[PATCH v3 8/8] Add documentation for new instruction record Python bindings.

Tim Wiederhake
2016-11-21T15:49:18Z

2016-11-21 Tim Wiederhake <tim.wiederhake@intel.com>

gdb/ChangeLog:

* NEWS: Add record Python bindings entry.

gdb/doc/ChangeLog:

* python.texi (Recordings In Python): New section.

---
gdb/NEWS | 4 +
gdb/doc/python.texi | 237 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 241 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index a597405..b39860e 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.
+
* Building GDB and GDBserver now requires a C++11 compiler.

For example, GCC 4.8 or later.
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index d6507e5..70b8d37 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 +3063,242 @@ 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.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} or
+@code{pts}. Can be empty.
+@end defvar
+
+@defvar Record.begin
+A format specific instruction object representing the first instruction
+in this recording.
+@end defvar
+
+@defvar Record.end
+A format 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 format. 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 record.
+@code{None} for regular instructions.
+@end defvar
+
+@defvar BtraceInstruction.symbol
+A @code{gdb.Symtab_and_line} object representing the associated line
+and symbol 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 decoded 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{Node} 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 instructions 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].symbol.symtab.fullname ()
+ except:
+ filename = None
+
+ for i in reversed (insn[:position]):
+ try:
+ current = i.symbol.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.symbol.line in linerange:
+ count += 1
+ break;
+ except:
+ pass
+
+ return count
+@end smallexample
+
@node Commands In Python
@subsubsection Commands In Python

--
2.7.4