diff mbox

[00/15] sysctl: Remove sentinel elements from drivers

Message ID 20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca9f9@samsung.com (mailing list archive)
State Not Applicable
Headers show

Commit Message

Joel Granados via B4 Relay Sept. 28, 2023, 1:21 p.m. UTC
From: Joel Granados <j.granados@samsung.com>

What?
These commits remove the sentinel element (last empty element) from the
sysctl arrays of all the files under the "drivers/" directory that use a
sysctl array for registration. The merging of the preparation patches
(in https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
to mainline allows us to just remove sentinel elements without changing
behavior (more info here [1]).

These commits are part of a bigger set (here
https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4)
that remove the ctl_table sentinel. Make the review process easier by
chunking the commits into manageable pieces. Each chunk can be reviewed
separately without noise from parallel sets.

Now that the architecture chunk has been mostly reviewed [6], we send
the "drivers/" directory. Once this one is done, it will be follwed by
"fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove
the unneeded check for ->procname == NULL.

Why?
By removing the sysctl sentinel elements we avoid kernel bloat as
ctl_table arrays get moved out of kernel/sysctl.c into their own
respective subsystems. This move was started long ago to avoid merge
conflicts; the sentinel removal bit came after Mathew Wilcox suggested
it to avoid bloating the kernel by one element as arrays moved out. This
patchset will reduce the overall build time size of the kernel and run
time memory bloat by about ~64 bytes per declared ctl_table array. I
have consolidated some links that shed light on the history of this
effort [2].

Testing:
* Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh)
* Ran this through 0-day with no errors or warnings

Size saving after removing all sentinels:
  These are the bytes that we save after removing all the sentinels
  (this plus all the other chunks). I included them to get an idea of
  how much memory we are talking about.
    * bloat-o-meter:
        - The "yesall" configuration results save 9158 bytes
          https://lore.kernel.org/all/20230621091000.424843-1-j.granados@samsung.com/
        - The "tiny" config + CONFIG_SYSCTL save 1215 bytes
          https://lore.kernel.org/all/20230809105006.1198165-1-j.granados@samsung.com/
    * memory usage:
        In memory savings are measured to be 7296 bytes. (here is how to
        measure [3])

Size saving after this patchset:
    * bloat-o-meter
        - The "yesall" config saves 2432 bytes [4]
        - The "tiny" config saves 64 bytes [5]
    * memory usage:
        In this case there were no bytes saved because I do not have any
        of the drivers in the patch. To measure it comment the printk in
        `new_dir` and uncomment the if conditional in `new_links` [3].

Comments/feedback greatly appreciated

Best
Joel

[1]
We are able to remove a sentinel table without behavioral change by
introducing a table_size argument in the same place where procname is
checked for NULL. The idea is for it to keep stopping when it hits
->procname == NULL, while the sentinel is still present. And when the
sentinel is removed, it will stop on the table_size. You can go to 
(https://lore.kernel.org/all/20230809105006.1198165-1-j.granados@samsung.com/)
for more information.

[2]
Links Related to the ctl_table sentinel removal:
* Good summary from Luis sent with the "pull request" for the
  preparation patches.
  https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/
* Another very good summary from Luis.
  https://lore.kernel.org/all/ZMFizKFkVxUFtSqa@bombadil.infradead.org/
* This is a patch set that replaces register_sysctl_table with register_sysctl
  https://lore.kernel.org/all/20230302204612.782387-1-mcgrof@kernel.org/
* Patch set to deprecate register_sysctl_paths()
  https://lore.kernel.org/all/20230302202826.776286-1-mcgrof@kernel.org/
* Here there is an explicit expectation for the removal of the sentinel element.
  https://lore.kernel.org/all/20230321130908.6972-1-frank.li@vivo.com
* The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
  https://lore.kernel.org/all/20220220060626.15885-1-tangmeng@uniontech.com

[3]
To measure the in memory savings apply this on top of this patchset.

"
"
and then run the following bash script in the kernel:

accum=0
for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
    echo $n
    accum=$(calc "$accum + $n")
done
echo $accum

[4]
add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
Function                                     old     new   delta
xpc_sys_xpc_hb                               192     128     -64
xpc_sys_xpc                                  128      64     -64
vrf_table                                    128      64     -64
ucma_ctl_table                               128      64     -64
tty_table                                    192     128     -64
sg_sysctls                                   128      64     -64
scsi_table                                   128      64     -64
random_table                                 448     384     -64
raid_table                                   192     128     -64
oa_table                                     192     128     -64
mac_hid_files                                256     192     -64
iwcm_ctl_table                               128      64     -64
ipmi_table                                   128      64     -64
hv_ctl_table                                 128      64     -64
hpet_table                                   128      64     -64
firmware_config_table                        192     128     -64
cdrom_table                                  448     384     -64
balloon_table                                128      64     -64
parport_sysctl_template                      912     720    -192
parport_default_sysctl_table                 584     136    -448
parport_device_sysctl_template               776     136    -640
Total: Before=429940038, After=429937606, chg -0.00%

