linux-kernel - [PATCH v6 0/5] asdf

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Message-Id: <20251203233029.it.641-kees@kernel.org>
Date: Wed,  3 Dec 2025 15:30:30 -0800
From: Kees Cook <kees@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Kees Cook <kees@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	John Hubbard <jhubbard@...dia.com>,
	Joe Perches <joe@...ches.com>,
	Christoph Lameter <cl@...ux.com>,
	Marco Elver <elver@...gle.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Harry Yoo <harry.yoo@...cle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Jann Horn <jannh@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>,
	linux-mm@...ck.org,
	Nathan Chancellor <nathan@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Jakub Kicinski <kuba@...nel.org>,
	Yafang Shao <laoar.shao@...il.com>,
	Tony Ambardar <tony.ambardar@...il.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Jan Hendrik Farr <kernel@...rr.cc>,
	Alexander Potapenko <glider@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	linux-doc@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH v6 0/5] asdf

Hi,

Here's an update for the kmalloc_obj() API proposal based on Linus's
feedback. I normally wouldn't send this during the merge window,
but I wanted to have it updated for discussion at LPC[1] (and here in
email). Please see patches 1 and 4 for the bulk of the details. This is
obviously not v6.19 material! :)

Replacing[2] all existing simple code patterns found via Coccinelle
shows what could be replaced immediately (also saving roughly 1000 lines):

 7971 files changed, 19880 insertions(+), 20752 deletions(-)

This would take us from 24515 size-based k*alloc assignments to 7682:

$ git grep ' = kv\?[mzcv]alloc\(\|_array\)(' | wc -l
24515
$ git reset --hard HEAD^
HEAD is now at 8bccc91e6cdf treewide: kmalloc_obj conversion
$ git grep ' = kv\?[mzcv]alloc\(\|_array\)(' | wc -l
7682

This treewide change could be done at the end of the merge window just
before -rc1 is released (as is common for treewide changes). Handling
this API change in backports to -stable should be possible without much
hassle by backporting the __flex_counter() patch and this patch, while
taking conversions as-needed.

The impact on my bootable testing image size (with the treewide patch
applied) is tiny. With both GCC 13 (no __counted_by support) and GCC 15
(with __counted_by) the images are actually very slightly smaller:

$ size -G gcc-boot/vmlinux.gcc*
      text       data        bss      total filename
  29975593   21527689   16601200   68104482 gcc-boot/vmlinux.gcc13-before
  29969263   21528663   16601112   68099038 gcc-boot/vmlinux.gcc13-after
  30555626   21291299   17086620   68933545 gcc-boot/vmlinux.gcc15-before
  30550144   21292039   17086540   68928723 gcc-boot/vmlinux.gcc15-after

Thanks!

-Kees

[1] https://lpc.events/event/19/contributions/2136/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=dev/v6.18-rc6/alloc_obj/v5&id=f79ee96ad6a3cafdb274fe15d3ae067724e72327

 v6:
   - Drop _sz() helpers and simplify the resulting internals
   - Split _flex() helper into its own patch to make review easier
   - Explicitly use TYPE within the internals to make things more readable
   - Move treewide change details into the cover letter
 v5: https://lore.kernel.org/lkml/20251122014258.do.018-kees@kernel.org/
 v4: https://lore.kernel.org/lkml/20250315025852.it.568-kees@kernel.org/
 v3: https://lore.kernel.org/lkml/20240822231324.make.666-kees@kernel.org/
 v2: https://lore.kernel.org/lkml/20240807235433.work.317-kees@kernel.org/
 v1: https://lore.kernel.org/lkml/20240719192744.work.264-kees@kernel.org/

Kees Cook (5):
  slab: Introduce kmalloc_obj() and family
  checkpatch: Suggest kmalloc_obj family for sizeof allocations
  compiler_types: Introduce __flex_counter() and family
  slab: Introduce kmalloc_flex() and family
  coccinelle: Add kmalloc_objs conversion script

 scripts/checkpatch.pl                     |  39 ++++++--
 scripts/coccinelle/api/kmalloc_objs.cocci | 109 ++++++++++++++++++++++
 Documentation/process/deprecated.rst      |  31 ++++++
 include/linux/compiler_types.h            |  31 ++++++
 include/linux/overflow.h                  |  42 +++++++++
 include/linux/slab.h                      | 106 +++++++++++++++++++++
 6 files changed, 352 insertions(+), 6 deletions(-)
 create mode 100644 scripts/coccinelle/api/kmalloc_objs.cocci

-- 
2.34.1