Patchwork [10/10] btrace: Extend event decoding for ptwrite.

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Submitter felix.willgerodt@intel.com
Date May 29, 2019, 8:47 a.m.
Message ID <1559119673-30516-11-git-send-email-felix.willgerodt@intel.com>
Download mbox | patch
Permalink /patch/32891/
State New
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Comments

felix.willgerodt@intel.com - May 29, 2019, 8:47 a.m.
From: Felix Willgerodt <felix.willgerodt@intel.com>

Call the ptwrite listener function whenever a ptwrite event is decoded.
The returned string is written to the aux_data string table and a
corresponding auxiliary instruction is appended to the function segment.

2019-05-29  Felix Willgerodt  <felix.willgerodt@intel.com>

gdb/ChangeLog:
	* btrace.c (handle_pt_insn_events): Handle ptev_ptwrite.

gdb/testsuite/ChangeLog:
	* gdb.btrace/ptwrite.c: New file.
	* gdb.btrace/ptwrite.exp: New file.
	* gdb.btrace/x86_64-ptwrite.S: New file.
	* lib/gdb.exp (skip_btrace_ptw_tests): New function.

gdb/doc/ChangeLog:
	* python.texi (gdb.ptwrite): New documentation.

---
 gdb/NEWS                                  |   6 +
 gdb/btrace.c                              |  47 +++
 gdb/doc/python.texi                       | 111 +++++
 gdb/testsuite/gdb.btrace/ptwrite.c        |  40 ++
 gdb/testsuite/gdb.btrace/ptwrite.exp      | 212 ++++++++++
 gdb/testsuite/gdb.btrace/x86_64-ptwrite.S | 479 ++++++++++++++++++++++
 gdb/testsuite/lib/gdb.exp                 |  92 +++++
 7 files changed, 987 insertions(+)
 create mode 100644 gdb/testsuite/gdb.btrace/ptwrite.c
 create mode 100644 gdb/testsuite/gdb.btrace/ptwrite.exp
 create mode 100644 gdb/testsuite/gdb.btrace/x86_64-ptwrite.S
Eli Zaretskii - May 29, 2019, 2:53 p.m.
> From: felix.willgerodt@intel.com
> Cc: markus.t.metzger@intel.com, Felix Willgerodt <felix.willgerodt@intel.com>
> Date: Wed, 29 May 2019 10:47:53 +0200
> 
> +* GDB now supports printing of ptwrite payloads from the Intel Processor
> +  Trace during 'record instruction-history', 'record  function-call-history',
                                                       ^^
Extra blank.

> +  all stepping commands and in  Python.  Printing is customizable via a
                          ^
A comma missing there.
> +use of the PTWRITE instruction. PTWRITE is a x86 instruction that allows to
                                 ^^
Two spaces between sentences, please.

> +The @value{NGCC} built-in functions for it are:
> +@smallexample
> +void __builtin_ia32_ptwrite32 (unsigned)
> +void __builtin_ia32_ptwrite64 (unsigned long long)
> +@end smallexample

Should there be a semi-colon at the end of each function prototype?

> +as auxiliary information into the execution history.  Auxiliary information
> +is by default printed during 'record instruction-history',
> +'record function-call-history' and all stepping commands and is accessible

The two "record" commands should be in @code and without quotes.
Also, please add a comma before the last "and".

> +in Python as a @code{RecordAuxiliary} object. 
> +
> +@exdent Sample program:
> +@smallexample
> +void
> +ptwrite64 (unsigned long long value)
> +@{
> +  __builtin_ia32_ptwrite64 (value);
> +@}
> +
> +int
> +main (void)
> +@{
> +  ptwrite64 (0x42);
> +  return 0; /* break here.  */
> +@}
> +@end smallexample
> +
> +@exdent @value{GDBN} output after recording the sample program in pt format:
> +@smallexample
> +(gdb) record instruction-history 12,14
> +12         0x000000000040074c <ptwrite64+16>:	ptwrite %rbx
> +13         [payload: 0x42]
> +14         0x0000000000400751 <ptwrite64+21>:	mov    -0x8(%rbp),%rbx
> +(gdb) record function-call-history
> +1       main
> +2       ptwrite64
> +                [payload: 0x42]
> +3       main
> +@end smallexample

Long examples such as the two above should use @group to avoid being
split between two pages in an unfortunate place.

> +auxiliary information. A custom Python function can be registered via
                        ^^
Two spaces.

> +@code{gdb.ptwrite.register_listener()} as the @dfn{ptwrite listener function}.

Every term you put in @dfn should have an index entry, as this is
generally terminology people will later look up in the manual.

> +This function will be called with the ptwrite payload and IP as arguments
> +during trace decoding.

If "IP" stands for "instruction pointer", I think that we prefer "PC"
instead.

> +@table @code
> +
> +@item register_listener (@var{listener})
> +Used to register the ptwrite listener.  The listener can be any callable
> +object that accepts two arguments.   It can return a string, which will be
                                     ^^^
Extra space.

> +printed by @value{GDBN} during the aforementioned commands, or @code{None},
> +resulting in no output.  @code{None} can also be registered to deactivate
> +printing.
> +
> +@item get_listener ()
> +Returns the currently active ptwrite listener function.
> +
> +@item default_listener (@var{payload}, @var{ip})
> +The listener function active by default.
> +@end table

Why is this a @table, and not a series of @defun's?

> +threads. The listener can however distinguish between multiple threads
          ^^
Missing space.

> +with the help of @code{gdb.selected_thread().global_num} or similar.

Please add a cross-reference to where gdb.selected_thread is described
in the manual.

Thanks.
Metzger, Markus T - June 4, 2019, 12:37 p.m.
Hello Felix,

> @@ -1244,6 +1244,53 @@ handle_pt_insn_events (struct btrace_thread_info
> *btinfo,
>  		   bfun->insn_offset - 1, offset);
> 
>  	  break;
> +
> +	case ptev_ptwrite:
> +	  {
> +	    uint64_t *ip = nullptr;
> +	    gdb::unique_xmalloc_ptr<char> ptw_string = nullptr;
> +	    struct btrace_insn ptw_insn;
> +
> +	    /* Lookup the ip.  */
> +	    if (event.ip_suppressed == 0)
> +	      ip = &event.variant.ptwrite.ip;
> +	    else if (!btinfo->functions.empty ()
> +		     && !btinfo->functions.back ().insn.empty ())
> +	      ip = &btinfo->functions.back ().insn.back ().pc;

Libipt will provide the PTWRITE instruction's IP.  We may get PTW events without IP
but those wouldn't bind to the previous instruction - or libipt would have filled in
the event IP.

If EVENT.IP_SUPPRESSED is set, there is no IP.

> +	    else
> +	      /* This should never happen.  */
> +	      error (_("Failed to obtain the PC of the current instruction."));

We explicitly allow a nullptr IP in the callback function.