[5]
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-64 (-64)
Function                                     old     new   delta
random_table                                 448     384     -64
Total: Before=1885527, After=1885463, chg -0.00%

[6] https://lore.kernel.org/all/20230913-jag-sysctl_remove_empty_elem_arch-v2-0-d1bd13a29bae@samsung.com/

Signed-off-by: Joel Granados <j.granados@samsung.com>

---

---
Joel Granados (15):
      cdrom: Remove now superfluous sentinel element from ctl_table array
      hpet: Remove now superfluous sentinel element from ctl_table array
      xen: Remove now superfluous sentinel element from ctl_table array
      tty: Remove now superfluous sentinel element from ctl_table array
      scsi: Remove now superfluous sentinel element from ctl_table array
      parport: Remove the now superfluous sentinel element from ctl_table array
      macintosh: Remove the now superfluous sentinel element from ctl_table array
      infiniband: Remove the now superfluous sentinel element from ctl_table array
      char-misc: Remove the now superfluous sentinel element from ctl_table array
      vrf: Remove the now superfluous sentinel element from ctl_table array
      sgi-xp: Remove the now superfluous sentinel element from ctl_table array
      fw loader: Remove the now superfluous sentinel element from ctl_table array
      raid: Remove now superfluous sentinel element from ctl_table array
      hyper-v/azure: Remove now superfluous sentinel element from ctl_table array
      intel drm: Remove now superfluous sentinel element from ctl_table array

 drivers/base/firmware_loader/fallback_table.c |  3 +-
 drivers/cdrom/cdrom.c                         |  3 +-
 drivers/char/hpet.c                           |  3 +-
 drivers/char/ipmi/ipmi_poweroff.c             |  3 +-
 drivers/char/random.c                         |  3 +-
 drivers/gpu/drm/i915/i915_perf.c              |  3 +-
 drivers/hv/hv_common.c                        |  3 +-
 drivers/infiniband/core/iwcm.c                |  3 +-
 drivers/infiniband/core/ucma.c                |  3 +-
 drivers/macintosh/mac_hid.c                   |  3 +-
 drivers/md/md.c                               |  3 +-
 drivers/misc/sgi-xp/xpc_main.c                |  6 ++--
 drivers/net/vrf.c                             |  3 +-
 drivers/parport/procfs.c                      | 42 ++++++++++++---------------
 drivers/scsi/scsi_sysctl.c                    |  3 +-
 drivers/scsi/sg.c                             |  3 +-
 drivers/tty/tty_io.c                          |  3 +-
 drivers/xen/balloon.c                         |  3 +-
 18 files changed, 36 insertions(+), 60 deletions(-)
---
base-commit: 0e945134b680040b8613e962f586d91b6d40292d
change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c

Best regards,

Comments

Song Liu Sept. 28, 2023, 3:20 p.m. UTC | #1
On Thu, Sep 28, 2023 at 6:20 AM Joel Granados via B4 Relay
<devnull+j.granados.samsung.com@kernel.org> wrote:
>
> From: Joel Granados <j.granados@samsung.com>
>
> This commit comes at the tail end of a greater effort to remove the
> empty elements at the end of the ctl_table arrays (sentinels) which
> will reduce the overall build time size of the kernel and run time
> memory bloat by ~64 bytes per sentinel (further information Link :
> https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
>
> Remove sentinel from raid_table
>
> Signed-off-by: Joel Granados <j.granados@samsung.com>
> ---
>  drivers/md/md.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index a104a025084d..3866d8f754a0 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -304,8 +304,7 @@ static struct ctl_table raid_table[] = {
>                 .maxlen         = sizeof(int),
>                 .mode           = S_IRUGO|S_IWUSR,
>                 .proc_handler   = proc_dointvec,
> -       },
> -       { }
> +       }
>  };

Please keep "}," as Greg suggested. Otherwise,

Acked-by: Song Liu <song@kernel.org>

Thanks,
Song
Wei Liu Sept. 28, 2023, 3:26 p.m. UTC | #2
Please change the prefix to "Drivers: hv:" in the subject line in the
two patches.

