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Re: Fwd: Can GDB interact with serial ports on remote targets?

Hi Brendan,

On 02/20/2015 12:27 PM, Brendan J wrote:
I am using GDB to debug a remote target: I start GDB then type `target
remote foo:1234`. I do I/O with the target via a serial port. So I
have to have two terminals open: one with picocom (connected to
something like /dev/ttyUSB0) and one with GDB (connected to OpenOCD
via a socket). To be clear: the debug connection is *not over the
serial port*, it's over a totally separate JTAG interface.

As you know, when you debug a "normal" (i.e. not "remote") inferior in
GDB, its stdin and stdout are multiplexed into GDB's TTY so that you
can interact with it while it's running [1].

Is it possible to achieve that for a remote target - that is: can GDB
connect to the serial port itself so I can do I/O with the target from
within the GDB session?

If not, is this something that might be feasible? Maybe GDB could
multiplex its I/O so that while the inferior is running it passes
characters to/from an external tool like picocom? (As you can see I'm
fairly ignorant about this whole issue at the moment).


PS: I'm using arm-none-eabi-gdb, in case that happens to be relevant.


It sounds like what you want is semihosting support, an I/O operation that is initiated on the remote end, passing through the host and then back again to the remote end.

For example, the remote program needs to read a character. In this case the remote debug agent issues a vFile request with the right system call, GDB receives it, the user enters the character via GDB and then GDB sends the reply back to the target. The remote program then reads the character and continues executing.

You can check the documentation here:

Check this one as well:

This feature is only available on all-stop mode.


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