> +
> +	    try
> +	      {
> +		if (btinfo->ptw_callback_fun != nullptr)
> +		  ptw_string = btinfo->ptw_callback_fun (
> +					  &event.variant.ptwrite.payload, ip,
> +					  btinfo->ptw_listener);
> +	      }
> +	    catch (const gdb_exception_error &error)
> +	      {
> +		warning (_("Failed to call ptwrite listener."));

This indicates a bug in the user's ptwrite-listener object.  Should we print a
backtrace and fail with an error?

> +	      }
> +
> +	    if (ptw_string == nullptr)
> +	      break;
> +
> +	    btinfo->aux_data.emplace_back (ptw_string.get ());
> +
> +	    /* Update insn list with ptw payload insn.  */
> +	    ptw_insn.aux_data_index = btinfo->aux_data.size () - 1;
> +	    ptw_insn.flags = 0;

Can we preserve the SPECULATIVE flag?

> +	    ptw_insn.iclass = BTRACE_INSN_AUX;
> +	    ptw_insn.size = 0;
> +
> +	    bfun = ftrace_update_function (btinfo, *ip);
> +	    bfun->flags |= BFUN_AUX_DECODED;
> +
> +	    ftrace_update_insns (bfun, ptw_insn);
> +
> +	    break;
> +	  }
>  	}
>      }
>  #endif /* defined (HAVE_PT_INSN_EVENT) */

[...]

> +When recording multithreaded programs, @value{GDBN} creates a new copy of

Also when recording a single threaded program.  Maybe just remove this part.

> the
> +listener function for each thread to allow for independent internal states.
> +There is currently no support for registering different listeners for different
> +threads. The listener can however distinguish between multiple threads

You write 'currently'.  Are there plans to support different listeners for different threads?

> +with the help of @code{gdb.selected_thread().global_num} or similar.
> +
> +@exdent For example:
> +@smallexample
> +(gdb) python-interactive
> +>>> def my_listener(payload, ip):
> +...     if gdb.selected_thread().global_num == 1:
> +...         return "payload: @{0@}, ip: @{:#x@}".format(payload, ip)
> +...     else:
> +...         return None
> +...

An example where the listener accumulates payloads would be nice.

> +++ b/gdb/testsuite/gdb.btrace/ptwrite.c
> @@ -0,0 +1,40 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + Copyright 2018 Free Software Foundation, Inc.

It's 2019, meanwhile.

> +
> + This program is free software; you can redistribute it and/or modify
> + it under the terms of the GNU General Public License as published by
> + the Free Software Foundation; either version 3 of the License, or
> + (at your option) any later version.
> +
> + This program is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + GNU General Public License for more details.
> +
> + You should have received a copy of the GNU General Public License
> + along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdint.h>
> +
> +void
> +ptwrite64 (uint64_t value)
> +{
> +  asm volatile ("PTWRITE %0;" : : "b" (value));
> +}
> +
> +void
> +ptwrite32 (uint32_t value)
> +{
> +  asm volatile ("PTWRITE %0;" : : "b" (value));
> +}
> +
> +int
> +main (void)
> +{
> +

Spurious empty line.

> +  ptwrite64 (0x42);
> +  ptwrite32 (0x43);
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.btrace/ptwrite.exp
> b/gdb/testsuite/gdb.btrace/ptwrite.exp
> new file mode 100644
> index 00000000000..4cbd030be44
> --- /dev/null
> +++ b/gdb/testsuite/gdb.btrace/ptwrite.exp
> @@ -0,0 +1,212 @@
> +# This testcase is part of GDB, the GNU debugger.
> +#
> +# Copyright 2018 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +load_lib gdb-python.exp
> +
> +if { [skip_btrace_pt_tests] } {
> +    unsupported "Target does not support record btrace pt."
> +    return -1
> +}
> +
> +if { [skip_btrace_ptw_tests] } {
> +    unsupported "Hardware does not support ptwrite instructions."
> +    return -1
> +}
> +
> +set comp_flags "additional_flags=-I${srcdir}/.."

If we need this only in the COMPILE case, I'd move it there; or just inline it.

> +set opts {}
> +
> +if [info exists COMPILE] {
> +    # make check RUNTESTFLAGS="gdb.btrace/ptwrite.exp COMPILE=1"
> +    standard_testfile ptwrite.c
> +    lappend opts debug comp_flags
> +} elseif {[istarget "i?86-*-*"] || [istarget "x86_64-*-*"]} {
> +	if {[is_amd64_regs_target]} {
> +		standard_testfile x86_64-ptwrite.S
> +	} else {
> +		unsupported "target architecture not supported"
> +		return -1
> +	}
> +} else {
> +    unsupported "target architecture not supported"
> +    return -1
> +}
> +
> +if [prepare_for_testing "failed to prepare" $testfile $srcfile $opts] {
> +    unsupported "Compiler does not support ptwrite."

I don't think we need an 'unsupported' here.  We should get 'failed to prepare', already.

> +    return -1
> +}
> +
> +
> +if { ![runto_main] } {
> +    untested "failed to run to main"
> +    return -1
> +}
> +
> +# This needs to be after runto_main
> +if { [skip_python_tests] } {
> +    unsupported "Configuration doesn't support python scripting."
> +    return -1
> +}
> +
> +
> +### 1. Default testrun
> +
> +# Setup recording

You can use with_test_prefix to avoid repeating the prefix in each test.

> +gdb_test_no_output "set record instruction-history-size unlimited" "Default:
> set unlimited"
> +gdb_test_no_output "record btrace pt" "Default: record btrace pt"
> +gdb_test "next" ".*" "Default: first next"
> +gdb_test "next" ".*" "Default: second next"


> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index c703a7e6338..ba7ccfd46ba 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -2874,6 +2874,98 @@ gdb_caching_proc skip_btrace_pt_tests {
>      return $skip_btrace_tests
>  }
> 
> +# Run a test on the target to see if it supports ptwrite instructions.
> +# Return 0 if so, 1 if it does not.  Based on 'check_vmx_hw_available'
> +# from the GCC testsuite.
> +
> +gdb_caching_proc skip_btrace_ptw_tests {
> +    global srcdir subdir gdb_prompt inferior_exited_re
> +
> +    set me "skip_ptw_tests"
> +
> +    # Set up, compile, and execute a test program.
> +    # Include the current process ID in the file names to prevent conflicts
> +    # with invocations for multiple testsuites.
> +    set src [standard_temp_file ptw[pid].c]
> +    set exe [standard_temp_file ptw[pid].x]
> +
> +    gdb_produce_source $src {
> +	#include <stdbool.h>
> +	#include <stdint.h>
> +	#include <stdio.h>
> +	#include "x86-cpuid.h"
> +
> +	#define bit_PTW (1 << 4)
> +
> +	bool
> +	have_ptw ()
> +	{
> +	  unsigned int eax, ebx, ecx, edx;
> +
> +	  if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
> +	      return false;
> +
> +	  if ((ecx & bit_OSXSAVE) != bit_OSXSAVE)
> +	      return false;
> +
> +	  if (__get_cpuid_max (0, NULL) < 0x14)
> +	      return false;
> +
> +	  __cpuid_count (0x14, 0, eax, ebx, ecx, edx);
> +
> +	  return (ebx & bit_PTW) == bit_PTW;
> +	}
> +
> +	int
> +	main ()
> +	{
> +	  return have_ptw ();
> +	}
> +
> +    }
> +
> +    verbose "$me:  compiling testfile $src" 2
> +
> +    set test_flags [list additional_flags=-I${srcdir}/../nat]
> +
> +    set compile_flags [concat {debug nowarnings quiet} ${test_flags}]
> +    set lines [gdb_compile $src $exe executable $compile_flags]
> +
> +    if ![string match "" $lines] then {
> +	verbose "$me:  testfile compilation failed, returning 1" 2
> +	file delete $src
> +	return 1
> +    }
> +
> +    # No error message, compilation succeeded so now run it via gdb.
> +    gdb_exit
> +    gdb_start
> +    gdb_reinitialize_dir $srcdir/$subdir
> +    gdb_load $exe
> +    if ![runto_main] {
> +	file delete $src
> +	return 1
> +    }
> +    file delete $src
> +
> +    # In case of an unexpected output, we return 2 as a fail value.
> +    set skip_ptw_tests 2
> +    gdb_test_multiple "print (int) have_ptw ()" "check ptw support" {
> +	-re ".. = 1\r\n$gdb_prompt $" {
> +	    set skip_ptw_tests 0
> +	}
> +	-re ".. = 0\r\n$gdb_prompt $" {
> +	    set skip_ptw_tests 1
> +	}
> +    }
> +
> +    gdb_exit
> +    remote_file build delete $exe
> +
> +    verbose "$me:  returning $skip_ptw_tests" 2
> +    return $skip_ptw_tests

We still don't know if the OS supports it, do we?

> +}
> +
>  # Run a test on the target to see if it supports Aarch64 SVE hardware.
>  # Return 0 if so, 1 if it does not.  Note this causes a restart of GDB.
> 
> --
> 2.20.1

Thanks,
Markus.
Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Gary Kershaw
Chairperson of the Supervisory Board: Nicole Lau
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Commercial Register: Amtsgericht Muenchen HRB 186928

Patch

diff --git a/gdb/NEWS b/gdb/NEWS
index 6546b7243a9..1fca2f0cfd2 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,12 @@ 
 
 *** Changes since GDB 8.3
 
+* GDB now supports printing of ptwrite payloads from the Intel Processor
+  Trace during 'record instruction-history', 'record  function-call-history',
+  all stepping commands and in  Python.  Printing is customizable via a
+  ptwrite listener function in  Python.  By default, the raw ptwrite
+  payload is printed for each ptwrite that is encountered.
+
 * New built-in convenience variables $_gdb_major and $_gdb_minor
   provide the GDB version.  They are handy for conditionally using
   features available only in or since specific GDB versions, in
diff --git a/gdb/btrace.c b/gdb/btrace.c
index 5bdef1c1768..e098abba514 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -1244,6 +1244,53 @@  handle_pt_insn_events (struct btrace_thread_info *btinfo,
 		   bfun->insn_offset - 1, offset);
 
 	  break;
+
+	case ptev_ptwrite:
+	  {
+	    uint64_t *ip = nullptr;
+	    gdb::unique_xmalloc_ptr<char> ptw_string = nullptr;
+	    struct btrace_insn ptw_insn;
+
+	    /* Lookup the ip.  */
+	    if (event.ip_suppressed == 0)
+	      ip = &event.variant.ptwrite.ip;
+	    else if (!btinfo->functions.empty ()
+		     && !btinfo->functions.back ().insn.empty ())
+	      ip = &btinfo->functions.back ().insn.back ().pc;
+	    else
+	      /* This should never happen.  */
+	      error (_("Failed to obtain the PC of the current instruction."));
+
+	    try
+	      {
+		if (btinfo->ptw_callback_fun != nullptr)
+		  ptw_string = btinfo->ptw_callback_fun (
+					  &event.variant.ptwrite.payload, ip,
+					  btinfo->ptw_listener);
+	      }
+	    catch (const gdb_exception_error &error)
+	      {
+		warning (_("Failed to call ptwrite listener."));
+	      }
+
+	    if (ptw_string == nullptr)
+	      break;
+
+	    btinfo->aux_data.emplace_back (ptw_string.get ());
+
+	    /* Update insn list with ptw payload insn.  */
+	    ptw_insn.aux_data_index = btinfo->aux_data.size () - 1;
+	    ptw_insn.flags = 0;
+	    ptw_insn.iclass = BTRACE_INSN_AUX;
+	    ptw_insn.size = 0;
+
+	    bfun = ftrace_update_function (btinfo, *ip);
+	    bfun->flags |= BFUN_AUX_DECODED;
+
+	    ftrace_update_insns (bfun, ptw_insn);
+
+	    break;
+	  }
 	}
     }
 #endif /* defined (HAVE_PT_INSN_EVENT) */
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index e892caf9e18..8fb052c3b83 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -5683,6 +5683,7 @@  registering objfile-specific pretty-printers and frame-filters.
 * gdb.printing::       Building and registering pretty-printers.
 * gdb.types::          Utilities for working with types.
 * gdb.prompt::         Utilities for prompt value substitution.
+* gdb.ptwrite::        Utilities for ptwrite listener registration.
 @end menu
 
