Date: Thu, 23 Nov 2017 23:34:39 +0100 From: Oliver Pinter <oliver.pinter@hardenedbsd.org> To: Hans Petter Selasky <hps@selasky.org> Cc: Julian Elischer <julian@freebsd.org>, Farhan Khan <khanzf@gmail.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: Is ddb(4) over a USB-to-Serial port possible? Message-ID: <CAPQ4ffuvUtSwoFRrLdEZ5e63nhovhR9rnqrZ-=L1RT1d_9k=YA@mail.gmail.com> In-Reply-To: <cc2c013c-0e38-5973-2323-5d08c27c2de3@selasky.org> References: <11ce9826-f768-3ea0-547d-2d182d1552f0@gmail.com> <36165883-5cb7-aabc-c81e-cb5458029803@freebsd.org> <5c6da274-102c-33c6-50f0-20597cf8e7ef@selasky.org> <aad5dce5-ae76-f2af-0d1b-3e39e5f9cdfb@freebsd.org> <cc2c013c-0e38-5973-2323-5d08c27c2de3@selasky.org>
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On Thursday, November 23, 2017, Hans Petter Selasky <hps@selasky.org> wrote: > On 11/23/17 16:59, Julian Elischer wrote: > >> On 22/11/17 4:33 pm, Hans Petter Selasky wrote: >> >>> On 11/22/17 08:40, Julian Elischer wrote: >>> >>>> On 22/11/17 3:08 pm, Farhan Khan wrote: >>>> >>>>> Hi all >>>>> >>>>> I am reading here in section "10.5, On-Line Kernel Debugging User >>>>> Remote GDB" that you can run ddb(4) over a serial cable. I am interested in >>>>> setting this up. >>>>> >>>>> My development box does not have a serial port (however, I do see a >>>>> uart0 device in the kernel messages), so I attached a USB serial port >>>>> attached to a machine with a serial port. The device uses the uslcom(4) >>>>> driver and is listed as "Silicon Labs CP2102 USB to UART Bridge >>>>> Controller". When I enter ddb and enter "gdb" I receive the error "The >>>>> remote GDB backend could not be selected." >>>>> >>>>> The hint.uart.0.port in /boot/device.hints is still set to 0x3F8, >>>>> which corresponds to the aforementioned kernel messages. I am not certain >>>>> if this is the same port as the USB-based serial port. Does this feature >>>>> work over USB? >>>>> >>>>> Thanks, >>>>> Farhan Khan >>>>> _______________________________________________ >>>>> freebsd-hackers@freebsd.org mailing list >>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-hackers >>>>> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@ >>>>> freebsd.org" >>>>> >>>>> generally speaking the answer is no, unless the device is emulated >>>> using SMI or some other mechanism that is independent of FreeBSD. >>>> >>>> uart0 is not the device on the USB but a hardware device at 3F8, >>>> regardless of whether it actually exists. Since the USB stack is not really >>>> functional when in the debugger, it can not be used to communicate with the >>>> debugger. >>>> >>>> I find a better answer is to fire up the test machine under bhyve, in >>>> which case its console is accessible through any stream session. (e.g. >>>> ssh).. >>>> >>>> >>> Hi, >>> >>> There is another setting for this: >>> >>> Try setting cons_baud and cons_unit below. USB serial supports polling >>> from the debugger after panic. >>> >>> hw.usb.ucom.cons_baud: 9600 >>> hw.usb.ucom.cons_subunit: 0 >>> hw.usb.ucom.cons_unit: -1 >>> hw.usb.ucom.debug: 0 >>> hw.usb.ucom.pps_mode: 0 >>> >>> wow.. I will need to try this when I have the appropriate setup. >> is this in the kenv? is it in loader.conf or sysctl.conf? >> >> > Hi, > > /boot/loader.conf > > or > > kenv > > or > > sysctl > > Before attaching the device. Could we somehow change these after attached device? Ergo could we setup two USB context, one for normal operation and one for the debugger? > > --HPS > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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