On Thu, Sep 28, 2023 at 03:21:39PM +0200, Joel Granados via B4 Relay wrote:
> From: Joel Granados <j.granados@samsung.com>
> 
> This commit comes at the tail end of a greater effort to remove the
> empty elements at the end of the ctl_table arrays (sentinels) which
> will reduce the overall build time size of the kernel and run time
> memory bloat by ~64 bytes per sentinel (further information Link :
> https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> 
> Remove sentinel from hv_ctl_table
> 
> Signed-off-by: Joel Granados <j.granados@samsung.com>
> ---
>  drivers/hv/hv_common.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index ccad7bca3fd3..bc7d678030aa 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -147,8 +147,7 @@ static struct ctl_table hv_ctl_table[] = {
>  		.proc_handler	= proc_dointvec_minmax,
>  		.extra1		= SYSCTL_ZERO,
>  		.extra2		= SYSCTL_ONE
> -	},
> -	{}
> +	}

Please keep the comma at the end.

>  };
>  
>  static int hv_die_panic_notify_crash(struct notifier_block *self,
> 
> -- 
> 2.30.2
>
Christophe Leroy Sept. 28, 2023, 4:31 p.m. UTC | #3
Le 28/09/2023 à 15:21, Joel Granados via B4 Relay a écrit :
> From: Joel Granados <j.granados@samsung.com>

Automatic test fails on powerpc, see 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20230928-jag-sysctl_remove_empty_elem_drivers-v1-15-e59120fca9f9@samsung.com/

Kernel attempted to read user page (1a111316) - exploit attempt? (uid: 0)
BUG: Unable to handle kernel data access on read at 0x1a111316
Faulting instruction address: 0xc0545338
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 1 Comm: swapper Not tainted 6.5.0-rc6-gdef13277bacb #1
Hardware name: amcc,bamboo 440GR Rev. B 0x422218d3 PowerPC 44x Platform
NIP:  c0545338 LR: c0548468 CTR: ffffffff
REGS: c084fae0 TRAP: 0300   Not tainted  (6.5.0-rc6-gdef13277bacb)
MSR:  00021000 <CE,ME>  CR: 84004288  XER: 00000000
DEAR: 1a111316 ESR: 00000000
GPR00: c0548468 c084fbd0 c0888000 c084fc99 00000000 c084fc7c 1a110316 
000affff
GPR08: ffffffff c084fd18 1a111316 04ffffff 22000282 00000000 c00027c0 
00000000
GPR16: 00000000 00000000 c0040000 c003d544 00000001 c003eb2c 096023d4 
00000000
GPR24: c0636502 c0636502 c084fc74 c0588510 c084fc68 c084fc7c c084fc99 
00000002
NIP [c0545338] string+0x78/0x148
LR [c0548468] vsnprintf+0x3d8/0x824
Call Trace:
[c084fbd0] [c084fc7c] 0xc084fc7c (unreliable)
[c084fbe0] [c0548468] vsnprintf+0x3d8/0x824
[c084fc30] [c0072dec] vprintk_store+0x17c/0x4c8
[c084fcc0] [c007322c] vprintk_emit+0xf4/0x2a0
[c084fd00] [c0073d04] _printk+0x60/0x88
[c084fd40] [c01ab63c] sysctl_err+0x78/0xa4
[c084fd80] [c01ab404] __register_sysctl_table+0x6a0/0x6c4
[c084fde0] [c06a585c] __register_sysctl_init+0x30/0x78
[c084fe00] [c06a8cc8] tty_init+0x44/0x168
[c084fe30] [c00023c4] do_one_initcall+0x64/0x2a0
[c084fea0] [c068f060] kernel_init_freeable+0x184/0x230
[c084fee0] [c00027e4] kernel_init+0x24/0x124
[c084ff00] [c000f1fc] ret_from_kernel_user_thread+0x14/0x1c
--- interrupt: 0 at 0x0
NIP:  00000000 LR: 00000000 CTR: 00000000
REGS: c084ff10 TRAP: 0000   Not tainted  (6.5.0-rc6-gdef13277bacb)
MSR:  00000000 <>  CR: 00000000  XER: 00000000

GPR00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
GPR08: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
GPR24: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
NIP [00000000] 0x0
LR [00000000] 0x0
--- interrupt: 0
Code: 91610008 90e1000c 4bffd0b5 80010014 38210010 7c0803a6 4e800020 
409d0008 99230000 38630001 38840001 4240ffd0 <7d2a20ae> 7f851840 
5528063e 2c080000
---[ end trace 0000000000000000 ]---

note: swapper[1] exited with irqs disabled
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b