 @node gdb.printing
@@ -5874,3 +5875,113 @@  substitute_prompt (``frame: \f,
 "frame: main, print arguments: scalars"
 @end smallexample
 @end table
+
+@node gdb.ptwrite
+@subsubsection gdb.ptwrite
+@cindex gdb.ptwrite
+
+This module provides additional functionality for recording programs that make
+use of the PTWRITE instruction. PTWRITE is a x86 instruction that allows to
+write values into the Intel Processor Trace (@pxref{Process Record and Replay}).
+The @value{NGCC} built-in functions for it are:
+@smallexample
+void __builtin_ia32_ptwrite32 (unsigned)
+void __builtin_ia32_ptwrite64 (unsigned long long)
+@end smallexample
+
+If an inferior uses the instruction, @value{GDBN} inserts the raw payload value
+as auxiliary information into the execution history.  Auxiliary information
+is by default printed during 'record instruction-history',
+'record function-call-history' and all stepping commands and is accessible
+in Python as a @code{RecordAuxiliary} object. 
+
+@exdent Sample program:
+@smallexample
+void
+ptwrite64 (unsigned long long value)
+@{
+  __builtin_ia32_ptwrite64 (value);
+@}
+
+int
+main (void)
+@{
+  ptwrite64 (0x42);
+  return 0; /* break here.  */
+@}
+@end smallexample
+
+@exdent @value{GDBN} output after recording the sample program in pt format:
+@smallexample
+(gdb) record instruction-history 12,14
+12         0x000000000040074c <ptwrite64+16>:	ptwrite %rbx
+13         [payload: 0x42]
+14         0x0000000000400751 <ptwrite64+21>:	mov    -0x8(%rbp),%rbx
+(gdb) record function-call-history
+1       main
+2       ptwrite64
+                [payload: 0x42]
+3       main
+@end smallexample
+
+The @code{gdb.ptwrite} module allows customizing the default output of ptwrite
+auxiliary information. A custom Python function can be registered via
+@code{gdb.ptwrite.register_listener()} as the @dfn{ptwrite listener function}.
+This function will be called with the ptwrite payload and IP as arguments
+during trace decoding.
+
+@table @code
+
+@item register_listener (@var{listener})
+Used to register the ptwrite listener.  The listener can be any callable
+object that accepts two arguments.   It can return a string, which will be
+printed by @value{GDBN} during the aforementioned commands, or @code{None},
+resulting in no output.  @code{None} can also be registered to deactivate
+printing.
+
+@item get_listener ()
+Returns the currently active ptwrite listener function.
+
+@item default_listener (@var{payload}, @var{ip})
+The listener function active by default.
+@end table
+
+When recording multithreaded programs, @value{GDBN} creates a new copy of the
+listener function for each thread to allow for independent internal states.
+There is currently no support for registering different listeners for different
+threads. The listener can however distinguish between multiple threads
+with the help of @code{gdb.selected_thread().global_num} or similar.
+
+@exdent For example:
+@smallexample
+(gdb) python-interactive
+>>> def my_listener(payload, ip):
+...     if gdb.selected_thread().global_num == 1:
+...         return "payload: @{0@}, ip: @{:#x@}".format(payload, ip)
+...     else:
+...         return None
+...
+>>> import gdb.ptwrite
+>>> gdb.ptwrite.register_listener(my_listener)
+>>>
+(gdb) record instruction-history 127,129
+127	   0x000000000040116c <ptwrite32(unsigned int)+13>:	ptwrite %ebx
+128        [payload: 4919, ip: 0x40074c]
+129	   0x0000000000401170 <ptwrite32(unsigned int)+17>:	nop
+(gdb) info threads 
+* 1    Thread 0x7ffff7fd8740 (LWP 25796) "ptwrite_threads" task (arg=0x0)
+    at bin/ptwrite/ptwrite_threads.c:45
+  2    Thread 0x7ffff6eb8700 (LWP 25797) "ptwrite_threads" task (arg=0x0)
+    at bin/ptwrite/ptwrite_threads.c:45
+(gdb) thread 2
+[Switching to thread 2 (Thread 0x7ffff6eb8700 (LWP 25797))]
+#0  task (arg=0x0) at ptwrite_threads.c:45
+45	  return NULL;
+(gdb) record instruction-history 1753,1755
+1753	   0x000000000040116c <ptwrite32(unsigned int)+13>:	ptwrite %ebx
+1754	   0x0000000000401170 <ptwrite32(unsigned int)+17>:	nop
+1755	   0x0000000000401171 <ptwrite32(unsigned int)+18>:	pop    %rbx
+@end smallexample
+
+This GDB feature is dependent on hardware and operating system support and
+requires the Intel Processor Trace decoder library in version 2.0.0 or newer.
diff --git a/gdb/testsuite/gdb.btrace/ptwrite.c b/gdb/testsuite/gdb.btrace/ptwrite.c
new file mode 100644
index 00000000000..5e7ecb75e02
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/ptwrite.c
@@ -0,0 +1,40 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2018 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdint.h>
+
+void
+ptwrite64 (uint64_t value)
+{
+  asm volatile ("PTWRITE %0;" : : "b" (value));
+}
+
+void
+ptwrite32 (uint32_t value)
+{
+  asm volatile ("PTWRITE %0;" : : "b" (value));
+}
+
+int
+main (void)
+{
+
+  ptwrite64 (0x42);
+  ptwrite32 (0x43);
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.btrace/ptwrite.exp b/gdb/testsuite/gdb.btrace/ptwrite.exp
new file mode 100644
index 00000000000..4cbd030be44
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/ptwrite.exp
@@ -0,0 +1,212 @@ 
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2018 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib gdb-python.exp
+
+if { [skip_btrace_pt_tests] } {
+    unsupported "Target does not support record btrace pt."
+    return -1
+}
+
+if { [skip_btrace_ptw_tests] } {
+    unsupported "Hardware does not support ptwrite instructions."
+    return -1
+}
+
+set comp_flags "additional_flags=-I${srcdir}/.."
+set opts {}
+
+if [info exists COMPILE] {
+    # make check RUNTESTFLAGS="gdb.btrace/ptwrite.exp COMPILE=1"
+    standard_testfile ptwrite.c
+    lappend opts debug comp_flags
+} elseif {[istarget "i?86-*-*"] || [istarget "x86_64-*-*"]} {
+	if {[is_amd64_regs_target]} {
+		standard_testfile x86_64-ptwrite.S
+	} else {
+		unsupported "target architecture not supported"
+		return -1
+	}
+} else {
+    unsupported "target architecture not supported"
+    return -1
+}
+
+if [prepare_for_testing "failed to prepare" $testfile $srcfile $opts] {
+    unsupported "Compiler does not support ptwrite."
