buildroot

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==== Using +gdb+ in Buildroot

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Buildroot allows to do cross-debugging, where the debugger runs on the

build machine and communicates with +gdbserver+ on the target to

control the execution of the program.

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To achieve this:

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* If you are using an _internal toolchain_ (built by Buildroot), you

  must enable +BR2_PACKAGE_HOST_GDB+, +BR2_PACKAGE_GDB+ and

  +BR2_PACKAGE_GDB_SERVER+. This ensures that both the cross gdb and

  gdbserver get built, and that gdbserver gets installed to your target.

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* If you are using an _external toolchain_, you should enable

  +BR2_TOOLCHAIN_EXTERNAL_GDB_SERVER_COPY+, which will copy the

  gdbserver included with the external toolchain to the target. If your

  external toolchain does not have a cross gdb or gdbserver, it is also

  possible to let Buildroot build them, by enabling the same options as

  for the _internal toolchain backend_.

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Now, to start debugging a program called +foo+, you should run on the

target:

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----------------------------

gdbserver :2345 foo

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This will cause +gdbserver+ to listen on TCP port 2345 for a connection

from the cross gdb.

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Then, on the host, you should start the cross gdb using the following

command line:

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<buildroot>/output/host/usr/bin/<tuple>-gdb -x <buildroot>/output/staging/usr/share/buildroot/gdbinit foo

----------------------------

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Of course, +foo+ must be available in the current directory, built

with debugging symbols. Typically you start this command from the

directory where +foo+ is built (and not from +output/target/+ as the

binaries in that directory are stripped).

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The +<buildroot>/output/staging/usr/share/buildroot/gdbinit+ file will tell the

cross gdb where to find the libraries of the target.

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Finally, to connect to the target from the cross gdb:

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(gdb) target remote <target ip address>:2345

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