linux-kernel - Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module libcrc32c"

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: <201006032236.46943.rusty@rustcorp.com.au>
Date:	Thu, 3 Jun 2010 22:36:45 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Brandon Philips <brandon@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Jon Masters <jonathan@...masters.org>,
	Tejun Heo <htejun@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module libcrc32c"

On Thu, 3 Jun 2010 12:20:48 am Linus Torvalds wrote:
> 
> On Wed, 2 Jun 2010, Rusty Russell wrote:
> > 
> > Found another locking issue: the code which verifies we don't export over
> > an existing symbol needs to be atomic wrt. adding us to the list.
> 
> Yup.
> 
> And now that I'm looking at that call-chain (to see if it would make sense 
> to use some other more specific lock - doesn't look like it: all the 
> readers are using RCU and this is the only writer), I also give you this 
> trivial one-liner. It changes each_symbol() to not put that constant array 
> on the stack, resulting in changing
> 
>         movq    $C.388.31095, %rsi      #, tmp85
>         subq    $376, %rsp      #,
>         movq    %rdi, %rbx      # fn, fn
>         leaq    -208(%rbp), %rdi        #, tmp84
>         movq    %rbx, %rdx      # fn,
>         rep movsl
>         xorl    %esi, %esi      #
>         leaq    -208(%rbp), %rdi        #, tmp87
>         movq    %r12, %rcx      # data,
>         call    each_symbol_in_section.clone.0  #
> 
> into
> 
>         xorl    %esi, %esi      #
>         subq    $216, %rsp      #,
>         movq    %rdi, %rbx      # fn, fn  
>         movq    $arr.31078, %rdi        #,
>         call    each_symbol_in_section.clone.0  #
> 
> which is not so much about being obviously shorter and simpler because we 
> don't unnecessarily copy that constant array around onto the stack, but 
> also about having a much smaller stack footprint (376 vs 216 bytes - see 
> the update of 'rsp').
> 
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

BTW, applied, thanks!

I've finished the cleanup now, and removed the noinline on load_module;
we're down to 124 bytes of stack for sys_init_module here (32 bit).

The following changes since commit aef4b9aaae1decc775778903922bd0075cce7a88:
  Linus Torvalds (1):
        Merge branch 'next' of git://git.kernel.org/.../benh/powerpc

are available in the git repository at:

  ssh://master.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6 modules

Eric Dumazet (1):
      module: module_unload_init() cleanup

Linus Torvalds (6):
      module: Make the 'usage' lists be two-way
      module: move find_module check to end
      module: refactor load_module
      module: refactor load_module part 2
      module: reduce stack usage for each_symbol()
      module: fix bne2 "gave up waiting for init of module libcrc32c"

Rusty Russell (18):
      module: fix kdb's illicit use of struct module_use.
      module: move sysfs exposure to end of load_module
      module: Make module sysfs functions private.
      module: make locking more fine-grained.
      module: verify_export_symbols under the lock
      module: fix bne2 "gave up waiting for init of module libcrc32c"
      module: refactor load_module part 3
      module: refactor load_module part 4
      module: refactor load_module part 5
      module: refactor out section header rewriting
      module: kallsyms functions take struct load_info
      module: layout_and_allocate
      module: sysfs cleanup
      module: pass load_info into other functions
      module: move module args strndup_user to just before use
      module: simplify per-cpu handling a little
      module: group post-relocation functions into post_relocation()
      module: cleanup comments, remove noinline

 include/linux/module.h      |   44 +--
 kernel/debug/kdb/kdb_main.c |   12 +-
 kernel/module.c             | 1361 ++++++++++++++++++++++++-------------------



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/