+    return -1
+}
+
+
+if { ![runto_main] } {
+    untested "failed to run to main"
+    return -1
+}
+
+# This needs to be after runto_main
+if { [skip_python_tests] } {
+    unsupported "Configuration doesn't support python scripting."
+    return -1
+}
+
+
+### 1. Default testrun
+
+# Setup recording
+gdb_test_no_output "set record instruction-history-size unlimited" "Default: set unlimited"
+gdb_test_no_output "record btrace pt" "Default: record btrace pt"
+gdb_test "next" ".*" "Default: first next"
+gdb_test "next" ".*" "Default: second next"
+
+
+# Test libipt version (must be >= 2.0.0)
+set libipt_supports_ptwrite 0
+
+gdb_test_multiple "maint info btrace" "check libipt version" {
+    -re ".*Version: \[01\]\.\[0-9\]+\.\[0-9\]+.*"
+    {
+	set libipt_supports_ptwrite 0
+    }
+    -re ".*Version: \[0-9\]+\.\[0-9\]+\.\[0-9\]+.*"
+    {
+	set libipt_supports_ptwrite 1
+    }
+    default {
+	set libipt_supports_ptwrite 0
+    }
+}
+
+if { $libipt_supports_ptwrite == 0 } {
+    unsupported "libipt version doesn't support ptwrite decoding."
+    return -1
+}
+
+# Test record instruction-history
+gdb_test "record instruction-history 1" [multi_line \
+  ".*\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[payload: 0x42\\\]" \
+  ".*\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[payload: 0x43\\\].*" \
+  ] "Default: record instruction-history 1"
+
+# Test function call history
+gdb_test "record function-call-history 1,4" [multi_line \
+  "1\tmain" \
+  "2\tptwrite64" \
+  "\t\t\\\[payload: 0x42\\\]" \
+  "3\tmain" \
+  "4\tptwrite32" \
+  "\t\t\\\[payload: 0x43\\\]" \
+  ] "Default: record function-call-history 1,4"
+
+gdb_test "record function-call-history /s 1,4" [multi_line \
+  "1\tmain" \
+  "2\tptwrite64" \
+  "3\tmain" \
+  "4\tptwrite32" \
+  ] "Default: record function-call-history /s 1,4"
+
+# Test payload printing during stepping
+gdb_test "record goto 10" "No such instruction\."
+gdb_test "record goto 9" ".*ptwrite64.* at .*ptwrite.c:23.*"
+gdb_test "stepi" ".*\\\[payload: 0x42\\\].*"
+gdb_test "reverse-stepi" ".*\\\[payload: 0x42\\\].*"
+gdb_test "continue" ".*\\\[payload: 0x42\\\].*\\\[payload: 0x43\\\].*"
+gdb_test "reverse-continue" ".*\\\[payload: 0x43\\\].*\\\[payload: 0x42\\\].*"
+
+# Test auxiliary type in python
+gdb_py_test_multiple "Default: auxiliary type in python" \
+  "python" "" \
+  "h = gdb.current_recording().instruction_history" "" \
+  "for insn in h: print(insn)" "" \
+  "end" [multi_line \
+  ".*RecordAuxiliary.*" \
+  ".*RecordAuxiliary.*" \
+  ]
+
+
+### 2. Test listener registration
+### 2.1 Custom listener
+
+gdb_py_test_multiple "Custom: register listener in python" \
+  "python" "" \
+  "def my_listener(payload, ip):" "" \
+  "    if  payload == 66:" "" \
+  "        return \"payload: {0}, ip: {1:#x}\".format(payload, ip)" "" \
+  "    else:" "" \
+  "        return None" "" \
+  "import gdb.ptwrite" "" \
+  "gdb.ptwrite.register_listener(my_listener)" "" \
+  "end" ""
+
+gdb_test "record instruction-history 1" [multi_line \
+  ".*\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[payload: 66, ip: $hex\\\]" \
+  ".*\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:.*" \
+  ] "Custom: record instruction-history 1"
+
+### 2.2 None as listener
+
+gdb_py_test_multiple "None: register listener in python" \
+  "python" "" \
+  "import gdb.ptwrite" "" \
+  "gdb.ptwrite.register_listener(None)" "" \
+  "end" ""
+
+gdb_test "record instruction-history 1" [multi_line \
+  ".*\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:.*" \
+  "\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:.*" \
+  ] "None: record instruction-history 1"
+
+### 2.3 Lambdas as listener
+
+gdb_py_test_multiple "Lambdas: register listener in python" \
+  "python" "" \
+  "import gdb.ptwrite" "" \
+  "gdb.ptwrite.register_listener(lambda payload, ip: \"{}\".format(payload + 2))" "" \
+  "end" ""
+
+gdb_test "record instruction-history 1" [multi_line \
+  ".*\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[68\\\]" \
+  ".*\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[69\\\].*" \
+  ] "Lambdas: record instruction-history 1"
+
+### 2.4 Functors as listener
+
+gdb_py_test_multiple "Functors: register listener in python" \
+  "python" "" \
+  "import gdb.ptwrite" "" \
+  "class foobar(object):" "" \
+  "    def __init__(self):" "" \
+  "        self.variable = 0" "" \
+  "    def __call__(self, payload, ip):" "" \
+  "        self.variable += 1" "" \
+  "        return \"{}, {}\".format(self.variable, payload)" "" \
+  "gdb.ptwrite.register_listener(foobar())" "" \
+  "end" ""
+
+gdb_test "record instruction-history 1" [multi_line \
+  ".*\[0-9\]+\t   $hex <ptwrite64\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[1, 66\\\]" \
+  ".*\[0-9\]+\t   $hex <ptwrite32\\+\[0-9\]+>:\tptwrite %\[a-z\]+" \
+  "\[0-9\]+\t   \\\[2, 67\\\].*" \
+  ] "Functors: record instruction-history 1"
diff --git a/gdb/testsuite/gdb.btrace/x86_64-ptwrite.S b/gdb/testsuite/gdb.btrace/x86_64-ptwrite.S
new file mode 100644
index 00000000000..138ed17a42a
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/x86_64-ptwrite.S
@@ -0,0 +1,479 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+   This file has been generated using gcc version 8.1.1 20180502:
+   gcc -S -dA -g ptwrite.c -o x86_64-ptwrite.S.  */
+
+	.file	"ptwrite.c"
+	.text
+.Ltext0:
+	.globl	ptwrite64
+	.type	ptwrite64, @function
+ptwrite64:
+.LFB0:
+	.file 1 "ptwrite.c"
+	# ptwrite.c:22:1
+	.loc 1 22 1
+	.cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (FALLTHRU)
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	pushq	%rbx
+	.cfi_offset 3, -24
+	movq	%rdi, -16(%rbp)
+	# ptwrite.c:23:3
+	.loc 1 23 3
+	movq	-16(%rbp), %rax
+	movq	%rax, %rbx
+#APP
+# 23 "ptwrite.c" 1
+	PTWRITE %rbx;
+# 0 "" 2
+	# ptwrite.c:24:1
+	.loc 1 24 1
+#NO_APP
+	nop
+	popq	%rbx
+	popq	%rbp
+	.cfi_def_cfa 7, 8
+# SUCC: EXIT [always] 
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	ptwrite64, .-ptwrite64
+	.globl	ptwrite32
+	.type	ptwrite32, @function
+ptwrite32:
+.LFB1:
+	# ptwrite.c:28:1
+	.loc 1 28 1
