mm-commits Archive on lore.kernel.org
 help / color / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, bp@alien8.de, corbet@lwn.net,
	gregkh@linuxfoundation.org, jeyu@kernel.org, linux-mm@kvack.org,
	linux@rasmusvillemoes.dk, mcgrof@kernel.org,
	mm-commits@vger.kernel.org, ndesaulniers@google.com,
	tiwai@suse.de, torvalds@linux-foundation.org
Subject: [patch 71/91] modules: add CONFIG_MODPROBE_PATH
Date: Thu, 06 May 2021 18:05:45 -0700
Message-ID: <20210507010545.7UnOF0TTk%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210506180126.03e1baee7ca52bedb6cc6003@linux-foundation.org>

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: modules: add CONFIG_MODPROBE_PATH

Allow the developer to specifiy the initial value of the modprobe_path[]
string.  This can be used to set it to the empty string initially, thus
effectively disabling request_module() during early boot until userspace
writes a new value via the /proc/sys/kernel/modprobe interface.  [1]

When building a custom kernel (often for an embedded target), it's normal
to build everything into the kernel that is needed for booting, and indeed
the initramfs often contains no modules at all, so every such
request_module() done before userspace init has mounted the real rootfs is
a waste of time.

This is particularly useful when combined with the previous patch, which
made the initramfs unpacking asynchronous - for that to work, it had to
make any usermodehelper call wait for the unpacking to finish before
attempting to invoke the userspace helper.  By eliminating all such
(known-to-be-futile) calls of usermodehelper, the initramfs unpacking and
the {device,late}_initcalls can proceed in parallel for much longer.

For a relatively slow ppc board I'm working on, the two patches combined
lead to 0.2s faster boot - but more importantly, the fact that the
initramfs unpacking proceeds completely in the background while devices
get probed means I get to handle the gpio watchdog in time without getting
reset.

[1] __request_module() already has an early -ENOENT return when
modprobe_path is the empty string.

Link: https://lkml.kernel.org/r/20210313212528.2956377-3-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 init/Kconfig  |   12 ++++++++++++
 kernel/kmod.c |    2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

--- a/init/Kconfig~modules-add-config_modprobe_path
+++ a/init/Kconfig
@@ -2299,6 +2299,18 @@ config MODULE_ALLOW_MISSING_NAMESPACE_IM
 
 	  If unsure, say N.
 
+config MODPROBE_PATH
+	string "Path to modprobe binary"
+	default "/sbin/modprobe"
+	help
+	  When kernel code requests a module, it does so by calling
+	  the "modprobe" userspace utility. This option allows you to
+	  set the path where that binary is found. This can be changed
+	  at runtime via the sysctl file
+	  /proc/sys/kernel/modprobe. Setting this to the empty string
+	  removes the kernel's ability to request modules (but
+	  userspace can still load modules explicitly).
+
 config TRIM_UNUSED_KSYMS
 	bool "Trim unused exported kernel symbols" if EXPERT
 	depends on !COMPILE_TEST
--- a/kernel/kmod.c~modules-add-config_modprobe_path
+++ a/kernel/kmod.c
@@ -58,7 +58,7 @@ static DECLARE_WAIT_QUEUE_HEAD(kmod_wq);
 /*
 	modprobe_path is set via /proc/sys.
 */
-char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
+char modprobe_path[KMOD_PATH_LEN] = CONFIG_MODPROBE_PATH;
 
