[binutils-gdb] Add documentation for new record Python bindings.

[Tim Wiederhake]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0a0faf9fc652903d6467fc2bc8609891be730bdb

commit 0a0faf9fc652903d6467fc2bc8609891be730bdb
Author: Tim Wiederhake <tim.wiederhake@intel.com>
Date:   Mon Nov 21 16:39:57 2016 +0100

    Add documentation for new record Python bindings.
    
    Signed-off-by: Tim Wiederhake <tim.wiederhake@intel.com>
    
    gdb/ChangeLog:
    
    	* NEWS: Add record Python bindings entry.
    
    gdb/doc/ChangeLog:
    
    	* python.texi (Recordings In Python): New section.
    
    Change-Id: Ibacb5930085bff36b0003fde30db9a8178cb280b

Diff:
---
 gdb/NEWS            |   4 +
 gdb/doc/python.texi | 245 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 249 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index 08f97c0..f412887 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,10 @@
 
 *** Changes since GDB 7.12
 
+* Python Scripting
+
+  ** New functions to start, stop and access a running btrace recording.
+
 * GDB now supports recording and replaying rdrand and rdseed Intel 64
   instructions.
 
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index fae45aa..d1cbadb 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -151,6 +151,7 @@ optional arguments while skipping others.  Example:
 * Inferiors In Python::         Python representation of inferiors (processes)
 * Events In Python::            Listening for events from @value{GDBN}.
 * Threads In Python::           Accessing inferior threads from Python.
+* Recordings In Python::        Accessing recordings from Python.
 * Commands In Python::          Implementing new commands in Python.
 * Parameters In Python::        Adding new @value{GDBN} parameters.
 * Functions In Python::         Writing new convenience functions.
@@ -3062,6 +3063,250 @@ Return a Boolean indicating whether the thread is running.
 Return a Boolean indicating whether the thread is exited.
 @end defun
 