+	.cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (FALLTHRU)
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	pushq	%rbx
+	.cfi_offset 3, -24
+	movl	%edi, -12(%rbp)
+	# ptwrite.c:29:3
+	.loc 1 29 3
+	movl	-12(%rbp), %eax
+	movl	%eax, %ebx
+#APP
+# 29 "ptwrite.c" 1
+	PTWRITE %ebx;
+# 0 "" 2
+	# ptwrite.c:30:1
+	.loc 1 30 1
+#NO_APP
+	nop
+	popq	%rbx
+	popq	%rbp
+	.cfi_def_cfa 7, 8
+# SUCC: EXIT [always] 
+	ret
+	.cfi_endproc
+.LFE1:
+	.size	ptwrite32, .-ptwrite32
+	.globl	main
+	.type	main, @function
+main:
+.LFB2:
+	# ptwrite.c:34:1
+	.loc 1 34 1
+	.cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (FALLTHRU)
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	# ptwrite.c:36:3
+	.loc 1 36 3
+	movl	$66, %edi
+	call	ptwrite64
+	# ptwrite.c:37:3
+	.loc 1 37 3
+	movl	$67, %edi
+	call	ptwrite32
+	# ptwrite.c:39:10
+	.loc 1 39 10
+	movl	$0, %eax
+	# ptwrite.c:40:1
+	.loc 1 40 1
+	popq	%rbp
+	.cfi_def_cfa 7, 8
+# SUCC: EXIT [always] 
+	ret
+	.cfi_endproc
+.LFE2:
+	.size	main, .-main
+.Letext0:
+	.file 2 "/usr/include/bits/types.h"
+	.file 3 "/usr/include/bits/stdint-uintn.h"
+	.section	.debug_info,"",@progbits
+.Ldebug_info0:
+	.long	0x10f	# Length of Compilation Unit Info
+	.value	0x4	# DWARF version number
+	.long	.Ldebug_abbrev0	# Offset Into Abbrev. Section
+	.byte	0x8	# Pointer Size (in bytes)
+	.uleb128 0x1	# (DIE (0xb) DW_TAG_compile_unit)
+	.long	.LASF13	# DW_AT_producer: "GNU C17 8.1.1 20180502 (Red Hat 8.1.1-1) -mtune=generic -march=x86-64 -g"
+	.byte	0xc	# DW_AT_language
+	.long	.LASF14	# DW_AT_name: "ptwrite.c"
+	.long	.LASF15	# DW_AT_comp_dir: "gdb/gdb/testsuite/gdb.btrace"
+	.quad	.Ltext0	# DW_AT_low_pc
+	.quad	.Letext0-.Ltext0	# DW_AT_high_pc
+	.long	.Ldebug_line0	# DW_AT_stmt_list
+	.uleb128 0x2	# (DIE (0x2d) DW_TAG_base_type)
+	.byte	0x1	# DW_AT_byte_size
+	.byte	0x8	# DW_AT_encoding
+	.long	.LASF0	# DW_AT_name: "unsigned char"
+	.uleb128 0x2	# (DIE (0x34) DW_TAG_base_type)
+	.byte	0x2	# DW_AT_byte_size
+	.byte	0x7	# DW_AT_encoding
+	.long	.LASF1	# DW_AT_name: "short unsigned int"
+	.uleb128 0x2	# (DIE (0x3b) DW_TAG_base_type)
+	.byte	0x4	# DW_AT_byte_size
+	.byte	0x7	# DW_AT_encoding
+	.long	.LASF2	# DW_AT_name: "unsigned int"
+	.uleb128 0x2	# (DIE (0x42) DW_TAG_base_type)
+	.byte	0x8	# DW_AT_byte_size
+	.byte	0x7	# DW_AT_encoding
+	.long	.LASF3	# DW_AT_name: "long unsigned int"
+	.uleb128 0x2	# (DIE (0x49) DW_TAG_base_type)
+	.byte	0x1	# DW_AT_byte_size
+	.byte	0x6	# DW_AT_encoding
+	.long	.LASF4	# DW_AT_name: "signed char"
+	.uleb128 0x2	# (DIE (0x50) DW_TAG_base_type)
+	.byte	0x2	# DW_AT_byte_size
+	.byte	0x5	# DW_AT_encoding
+	.long	.LASF5	# DW_AT_name: "short int"
+	.uleb128 0x3	# (DIE (0x57) DW_TAG_base_type)
+	.byte	0x4	# DW_AT_byte_size
+	.byte	0x5	# DW_AT_encoding
+	.ascii "int\0"	# DW_AT_name
+	.uleb128 0x4	# (DIE (0x5e) DW_TAG_typedef)
+	.long	.LASF7	# DW_AT_name: "__uint32_t"
+	.byte	0x2	# DW_AT_decl_file (/usr/include/bits/types.h)
+	.byte	0x29	# DW_AT_decl_line
+	.byte	0x16	# DW_AT_decl_column
+	.long	0x3b	# DW_AT_type
+	.uleb128 0x2	# (DIE (0x6a) DW_TAG_base_type)
+	.byte	0x8	# DW_AT_byte_size
+	.byte	0x5	# DW_AT_encoding
+	.long	.LASF6	# DW_AT_name: "long int"
+	.uleb128 0x4	# (DIE (0x71) DW_TAG_typedef)
+	.long	.LASF8	# DW_AT_name: "__uint64_t"
+	.byte	0x2	# DW_AT_decl_file (/usr/include/bits/types.h)
+	.byte	0x2c	# DW_AT_decl_line
+	.byte	0x1b	# DW_AT_decl_column
+	.long	0x42	# DW_AT_type
+	.uleb128 0x2	# (DIE (0x7d) DW_TAG_base_type)
+	.byte	0x1	# DW_AT_byte_size
+	.byte	0x6	# DW_AT_encoding
+	.long	.LASF9	# DW_AT_name: "char"
+	.uleb128 0x4	# (DIE (0x84) DW_TAG_typedef)
+	.long	.LASF10	# DW_AT_name: "uint32_t"
+	.byte	0x3	# DW_AT_decl_file (/usr/include/bits/stdint-uintn.h)
+	.byte	0x1a	# DW_AT_decl_line
+	.byte	0x14	# DW_AT_decl_column
+	.long	0x5e	# DW_AT_type
+	.uleb128 0x4	# (DIE (0x90) DW_TAG_typedef)
+	.long	.LASF11	# DW_AT_name: "uint64_t"
+	.byte	0x3	# DW_AT_decl_file (/usr/include/bits/stdint-uintn.h)
+	.byte	0x1b	# DW_AT_decl_line
+	.byte	0x14	# DW_AT_decl_column
+	.long	0x71	# DW_AT_type
+	.uleb128 0x5	# (DIE (0x9c) DW_TAG_subprogram)
+			# DW_AT_external
+	.long	.LASF16	# DW_AT_name: "main"
+	.byte	0x1	# DW_AT_decl_file (ptwrite.c)
+	.byte	0x21	# DW_AT_decl_line
+	.byte	0x1	# DW_AT_decl_column
+			# DW_AT_prototyped
+	.long	0x57	# DW_AT_type
+	.quad	.LFB2	# DW_AT_low_pc
+	.quad	.LFE2-.LFB2	# DW_AT_high_pc
+	.uleb128 0x1	# DW_AT_frame_base
+	.byte	0x9c	# DW_OP_call_frame_cfa
+			# DW_AT_GNU_all_tail_call_sites
+	.uleb128 0x6	# (DIE (0xba) DW_TAG_subprogram)
+			# DW_AT_external
+	.long	.LASF17	# DW_AT_name: "ptwrite32"
+	.byte	0x1	# DW_AT_decl_file (ptwrite.c)
+	.byte	0x1b	# DW_AT_decl_line
+	.byte	0x1	# DW_AT_decl_column
+			# DW_AT_prototyped
+	.quad	.LFB1	# DW_AT_low_pc
+	.quad	.LFE1-.LFB1	# DW_AT_high_pc
+	.uleb128 0x1	# DW_AT_frame_base
+	.byte	0x9c	# DW_OP_call_frame_cfa
+			# DW_AT_GNU_all_call_sites
+	.long	0xe8	# DW_AT_sibling
+	.uleb128 0x7	# (DIE (0xd8) DW_TAG_formal_parameter)
+	.long	.LASF12	# DW_AT_name: "value"
+	.byte	0x1	# DW_AT_decl_file (ptwrite.c)
+	.byte	0x1b	# DW_AT_decl_line
+	.byte	0x15	# DW_AT_decl_column
+	.long	0x84	# DW_AT_type
+	.uleb128 0x2	# DW_AT_location
+	.byte	0x91	# DW_OP_fbreg
+	.sleb128 -28
+	.byte	0	# end of children of DIE 0xba
+	.uleb128 0x8	# (DIE (0xe8) DW_TAG_subprogram)
+			# DW_AT_external
+	.long	.LASF18	# DW_AT_name: "ptwrite64"
+	.byte	0x1	# DW_AT_decl_file (ptwrite.c)
+	.byte	0x15	# DW_AT_decl_line
+	.byte	0x1	# DW_AT_decl_column
+			# DW_AT_prototyped
+	.quad	.LFB0	# DW_AT_low_pc
+	.quad	.LFE0-.LFB0	# DW_AT_high_pc
+	.uleb128 0x1	# DW_AT_frame_base
+	.byte	0x9c	# DW_OP_call_frame_cfa
+			# DW_AT_GNU_all_call_sites
+	.uleb128 0x7	# (DIE (0x102) DW_TAG_formal_parameter)
+	.long	.LASF12	# DW_AT_name: "value"
+	.byte	0x1	# DW_AT_decl_file (ptwrite.c)
+	.byte	0x15	# DW_AT_decl_line
+	.byte	0x15	# DW_AT_decl_column
+	.long	0x90	# DW_AT_type
+	.uleb128 0x2	# DW_AT_location
+	.byte	0x91	# DW_OP_fbreg
+	.sleb128 -32
+	.byte	0	# end of children of DIE 0xe8
+	.byte	0	# end of children of DIE 0xb
+	.section	.debug_abbrev,"",@progbits
+.Ldebug_abbrev0:
+	.uleb128 0x1	# (abbrev code)
+	.uleb128 0x11	# (TAG: DW_TAG_compile_unit)
+	.byte	0x1	# DW_children_yes