> 
> What?
> These commits remove the sentinel element (last empty element) from the
> sysctl arrays of all the files under the "drivers/" directory that use a
> sysctl array for registration. The merging of the preparation patches
> (in https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> to mainline allows us to just remove sentinel elements without changing
> behavior (more info here [1]).
> 
> These commits are part of a bigger set (here
> https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4)
> that remove the ctl_table sentinel. Make the review process easier by
> chunking the commits into manageable pieces. Each chunk can be reviewed
> separately without noise from parallel sets.
> 
> Now that the architecture chunk has been mostly reviewed [6], we send
> the "drivers/" directory. Once this one is done, it will be follwed by
> "fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove
> the unneeded check for ->procname == NULL.
> 
> Why?
> By removing the sysctl sentinel elements we avoid kernel bloat as
> ctl_table arrays get moved out of kernel/sysctl.c into their own
> respective subsystems. This move was started long ago to avoid merge
> conflicts; the sentinel removal bit came after Mathew Wilcox suggested
> it to avoid bloating the kernel by one element as arrays moved out. This
> patchset will reduce the overall build time size of the kernel and run
> time memory bloat by about ~64 bytes per declared ctl_table array. I
> have consolidated some links that shed light on the history of this
> effort [2].
> 
> Testing:
> * Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh)
> * Ran this through 0-day with no errors or warnings
> 
> Size saving after removing all sentinels:
>    These are the bytes that we save after removing all the sentinels
>    (this plus all the other chunks). I included them to get an idea of
>    how much memory we are talking about.
>      * bloat-o-meter:
>          - The "yesall" configuration results save 9158 bytes
>            https://lore.kernel.org/all/20230621091000.424843-1-j.granados@samsung.com/
>          - The "tiny" config + CONFIG_SYSCTL save 1215 bytes
>            https://lore.kernel.org/all/20230809105006.1198165-1-j.granados@samsung.com/
>      * memory usage:
>          In memory savings are measured to be 7296 bytes. (here is how to
>          measure [3])
> 
> Size saving after this patchset:
>      * bloat-o-meter
>          - The "yesall" config saves 2432 bytes [4]
>          - The "tiny" config saves 64 bytes [5]
>      * memory usage:
>          In this case there were no bytes saved because I do not have any
>          of the drivers in the patch. To measure it comment the printk in
>          `new_dir` and uncomment the if conditional in `new_links` [3].
> 
> Comments/feedback greatly appreciated
> 
> Best
> Joel
> 
> [1]
> We are able to remove a sentinel table without behavioral change by
> introducing a table_size argument in the same place where procname is
> checked for NULL. The idea is for it to keep stopping when it hits
> ->procname == NULL, while the sentinel is still present. And when the
> sentinel is removed, it will stop on the table_size. You can go to
> (https://lore.kernel.org/all/20230809105006.1198165-1-j.granados@samsung.com/)
> for more information.
> 
> [2]
> Links Related to the ctl_table sentinel removal:
> * Good summary from Luis sent with the "pull request" for the
>    preparation patches.
>    https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/
> * Another very good summary from Luis.
>    https://lore.kernel.org/all/ZMFizKFkVxUFtSqa@bombadil.infradead.org/
> * This is a patch set that replaces register_sysctl_table with register_sysctl
>    https://lore.kernel.org/all/20230302204612.782387-1-mcgrof@kernel.org/
> * Patch set to deprecate register_sysctl_paths()
>    https://lore.kernel.org/all/20230302202826.776286-1-mcgrof@kernel.org/
> * Here there is an explicit expectation for the removal of the sentinel element.
>    https://lore.kernel.org/all/20230321130908.6972-1-frank.li@vivo.com
> * The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
>    https://lore.kernel.org/all/20220220060626.15885-1-tangmeng@uniontech.com
> 
> [3]
> To measure the in memory savings apply this on top of this patchset.
> 
> "
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c88854df0b62..e0073a627bac 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
>          table[0].procname = new_name;
>          table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
>          init_header(&new->header, set->dir.header.root, set, node, table, 1);
> +       // Counts additional sentinel used for each new dir.
> +       printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
> 
>          return new;
>   }
> @@ -1199,6 +1201,9 @@ static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_
>                  link_name += len;
>                  link++;
>          }
> +       // Counts additional sentinel used for each new registration
> +       //if ((head->ctl_table + head->ctl_table_size)->procname)
> +               printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
>          init_header(links, dir->header.root, dir->header.set, node, link_table,
>                      head->ctl_table_size);
>          links->nreg = nr_entries;
> "
> and then run the following bash script in the kernel:
> 
> accum=0
> for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
>      echo $n
>      accum=$(calc "$accum + $n")
> done
> echo $accum
> 
> [4]
> add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
> Function                                     old     new   delta
> xpc_sys_xpc_hb                               192     128     -64
> xpc_sys_xpc                                  128      64     -64
