cvs commit: src/sys/dev/uart uart_core.c

Ben Kaduk minimarmot at
Wed Mar 28 21:47:23 UTC 2007

On 3/28/07, Marcel Moolenaar <marcel at> wrote:
> marcel      2007-03-28 18:26:12 UTC
>   FreeBSD src repository
>   Modified files:
>     sys/dev/uart         uart_core.c
>   Log:
>   When we match UARTs found during bus-enumeration with UARTs used for
>   system devices (i.e. console, debug port or keyboard), don't stop
>   after the first match. Find them all and keep track of the last.
>   The reason for this change is that the low-level console is always
>   added to the list of system devices first, with other devices added
>   later. Since new devices are added to the list at the head, we have
>   the console always at the end. When a debug port is using the same
>   UART as the console, we would previously mark the "newbus" UART as
>   a debug port instead of as a console. This would later result in a
>   panic because no "newbus" device was associated with the console.
>   By matching all possible system devices we would mark the "newbus"
>   UART as a console and not as a debug port.
>   While it is arguably better to be able to mark a "newbus" UART as
>   both console and debug port, this fix is lightweight and allows
>   a single UART to be used as the console as well as a debug port
>   with only the aesthetic bug of not telling the user about it also
>   being a debug port.

I am rather ignorant about such things, but is there any security risk
in having an "undocumented" debug port?  I am under the impression
that debug ports can do such things as break to the debugger and
access arbitrary memory, which a console is not guaranteed to be able
to do.

-Ben Kaduk


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