Messages in this thread | | | Date | Thu, 30 Nov 2017 14:17:11 +0100 | From | Jessica Yu <> | Subject | Re: module: add debugging alias parsing support |
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+++ Luis R. Rodriguez [29/11/17 18:36 -0800]: >Debugging modules can often lead to an alias question. We purposely >don't have alias parsing support upstream as this is all dealt with >in userpace with the assumption that in-kernel we just process aliases >and userspace Does The Right Thing (TM) about aliases. > >Obviously userspace can be buggy though, and it can lie to us. We >currently have no easy way to determine this. Parsing aliases is >an example debugging facility we can use to help with these sorts >of problems. > >You can debug by adding to your dynamic debug: > >GRUB_CMDLINE_LINUX_DEFAULT="dyndbg=\"func module_process_aliases +p;\" " > >Upon boot for example here a few entries: > >module ext4 num_aliases: 5 >alias[0] = fs-ext4 >alias[1] = ext3 >alias[2] = fs-ext3 >alias[3] = ext2 >alias[4] = fs-ext2 > >module xfs num_aliases: 1 >alias[0] = fs-xfs > >module floppy num_aliases: 3 >alias[0] = block-major-2-* >alias[1] = acpi*:PNP0700:* >alias[2] = pnp:dPNP0700* > >module ata_piix num_aliases: 89 >alias[0] = pci:v00008086d00008C81sv*sd*bc*sc*i* >alias[1] = pci:v00008086d00008C80sv*sd*bc*sc*i* >alias[2] = pci:v00008086d00008C89sv*sd*bc*sc*i* >alias[3] = pci:v00008086d00008C88sv*sd*bc*sc*i* >... etc ... > >Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> >Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Hi Luis,
Just some quick questions - are there any plans to use these in-kernel module aliases anywhere else? Or are you using them just for debugging?
And if it's only for debugging, what's the benefit of printing the aliases in-kernel when one could already use modinfo to print the exact same information (namely, in-kernel module name, which was recently added by Kees, + aliases)? We're essentially parsing the .modinfo section of the module binary in two different places, just that this patchset does it in-kernel and modinfo does it from userspace, so I'm curious why we want to bring this into the kernel as well without any additional users..
Thanks!
Jessica
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