[v6,2/7] add btrace coresight related commands

Message ID 20210531213307.275079-3-zied.guermazi@trande.de
State New
Headers show
Series
  • extend branch tracing to use ARM CoreSight traces
Related show

Commit Message

Zied Guermazi May 31, 2021, 9:33 p.m.
This patch extends the commands needed for using branch tracing
with ARM CoreSight traces.
Those commands are:
set record btrace etm sink
set record btrace etm buffer-size
record btrace etm

gdb/ChangeLog

	* NEWS: list new commands for extending btrace
	to support using ARM CoreSight Traces.
	* record-btrace.c (record_btrace_print_etm_conf): New.
	(record_btrace_print_conf): handle BTRACE_FORMAT_ETM.
	(cmd_record_btrace_etm_start): New.
	(cmd_record_btrace_start): handle starting ETM tracing.
	(cmd_show_record_btrace_cpu): extend for ARM cpus.
	(show_record_etm_buffer_size_value): New.
	(_initialize_record_btrace): add commands for ETM traces.
	(record_start): add starting ETM traces.

gdb/doc/ChangeLog

	* gdb.texinfo (Process Record and Replay): Document extending
	GDB btrace commands to support using ARM CoreSight traces.

gdbsupport/ChangeLog

	* btrace-common.h (btrace_format): add BTRACE_FORMAT_ETM
	to the enum.
	(btrace_config_etm): new struct.
	(btrace_config): add btrace_config_etm etm.
	* btrace-common.cc (btrace_format_string): add BTRACE_FORMAT_ETM.
	(btrace_format_short_string): add BTRACE_FORMAT_ETM.
---
 gdb/NEWS                    |  16 +++++
 gdb/doc/gdb.texinfo         |  51 +++++++++++++++-
 gdb/record-btrace.c         | 117 +++++++++++++++++++++++++++++++++++-
 gdb/record.c                |   2 +
 gdbsupport/btrace-common.cc |   6 ++
 gdbsupport/btrace-common.h  |  22 ++++++-
 6 files changed, 210 insertions(+), 4 deletions(-)

-- 
2.25.1

Comments

Simon Marchi via Gdb-patches June 1, 2021, 12:07 p.m. | #1
> From: Zied Guermazi <zied.guermazi@trande.de>

> Date: Mon, 31 May 2021 23:33:02 +0200

> Cc: Zied Guermazi <zied.guermazi@trande.de>

> 

> This patch extends the commands needed for using branch tracing

> with ARM CoreSight traces.

> Those commands are:

> set record btrace etm sink

> set record btrace etm buffer-size

> record btrace etm

> 

> gdb/ChangeLog

> 

> 	* NEWS: list new commands for extending btrace

> 	to support using ARM CoreSight Traces.

> 	* record-btrace.c (record_btrace_print_etm_conf): New.

> 	(record_btrace_print_conf): handle BTRACE_FORMAT_ETM.

> 	(cmd_record_btrace_etm_start): New.

> 	(cmd_record_btrace_start): handle starting ETM tracing.

> 	(cmd_show_record_btrace_cpu): extend for ARM cpus.

> 	(show_record_etm_buffer_size_value): New.

> 	(_initialize_record_btrace): add commands for ETM traces.

> 	(record_start): add starting ETM traces.

> 

> gdb/doc/ChangeLog

> 

> 	* gdb.texinfo (Process Record and Replay): Document extending

> 	GDB btrace commands to support using ARM CoreSight traces.

> 

> gdbsupport/ChangeLog

> 

> 	* btrace-common.h (btrace_format): add BTRACE_FORMAT_ETM

> 	to the enum.

> 	(btrace_config_etm): new struct.

> 	(btrace_config): add btrace_config_etm etm.

> 	* btrace-common.cc (btrace_format_string): add BTRACE_FORMAT_ETM.

> 	(btrace_format_short_string): add BTRACE_FORMAT_ETM.


Are there any changes in the documentation parts since the last time?
If not, I think I already approved the doc parts.

Thanks.
Zied Guermazi June 1, 2021, 3:47 p.m. | #2
Hi Eli,

there is no change in documentation part. so we can consider this part 
as approved.

Kind Regards

Zied Guermazi

On 01.06.21 14:07, Eli Zaretskii wrote:
>> From: Zied Guermazi <zied.guermazi@trande.de>

>> Date: Mon, 31 May 2021 23:33:02 +0200

>> Cc: Zied Guermazi <zied.guermazi@trande.de>

>>

>> This patch extends the commands needed for using branch tracing

>> with ARM CoreSight traces.

>> Those commands are:

>> set record btrace etm sink

>> set record btrace etm buffer-size

>> record btrace etm

>>

>> gdb/ChangeLog

>>

>> 	* NEWS: list new commands for extending btrace

>> 	to support using ARM CoreSight Traces.

>> 	* record-btrace.c (record_btrace_print_etm_conf): New.

>> 	(record_btrace_print_conf): handle BTRACE_FORMAT_ETM.

>> 	(cmd_record_btrace_etm_start): New.

>> 	(cmd_record_btrace_start): handle starting ETM tracing.

>> 	(cmd_show_record_btrace_cpu): extend for ARM cpus.

>> 	(show_record_etm_buffer_size_value): New.

