Re: [PATCH v5 4/4] mm: Use ARRAY_END() instead of open-coding it

[Alejandro Colomar <alx@kernel.org>]

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Hi Kees, Andrew,

On Wed, Dec 10, 2025 at 05:37:13PM -0800, Kees Cook wrote:
> > > Are there other open-coded instances that could be replaced? This seems like a great task for a coccinelle script.
> > 
> > There are many, but I wanted to keep them out of this initial patch set,
> > to make it easy to apply.  When this one is applied, I could work on a
> > second round that replaces more of them with coccinelle.  This is just
> > for showing that this is beneficial, and to make sure that you ask for
> > more.  :)
> > 
> > Also, it's easier if there are few maintainers that would block an
> > initial patch set.  If restrict the patch set to a few files, I don't
> > have to deal with many of them.  Once I get used to this, I'll deal with
> > all of them.
> 
> Sounds good!

Now that the first patch set has been merged, I'm working on a second
round.

I've written a semantic patch:

	$ cat src/spatch/array_end.sp 
	@@
	expression a;
	@@

	- a + ARRAY_SIZE(a)
	+ ARRAY_END(a)

	@@
	expression a;
	@@

	- ARRAY_SIZE(a) + a
	+ ARRAY_END(a)

	@@
	expression a;
	@@

	- &a[0] + ARRAY_SIZE(a)
	+ ARRAY_END(a)

	@@
	expression a;
	@@

	- ARRAY_SIZE(a) + &a[0]
	+ ARRAY_END(a)

	@@
	expression a;
	@@

	- &a[ARRAY_SIZE(a)]
	+ ARRAY_END(a)

Apart from the cases covered by this semantic patch, I've found one case
which needs manual intervention (I don't know if a semantic patch can
handle this case):

	diff --git i/fs/proc/base.c w/fs/proc/base.c
	index c5114e9a0323..e99c8cad49c3 100644
	--- i/fs/proc/base.c
	+++ w/fs/proc/base.c
	@@ -2876,7 +2876,7 @@ static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
	 { \
		return proc_pident_lookup(dir, dentry, \
					  LSM##_attr_dir_stuff, \
	-                                 LSM##_attr_dir_stuff + ARRAY_SIZE(LSM##_attr_dir_stuff)); \
	+                                 ARRAY_END(LSM##_attr_dir_stuff)); \
	 } \
	 \
	 static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \

Anyway, I made sure there's only one of these.  There are no similar
cases in the kernel.

Here's a summary of what the semantic patch finds:

 arch/arm/kernel/hibernate.c                               | 2 +-
 arch/arm/kernel/reboot.c                                  | 2 +-
 arch/arm/mach-omap1/clock_data.c                          | 2 +-
 arch/arm64/kvm/sys_regs.c                                 | 2 +-
 arch/mips/fw/sni/sniprom.c                                | 2 +-
 arch/mips/include/asm/sgiarcs.h                           | 2 +-
 arch/riscv/purgatory/purgatory.c                          | 2 +-
 arch/s390/purgatory/purgatory.c                           | 2 +-
 arch/x86/kernel/cpu/hypervisor.c                          | 2 +-
 arch/x86/purgatory/purgatory.c                            | 2 +-
 block/bio.c                                               | 2 +-
 crypto/adiantum.c                                         | 2 +-
 drivers/base/regmap/regmap-spi-avmm.c                     | 2 +-
 drivers/cpufreq/sa1110-cpufreq.c                          | 2 +-
 drivers/firmware/efi/libstub/vsprintf.c                   | 2 +-
 drivers/gpu/drm/i915/selftests/i915_vma.c                 | 2 +-
 drivers/gpu/drm/xe/xe_guc_ads.c                           | 2 +-
 drivers/md/bcache/btree.c                                 | 6 +++---
 drivers/md/bcache/util.h                                  | 2 +-
 drivers/md/dm-raid.c                                      | 6 +++---
 drivers/mtd/devices/mtd_dataflash.c                       | 2 +-
 drivers/net/ethernet/marvell/mvneta.c                     | 2 +-
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c           | 2 +-
 drivers/net/ethernet/sfc/falcon/nic.c                     | 8 ++++----
 drivers/net/ethernet/sfc/nic.c                            | 8 ++++----
 drivers/net/ethernet/sfc/siena/nic.c                      | 8 ++++----
 drivers/net/wireless/intel/iwlwifi/mei/net.c              | 4 ++--
 drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c         | 3 +--
 drivers/tty/serial/msm_serial.c                           | 2 +-
 fs/erofs/zdata.c                                          | 4 ++--
 fs/proc/base.c                                            | 6 +++---
 fs/proc/namespaces.c                                      | 2 +-
 kernel/bpf/log.c                                          | 2 +-
 lib/crypto/tests/hash-test-template.h                     | 4 ++--
 mm/kmemleak.c                                             | 2 +-
 mm/memcontrol-v1.c                                        | 4 ++--
 net/ipv4/tcp_input.c                                      | 4 ++--
 tools/bpf/bpftool/tracelog.c                              | 2 +-
 tools/testing/selftests/bpf/prog_tests/select_reuseport.c | 4 ++--
 tools/testing/selftests/bpf/prog_tests/sk_lookup.c        | 8 ++++----
 tools/testing/selftests/bpf/prog_tests/sockmap_listen.c   | 8 ++++----
 tools/testing/selftests/bpf/prog_tests/sockmap_redir.c    | 8 ++++----
 42 files changed, 72 insertions(+), 73 deletions(-)

I applied the semantic patch as

            $ time find * -type f \
            | grep '\.[ch]$' \
            | xargs grep -l ARRAY_SIZE \
            | xargs grep -L '^#define ARRAY_END' \
            | xargs grep -l \
		-e '+ *ARRAY_SIZE' \
		-e 'ARRAY_SIZE(.*) *+' \
		-e '&.*ARRAY_SIZE' \
            | xargs spatch --sp-file ~/src/spatch/array_end.sp --in-place;

How should I proceed with this?  Should I send separate patches for each
subtree?  Or should I just send the semantic patch and let maintainers
run it?  Or should I senda big patch?

Also, I don't know if all of those files are able to use
include/linux/array_size.h.  Do tools/ need a separate definition?


Have a lovely day!
Alex

-- 
<https://www.alejandro-colomar.es>

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