+@node Recordings In Python
+@subsubsection Recordings In Python
+@cindex recordings in python
+
+The following recordings-related functions
+(@pxref{Process Record and Replay}) are available in the @code{gdb}
+module:
+
+@defun gdb.start_recording (@r{[}method@r{]}, @r{[}format@r{]})
+Start a recording using the given @var{method} and @var{format}.  If
+no @var{format} is given, the default format for the recording method
+is used.  If no @var{method} is given, the default method will be used.
+Returns a @code{gdb.Record} object on success.  Throw an exception on
+failure.
+
+The following strings can be passed as @var{method}:
+
+@itemize @bullet
+@item
+@code{"full"}
+@item
+@code{"btrace"}: Possible values for @var{format}: @code{"pt"},
+@code{"bts"} or leave out for default format.
+@end itemize
+@end defun
+
+@defun gdb.current_recording ()
+Access a currently running recording.  Return a @code{gdb.Record}
+object on success.  Return @code{None} if no recording is currently
+active.
+@end defun
+
+@defun gdb.stop_recording ()
+Stop the current recording.  Throw an exception if no recording is
+currently active.  All record objects become invalid after this call.
+@end defun
+
+A @code{gdb.Record} object has the following attributes:
+
+@defvar Record.ptid
+ID of the thread associated with this object as a tuple of three integers.  The
+first is the Process ID (PID); the second is the Lightweight Process ID (LWPID),
+and the third is the Thread ID (TID). Either the LWPID or TID may be 0, which
+indicates that the operating system does not use that identifier.
+@end defvar
+
+@defvar Record.method
+A string with the current recording method, e.g.@: @code{full} or
+@code{btrace}.
+@end defvar
+
+@defvar Record.format
+A string with the current recording format, e.g.@: @code{bt}, @code{pts} or
+@code{None}.
+@end defvar
+
+@defvar Record.begin
+A method specific instruction object representing the first instruction
+in this recording.
+@end defvar
+
+@defvar Record.end
+A method specific instruction object representing the current
+instruction, that is not actually part of the recording.
+@end defvar
+
+@defvar Record.replay_position
+The instruction representing the current replay position.  If there is
+no replay active, this will be @code{None}.
+@end defvar
+
+@defvar Record.instruction_history
+A list with all recorded instructions.
+@end defvar
+
+@defvar Record.function_call_history
+A list with all recorded function call segments.
+@end defvar
+
+A @code{gdb.Record} object has the following methods:
+
+@defun Record.goto (instruction)
+Move the replay position to the given @var{instruction}.
+@end defun
+
+The attributes and methods of instruction objects depend on the current
+recording method.  Currently, only btrace instructions are supported.
+
+A @code{gdb.BtraceInstruction} object has the following attributes:
+
+@defvar BtraceInstruction.number
+An integer identifying this instruction.  @var{number} corresponds to
+the numbers seen in @code{record instruction-history}
+(@pxref{Process Record and Replay}).
+@end defvar
+
+@defvar BtraceInstruction.error
+An integer identifying the error code for gaps in the history.
+@code{None} for regular instructions.
+@end defvar
+
+@defvar BtraceInstruction.sal
+A @code{gdb.Symtab_and_line} object representing the associated symtab
+and line of this instruction.  May be @code{None} if the instruction
+is a gap.
+@end defvar
+
+@defvar BtraceInstruction.pc
+An integer representing this instruction's address.  May be @code{None}
+if the instruction is a gap or the debug symbols could not be read.
+@end defvar
+
+@defvar BtraceInstruction.data
+A buffer with the raw instruction data.  May be @code{None} if the
+instruction is a gap.
+@end defvar
+
+@defvar BtraceInstruction.decoded
+A human readable string with the disassembled instruction.  Contains the
+error message for gaps.
+@end defvar
+
+@defvar BtraceInstruction.size
+The size of the instruction in bytes.  Will be @code{None} if the
+instruction is a gap.
+@end defvar
+
+@defvar BtraceInstruction.is_speculative
+A boolean indicating whether the instruction was executed
+speculatively.  Will be @code{None} for gaps.
+@end defvar
+
+The attributes and methods of function call objects depend on the
+current recording format.  Currently, only btrace function calls are
+supported.
+
+A @code{gdb.BtraceFunctionCall} object has the following attributes:
+
+@defvar BtraceFunctionCall.number
+An integer identifying this function call.  @var{number} corresponds to
+the numbers seen in @code{record function-call-history}
+(@pxref{Process Record and Replay}).
+@end defvar
+
+@defvar BtraceFunctionCall.symbol
+A @code{gdb.Symbol} object representing the associated symbol.  May be
+@code{None} if the function call is a gap or the debug symbols could
+not be read.
+@end defvar
+
+@defvar BtraceFunctionCall.level
+An integer representing the function call's stack level.  May be
+@code{None} if the function call is a gap.
+@end defvar
+
+@defvar BtraceFunctionCall.instructions
+A list of @code{gdb.BtraceInstruction} objects associated with this function
+call.
+@end defvar
+
+@defvar BtraceFunctionCall.up
+A @code{gdb.BtraceFunctionCall} object representing the caller's
+function segment.  If the call has not been recorded, this will be the
+function segment to which control returns.  If neither the call nor the
+return have been recorded, this will be @code{None}.
+@end defvar
+
+@defvar BtraceFunctionCall.prev_sibling
+A @code{gdb.BtraceFunctionCall} object representing the previous
+segment of this function call.  May be @code{None}.
+@end defvar
+
+@defvar BtraceFunctionCall.next_sibling
+A @code{gdb.BtraceFunctionCall} object representing the next segment of
+this function call.  May be @code{None}.
+@end defvar
+
+The following example demonstrates the usage of these objects and
+functions to create a function that will rewind a record to the last
+time a function in a different file was executed.  This would typically
+be used to track the execution of user provided callback functions in a
+library which typically are not visible in a back trace.
+
+@smallexample
+def bringback ():
+    rec = gdb.current_recording ()
+    if not rec:
+        return
+
+    insn = rec.instruction_history
+    if len (insn) == 0:
+        return
+
+    try:
+        position = insn.index (rec.replay_position)
+    except:
+        position = -1
+    try:
+        filename = insn[position].sal.symtab.fullname ()
+    except:
+        filename = None
+
+    for i in reversed (insn[:position]):
+	try:
+            current = i.sal.symtab.fullname ()
+	except:
+            current = None
+
+        if filename == current:
+            continue
+
+        rec.goto (i)
+        return
+@end smallexample
+
+Another possible application is to write a function that counts the
+number of code executions in a given line range.  This line range can
+contain parts of functions or span across several functions and is not
+limited to be contiguous.
+
+@smallexample
+def countrange (filename, linerange):
+    count = 0
+
+    def filter_only (file_name):
+        for call in gdb.current_recording ().function_call_history:
+            try:
+                if file_name in call.symbol.symtab.fullname ():
+                    yield call
+            except:
+                pass
+
+    for c in filter_only (filename):
+        for i in c.instructions:
+            try:
+                if i.sal.line in linerange:
+                    count += 1
+                    break;
+            except:
+                    pass
+
+    return count
+@end smallexample
+
 @node Commands In Python
 @subsubsection Commands In Python