>> 	(_initialize_record_btrace): add commands for ETM traces.

>> 	(record_start): add starting ETM traces.

>>

>> gdb/doc/ChangeLog

>>

>> 	* gdb.texinfo (Process Record and Replay): Document extending

>> 	GDB btrace commands to support using ARM CoreSight traces.

>>

>> gdbsupport/ChangeLog

>>

>> 	* btrace-common.h (btrace_format): add BTRACE_FORMAT_ETM

>> 	to the enum.

>> 	(btrace_config_etm): new struct.

>> 	(btrace_config): add btrace_config_etm etm.

>> 	* btrace-common.cc (btrace_format_string): add BTRACE_FORMAT_ETM.

>> 	(btrace_format_short_string): add BTRACE_FORMAT_ETM.

> Are there any changes in the documentation parts since the last time?

> If not, I think I already approved the doc parts.

>

> Thanks.
Simon Marchi via Gdb-patches June 30, 2021, 12:26 p.m. | #3
On 5/31/21 6:33 PM, Zied Guermazi wrote:
> This patch extends the commands needed for using branch tracing

> with ARM CoreSight traces.

> Those commands are:

> set record btrace etm sink

> set record btrace etm buffer-size

> record btrace etm

> 

> gdb/ChangeLog

> 

> 	* NEWS: list new commands for extending btrace

> 	to support using ARM CoreSight Traces.

> 	* record-btrace.c (record_btrace_print_etm_conf): New.

> 	(record_btrace_print_conf): handle BTRACE_FORMAT_ETM.

> 	(cmd_record_btrace_etm_start): New.

> 	(cmd_record_btrace_start): handle starting ETM tracing.

> 	(cmd_show_record_btrace_cpu): extend for ARM cpus.

> 	(show_record_etm_buffer_size_value): New.

> 	(_initialize_record_btrace): add commands for ETM traces.

> 	(record_start): add starting ETM traces.

> 

> gdb/doc/ChangeLog

> 

> 	* gdb.texinfo (Process Record and Replay): Document extending

> 	GDB btrace commands to support using ARM CoreSight traces.

> 

> gdbsupport/ChangeLog

> 

> 	* btrace-common.h (btrace_format): add BTRACE_FORMAT_ETM

> 	to the enum.

> 	(btrace_config_etm): new struct.

> 	(btrace_config): add btrace_config_etm etm.

> 	* btrace-common.cc (btrace_format_string): add BTRACE_FORMAT_ETM.

> 	(btrace_format_short_string): add BTRACE_FORMAT_ETM.

> ---

>   gdb/NEWS                    |  16 +++++

>   gdb/doc/gdb.texinfo         |  51 +++++++++++++++-

>   gdb/record-btrace.c         | 117 +++++++++++++++++++++++++++++++++++-

>   gdb/record.c                |   2 +

>   gdbsupport/btrace-common.cc |   6 ++

>   gdbsupport/btrace-common.h  |  22 ++++++-

>   6 files changed, 210 insertions(+), 4 deletions(-)

> 

> diff --git a/gdb/NEWS b/gdb/NEWS

> index ab678acec8b..02035901f6e 100644

> --- a/gdb/NEWS

> +++ b/gdb/NEWS

> @@ -2,6 +2,7 @@

>   	     (Organized release by release)

>   

>   *** Changes since GDB 10

> +* Record btrace now  supports using ARM CoreSight ETM traces.


Spurious white-space above.

>   

>   * GDB now supports general memory tagging functionality if the underlying

>     architecture supports the proper primitives and hooks.  Currently this is

> @@ -77,6 +78,21 @@

>   

>   * New commands

>   

> +record btrace etm

> +record etm

> +  Start branch trace recording using ARM CoreSight trace format (ETM).

> +

> +set|show record btrace etm buffer-size

> +  Set and show the size of the ring buffer used for branch tracing in

> +  ETM format.

> +  The obtained size may differ from the requested size.  Use "info

> +  record" to see the obtained buffer size.

> +

> +set|show record btrace etm sink

> +  Set and show the trace sink used for branch tracing in

> +  ETM format.

> +  Use "default" to reset it to default sink.

> +

>   set debug event-loop

>   show debug event-loop

>     Control the display of debug output about GDB's event loop.

> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo

> index 90d827a50e7..b9b09ff97f2 100644

> --- a/gdb/doc/gdb.texinfo

> +++ b/gdb/doc/gdb.texinfo

> @@ -7479,15 +7479,19 @@ For architecture environments that support process record and replay,

>   @kindex record btrace

>   @kindex record btrace bts

>   @kindex record btrace pt

> +@kindex record btrace etm

>   @kindex record bts

>   @kindex record pt

> +@kindex record etm

>   @kindex rec

>   @kindex rec full

>   @kindex rec btrace

>   @kindex rec btrace bts

>   @kindex rec btrace pt

> +@kindex rec btrace etm

>   @kindex rec bts

>   @kindex rec pt

> +@kindex rec etm

>   @item record @var{method}

>   This command starts the process record and replay target.  The

>   recording method can be specified as parameter.  Without a parameter

> @@ -7501,7 +7505,7 @@ replay implementation.  This method allows replaying and reverse

>   execution.