 static void free_modprobe_argv(struct subprocess_info *info)
 {
_

  parent reply index

Thread overview: 119+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-07  1:01 incoming Andrew Morton
2021-05-07  1:02 ` [patch 01/91] alpha: eliminate old-style function definitions Andrew Morton
2021-05-07  1:02 ` [patch 02/91] alpha: csum_partial_copy.c: add function prototypes from <net/checksum.h> Andrew Morton
2021-05-07  1:02 ` [patch 03/91] fs/proc/generic.c: fix incorrect pde_is_permanent check Andrew Morton
2021-05-07  1:02 ` [patch 04/91] proc: save LOC in __xlate_proc_name() Andrew Morton
2021-05-07  2:24   ` Linus Torvalds
2021-05-07  1:02 ` [patch 05/91] proc: mandate ->proc_lseek in "struct proc_ops" Andrew Morton
2021-05-07  1:02 ` [patch 06/91] proc: delete redundant subset=pid check Andrew Morton
2021-05-07  1:02 ` [patch 07/91] selftests: proc: test subset=pid Andrew Morton
2021-05-07  1:02 ` [patch 08/91] proc/sysctl: fix function name error in comments Andrew Morton
2021-05-07  1:02 ` [patch 09/91] include: remove pagemap.h from blkdev.h Andrew Morton
2021-05-07  1:02 ` [patch 10/91] kernel.h: drop inclusion in bitmap.h Andrew Morton
2021-05-07  1:02 ` [patch 11/91] linux/profile.h: remove unnecessary declaration Andrew Morton
2021-05-07  1:02 ` [patch 12/91] kernel/async.c: fix pr_debug statement Andrew Morton
2021-05-07  1:02 ` [patch 13/91] kernel/cred.c: make init_groups static Andrew Morton
2021-05-07  1:02 ` [patch 14/91] tools: disable -Wno-type-limits Andrew Morton
2021-05-07  1:02 ` [patch 15/91] tools: bitmap: sync function declarations with the kernel Andrew Morton
2021-05-07  1:02 ` [patch 16/91] tools: sync BITMAP_LAST_WORD_MASK() macro " Andrew Morton
2021-05-07  1:02 ` [patch 17/91] arch: rearrange headers inclusion order in asm/bitops for m68k, sh and h8300 Andrew Morton
2021-05-07  1:02 ` [patch 18/91] lib: extend the scope of small_const_nbits() macro Andrew Morton
2021-05-07  1:03 ` [patch 19/91] tools: sync small_const_nbits() macro with the kernel Andrew Morton
2021-05-07  1:03 ` [patch 20/91] lib: inline _find_next_bit() wrappers Andrew Morton
2021-05-07  1:03 ` [patch 21/91] tools: sync find_next_bit implementation Andrew Morton
2021-05-07  1:03 ` [patch 22/91] lib: add fast path for find_next_*_bit() Andrew Morton
2021-05-07  1:03 ` [patch 23/91] lib: add fast path for find_first_*_bit() and find_last_bit() Andrew Morton
2021-05-07  1:03 ` [patch 24/91] tools: sync lib/find_bit implementation Andrew Morton
2021-05-07  1:03 ` [patch 25/91] MAINTAINERS: add entry for the bitmap API Andrew Morton
2021-05-07  1:03 ` [patch 26/91] lib/bch.c: fix a typo in the file bch.c Andrew Morton
2021-05-07  1:03 ` [patch 27/91] lib: fix inconsistent indenting in process_bit1() Andrew Morton
2021-05-07  1:03 ` [patch 28/91] lib/list_sort.c: fix typo in function description Andrew Morton
2021-05-07  1:03 ` [patch 29/91] lib/genalloc.c: fix a typo Andrew Morton
2021-05-07  1:03 ` [patch 30/91] lib: crc8: pointer to data block should be const Andrew Morton
2021-05-07  1:03 ` [patch 31/91] lib: stackdepot: turn depot_lock spinlock to raw_spinlock Andrew Morton
2021-05-07  1:03 ` [patch 32/91] lib/percpu_counter: tame kernel-doc compile warning Andrew Morton
2021-05-07  1:03 ` [patch 33/91] lib/genalloc: add parameter description to fix doc " Andrew Morton
2021-05-07  1:03 ` [patch 34/91] lib: parser: clean up kernel-doc Andrew Morton
2021-05-07  1:03 ` [patch 35/91] include/linux/compat.h: remove unneeded declaration from COMPAT_SYSCALL_DEFINEx() Andrew Morton