> vrf_table                                    128      64     -64
> ucma_ctl_table                               128      64     -64
> tty_table                                    192     128     -64
> sg_sysctls                                   128      64     -64
> scsi_table                                   128      64     -64
> random_table                                 448     384     -64
> raid_table                                   192     128     -64
> oa_table                                     192     128     -64
> mac_hid_files                                256     192     -64
> iwcm_ctl_table                               128      64     -64
> ipmi_table                                   128      64     -64
> hv_ctl_table                                 128      64     -64
> hpet_table                                   128      64     -64
> firmware_config_table                        192     128     -64
> cdrom_table                                  448     384     -64
> balloon_table                                128      64     -64
> parport_sysctl_template                      912     720    -192
> parport_default_sysctl_table                 584     136    -448
> parport_device_sysctl_template               776     136    -640
> Total: Before=429940038, After=429937606, chg -0.00%
> 
> [5]
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-64 (-64)
> Function                                     old     new   delta
> random_table                                 448     384     -64
> Total: Before=1885527, After=1885463, chg -0.00%
> 
> [6] https://lore.kernel.org/all/20230913-jag-sysctl_remove_empty_elem_arch-v2-0-d1bd13a29bae@samsung.com/
> 
> Signed-off-by: Joel Granados <j.granados@samsung.com>
> 
> ---
> 
> ---
> Joel Granados (15):
>        cdrom: Remove now superfluous sentinel element from ctl_table array
>        hpet: Remove now superfluous sentinel element from ctl_table array
>        xen: Remove now superfluous sentinel element from ctl_table array
>        tty: Remove now superfluous sentinel element from ctl_table array
>        scsi: Remove now superfluous sentinel element from ctl_table array
>        parport: Remove the now superfluous sentinel element from ctl_table array
>        macintosh: Remove the now superfluous sentinel element from ctl_table array
>        infiniband: Remove the now superfluous sentinel element from ctl_table array
>        char-misc: Remove the now superfluous sentinel element from ctl_table array
>        vrf: Remove the now superfluous sentinel element from ctl_table array
>        sgi-xp: Remove the now superfluous sentinel element from ctl_table array
>        fw loader: Remove the now superfluous sentinel element from ctl_table array
>        raid: Remove now superfluous sentinel element from ctl_table array
>        hyper-v/azure: Remove now superfluous sentinel element from ctl_table array
>        intel drm: Remove now superfluous sentinel element from ctl_table array
> 
>   drivers/base/firmware_loader/fallback_table.c |  3 +-
>   drivers/cdrom/cdrom.c                         |  3 +-
>   drivers/char/hpet.c                           |  3 +-
>   drivers/char/ipmi/ipmi_poweroff.c             |  3 +-
>   drivers/char/random.c                         |  3 +-
>   drivers/gpu/drm/i915/i915_perf.c              |  3 +-
>   drivers/hv/hv_common.c                        |  3 +-
>   drivers/infiniband/core/iwcm.c                |  3 +-
>   drivers/infiniband/core/ucma.c                |  3 +-
>   drivers/macintosh/mac_hid.c                   |  3 +-
>   drivers/md/md.c                               |  3 +-
>   drivers/misc/sgi-xp/xpc_main.c                |  6 ++--
>   drivers/net/vrf.c                             |  3 +-
>   drivers/parport/procfs.c                      | 42 ++++++++++++---------------
>   drivers/scsi/scsi_sysctl.c                    |  3 +-
>   drivers/scsi/sg.c                             |  3 +-
>   drivers/tty/tty_io.c                          |  3 +-
>   drivers/xen/balloon.c                         |  3 +-
>   18 files changed, 36 insertions(+), 60 deletions(-)
> ---
> base-commit: 0e945134b680040b8613e962f586d91b6d40292d
> change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c
> 
> Best regards,
Steve Wahl Sept. 28, 2023, 5:51 p.m. UTC | #4
On Thu, Sep 28, 2023 at 03:21:36PM +0200, Joel Granados via B4 Relay wrote:
> From: Joel Granados <j.granados@samsung.com>
> 
> This commit comes at the tail end of a greater effort to remove the
> empty elements at the end of the ctl_table arrays (sentinels) which
> will reduce the overall build time size of the kernel and run time
> memory bloat by ~64 bytes per sentinel (further information Link :
> https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> 
> Remove sentinel from xpc_sys_xpc_hb and xpc_sys_xpc
> 
> Signed-off-by: Joel Granados <j.granados@samsung.com>
> ---
>  drivers/misc/sgi-xp/xpc_main.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/sgi-xp/xpc_main.c b/drivers/misc/sgi-xp/xpc_main.c
> index 6da509d692bb..c898092ff3ac 100644
> --- a/drivers/misc/sgi-xp/xpc_main.c
> +++ b/drivers/misc/sgi-xp/xpc_main.c
> @@ -109,8 +109,7 @@ static struct ctl_table xpc_sys_xpc_hb[] = {
>  	 .mode = 0644,
>  	 .proc_handler = proc_dointvec_minmax,
>  	 .extra1 = &xpc_hb_check_min_interval,
> -	 .extra2 = &xpc_hb_check_max_interval},
> -	{}
> +	 .extra2 = &xpc_hb_check_max_interval}
>  };
>  static struct ctl_table xpc_sys_xpc[] = {
>  	{
> @@ -120,8 +119,7 @@ static struct ctl_table xpc_sys_xpc[] = {
>  	 .mode = 0644,
>  	 .proc_handler = proc_dointvec_minmax,
>  	 .extra1 = &xpc_disengage_min_timelimit,
> -	 .extra2 = &xpc_disengage_max_timelimit},
> -	{}
> +	 .extra2 = &xpc_disengage_max_timelimit}
>  };
>  
>  static struct ctl_table_header *xpc_sysctl;
> 
> -- 
> 2.30.2
> 

