2010-06-11 Stan Shebs <stan@codesourcery.com>

	Add per-operation permission flags.

	* target.h (struct target_ops): New method to_set_permissions.
	(target_set_permissions): New macro.
	(target_insert_breakpoint): Change macro to function.
	(target_remove_breakpoint): Ditto.
	(target_stop): Ditto.
	(may_write_registers): Declare.
	(may_write_memory): Declare.
	(may_insert_breakpoints): Declare.
	(may_insert_tracepoints): Declare.
	(may_insert_fast_tracepoints): Declare.
	(may_stop): Declare.
	* target.c (may_write_registers, may_write_registers_1): New globals.
	(may_write_memory, may_write_memory_1): New globals.
	(may_insert_breakpoints, may_insert_breakpoints_1): New globals.
	(may_insert_tracepoints, may_insert_tracepoints_1): New globals.
	(may_insert_fast_tracepoints, may_insert_fast_tracepoints_1): New
	globals.
	(may_stop, may_stop_1): New global.
	(target_xfer_partial): Test for write permission.
	(target_store_registers): Ditto.
	(target_insert_breakpoint): New function.
	(target_remove_breakpoint): New function.
	(target_stop): New function.
	(_initialize_targets): Add new set/show variables.
	(set_write_memory_permission): New function.
	(update_target_permissions): New function.
	(set_target_permissions): New function.
	(update_current_target): Default to_set_permissions.
	(_initialize_targets): Use new globals and setter function.
	* tracepoint.c (start_tracing): Test for permission.
	* inferior.h (update_observer_mode): Declare.
	* infrun.c (non_stop_1): Define earlier.
	(observer_mode, observer_mode_1): New globals.
	(set_observer_mode, show_observer_mode): New functions.
	(update_observer_mode): New function.
	(_initialize_infrun): Define "set observer" command.
	* remote.c (PACKET_QAllow): New optional packet.
	(remote_protocol_features): Add QAllow.
	(remote_set_permissions): New function.
	(remote_start_remote): Call it.
	(init_remote_ops): Add it to target vector.
	(_initialize_remote): Add config command for QAllow.

	* gdb.texinfo (Observer Mode): New section.
	(General Query Packets): Document QAllow.

	* gdb.base/permissions.exp: New file.

2 files changed, 123 insertions, 0 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 071a409..0525c5f 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,8 @@
+2010-06-11  Stan Shebs  <stan@codesourcery.com>
+
+	* gdb.texinfo (Observer Mode): New section.
+	(General Query Packets): Document QAllow.
+	 
 2010-06-04  Doug Evans  <dje@google.com>
 
 	* gdb.texinfo (Python API): New node `Disabling Pretty-Printers'.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index fa7a0ec..6ac7d16 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -4958,6 +4958,7 @@ you examine the stopped thread in the debugger.
 * Background Execution::	Running your program asynchronously
 * Thread-Specific Breakpoints::	Controlling breakpoints
 * Interrupted System Calls::	GDB may interfere with system calls
+* Observer Mode::               GDB does not alter program behavior
 @end menu
 
 @node All-Stop Mode
@@ -5318,6 +5319,103 @@ monitor certain events such as thread creation and thread destruction.
 When such an event happens, a system call in another thread may return
 prematurely, even though your program does not appear to stop.
 
