linux-kernel - Re: [PATCH 09/12] i386/x86_64: EHCI usb debug port early printk support.

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]

Date:	Mon, 30 Apr 2007 19:56:08 +0200
From:	Andi Kleen <ak@...e.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andi Kleen <ak@...e.de>,
	virtualization <virtualization@...ts.linux-foundation.org>,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH 09/12] i386/x86_64: EHCI usb debug port early printk support.

Thanks for writing that code. It should be an interesting alternative
on boxes where firescope doesn't work.

I hope I can eventually merge early firewire support code too.

On Mon, Apr 30, 2007 at 10:32:02AM -0600, Eric W. Biederman wrote:
> 
> With legacy free systems serial ports have stopped being an option
> to get early boot traces and other debug information out of a machine.

This needs a CONFIG_* at least. And some documentation on how to set it
up on both sides.

> 
> This debug device can be used to replace serial ports for
> kgdb, kdb, and console support.  And gregkh has a simple usb
> serial driver for it so user space applications that control
> serial ports should work unmodified.

But not merged yet, right? I was hoping it could be done from
user space anyways.

> For users the hard part looks like it will be finding cables and
> finding which is usb debug port 1 and realizing that there is
> flow control so the kernel boot will not happen if someone is not
> reading the serial console data.

That's nasty. Any way to work around that?

> index 92213d2..dc097aa 100644
> --- a/arch/x86_64/kernel/early_printk.c
> +++ b/arch/x86_64/kernel/early_printk.c
> @@ -3,9 +3,19 @@
>  #include <linux/init.h>
>  #include <linux/string.h>
>  #include <linux/screen_info.h>
> +#include <linux/usb/ch9.h>
> +#include <linux/pci_regs.h>
> +#include <linux/pci_ids.h>
> +#include <linux/errno.h>

Can you put it in a separate file please?
Perhaps with a little abstraction in drivers/usb ? 

> +static void dbgp_breath(void)
> +{
> +	/* Sleep to give the debug port a chance to breathe */

But you don't?

> +static __u32 __init find_dbgp(int ehci_num, unsigned *rbus, unsigned *rslot, unsigned *rfunc)

This should be probably merged into the early quirks loop

>   		early_console = &simnow_console;
>   		keep_early = 1;
> +	} else if (!strncmp(buf, "dbgp", 4)) {

usb would seem to be more intuitive

-Andi
-
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/