>   

>   @item btrace @var{format}

> -Hardware-supported instruction recording, supported on Intel

> +Hardware-supported instruction recording, supported on Intel and ARM

>   processors.  This method does not record data.  Further, the data is

>   collected in a ring buffer so old data will be overwritten when the

>   buffer is full.  It allows limited reverse execution.  Variables and

> @@ -7535,6 +7539,13 @@ Decoding the recorded execution trace, on the other hand, is more

>   expensive than decoding @acronym{BTS} trace.  This is mostly due to the

>   increased number of instructions to process.  You should increase the

>   buffer-size with care.

> +

> +@item etm

> +@cindex ARM CoreSight Trace

> +Use the @dfn{ARM CoreSight Trace} recording format.  In this

> +format, @acronym{ETM, Extended Trace Macrocell} stores the processor

> +execution trace in a compressed form that is afterwards

> +decoded by @value{GDBN}.

>   @end table

>   

>   Not all recording formats may be available on all processors.

> @@ -7682,6 +7693,12 @@ and to read-write memory.  Beware that the accessed memory corresponds

>   to the live target and not necessarily to the current replay

>   position.

>   

> +@item set record btrace etm sink @var{sink}

> +Set ARM CoreSight ETM sink to collect traces.

> +On @sc{gnu}/Linux systems, possible values for @var{sink} are the name of the

> +files in the directory @file{/sys/bus/event_source/devices/cs_etm/sinks/}.

> +Use the value @kbd{default} to reset it to default sink.

> +

>   @item set record btrace cpu @var{identifier}

>   Set the processor to be used for enabling workarounds for processor

>   errata when decoding the trace.

> @@ -7745,6 +7762,9 @@ Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).

>   @item show record btrace replay-memory-access

>   Show the current setting of @code{replay-memory-access}.

>   

> +@item show record btrace etm sink

> +Show ARM CoreSight ETM sink.

> +

>   @item show record btrace cpu

>   Show the processor to be used for enabling trace decode errata

>   workarounds.

> @@ -7796,6 +7816,29 @@ also need longer to process the branch trace data before it can be used.

>   Show the current setting of the requested ring buffer size for branch

>   tracing in Intel Processor Trace format.

>   

> +@kindex set record btrace etm

> +@item set record btrace etm buffer-size @var{size}

> +@itemx set record btrace etm buffer-size unlimited

> +Set the requested ring buffer size for branch tracing in ARM

> +CoreSight ETM Trace format.  Default is 16KB.

> +

> +If @var{size} is a positive number, then @value{GDBN} will try to

> +allocate a buffer of at least @var{size} bytes for each new thread

> +that uses the btrace recording method and the ARM CoreSight ETM

> +format.  The actually obtained buffer size may differ from the

> +requested @var{size}.  Use the @code{info record} command to see the

> +actual buffer size for each thread.

> +

> +If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to

> +allocate a buffer of 4MB.

> +

> +Bigger buffers mean longer traces.  On the other hand, @value{GDBN} will

> +also need longer to process the branch trace data before it can be used.

> +

> +@item show record btrace etm buffer-size @var{size}

> +Show the current setting of the requested ring buffer size for branch

> +tracing in ARM CoreSight ETM Trace format.

> +

>   @kindex info record

>   @item info record

>   Show various statistics about the recording depending on the recording

> @@ -7847,6 +7890,12 @@ For the @code{pt} recording format, it also shows:

>   @item

>   Size of the perf ring buffer.

>   @end itemize

> +

> +For the @code{etm} recording format, it also shows:

> +@itemize @bullet

> +@item

> +Size of the perf ring buffer.

> +@end itemize

>   @end table

>   

>   @kindex record delete

> diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c

> index 00affb85d22..16ffb76272b 100644

> --- a/gdb/record-btrace.c

> +++ b/gdb/record-btrace.c

> @@ -201,6 +201,10 @@ static struct cmd_list_element *show_record_btrace_bts_cmdlist;

>   static struct cmd_list_element *set_record_btrace_pt_cmdlist;

>   static struct cmd_list_element *show_record_btrace_pt_cmdlist;

>   

> +/* Command lists for "set/show record btrace etm".  */

> +static struct cmd_list_element *set_record_btrace_etm_cmdlist;

> +static struct cmd_list_element *show_record_btrace_etm_cmdlist;

> +

>   /* Command list for "set record btrace cpu".  */

>   static struct cmd_list_element *set_record_btrace_cpu_cmdlist;

>   

> @@ -526,6 +530,22 @@ record_btrace_print_pt_conf (const struct btrace_config_pt *conf)

>       }

>   }

>   

> +/* Print an ARM Processor Trace configuration.  */

> +

> +static void

> +record_btrace_print_etm_conf (const struct btrace_config_etm *conf)

> +{

> +  unsigned int size;

> +

> +  size = conf->size;

> +  if (size > 0)

> +    {

> +      const char *suffix;

> +      suffix = record_btrace_adjust_size (&size);

> +      printf_unfiltered (_("Buffer size: %u%s.\n"), size, suffix);

> +    }

> +}

> +

>   /* Print a branch tracing configuration.  */

>   

>   static void

> @@ -546,6 +566,10 @@ record_btrace_print_conf (const struct btrace_config *conf)

>       case BTRACE_FORMAT_PT:

>         record_btrace_print_pt_conf (&conf->pt);

>         return;

> +

> +    case BTRACE_FORMAT_ETM:

> +      record_btrace_print_etm_conf (&conf->etm);

> +      return;

>       }

>   

>     internal_error (__FILE__, __LINE__, _("Unknown branch trace format."));

> @@ -2676,7 +2700,7 @@ record_btrace_target::stop (ptid_t ptid)

>   	  tp->btrace.flags |= BTHR_STOP;

>   	}

>       }

> - }

> +}

>   


I keep seeing the above change. It looks spurious.