2021-05-07  1:03 ` [patch 36/91] checkpatch: warn when missing newline in return sysfs_emit() formats Andrew Morton
2021-05-07  1:03 ` [patch 37/91] checkpatch: exclude four preprocessor sub-expressions from MACRO_ARG_REUSE Andrew Morton
2021-05-07  1:04 ` [patch 38/91] checkpatch: improve ALLOC_ARRAY_ARGS test Andrew Morton
2021-05-07  1:04 ` [patch 39/91] kselftest: introduce new epoll test case Andrew Morton
2021-05-07  1:04 ` [patch 40/91] fs/epoll: restore waking from ep_done_scan() Andrew Morton
2021-05-07  1:04 ` [patch 41/91] isofs: fix fall-through warnings for Clang Andrew Morton
2021-05-07  1:04 ` [patch 42/91] fs/nilfs2: fix misspellings using codespell tool Andrew Morton
2021-05-07  1:04 ` [patch 43/91] nilfs2: fix typos in comments Andrew Morton
2021-05-07  1:04 ` [patch 44/91] hpfs: replace one-element array with flexible-array member Andrew Morton
2021-05-07  1:04 ` [patch 45/91] do_wait: make PIDTYPE_PID case O(1) instead of O(n) Andrew Morton
2021-05-07  1:04 ` [patch 46/91] kernel/fork.c: simplify copy_mm() Andrew Morton
2021-05-07  1:04 ` [patch 47/91] kernel/fork.c: fix typos Andrew Morton
2021-05-07  1:04 ` [patch 48/91] kernel/crash_core: add crashkernel=auto for vmcore creation Andrew Morton
2021-05-07  7:25   ` Linus Torvalds
2021-05-08  3:13     ` Baoquan He
2021-05-08  3:29       ` Baoquan He
2021-05-07  8:16   ` David Hildenbrand
2021-05-08  8:51     ` Baoquan He
2021-05-08  9:22       ` David Hildenbrand
2021-05-10  4:53         ` Baoquan He
2021-05-10  8:32           ` David Hildenbrand
2021-05-10 10:43             ` Baoquan He
2021-05-10 11:01               ` David Hildenbrand
2021-05-10 11:44                 ` Dave Young
2021-05-10 11:56                   ` David Hildenbrand
2021-05-11 13:36                     ` Baoquan He
2021-05-11 16:31                       ` Mike Rapoport
2021-05-11 17:07                         ` David Hildenbrand
2021-05-12 14:51                           ` Baoquan He
2021-05-12 15:07                             ` David Hildenbrand
2021-05-13  5:04                               ` Baoquan He
2021-05-12 19:03                             ` Kairui Song
2021-05-17  8:22                             ` David Hildenbrand
2021-05-18  8:49                               ` Baoquan He
2021-05-18  8:51                                 ` David Hildenbrand
2021-05-18  9:24                                   ` Dave Young
2021-05-12 14:13                         ` Baoquan He
2021-05-12  7:42                     ` Dave Young
2021-05-07  1:04 ` [patch 49/91] kexec: add kexec reboot string Andrew Morton
2021-05-07  1:04 ` [patch 50/91] kernel: kexec_file: fix error return code of kexec_calculate_store_digests() Andrew Morton
2021-05-07  1:04 ` [patch 51/91] kexec: dump kmessage before machine_kexec Andrew Morton
2021-05-07  1:04 ` [patch 52/91] gcov: combine common code Andrew Morton
2021-05-07  1:04 ` [patch 53/91] gcov: simplify buffer allocation Andrew Morton
2021-05-07  1:04 ` [patch 54/91] gcov: use kvmalloc() Andrew Morton
2021-05-07  1:04 ` [patch 55/91] gcov: clang: drop support for clang-10 and older Andrew Morton
2021-05-07  1:04 ` [patch 56/91] smp: kernel/panic.c - silence warnings Andrew Morton
2021-05-07  1:05 ` [patch 57/91] delayacct: clear right task's flag after blkio completes Andrew Morton
2021-05-07  1:05 ` [patch 58/91] gdb: lx-symbols: store the abspath() Andrew Morton
2021-05-07  1:05 ` [patch 59/91] scripts/gdb: document lx_current is only supported by x86 Andrew Morton
2021-05-07  1:05 ` [patch 60/91] scripts/gdb: add lx_current support for arm64 Andrew Morton