I assume you'll match the rest of the changes with regards to the
trailing comma.

Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Joel Granados Sept. 29, 2023, 12:14 p.m. UTC | #5
On Thu, Sep 28, 2023 at 12:51:15PM -0500, Steve Wahl wrote:
> On Thu, Sep 28, 2023 at 03:21:36PM +0200, Joel Granados via B4 Relay wrote:
> > From: Joel Granados <j.granados@samsung.com>
> > 
> > This commit comes at the tail end of a greater effort to remove the
> > empty elements at the end of the ctl_table arrays (sentinels) which
> > will reduce the overall build time size of the kernel and run time
> > memory bloat by ~64 bytes per sentinel (further information Link :
> > https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> > 
> > Remove sentinel from xpc_sys_xpc_hb and xpc_sys_xpc
> > 
> > Signed-off-by: Joel Granados <j.granados@samsung.com>
> > ---
> >  drivers/misc/sgi-xp/xpc_main.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/misc/sgi-xp/xpc_main.c b/drivers/misc/sgi-xp/xpc_main.c
> > index 6da509d692bb..c898092ff3ac 100644
> > --- a/drivers/misc/sgi-xp/xpc_main.c
> > +++ b/drivers/misc/sgi-xp/xpc_main.c
> > @@ -109,8 +109,7 @@ static struct ctl_table xpc_sys_xpc_hb[] = {
> >  	 .mode = 0644,
> >  	 .proc_handler = proc_dointvec_minmax,
> >  	 .extra1 = &xpc_hb_check_min_interval,
> > -	 .extra2 = &xpc_hb_check_max_interval},
> > -	{}
> > +	 .extra2 = &xpc_hb_check_max_interval}
> >  };
> >  static struct ctl_table xpc_sys_xpc[] = {
> >  	{
> > @@ -120,8 +119,7 @@ static struct ctl_table xpc_sys_xpc[] = {
> >  	 .mode = 0644,
> >  	 .proc_handler = proc_dointvec_minmax,
> >  	 .extra1 = &xpc_disengage_min_timelimit,
> > -	 .extra2 = &xpc_disengage_max_timelimit},
> > -	{}
> > +	 .extra2 = &xpc_disengage_max_timelimit}
> >  };
> >  
> >  static struct ctl_table_header *xpc_sysctl;
> > 
> > -- 
> > 2.30.2
> > 
> 
> I assume you'll match the rest of the changes with regards to the
> trailing comma.
If you are refering to Greg's comments. yes. I'll send a V2 with the
trailing comma.

Best

> 
> Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
> 
> -- 
> Steve Wahl, Hewlett Packard Enterprise
Joel Granados Sept. 29, 2023, 12:15 p.m. UTC | #6
On Thu, Sep 28, 2023 at 03:26:16PM +0000, Wei Liu wrote:
> Please change the prefix to "Drivers: hv:" in the subject line in the
> two patches.
> 
> On Thu, Sep 28, 2023 at 03:21:39PM +0200, Joel Granados via B4 Relay wrote:
> > From: Joel Granados <j.granados@samsung.com>
> > 
> > This commit comes at the tail end of a greater effort to remove the
> > empty elements at the end of the ctl_table arrays (sentinels) which
> > will reduce the overall build time size of the kernel and run time
> > memory bloat by ~64 bytes per sentinel (further information Link :
> > https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> > 
> > Remove sentinel from hv_ctl_table
> > 
> > Signed-off-by: Joel Granados <j.granados@samsung.com>
> > ---
> >  drivers/hv/hv_common.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> > index ccad7bca3fd3..bc7d678030aa 100644
> > --- a/drivers/hv/hv_common.c
> > +++ b/drivers/hv/hv_common.c
> > @@ -147,8 +147,7 @@ static struct ctl_table hv_ctl_table[] = {
> >  		.proc_handler	= proc_dointvec_minmax,
> >  		.extra1		= SYSCTL_ZERO,
> >  		.extra2		= SYSCTL_ONE
> > -	},
> > -	{}
> > +	}
> 
> Please keep the comma at the end.
My V2 will have this.