+	.uleb128 0x25	# (DW_AT_producer)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x13	# (DW_AT_language)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x1b	# (DW_AT_comp_dir)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x11	# (DW_AT_low_pc)
+	.uleb128 0x1	# (DW_FORM_addr)
+	.uleb128 0x12	# (DW_AT_high_pc)
+	.uleb128 0x7	# (DW_FORM_data8)
+	.uleb128 0x10	# (DW_AT_stmt_list)
+	.uleb128 0x17	# (DW_FORM_sec_offset)
+	.byte	0
+	.byte	0
+	.uleb128 0x2	# (abbrev code)
+	.uleb128 0x24	# (TAG: DW_TAG_base_type)
+	.byte	0	# DW_children_no
+	.uleb128 0xb	# (DW_AT_byte_size)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3e	# (DW_AT_encoding)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.byte	0
+	.byte	0
+	.uleb128 0x3	# (abbrev code)
+	.uleb128 0x24	# (TAG: DW_TAG_base_type)
+	.byte	0	# DW_children_no
+	.uleb128 0xb	# (DW_AT_byte_size)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3e	# (DW_AT_encoding)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0x8	# (DW_FORM_string)
+	.byte	0
+	.byte	0
+	.uleb128 0x4	# (abbrev code)
+	.uleb128 0x16	# (TAG: DW_TAG_typedef)
+	.byte	0	# DW_children_no
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x3a	# (DW_AT_decl_file)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3b	# (DW_AT_decl_line)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x39	# (DW_AT_decl_column)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x49	# (DW_AT_type)
+	.uleb128 0x13	# (DW_FORM_ref4)
+	.byte	0
+	.byte	0
+	.uleb128 0x5	# (abbrev code)
+	.uleb128 0x2e	# (TAG: DW_TAG_subprogram)
+	.byte	0	# DW_children_no
+	.uleb128 0x3f	# (DW_AT_external)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x3a	# (DW_AT_decl_file)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3b	# (DW_AT_decl_line)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x39	# (DW_AT_decl_column)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x27	# (DW_AT_prototyped)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x49	# (DW_AT_type)
+	.uleb128 0x13	# (DW_FORM_ref4)
+	.uleb128 0x11	# (DW_AT_low_pc)
+	.uleb128 0x1	# (DW_FORM_addr)
+	.uleb128 0x12	# (DW_AT_high_pc)
+	.uleb128 0x7	# (DW_FORM_data8)
+	.uleb128 0x40	# (DW_AT_frame_base)
+	.uleb128 0x18	# (DW_FORM_exprloc)
+	.uleb128 0x2116	# (DW_AT_GNU_all_tail_call_sites)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.byte	0
+	.byte	0
+	.uleb128 0x6	# (abbrev code)
+	.uleb128 0x2e	# (TAG: DW_TAG_subprogram)
+	.byte	0x1	# DW_children_yes
+	.uleb128 0x3f	# (DW_AT_external)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x3a	# (DW_AT_decl_file)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3b	# (DW_AT_decl_line)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x39	# (DW_AT_decl_column)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x27	# (DW_AT_prototyped)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x11	# (DW_AT_low_pc)
+	.uleb128 0x1	# (DW_FORM_addr)
+	.uleb128 0x12	# (DW_AT_high_pc)
+	.uleb128 0x7	# (DW_FORM_data8)
+	.uleb128 0x40	# (DW_AT_frame_base)
+	.uleb128 0x18	# (DW_FORM_exprloc)
+	.uleb128 0x2117	# (DW_AT_GNU_all_call_sites)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x1	# (DW_AT_sibling)
+	.uleb128 0x13	# (DW_FORM_ref4)
+	.byte	0
+	.byte	0
+	.uleb128 0x7	# (abbrev code)
+	.uleb128 0x5	# (TAG: DW_TAG_formal_parameter)
+	.byte	0	# DW_children_no
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x3a	# (DW_AT_decl_file)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3b	# (DW_AT_decl_line)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x39	# (DW_AT_decl_column)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x49	# (DW_AT_type)
+	.uleb128 0x13	# (DW_FORM_ref4)
+	.uleb128 0x2	# (DW_AT_location)
+	.uleb128 0x18	# (DW_FORM_exprloc)
+	.byte	0
+	.byte	0
+	.uleb128 0x8	# (abbrev code)
+	.uleb128 0x2e	# (TAG: DW_TAG_subprogram)
+	.byte	0x1	# DW_children_yes
+	.uleb128 0x3f	# (DW_AT_external)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x3	# (DW_AT_name)
+	.uleb128 0xe	# (DW_FORM_strp)
+	.uleb128 0x3a	# (DW_AT_decl_file)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x3b	# (DW_AT_decl_line)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x39	# (DW_AT_decl_column)
+	.uleb128 0xb	# (DW_FORM_data1)
+	.uleb128 0x27	# (DW_AT_prototyped)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.uleb128 0x11	# (DW_AT_low_pc)
+	.uleb128 0x1	# (DW_FORM_addr)
+	.uleb128 0x12	# (DW_AT_high_pc)
+	.uleb128 0x7	# (DW_FORM_data8)
+	.uleb128 0x40	# (DW_AT_frame_base)
+	.uleb128 0x18	# (DW_FORM_exprloc)
+	.uleb128 0x2117	# (DW_AT_GNU_all_call_sites)
+	.uleb128 0x19	# (DW_FORM_flag_present)
+	.byte	0
+	.byte	0
+	.byte	0
+	.section	.debug_aranges,"",@progbits
+	.long	0x2c	# Length of Address Ranges Info
+	.value	0x2	# DWARF aranges version
+	.long	.Ldebug_info0	# Offset of Compilation Unit Info
+	.byte	0x8	# Size of Address
+	.byte	0	# Size of Segment Descriptor
+	.value	0	# Pad to 16 byte boundary
+	.value	0
+	.quad	.Ltext0	# Address
+	.quad	.Letext0-.Ltext0	# Length
+	.quad	0
+	.quad	0
+	.section	.debug_line,"",@progbits
+.Ldebug_line0:
+	.section	.debug_str,"MS",@progbits,1
+.LASF2:
+	.string	"unsigned int"
+.LASF7:
+	.string	"__uint32_t"
+.LASF15:
+	.string	"gdb/gdb/testsuite/gdb.btrace"
+.LASF14:
+	.string	"ptwrite.c"
+.LASF18:
+	.string	"ptwrite64"
+.LASF3:
+	.string	"long unsigned int"
+.LASF11:
+	.string	"uint64_t"
+.LASF0:
+	.string	"unsigned char"
+.LASF16:
+	.string	"main"
+.LASF10:
+	.string	"uint32_t"
+.LASF6:
+	.string	"long int"
+.LASF8:
+	.string	"__uint64_t"
+.LASF13:
+	.string	"GNU C17 8.1.1 20180502 (Red Hat 8.1.1-1) -mtune=generic -march=x86-64 -g"
+.LASF1:
+	.string	"short unsigned int"
+.LASF4:
+	.string	"signed char"
+.LASF12:
+	.string	"value"
+.LASF5:
+	.string	"short int"
+.LASF17:
+	.string	"ptwrite32"
+.LASF9:
+	.string	"char"
+	.ident	"GCC: (GNU) 8.1.1 20180502 (Red Hat 8.1.1-1)"
+	.section	.note.GNU-stack,"",@progbits
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index c703a7e6338..ba7ccfd46ba 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -2874,6 +2874,98 @@  gdb_caching_proc skip_btrace_pt_tests {
     return $skip_btrace_tests
 }
 