+@node Observer Mode
+@subsection Observer Mode
+
+If you want to build on non-stop mode and observe program behavior
+without any chance of disruption by @value{GDBN}, you can set
+variables to disable all of the debugger's attempts to modify state,
+whether by writing memory, inserting breakpoints, etc.  These operate
+at a low level, intercepting operations from all commands.
+
+When all of these are set to @code{off}, then @value{GDBN} is said to
+be @dfn{observer mode}.  As a convenience, the variable
+@code{observer} can be set to disable these, plus enable non-stop
+mode.
+
+Note that @value{GDBN} will not prevent you from making nonsensical
+combinations of these settings. For instance, if you have enabled
+@code{may-insert-breakpoints} but disabled @code{may-write-memory},
+then breakpoints that work by writing trap instructions into the code
+stream will still not be able to be placed.
+
+@table @code
+
+@kindex observer
+@item set observer on
+@itemx set observer off
+When set to @code{on}, this disables all the permission variables
+below (except for @code{insert-fast-tracepoints}), plus enables
+non-stop debugging.  Setting this to @code{off} switches back to
+normal debugging, though remaining in non-stop mode.
+
+@item show observer
+Show whether observer mode is on or off.
+
+@kindex may-write-registers
+@item set may-write-registers on
+@itemx set may-write-registers off
+This controls whether @value{GDBN} will attempt to alter the values of
+registers, such as with assignment expressions in @code{print}, or the
+@code{jump} command.  It defaults to @code{on}.
+
+@item show may-write-registers
+Show the current permission to write registers.
+
+@kindex may-write-memory
+@item set may-write-memory on
+@itemx set may-write-memory off
+This controls whether @value{GDBN} will attempt to alter the contents
+of memory, such as with assignment expressions in @code{print}.  It
+defaults to @code{on}.
+
+@item show may-write-memory
+Show the current permission to write memory.
+
+@kindex may-insert-breakpoints
+@item set may-insert-breakpoints on
+@itemx set may-insert-breakpoints off
+This controls whether @value{GDBN} will attempt to insert breakpoints.
+This affects all breakpoints, including internal breakpoints defined
+by @value{GDBN}.  It defaults to @code{on}.
+
+@item show may-insert-breakpoints
+Show the current permission to insert breakpoints.
+
+@kindex may-insert-tracepoints
+@item set may-insert-tracepoints on
+@itemx set may-insert-tracepoints off
+This controls whether @value{GDBN} will attempt to insert (regular)
+tracepoints at the beginning of a tracing experiment.  It affects only
+non-fast tracepoints, fast tracepoints being under the control of
+@code{may-insert-fast-tracepoints}.  It defaults to @code{on}.
+
+@item show may-insert-tracepoints
+Show the current permission to insert tracepoints.
+
+@kindex may-insert-fast-tracepoints
+@item set may-insert-fast-tracepoints on
+@itemx set may-insert-fast-tracepoints off
+This controls whether @value{GDBN} will attempt to insert fast
+tracepoints at the beginning of a tracing experiment.  It affects only
+fast tracepoints, regular (non-fast) tracepoints being under the
+control of @code{may-insert-tracepoints}.  It defaults to @code{on}.
+
+@item show may-insert-fast-tracepoints
+Show the current permission to insert fast tracepoints.
+
+@kindex may-interrupt
+@item set may-interrupt on
+@itemx set may-interrupt off
+This controls whether @value{GDBN} will attempt to interrupt or stop
+program execution.  When this variable is @code{off}, the
+@code{interrupt} command will have no effect, nor will
+@kbd{Ctrl-c}. It defaults to @code{on}.
+
+@item show may-interrupt
+Show the current permission to interrupt or stop the program.
+
+@end table
 
 @node Reverse Execution
 @chapter Running programs backward
@@ -31190,6 +31288,18 @@ Here are the currently defined query and set packets:
 
 @table @samp
 
+@item QAllow:@var{op}:@var{val}@dots{}
+@cindex @samp{QAllow} packet
+Specify which operations @value{GDBN} expects to request of the
+target, as a semicolon-separated list of operation name and value
+pairs.  Possible values for @var{op} include @samp{WriteReg},
+@samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
+@samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
+indicating that @value{GDBN} will not request the operation, or 1,
+indicating that it may.  (The target can then use this to set up its
+own internals optimally, for instance if the debugger never expects to
+insert breakpoints, it may not need to install its own trap handler.)
+
 @item qC
 @cindex current thread, remote request
 @cindex @samp{qC} packet
@@ -31711,6 +31821,11 @@ These are the currently defined stub features and their properties:
 @tab @samp{-}
 @tab No
 
+@item @samp{QAllow}
+@tab No
+@tab @samp{-}
+@tab No
+
 @end multitable
 
 These are the currently defined stub features, in more detail:
@@ -31808,6 +31923,9 @@ The remote stub accepts and implements the reverse step packet
 The remote stub understands the @samp{QTDPsrc} packet that supplies
 the source form of tracepoint definitions.
 
+@item QAllow
+The remote stub understands the @samp{QAllow} packet.
+
 @end table
 
 @item qSymbol::