> 
> >  };
> >  
> >  static int hv_die_panic_notify_crash(struct notifier_block *self,
> > 
> > -- 
> > 2.30.2
> >
Joel Granados Sept. 29, 2023, 2:03 p.m. UTC | #7
On Thu, Sep 28, 2023 at 03:26:16PM +0000, Wei Liu wrote:
> Please change the prefix to "Drivers: hv:" in the subject line in the
> two patches.
I'll change the commit message for the 14/15 patch from "hyper-v/azure"
to "Drivers: hv:". But I only see one patch that needs this. Which is
the other one?

best
> 
> On Thu, Sep 28, 2023 at 03:21:39PM +0200, Joel Granados via B4 Relay wrote:
> > From: Joel Granados <j.granados@samsung.com>
> > 
> > This commit comes at the tail end of a greater effort to remove the
> > empty elements at the end of the ctl_table arrays (sentinels) which
> > will reduce the overall build time size of the kernel and run time
> > memory bloat by ~64 bytes per sentinel (further information Link :
> > https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> > 
> > Remove sentinel from hv_ctl_table
> > 
> > Signed-off-by: Joel Granados <j.granados@samsung.com>
> > ---
> >  drivers/hv/hv_common.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> > index ccad7bca3fd3..bc7d678030aa 100644
> > --- a/drivers/hv/hv_common.c
> > +++ b/drivers/hv/hv_common.c
> > @@ -147,8 +147,7 @@ static struct ctl_table hv_ctl_table[] = {
> >  		.proc_handler	= proc_dointvec_minmax,
> >  		.extra1		= SYSCTL_ZERO,
> >  		.extra2		= SYSCTL_ONE
> > -	},
> > -	{}
> > +	}
> 
> Please keep the comma at the end.
> 
> >  };
> >  
> >  static int hv_die_panic_notify_crash(struct notifier_block *self,
> > 
> > -- 
> > 2.30.2
> >
Joel Granados Oct. 2, 2023, 8:47 a.m. UTC | #8
On Thu, Sep 28, 2023 at 04:31:30PM +0000, Christophe Leroy wrote:
> 
> 
> Le 28/09/2023 à 15:21, Joel Granados via B4 Relay a écrit :
> > From: Joel Granados <j.granados@samsung.com>
> 
> Automatic test fails on powerpc, see 
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20230928-jag-sysctl_remove_empty_elem_drivers-v1-15-e59120fca9f9@samsung.com/
From this I got to this URL
https://github.com/linuxppc/linux-snowpatch/actions/runs/6339718136/job/17221399242
and saw this message "sysctl table check failed: dev/tty/ No proc_handler".
This means that we hit the check for entry->proc_handler in
sysctl_check_table.

> 
> Kernel attempted to read user page (1a111316) - exploit attempt? (uid: 0)
> BUG: Unable to handle kernel data access on read at 0x1a111316
> Faulting instruction address: 0xc0545338
> Oops: Kernel access of bad area, sig: 11 [#1]
> BE PAGE_SIZE=4K PowerPC 44x Platform
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 6.5.0-rc6-gdef13277bacb #1
> Hardware name: amcc,bamboo 440GR Rev. B 0x422218d3 PowerPC 44x Platform
> NIP:  c0545338 LR: c0548468 CTR: ffffffff
> REGS: c084fae0 TRAP: 0300   Not tainted  (6.5.0-rc6-gdef13277bacb)
> MSR:  00021000 <CE,ME>  CR: 84004288  XER: 00000000
> DEAR: 1a111316 ESR: 00000000
> GPR00: c0548468 c084fbd0 c0888000 c084fc99 00000000 c084fc7c 1a110316 
> 000affff
> GPR08: ffffffff c084fd18 1a111316 04ffffff 22000282 00000000 c00027c0 
> 00000000
> GPR16: 00000000 00000000 c0040000 c003d544 00000001 c003eb2c 096023d4 
> 00000000
> GPR24: c0636502 c0636502 c084fc74 c0588510 c084fc68 c084fc7c c084fc99 
> 00000002
> NIP [c0545338] string+0x78/0x148
> LR [c0548468] vsnprintf+0x3d8/0x824
> Call Trace:
> [c084fbd0] [c084fc7c] 0xc084fc7c (unreliable)
> [c084fbe0] [c0548468] vsnprintf+0x3d8/0x824
> [c084fc30] [c0072dec] vprintk_store+0x17c/0x4c8
> [c084fcc0] [c007322c] vprintk_emit+0xf4/0x2a0
> [c084fd00] [c0073d04] _printk+0x60/0x88
> [c084fd40] [c01ab63c] sysctl_err+0x78/0xa4
> [c084fd80] [c01ab404] __register_sysctl_table+0x6a0/0x6c4
> [c084fde0] [c06a585c] __register_sysctl_init+0x30/0x78
> [c084fe00] [c06a8cc8] tty_init+0x44/0x168
> [c084fe30] [c00023c4] do_one_initcall+0x64/0x2a0
> [c084fea0] [c068f060] kernel_init_freeable+0x184/0x230
> [c084fee0] [c00027e4] kernel_init+0x24/0x124
> [c084ff00] [c000f1fc] ret_from_kernel_user_thread+0x14/0x1c
I followed this trace and proc_handler is correctly defined in tty_table
(struct ctl_table) in drivers/tty/tty_io.c:tty_init and there is not
path that changes these values.
Additionally, we then fail trying to print instead of continuing with
the initialization. My conjecture is that this might be due to something
different than tht sysctl register call.

