audio ok

hc

2023-12-11 223293205a7265c8b02882461ba8996650048ade

 kernel/Documentation/dev-tools/kgdb.rst
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 on the initial connect, or to use a debugger proxy that allows an
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 unmodified gdb to do the debugging.
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+Kernel parameter: ``kgdboc_earlycon``
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+-------------------------------------
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+
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+If you specify the kernel parameter ``kgdboc_earlycon`` and your serial
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+driver registers a boot console that supports polling (doesn't need
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+interrupts and implements a nonblocking read() function) kgdb will attempt
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+to work using the boot console until it can transition to the regular
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+tty driver specified by the ``kgdboc`` parameter.
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+
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+Normally there is only one boot console (especially that implements the
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+read() function) so just adding ``kgdboc_earlycon`` on its own is
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+sufficient to make this work. If you have more than one boot console you
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+can add the boot console's name to differentiate. Note that names that
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+are registered through the boot console layer and the tty layer are not
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+the same for the same port.
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+
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+For instance, on one board to be explicit you might do::
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+   kgdboc_earlycon=qcom_geni kgdboc=ttyMSM0
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+If the only boot console on the device was "qcom_geni", you could simplify::
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+   kgdboc_earlycon kgdboc=ttyMSM0
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+
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 Kernel parameter: ``kgdbwait``
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 ------------------------------
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 Kernel parameter: ``kgdbcon``
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 -----------------------------
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-The ``kgdbcon`` feature allows you to see :c:func:`printk` messages inside gdb
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+The ``kgdbcon`` feature allows you to see printk() messages inside gdb
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 while gdb is connected to the kernel. Kdb does not make use of the kgdbcon
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 feature.
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    ``ps``      Displays only the active processes
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    ``ps A``    Shows all the processes
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    ``summary`` Shows kernel version info and memory usage
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-   ``bt``      Get a backtrace of the current process using :c:func:`dump_stack`
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+   ``bt``      Get a backtrace of the current process using dump_stack()
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    ``dmesg``   View the kernel syslog buffer
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    ``go``      Continue the system
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    =========== =================================================================
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    The arch-specific portion implements:
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    -  contains an arch-specific trap catcher which invokes
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-      :c:func:`kgdb_handle_exception` to start kgdb about doing its work
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+      kgdb_handle_exception() to start kgdb about doing its work
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-   -  translation to and from gdb specific packet format to :c:type:`pt_regs`
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+   -  translation to and from gdb specific packet format to struct pt_regs
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    -  Registration and unregistration of architecture specific trap
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       hooks
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          config. Later run ``modprobe kdb_hello`` and the next time you
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          enter the kdb shell, you can run the ``hello`` command.
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-   -  The implementation for :c:func:`kdb_printf` which emits messages directly
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+   -  The implementation for kdb_printf() which emits messages directly
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       to I/O drivers, bypassing the kernel log.
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    -  SW / HW breakpoint management for the kdb shell
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 the UART driver.
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 When using kgdboc with a UART, the UART driver must implement two
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-callbacks in the :c:type:`struct uart_ops <uart_ops>`.
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+callbacks in the struct uart_ops.
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 Example from ``drivers/8250.c``::
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 attached keyboard. The keyboard infrastructure is only compiled into the
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 kernel when ``CONFIG_KDB_KEYBOARD=y`` is set in the kernel configuration.
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-The core polled keyboard driver driver for PS/2 type keyboards is in
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+The core polled keyboard driver for PS/2 type keyboards is in
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 ``drivers/char/kdb_keyboard.c``. This driver is hooked into the debug core
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 when kgdboc populates the callback in the array called
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-:c:type:`kdb_poll_funcs[]`. The :c:func:`kdb_get_kbd_char` is the top-level
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+:c:expr:`kdb_poll_funcs[]`. The kdb_get_kbd_char() is the top-level
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 function which polls hardware for single character input.
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 kgdboc and kms
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 kernel mode setting support.
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 Every time the kernel debugger is entered it calls
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-:c:func:`kgdboc_pre_exp_handler` which in turn calls :c:func:`con_debug_enter`
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+kgdboc_pre_exp_handler() which in turn calls con_debug_enter()
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 in the virtual console layer. On resuming kernel execution, the kernel
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-debugger calls :c:func:`kgdboc_post_exp_handler` which in turn calls
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-:c:func:`con_debug_leave`.
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+debugger calls kgdboc_post_exp_handler() which in turn calls
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+con_debug_leave().
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 Any video driver that wants to be compatible with the kernel debugger
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 and the atomic kms callbacks must implement the ``mode_set_base_atomic``,