>   /* The can_execute_reverse method of target record-btrace.  */

>   

> @@ -2937,6 +2961,27 @@ cmd_record_btrace_pt_start (const char *args, int from_tty)

>       }

>   }

>   

> +/* Start recording in ARM CoreSight ETM Trace format.  */

> +

> +static void

> +cmd_record_btrace_etm_start (const char *args, int from_tty)

> +{

> +  if (args != nullptr && *args != 0)

> +    error (_("Invalid argument."));

> +

> +  record_btrace_conf.format = BTRACE_FORMAT_ETM;

> +

> +  try

> +    {

> +      execute_command ("target record-btrace", from_tty);

> +    }

> +  catch (const gdb_exception &exception)

> +    {

> +      record_btrace_conf.format = BTRACE_FORMAT_NONE;

> +      throw;

> +    }

> +}

> +

>   /* Alias for "target record".  */

>   

>   static void

> @@ -2951,10 +2996,18 @@ cmd_record_btrace_start (const char *args, int from_tty)

>       {

>         execute_command ("target record-btrace", from_tty);

>       }

> -  catch (const gdb_exception &exception)

> +  catch (const gdb_exception &exception_pt)

>       {

>         record_btrace_conf.format = BTRACE_FORMAT_BTS;

>   

> +      try

> +	{

> +	  execute_command ("target record-btrace", from_tty);

> +	}

> +      catch (const gdb_exception &exception_bts)

> +	{

> +	  record_btrace_conf.format = BTRACE_FORMAT_ETM;

> +

>   	  try

>   	    {

>   	      execute_command ("target record-btrace", from_tty);

> @@ -2965,6 +3018,7 @@ cmd_record_btrace_start (const char *args, int from_tty)

>   	      throw;

>   	    }

>   	}

> +    }

>   }

>   

>   /* The "show record btrace replay-memory-access" command.  */

> @@ -3103,6 +3157,17 @@ show_record_pt_buffer_size_value (struct ui_file *file, int from_tty,

>   		    value);

>   }

>   

> +/* The "record etm buffer-size" show value function.  */

> +

> +static void

> +show_record_etm_buffer_size_value (struct ui_file *file, int from_tty,

> +				   struct cmd_list_element *c,

> +				   const char *value)

> +{

> +  fprintf_filtered (file, _("The record/replay etm buffer size is %s.\n"),

> +		    value);

> +}

> +

>   /* Initialize btrace commands.  */

>   

>   void _initialize_record_btrace ();

> @@ -3170,6 +3235,15 @@ When set to \"none\", errata workarounds are disabled."),

>   		  1,

>   		  &set_record_btrace_cmdlist);

>   

> +

> +  cmd_list_element *record_btrace_etm_cmd

> +    = add_cmd ("etm", class_obscure, cmd_record_btrace_etm_start,

> +	       _("\

> +Start branch trace recording in ARM CoreSight ETM Trace format.\n\n\

> +This format may not be available on all processors."),

> +	     &record_btrace_cmdlist);

> +  add_alias_cmd ("etm", record_btrace_etm_cmd, class_obscure, 1, &record_cmdlist);

> +

>     add_cmd ("auto", class_support, cmd_set_record_btrace_cpu_auto, _("\

>   Automatically determine the cpu to be used for trace decode."),

>   	   &set_record_btrace_cpu_cmdlist);

> @@ -3231,6 +3305,43 @@ to see the actual buffer size."), NULL, show_record_pt_buffer_size_value,

>   			    &set_record_btrace_pt_cmdlist,

>   			    &show_record_btrace_pt_cmdlist);

>   

> +  add_basic_prefix_cmd ("etm", class_support,

> +			_("Set record btrace etm options."),

> +			&set_record_btrace_etm_cmdlist,

> +			0,

> +			&set_record_btrace_cmdlist);

> +

> +  add_show_prefix_cmd ("etm", class_support,

> +		       _("Show record btrace etm options."),

> +		       &show_record_btrace_etm_cmdlist,

> +		       0,

> +		       &show_record_btrace_cmdlist);

> +

> +  add_setshow_uinteger_cmd ("buffer-size", no_class,

> +			    &record_btrace_conf.etm.size,

> +			    _("Set the record/replay etm buffer size."),

> +			    _("Show the record/replay etm buffer size."), _("\

> +Bigger buffers allow longer recording but also take more time to process \

> +the recorded execution.\n\

> +The actual buffer size may differ from the requested size.  Use \"info record\"\

> + to see the actual buffer size."), NULL, show_record_etm_buffer_size_value,


This is inconsistent with what the documentation says:

"Bigger buffers mean longer traces.  On the other hand, @value{GDBN} 
will also need longer to process the branch trace data before it can be 
used."

