239 lines
9.0 KiB
ReStructuredText
239 lines
9.0 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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=====================
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ACPICA Trace Facility
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=====================
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:Copyright: |copy| 2015, Intel Corporation
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:Author: Lv Zheng <lv.zheng@intel.com>
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Abstract
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========
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This document describes the functions and the interfaces of the
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method tracing facility.
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Functionalities and usage examples
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==================================
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ACPICA provides method tracing capability. And two functions are
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currently implemented using this capability.
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Log reducer
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-----------
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ACPICA subsystem provides debugging outputs when CONFIG_ACPI_DEBUG is
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enabled. The debugging messages which are deployed via
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ACPI_DEBUG_PRINT() macro can be reduced at 2 levels - per-component
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level (known as debug layer, configured via
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/sys/module/acpi/parameters/debug_layer) and per-type level (known as
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debug level, configured via /sys/module/acpi/parameters/debug_level).
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But when the particular layer/level is applied to the control method
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evaluations, the quantity of the debugging outputs may still be too
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large to be put into the kernel log buffer. The idea thus is worked out
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to only enable the particular debug layer/level (normally more detailed)
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logs when the control method evaluation is started, and disable the
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detailed logging when the control method evaluation is stopped.
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The following command examples illustrate the usage of the "log reducer"
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functionality:
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a. Filter out the debug layer/level matched logs when control methods
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are being evaluated::
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# cd /sys/module/acpi/parameters
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# echo "0xXXXXXXXX" > trace_debug_layer
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# echo "0xYYYYYYYY" > trace_debug_level
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# echo "enable" > trace_state
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b. Filter out the debug layer/level matched logs when the specified
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control method is being evaluated::
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# cd /sys/module/acpi/parameters
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# echo "0xXXXXXXXX" > trace_debug_layer
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# echo "0xYYYYYYYY" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "method" > /sys/module/acpi/parameters/trace_state
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c. Filter out the debug layer/level matched logs when the specified
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control method is being evaluated for the first time::
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# cd /sys/module/acpi/parameters
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# echo "0xXXXXXXXX" > trace_debug_layer
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# echo "0xYYYYYYYY" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "method-once" > /sys/module/acpi/parameters/trace_state
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Where:
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0xXXXXXXXX/0xYYYYYYYY
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Refer to Documentation/firmware-guide/acpi/debug.rst for possible debug layer/level
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masking values.
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\PPPP.AAAA.TTTT.HHHH
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Full path of a control method that can be found in the ACPI namespace.
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It needn't be an entry of a control method evaluation.
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AML tracer
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----------
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There are special log entries added by the method tracing facility at
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the "trace points" the AML interpreter starts/stops to execute a control
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method, or an AML opcode. Note that the format of the log entries are
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subject to change::
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[ 0.186427] exdebug-0398 ex_trace_point : Method Begin [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
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[ 0.186630] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905c88:If] execution.
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[ 0.186820] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:LEqual] execution.
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[ 0.187010] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905a20:-NamePath-] execution.
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[ 0.187214] exdebug-0398 ex_trace_point : Opcode End [0xf5905a20:-NamePath-] execution.
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[ 0.187407] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution.
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[ 0.187594] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution.
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[ 0.187789] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:LEqual] execution.
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[ 0.187980] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:Return] execution.
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[ 0.188146] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution.
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[ 0.188334] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution.
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[ 0.188524] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:Return] execution.
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[ 0.188712] exdebug-0398 ex_trace_point : Opcode End [0xf5905c88:If] execution.
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[ 0.188903] exdebug-0398 ex_trace_point : Method End [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
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Developers can utilize these special log entries to track the AML
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interpretation, thus can aid issue debugging and performance tuning. Note
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that, as the "AML tracer" logs are implemented via ACPI_DEBUG_PRINT()
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macro, CONFIG_ACPI_DEBUG is also required to be enabled for enabling
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"AML tracer" logs.
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The following command examples illustrate the usage of the "AML tracer"
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functionality:
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a. Filter out the method start/stop "AML tracer" logs when control
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methods are being evaluated::
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# cd /sys/module/acpi/parameters
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# echo "0x80" > trace_debug_layer
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# echo "0x10" > trace_debug_level
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# echo "enable" > trace_state
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b. Filter out the method start/stop "AML tracer" when the specified
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control method is being evaluated::
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# cd /sys/module/acpi/parameters
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# echo "0x80" > trace_debug_layer
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# echo "0x10" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "method" > trace_state
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c. Filter out the method start/stop "AML tracer" logs when the specified
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control method is being evaluated for the first time::
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# cd /sys/module/acpi/parameters
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# echo "0x80" > trace_debug_layer
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# echo "0x10" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "method-once" > trace_state
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d. Filter out the method/opcode start/stop "AML tracer" when the
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specified control method is being evaluated::
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# cd /sys/module/acpi/parameters
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# echo "0x80" > trace_debug_layer
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# echo "0x10" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "opcode" > trace_state
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e. Filter out the method/opcode start/stop "AML tracer" when the
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specified control method is being evaluated for the first time::
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# cd /sys/module/acpi/parameters
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# echo "0x80" > trace_debug_layer
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# echo "0x10" > trace_debug_level
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# echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
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# echo "opcode-opcode" > trace_state
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Note that all above method tracing facility related module parameters can
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be used as the boot parameters, for example::
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acpi.trace_debug_layer=0x80 acpi.trace_debug_level=0x10 \
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acpi.trace_method_name=\_SB.LID0._LID acpi.trace_state=opcode-once
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Interface descriptions
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======================
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All method tracing functions can be configured via ACPI module
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parameters that are accessible at /sys/module/acpi/parameters/:
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trace_method_name
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The full path of the AML method that the user wants to trace.
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Note that the full path shouldn't contain the trailing "_"s in its
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name segments but may contain "\" to form an absolute path.
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trace_debug_layer
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The temporary debug_layer used when the tracing feature is enabled.
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Using ACPI_EXECUTER (0x80) by default, which is the debug_layer
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used to match all "AML tracer" logs.
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trace_debug_level
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The temporary debug_level used when the tracing feature is enabled.
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Using ACPI_LV_TRACE_POINT (0x10) by default, which is the
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debug_level used to match all "AML tracer" logs.
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trace_state
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The status of the tracing feature.
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Users can enable/disable this debug tracing feature by executing
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the following command::
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# echo string > /sys/module/acpi/parameters/trace_state
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Where "string" should be one of the following:
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"disable"
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Disable the method tracing feature.
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"enable"
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Enable the method tracing feature.
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ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
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during any method execution will be logged.
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"method"
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Enable the method tracing feature.
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ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
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during method execution of "trace_method_name" will be logged.
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"method-once"
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Enable the method tracing feature.
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ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
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during method execution of "trace_method_name" will be logged only once.
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"opcode"
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Enable the method tracing feature.
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ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
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during method/opcode execution of "trace_method_name" will be logged.
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"opcode-once"
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Enable the method tracing feature.
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ACPICA debugging messages matching "trace_debug_layer/trace_debug_level"
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during method/opcode execution of "trace_method_name" will be logged only
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once.
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Note that, the difference between the "enable" and other feature
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enabling options are:
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1. When "enable" is specified, since
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"trace_debug_layer/trace_debug_level" shall apply to all control
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method evaluations, after configuring "trace_state" to "enable",
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"trace_method_name" will be reset to NULL.
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2. When "method/opcode" is specified, if
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"trace_method_name" is NULL when "trace_state" is configured to
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these options, the "trace_debug_layer/trace_debug_level" will
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apply to all control method evaluations.
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