linux-kernel - Re: Gaps in logs while using usb-serial as a console

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: <842a0d64-279d-4052-a243-95fee608ea76@infradead.org>
Date:   Mon, 30 Oct 2023 20:51:06 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Alan Stern <stern@...land.harvard.edu>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     ariel marcovitch <arielmarcovitch@...il.com>, johan@...nel.org,
        linux-usb@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Gaps in logs while using usb-serial as a console



On 10/30/23 07:19, Alan Stern wrote:
> On Mon, Oct 30, 2023 at 09:30:15AM +0100, Greg KH wrote:
>> On Mon, Oct 30, 2023 at 10:15:30AM +0200, ariel marcovitch wrote:
>>>> Please realize that usb-serial console was the result of me loosing a
>>>> drunken bet.  It's amazing it works at all.  For "fake" devices like
>>> LOL your drunken bet was quite helpful to some people
>>> Because modern PCs come without a serial port, I wanted to use it to
>>> see early logs on my crashing kernel without having to use printk
>>> delay and things like that.
>>> I'm curious as to how kernel people debug PCs in general...
>>
>> We use a usb debug port connection (it's a special cable).

For EHCI it is a special cable. For XHCI you can use a special cable but
it is not required. (I saw a few people on LKML say that a normal data cable
works so I tested it and it does work.)

But if you want the special cable (for XHCI), this one works:
  https://www.datapro.net/products/usb-3-0-super-speed-a-a-debugging-cable.html

So I tested with both the special debug cable and a normal A-A data cable,
both with satisfactory results.

> Sometimes people use netconsole (see 
> Documentation/networking/netconsole.rst).  I don't know how common it is 
> nowadays, and it may not be quite as reliable as a debug port device, 
> but it should still work.  And it doesn't require special hardware.

It would be great if netconsole worked with wifi and not wired (ethernet).

-- 
~Randy