How about using the same text so things are consistent across the codebase?


> +		  &set_record_btrace_etm_cmdlist,

> +		  &show_record_btrace_etm_cmdlist);

> +

> +  add_setshow_string_cmd ("sink", no_class,

> +			  &record_btrace_conf.etm.sink,

> +			  _("Set the record/replay ETM sink device."),

> +			  _("Show the record/replay ETM sink device."),

> +			  _("\

> +Sink device is the device that intercepts ETM traces and collects or routes \

> +them out of the System on Chip.\n\

> +The list of available sinks on linux targets corresponds to the files in \

> +the directory \"/sys/bus/event_source/devices/cs_etm/sinks/\".\n\

> +value \"default\" reset it to default sink"),

> +			  NULL, NULL,

> +			  &set_record_btrace_etm_cmdlist,

> +			  &show_record_btrace_etm_cmdlist);

> +

>     add_target (record_btrace_target_info, record_btrace_target_open);

>   

>     bfcache = htab_create_alloc (50, bfcache_hash, bfcache_eq, NULL,

> @@ -3238,4 +3349,6 @@ to see the actual buffer size."), NULL, show_record_pt_buffer_size_value,

>   

>     record_btrace_conf.bts.size = 64 * 1024;

>     record_btrace_conf.pt.size = 16 * 1024;

> +#define DEFAULT_ETM_BUFFER_SIZE (8 * 1024)

> +  record_btrace_conf.etm.size = DEFAULT_ETM_BUFFER_SIZE;

>   }

> diff --git a/gdb/record.c b/gdb/record.c

> index 6968c30d930..32492fb53c4 100644

> --- a/gdb/record.c

> +++ b/gdb/record.c

> @@ -118,6 +118,8 @@ record_start (const char *method, const char *format, int from_tty)

>   	execute_command_to_string ("record btrace bts", from_tty, false);

>         else if (strcmp (format, "pt") == 0)

>   	execute_command_to_string ("record btrace pt", from_tty, false);

> +      else if (strcmp (format, "etm") == 0)

> +	execute_command_to_string ("record btrace etm", from_tty, false);

>         else

>   	error (_("Invalid format."));

>       }

> diff --git a/gdbsupport/btrace-common.cc b/gdbsupport/btrace-common.cc

> index 4f9ef855e74..79ff21de44b 100644

> --- a/gdbsupport/btrace-common.cc

> +++ b/gdbsupport/btrace-common.cc

> @@ -36,6 +36,9 @@ btrace_format_string (enum btrace_format format)

>   

>       case BTRACE_FORMAT_PT:

>         return _("Intel Processor Trace");

> +

> +    case BTRACE_FORMAT_ETM:

> +      return _("ARM Processor CoreSight ETM Trace");

>       }

>   

>     internal_error (__FILE__, __LINE__, _("Unknown branch trace format"));

> @@ -56,6 +59,9 @@ btrace_format_short_string (enum btrace_format format)

>   

>       case BTRACE_FORMAT_PT:

>         return "pt";

> +

> +    case BTRACE_FORMAT_ETM:

> +      return "etm";

>       }

>   

>     internal_error (__FILE__, __LINE__, _("Unknown branch trace format"));

> diff --git a/gdbsupport/btrace-common.h b/gdbsupport/btrace-common.h

> index 26d26ec957f..153b977723a 100644

> --- a/gdbsupport/btrace-common.h

> +++ b/gdbsupport/btrace-common.h

> @@ -63,7 +63,10 @@ enum btrace_format

>     BTRACE_FORMAT_BTS,

>   

>     /* Branch trace is in Intel Processor Trace format.  */

> -  BTRACE_FORMAT_PT

> +  BTRACE_FORMAT_PT,

> +

> +  /* Branch trace is ARM CoreSight ETM format.  */

> +  BTRACE_FORMAT_ETM

>   };

>   

>   /* An enumeration of cpu vendors.  */

> @@ -119,6 +122,20 @@ struct btrace_config_pt

>     unsigned int size;

>   };

>   

> +/* An ARM CoreSight ETM Trace configuration.  */

> +

> +struct btrace_config_etm

> +{

> +  /* The size of the branch trace buffer in bytes.

> +

> +     This is unsigned int and not size_t since it is registered as

> +     control variable for "set record btrace etm buffer-size".  */

> +  unsigned int size;

> +

> +  /* The sink used to collect the traces.  */

> +  char *sink;

> +};

> +

>   /* A branch tracing configuration.

>   

>      This describes the requested configuration as well as the actually

> @@ -136,6 +153,9 @@ struct btrace_config

>   

>     /* The Intel Processor Trace format configuration.  */

>     struct btrace_config_pt pt;

> +

> +  /* The ARM CoreSight ETM Trace configuration.  */

> +  struct btrace_config_etm etm;

>   };

>   

>   /* Branch trace in BTS format.  */

> 


Other than those nits, I have no further comments on this.

