68 lines
2.7 KiB
ReStructuredText
68 lines
2.7 KiB
ReStructuredText
.. _debugmon:
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Cortex-M Debug Monitor
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######################
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Monitor mode debugging is a Cortex-M feature, that provides a non-halting approach to
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debugging. With this it's possible to continue the execution of high-priority interrupts,
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even when waiting on a breakpoint.
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This strategy makes it possible to debug time-sensitive software, that would
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otherwise crash when the core halts (e.g. applications that need to keep
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communication links alive).
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Zephyr provides support for enabling and configuring the Debug Monitor exception.
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It also contains a ready implementation of the interrupt, which can be used with
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SEGGER J-Link debuggers.
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Configuration
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*************
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Configure this module using the following options.
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* :kconfig:option:`CONFIG_CORTEX_M_DEBUG_MONITOR_HOOK`: enable the module. This option, by itself,
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requires an implementation of debug monitor interrupt that will be executed
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every time the program enters a breakpoint.
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With a SEGGER debug probe, it's possible to use a ready, SEGGER-provided implementation
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of the interrupt.
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* :kconfig:option:`CONFIG_SEGGER_DEBUGMON`: enables SEGGER debug monitor interrupt. Can be
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used with SEGGER JLinkGDBServer and a SEGGER debug probe.
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Usage
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*****
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When monitor mode debugging is enabled, entering a breakpoint will not halt the
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processor, but rather generate an interrupt with ISR implemented under
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``z_arm_debug_monitor`` symbol. :kconfig:option:`CONFIG_CORTEX_M_DEBUG_MONITOR_HOOK` config configures this interrupt
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to be the lowest available priority, which will allow other interrupts to execute
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while processor spins on a breakpoint.
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Using SEGGER-provided ISR
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=========================
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The ready implementation provided with :kconfig:option:`CONFIG_SEGGER_DEBUGMON` provides functionality
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required to debug in the monitor mode using regular GDB commands.
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Steps to configure SEGGER debug monitor:
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1. Build a sample with :kconfig:option:`CONFIG_CORTEX_M_DEBUG_MONITOR_HOOK`` and :kconfig:option:`CONFIG_SEGGER_DEBUGMON`
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configs enabled.
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2. Attach JLink GDB server to the target.
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Example linux command: ``JLinkGDBServerCLExe -device <device> -if swd``.
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3. Connect to the server with your GDB installation.
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Example linux command: ``arm-none-eabi-gdb --ex="file build/zephyr.elf" --ex="target remote localhost:2331"``.
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4. Enable monitor mode debugging in GDB using command: ``monitor exec SetMonModeDebug=1``.
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After these steps use regular gdb commands to debug your program.
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Using other custom ISR
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======================
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In order to provide a custom debug monitor interrupt, override ``z_arm_debug_monitor``
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symbol. Additionally, manual configuration of some registers is required
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(see :zephyr:code-sample:`debugmon` sample).
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