+# Run a test on the target to see if it supports ptwrite instructions.
+# Return 0 if so, 1 if it does not.  Based on 'check_vmx_hw_available'
+# from the GCC testsuite.
+
+gdb_caching_proc skip_btrace_ptw_tests {
+    global srcdir subdir gdb_prompt inferior_exited_re
+
+    set me "skip_ptw_tests"
+
+    # Set up, compile, and execute a test program.
+    # Include the current process ID in the file names to prevent conflicts
+    # with invocations for multiple testsuites.
+    set src [standard_temp_file ptw[pid].c]
+    set exe [standard_temp_file ptw[pid].x]
+
+    gdb_produce_source $src {
+	#include <stdbool.h>
+	#include <stdint.h>
+	#include <stdio.h>
+	#include "x86-cpuid.h"
+
+	#define bit_PTW (1 << 4)
+
+	bool
+	have_ptw ()
+	{
+	  unsigned int eax, ebx, ecx, edx;
+
+	  if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
+	      return false;
+
+	  if ((ecx & bit_OSXSAVE) != bit_OSXSAVE)
+	      return false;
+
+	  if (__get_cpuid_max (0, NULL) < 0x14)
+	      return false;
+
+	  __cpuid_count (0x14, 0, eax, ebx, ecx, edx);
+
+	  return (ebx & bit_PTW) == bit_PTW;
+	}
+
+	int
+	main ()
+	{
+	  return have_ptw ();
+	}
+
+    }
+
+    verbose "$me:  compiling testfile $src" 2
+
+    set test_flags [list additional_flags=-I${srcdir}/../nat]
+
+    set compile_flags [concat {debug nowarnings quiet} ${test_flags}]
+    set lines [gdb_compile $src $exe executable $compile_flags]
+
+    if ![string match "" $lines] then {
+	verbose "$me:  testfile compilation failed, returning 1" 2
+	file delete $src
+	return 1
+    }
+
+    # No error message, compilation succeeded so now run it via gdb.
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load $exe
+    if ![runto_main] {
+	file delete $src
+	return 1
+    }
+    file delete $src
+
+    # In case of an unexpected output, we return 2 as a fail value.
+    set skip_ptw_tests 2
+    gdb_test_multiple "print (int) have_ptw ()" "check ptw support" {
+	-re ".. = 1\r\n$gdb_prompt $" {
+	    set skip_ptw_tests 0
+	}
+	-re ".. = 0\r\n$gdb_prompt $" {
+	    set skip_ptw_tests 1
+	}
+    }
+
+    gdb_exit
+    remote_file build delete $exe
+
+    verbose "$me:  returning $skip_ptw_tests" 2
+    return $skip_ptw_tests
+}
+
 # Run a test on the target to see if it supports Aarch64 SVE hardware.
 # Return 0 if so, 1 if it does not.  Note this causes a restart of GDB.