Patch

diff --git a/gdb/NEWS b/gdb/NEWS
index ab678acec8b..02035901f6e 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -2,6 +2,7 @@ 
 	     (Organized release by release)
 
 *** Changes since GDB 10
+* Record btrace now  supports using ARM CoreSight ETM traces.
 
 * GDB now supports general memory tagging functionality if the underlying
   architecture supports the proper primitives and hooks.  Currently this is
@@ -77,6 +78,21 @@ 
 
 * New commands
 
+record btrace etm
+record etm
+  Start branch trace recording using ARM CoreSight trace format (ETM).
+
+set|show record btrace etm buffer-size
+  Set and show the size of the ring buffer used for branch tracing in
+  ETM format.
+  The obtained size may differ from the requested size.  Use "info
+  record" to see the obtained buffer size.
+
+set|show record btrace etm sink
+  Set and show the trace sink used for branch tracing in
+  ETM format.
+  Use "default" to reset it to default sink.
+
 set debug event-loop
 show debug event-loop
   Control the display of debug output about GDB's event loop.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 90d827a50e7..b9b09ff97f2 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -7479,15 +7479,19 @@  For architecture environments that support process record and replay,
 @kindex record btrace
 @kindex record btrace bts
 @kindex record btrace pt
+@kindex record btrace etm
 @kindex record bts
 @kindex record pt
+@kindex record etm
 @kindex rec
 @kindex rec full
 @kindex rec btrace
 @kindex rec btrace bts
 @kindex rec btrace pt
+@kindex rec btrace etm
 @kindex rec bts
 @kindex rec pt
+@kindex rec etm
 @item record @var{method}
 This command starts the process record and replay target.  The
 recording method can be specified as parameter.  Without a parameter
@@ -7501,7 +7505,7 @@  replay implementation.  This method allows replaying and reverse
 execution.
 
 @item btrace @var{format}
-Hardware-supported instruction recording, supported on Intel
+Hardware-supported instruction recording, supported on Intel and ARM
 processors.  This method does not record data.  Further, the data is
 collected in a ring buffer so old data will be overwritten when the
 buffer is full.  It allows limited reverse execution.  Variables and
@@ -7535,6 +7539,13 @@  Decoding the recorded execution trace, on the other hand, is more
 expensive than decoding @acronym{BTS} trace.  This is mostly due to the
 increased number of instructions to process.  You should increase the
 buffer-size with care.
+
+@item etm
+@cindex ARM CoreSight Trace
+Use the @dfn{ARM CoreSight Trace} recording format.  In this
+format, @acronym{ETM, Extended Trace Macrocell} stores the processor
+execution trace in a compressed form that is afterwards
+decoded by @value{GDBN}.
 @end table
 
 Not all recording formats may be available on all processors.
@@ -7682,6 +7693,12 @@  and to read-write memory.  Beware that the accessed memory corresponds
 to the live target and not necessarily to the current replay
 position.
 
+@item set record btrace etm sink @var{sink}
+Set ARM CoreSight ETM sink to collect traces.
+On @sc{gnu}/Linux systems, possible values for @var{sink} are the name of the
+files in the directory @file{/sys/bus/event_source/devices/cs_etm/sinks/}.
+Use the value @kbd{default} to reset it to default sink.
+
 @item set record btrace cpu @var{identifier}
 Set the processor to be used for enabling workarounds for processor
 errata when decoding the trace.
@@ -7745,6 +7762,9 @@  Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
 @item show record btrace replay-memory-access
 Show the current setting of @code{replay-memory-access}.
 
+@item show record btrace etm sink
+Show ARM CoreSight ETM sink.
+
 @item show record btrace cpu
 Show the processor to be used for enabling trace decode errata
 workarounds.
@@ -7796,6 +7816,29 @@  also need longer to process the branch trace data before it can be used.
 Show the current setting of the requested ring buffer size for branch
 tracing in Intel Processor Trace format.
 
+@kindex set record btrace etm
+@item set record btrace etm buffer-size @var{size}
+@itemx set record btrace etm buffer-size unlimited
+Set the requested ring buffer size for branch tracing in ARM
+CoreSight ETM Trace format.  Default is 16KB.
+
+If @var{size} is a positive number, then @value{GDBN} will try to
+allocate a buffer of at least @var{size} bytes for each new thread
+that uses the btrace recording method and the ARM CoreSight ETM
+format.  The actually obtained buffer size may differ from the
+requested @var{size}.  Use the @code{info record} command to see the
+actual buffer size for each thread.
+
+If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
+allocate a buffer of 4MB.
+
+Bigger buffers mean longer traces.  On the other hand, @value{GDBN} will
+also need longer to process the branch trace data before it can be used.
+
+@item show record btrace etm buffer-size @var{size}
+Show the current setting of the requested ring buffer size for branch
+tracing in ARM CoreSight ETM Trace format.
+
 @kindex info record
 @item info record
 Show various statistics about the recording depending on the recording
@@ -7847,6 +7890,12 @@  For the @code{pt} recording format, it also shows:
 @item
 Size of the perf ring buffer.
 @end itemize
+
+For the @code{etm} recording format, it also shows:
+@itemize @bullet
+@item
+Size of the perf ring buffer.
+@end itemize
 @end table
 
 @kindex record delete
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index 00affb85d22..16ffb76272b 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -201,6 +201,10 @@  static struct cmd_list_element *show_record_btrace_bts_cmdlist;
 static struct cmd_list_element *set_record_btrace_pt_cmdlist;
 static struct cmd_list_element *show_record_btrace_pt_cmdlist;
 
