Hi!

CC'ing Rusty and mailing lists

On Thu, Jan 28, 2016 at 8:40 PM, Samson Yeung [off-list ref] wrote:

On 01/28/2016 11:21 AM, Lucas De Marchi wrote:

quoted

Hi Samson,

On Wed, Jan 27, 2016 at 5:32 PM, Samson Yeung [off-list ref]
wrote:

quoted

Hi all,

Please reply directly as I am not on this list.

Commit "fd44a98ae2eb Fix race while loading modules" also broke 'modinfo
crc32', specifically, for me.

Is this a bug, is it something strange going on with crc32, or is it
intended behavior?

breaking is never intended ;-). What do you mean by "break"? Does it
crash?

'modinfo crc32' prints

modinfo: ERROR: Module crc32 not found.

and a return value of 1 using fd44a98ae2eb.

Without changing the contents of /lib/modules/`uname -r`/modules.* files,
using fd44a98ae2eb^, 'modinfo crc32' gives me the expected info about crc32
instead:

filename:       /lib/modules/4.2.0-25-generic/kernel/crypto/crc32.ko
alias:          crypto-crc32
alias:          crc32
license:        GPL
description:    CRC32 calculations wrapper for lib/crc32
author:         Alexander Boyko [off-list ref]
srcversion:     B0DE005719AC9ED9A3EEAD7
depends:
intree:         Y
vermagic:       4.2.0-25-generic SMP mod_unload modversions
signer:         Build time autogenerated kernel key
sig_key:        A4:10:30:FB:DF:1D:C9:62:B4:BB:7D:16:44:C3:33:7E:C4:16:DB:86
sig_hashalgo:   sha512

quoted

I can't see how this commit is related to modinfo. You will need to
give more details. Check if you can get the output by passing the
complete path to the module and make sure it's actually a module (and

Giving the full path to the module still works as expected, so
'modinfo /lib/modules/4.2.0-25-generic/kernel/crypto/crc32.ko' displays
module information and returns 0, using both fd44a98ae2eb^ and fd44a98ae2eb.

quoted

not builtin) in your kernel configuration

I must admit that I'm slightly confused wrt crc32, since there is
kernel/arch/x86/crypto/crc32-pclmul.ko as well as kernel/crypto/crc32.ko,
and 'modinfo crc32-pclmul' claims that crc32 is an alias.

I This happens with a stock Ubuntu kernel (4.2.0-25-generic for Wily),
however I first observed this behavior on Redhat/Oracle Linux 7.

So... it looks like we have both kernel/lib/crc32.ko and
kernel/crypto/crc32.ko - module names should be global. It doesn't clash in
the kernel build because kernel/lib/crc32 is builtin most of the time.

With that commit in kmod there was a change on the builtin detection to fix
the race. I'll take a look to fix this, but it should probably be
fixed in the kernel
 as well.

Rusty and ohers: it looks like both CONFIG_CRC32 and
CONFIG_CRYPTO_CRC32 can be compiled as module, and they generate
modules with the same name, crc32.  Could that be fixed?


Lucas De Marchi