Does this happen consistenly or is this just a one off issue?

To what branch are these patches being applied to?

I'm going to post my V2 and keep working on this issue if it pops up
again.

Thx for the report

Best

> --- interrupt: 0 at 0x0
> NIP:  00000000 LR: 00000000 CTR: 00000000
> REGS: c084ff10 TRAP: 0000   Not tainted  (6.5.0-rc6-gdef13277bacb)
> MSR:  00000000 <>  CR: 00000000  XER: 00000000
> 
> GPR00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
> GPR08: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
> GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
> GPR24: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
> NIP [00000000] 0x0
> LR [00000000] 0x0
> --- interrupt: 0
> Code: 91610008 90e1000c 4bffd0b5 80010014 38210010 7c0803a6 4e800020 
> 409d0008 99230000 38630001 38840001 4240ffd0 <7d2a20ae> 7f851840 
> 5528063e 2c080000
> ---[ end trace 0000000000000000 ]---
> 
> note: swapper[1] exited with irqs disabled
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> 
> 
> > 
> > What?
> > These commits remove the sentinel element (last empty element) from the
> > sysctl arrays of all the files under the "drivers/" directory that use a
> > sysctl array for registration. The merging of the preparation patches
> > (in https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> > to mainline allows us to just remove sentinel elements without changing
> > behavior (more info here [1]).
<--- snip --->
> >   drivers/macintosh/mac_hid.c                   |  3 +-
> >   drivers/md/md.c                               |  3 +-
> >   drivers/misc/sgi-xp/xpc_main.c                |  6 ++--
> >   drivers/net/vrf.c                             |  3 +-
> >   drivers/parport/procfs.c                      | 42 ++++++++++++---------------
> >   drivers/scsi/scsi_sysctl.c                    |  3 +-
> >   drivers/scsi/sg.c                             |  3 +-
> >   drivers/tty/tty_io.c                          |  3 +-
> >   drivers/xen/balloon.c                         |  3 +-
> >   18 files changed, 36 insertions(+), 60 deletions(-)
> > ---
> > base-commit: 0e945134b680040b8613e962f586d91b6d40292d
> > change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c
> > 
> > Best regards,
Christophe Leroy Oct. 2, 2023, 9:02 a.m. UTC | #9
Le 02/10/2023 à 10:47, Joel Granados a écrit :
> On Thu, Sep 28, 2023 at 04:31:30PM +0000, Christophe Leroy wrote:

> I followed this trace and proc_handler is correctly defined in tty_table
> (struct ctl_table) in drivers/tty/tty_io.c:tty_init and there is not
> path that changes these values.
> Additionally, we then fail trying to print instead of continuing with
> the initialization. My conjecture is that this might be due to something
> different than tht sysctl register call.
> 
> Does this happen consistenly or is this just a one off issue?

Don't know.

> 
> To what branch are these patches being applied to?

As far as I understand from 
https://github.com/linuxppc/linux-snowpatch/commits/snowpatch/375319, 
it's being applied on 
https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?id=d774975


> 
> I'm going to post my V2 and keep working on this issue if it pops up
> again.
> 

Christophe
diff mbox

Patch

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c88854df0b62..e0073a627bac 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -976,6 +976,8 @@  static struct ctl_dir *new_dir(struct ctl_table_set *set,
        table[0].procname = new_name;
        table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
        init_header(&new->header, set->dir.header.root, set, node, table, 1);
+       // Counts additional sentinel used for each new dir.
+       printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));

        return new;
 }
@@ -1199,6 +1201,9 @@  static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_
                link_name += len;
                link++;
        }
+       // Counts additional sentinel used for each new registration
+       //if ((head->ctl_table + head->ctl_table_size)->procname)
+               printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
        init_header(links, dir->header.root, dir->header.set, node, link_table,
                    head->ctl_table_size);
        links->nreg = nr_entries;