+/* Command lists for "set/show record btrace etm".  */
+static struct cmd_list_element *set_record_btrace_etm_cmdlist;
+static struct cmd_list_element *show_record_btrace_etm_cmdlist;
+
 /* Command list for "set record btrace cpu".  */
 static struct cmd_list_element *set_record_btrace_cpu_cmdlist;
 
@@ -526,6 +530,22 @@  record_btrace_print_pt_conf (const struct btrace_config_pt *conf)
     }
 }
 
+/* Print an ARM Processor Trace configuration.  */
+
+static void
+record_btrace_print_etm_conf (const struct btrace_config_etm *conf)
+{
+  unsigned int size;
+
+  size = conf->size;
+  if (size > 0)
+    {
+      const char *suffix;
+      suffix = record_btrace_adjust_size (&size);
+      printf_unfiltered (_("Buffer size: %u%s.\n"), size, suffix);
+    }
+}
+
 /* Print a branch tracing configuration.  */
 
 static void
@@ -546,6 +566,10 @@  record_btrace_print_conf (const struct btrace_config *conf)
     case BTRACE_FORMAT_PT:
       record_btrace_print_pt_conf (&conf->pt);
       return;
+
+    case BTRACE_FORMAT_ETM:
+      record_btrace_print_etm_conf (&conf->etm);
+      return;
     }
 
   internal_error (__FILE__, __LINE__, _("Unknown branch trace format."));
@@ -2676,7 +2700,7 @@  record_btrace_target::stop (ptid_t ptid)
 	  tp->btrace.flags |= BTHR_STOP;
 	}
     }
- }
+}
 
 /* The can_execute_reverse method of target record-btrace.  */
 
@@ -2937,6 +2961,27 @@  cmd_record_btrace_pt_start (const char *args, int from_tty)
     }
 }
 
+/* Start recording in ARM CoreSight ETM Trace format.  */
+
+static void
+cmd_record_btrace_etm_start (const char *args, int from_tty)
+{
+  if (args != nullptr && *args != 0)
+    error (_("Invalid argument."));
+
+  record_btrace_conf.format = BTRACE_FORMAT_ETM;
+
+  try
+    {
+      execute_command ("target record-btrace", from_tty);
+    }
+  catch (const gdb_exception &exception)
+    {
+      record_btrace_conf.format = BTRACE_FORMAT_NONE;
+      throw;
+    }
+}
+
 /* Alias for "target record".  */
 
 static void
@@ -2951,10 +2996,18 @@  cmd_record_btrace_start (const char *args, int from_tty)
     {
       execute_command ("target record-btrace", from_tty);
     }
-  catch (const gdb_exception &exception)
+  catch (const gdb_exception &exception_pt)
     {
       record_btrace_conf.format = BTRACE_FORMAT_BTS;
 
+      try
+	{
+	  execute_command ("target record-btrace", from_tty);
+	}
+      catch (const gdb_exception &exception_bts)
+	{
+	  record_btrace_conf.format = BTRACE_FORMAT_ETM;
+
 	  try
 	    {
 	      execute_command ("target record-btrace", from_tty);
@@ -2965,6 +3018,7 @@  cmd_record_btrace_start (const char *args, int from_tty)
 	      throw;
 	    }
 	}
+    }
 }
 
 /* The "show record btrace replay-memory-access" command.  */
@@ -3103,6 +3157,17 @@  show_record_pt_buffer_size_value (struct ui_file *file, int from_tty,
 		    value);
 }
 
+/* The "record etm buffer-size" show value function.  */
+
+static void
+show_record_etm_buffer_size_value (struct ui_file *file, int from_tty,
+				   struct cmd_list_element *c,
+				   const char *value)
+{
+  fprintf_filtered (file, _("The record/replay etm buffer size is %s.\n"),
+		    value);
+}
+
 /* Initialize btrace commands.  */
 
 void _initialize_record_btrace ();
@@ -3170,6 +3235,15 @@  When set to \"none\", errata workarounds are disabled."),
 		  1,
 		  &set_record_btrace_cmdlist);
 
+
+  cmd_list_element *record_btrace_etm_cmd
+    = add_cmd ("etm", class_obscure, cmd_record_btrace_etm_start,
+	       _("\
+Start branch trace recording in ARM CoreSight ETM Trace format.\n\n\
+This format may not be available on all processors."),
+	     &record_btrace_cmdlist);
+  add_alias_cmd ("etm", record_btrace_etm_cmd, class_obscure, 1, &record_cmdlist);
+
   add_cmd ("auto", class_support, cmd_set_record_btrace_cpu_auto, _("\
 Automatically determine the cpu to be used for trace decode."),
 	   &set_record_btrace_cpu_cmdlist);
@@ -3231,6 +3305,43 @@  to see the actual buffer size."), NULL, show_record_pt_buffer_size_value,
 			    &set_record_btrace_pt_cmdlist,
 			    &show_record_btrace_pt_cmdlist);
 
