
+		   -fno-inline-small-functions \
+		   -fno-inline-functions-called-once
+endif
+
 # change __FILE__ to the relative path to the source directory
 ifdef building_out_of_srctree
 KBUILD_CPPFLAGS += $(call cc-option,-ffile-prefix-map=$(srcroot)/=)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9fe4d8dfe5782981cc0b2b6614106aac570bd229..2ebb4802886ab4a48841dbdd8973b7d9883548b9 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -436,8 +436,23 @@ config GDB_SCRIPTS
 	  instance. See Documentation/process/debugging/gdb-kernel-debugging.rst
 	  for further details.
 
+
 endif # DEBUG_INFO
 
+config NO_AUTO_INLINE
+	bool "Disable compiler auto-inline optimizations (EXPERIMENTAL)"
+	default n
+	depends on CC_IS_GCC && (X86 || LOONGARCH)
+	help
+	  This will prevent the compiler from optimizing the kernel by
+	  auto-inlining functions not marked with the inline keyword.
+	  With this option, only functions explicitly marked with
+	  "inline" will be inlined. This will allow the function tracer
+	  to trace more functions because it only traces functions that
+	  the compiler has not inlined.
+
+	  If unsure, select N.
+
 config FRAME_WARN
 	int "Warn for stack frames larger than"
 	range 0 8192

-- 
2.48.1