2021-05-07  1:05 ` [patch 61/91] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM_RAM resources Andrew Morton
2021-05-07  1:05 ` [patch 62/91] kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources Andrew Morton
2021-05-07  1:05 ` [patch 63/91] kernel/resource: remove first_lvl / siblings_only logic Andrew Morton
2021-05-07  1:05 ` [patch 64/91] kernel/resource: allow region_intersects users to hold resource_lock Andrew Morton
2021-05-07  1:05 ` [patch 65/91] kernel/resource: refactor __request_region to allow external locking Andrew Morton
2021-05-07  1:05 ` [patch 66/91] kernel/resource: fix locking in request_free_mem_region Andrew Morton
2021-05-07  1:05 ` [patch 67/91] selftests: remove duplicate include Andrew Morton
2021-05-07  1:05 ` [patch 68/91] kernel/async.c: stop guarding pr_debug() statements Andrew Morton
2021-05-07  1:05 ` [patch 69/91] kernel/async.c: remove async_unregister_domain() Andrew Morton
2021-05-07  1:05 ` [patch 70/91] init/initramfs.c: do unpacking asynchronously Andrew Morton
2021-05-07  1:05 ` Andrew Morton [this message]
2021-05-07  1:05 ` [patch 72/91] ipc/sem.c: mundane typo fixes Andrew Morton
2021-05-07  1:05 ` [patch 73/91] mm: fix some typos and code style problems Andrew Morton
2021-05-07  1:05 ` [patch 74/91] drivers/char: remove /dev/kmem for good Andrew Morton
2021-05-07  1:06 ` [patch 75/91] mm: remove xlate_dev_kmem_ptr() Andrew Morton
2021-05-07  1:06 ` [patch 76/91] mm/vmalloc: remove vwrite() Andrew Morton
2021-05-07  1:06 ` [patch 77/91] arm: print alloc free paths for address in registers Andrew Morton
2021-05-07  1:06 ` [patch 78/91] scripts/spelling.txt: add "overlfow" Andrew Morton
2021-05-07  1:06 ` [patch 79/91] scripts/spelling.txt: add "diabled" typo Andrew Morton
2021-05-07  1:06 ` [patch 80/91] scripts/spelling.txt: add "overflw" Andrew Morton
2021-05-07  1:06 ` [patch 81/91] mm/slab.c: fix spelling mistake "disired" -> "desired" Andrew Morton
2021-05-07  1:06 ` [patch 82/91] include/linux/pgtable.h: few spelling fixes Andrew Morton
2021-05-07  1:06 ` [patch 83/91] kernel/umh.c: fix some spelling mistakes Andrew Morton
2021-05-07  1:06 ` [patch 84/91] kernel/user_namespace.c: fix typos Andrew Morton
2021-05-07  1:06 ` [patch 85/91] kernel/up.c: fix typo Andrew Morton
2021-05-07  1:06 ` [patch 86/91] kernel/sys.c: " Andrew Morton
2021-05-07  1:06 ` [patch 87/91] fs: fat: fix spelling typo of values Andrew Morton
2021-05-07  1:06 ` [patch 88/91] ipc/sem.c: spelling fix Andrew Morton
2021-05-07  1:06 ` [patch 89/91] treewide: remove editor modelines and cruft Andrew Morton
2021-05-07  1:06 ` [patch 90/91] mm: fix typos in comments Andrew Morton
2021-05-07  1:06 ` [patch 91/91] " Andrew Morton
2021-05-07  7:12 ` incoming Linus Torvalds

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210507010545.7UnOF0TTk%akpm@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=bp@alien8.de \
    --cc=corbet@lwn.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=jeyu@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux@rasmusvillemoes.dk \
    --cc=mcgrof@kernel.org \
    --cc=mm-commits@vger.kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=tiwai@suse.de \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

mm-commits Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/mm-commits/0 mm-commits/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 mm-commits mm-commits/ https://lore.kernel.org/mm-commits \
		mm-commits@vger.kernel.org
	public-inbox-index mm-commits

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.mm-commits


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git