+  add_basic_prefix_cmd ("etm", class_support,
+			_("Set record btrace etm options."),
+			&set_record_btrace_etm_cmdlist,
+			0,
+			&set_record_btrace_cmdlist);
+
+  add_show_prefix_cmd ("etm", class_support,
+		       _("Show record btrace etm options."),
+		       &show_record_btrace_etm_cmdlist,
+		       0,
+		       &show_record_btrace_cmdlist);
+
+  add_setshow_uinteger_cmd ("buffer-size", no_class,
+			    &record_btrace_conf.etm.size,
+			    _("Set the record/replay etm buffer size."),
+			    _("Show the record/replay etm buffer size."), _("\
+Bigger buffers allow longer recording but also take more time to process \
+the recorded execution.\n\
+The actual buffer size may differ from the requested size.  Use \"info record\"\
+ to see the actual buffer size."), NULL, show_record_etm_buffer_size_value,
+		  &set_record_btrace_etm_cmdlist,
+		  &show_record_btrace_etm_cmdlist);
+
+  add_setshow_string_cmd ("sink", no_class,
+			  &record_btrace_conf.etm.sink,
+			  _("Set the record/replay ETM sink device."),
+			  _("Show the record/replay ETM sink device."),
+			  _("\
+Sink device is the device that intercepts ETM traces and collects or routes \
+them out of the System on Chip.\n\
+The list of available sinks on linux targets corresponds to the files in \
+the directory \"/sys/bus/event_source/devices/cs_etm/sinks/\".\n\
+value \"default\" reset it to default sink"),
+			  NULL, NULL,
+			  &set_record_btrace_etm_cmdlist,
+			  &show_record_btrace_etm_cmdlist);
+
   add_target (record_btrace_target_info, record_btrace_target_open);
 
   bfcache = htab_create_alloc (50, bfcache_hash, bfcache_eq, NULL,
@@ -3238,4 +3349,6 @@  to see the actual buffer size."), NULL, show_record_pt_buffer_size_value,
 
   record_btrace_conf.bts.size = 64 * 1024;
   record_btrace_conf.pt.size = 16 * 1024;
+#define DEFAULT_ETM_BUFFER_SIZE (8 * 1024)
+  record_btrace_conf.etm.size = DEFAULT_ETM_BUFFER_SIZE;
 }
diff --git a/gdb/record.c b/gdb/record.c
index 6968c30d930..32492fb53c4 100644
--- a/gdb/record.c
+++ b/gdb/record.c
@@ -118,6 +118,8 @@  record_start (const char *method, const char *format, int from_tty)
 	execute_command_to_string ("record btrace bts", from_tty, false);
       else if (strcmp (format, "pt") == 0)
 	execute_command_to_string ("record btrace pt", from_tty, false);
+      else if (strcmp (format, "etm") == 0)
+	execute_command_to_string ("record btrace etm", from_tty, false);
       else
 	error (_("Invalid format."));
     }
diff --git a/gdbsupport/btrace-common.cc b/gdbsupport/btrace-common.cc
index 4f9ef855e74..79ff21de44b 100644
--- a/gdbsupport/btrace-common.cc
+++ b/gdbsupport/btrace-common.cc
@@ -36,6 +36,9 @@  btrace_format_string (enum btrace_format format)
 
     case BTRACE_FORMAT_PT:
       return _("Intel Processor Trace");
+
+    case BTRACE_FORMAT_ETM:
+      return _("ARM Processor CoreSight ETM Trace");
     }
 
   internal_error (__FILE__, __LINE__, _("Unknown branch trace format"));
@@ -56,6 +59,9 @@  btrace_format_short_string (enum btrace_format format)
 
     case BTRACE_FORMAT_PT:
       return "pt";
+
+    case BTRACE_FORMAT_ETM:
+      return "etm";
     }
 
   internal_error (__FILE__, __LINE__, _("Unknown branch trace format"));
diff --git a/gdbsupport/btrace-common.h b/gdbsupport/btrace-common.h
index 26d26ec957f..153b977723a 100644
--- a/gdbsupport/btrace-common.h
+++ b/gdbsupport/btrace-common.h
@@ -63,7 +63,10 @@  enum btrace_format
   BTRACE_FORMAT_BTS,
 
   /* Branch trace is in Intel Processor Trace format.  */
-  BTRACE_FORMAT_PT
+  BTRACE_FORMAT_PT,
+
+  /* Branch trace is ARM CoreSight ETM format.  */
+  BTRACE_FORMAT_ETM
 };
 
 /* An enumeration of cpu vendors.  */
@@ -119,6 +122,20 @@  struct btrace_config_pt
   unsigned int size;
 };
 
+/* An ARM CoreSight ETM Trace configuration.  */
+
+struct btrace_config_etm
+{
+  /* The size of the branch trace buffer in bytes.
+
+     This is unsigned int and not size_t since it is registered as
+     control variable for "set record btrace etm buffer-size".  */
+  unsigned int size;
+
+  /* The sink used to collect the traces.  */
+  char *sink;
+};
+
 /* A branch tracing configuration.
 
    This describes the requested configuration as well as the actually
@@ -136,6 +153,9 @@  struct btrace_config
 
   /* The Intel Processor Trace format configuration.  */
   struct btrace_config_pt pt;
+
+  /* The ARM CoreSight ETM Trace configuration.  */
+  struct btrace_config_etm etm;
 };
 
 /* Branch trace in BTS format.  */