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Convert frame unwinders to use the current frame and

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"struct value".

	* frame.c (frame_debug): Make global.
	(get_frame_id): Pass this frame to unwinder routines.
	(frame_pc_unwind): Remove unused unwind->prev_pc support.
	(do_frame_register_read): Do not discard the return value of
	frame_register_read.
	(frame_register_unwind): Remove debug messages.  Use
	frame_unwind_register_value.
	(frame_unwind_register_value, get_frame_register_value): New
	functions.
	(create_new_frame, get_frame_base_address, get_frame_locals_address)
	(get_frame_args_address, get_frame_type): Pass this frame to
	unwinder routines.
	(frame_cleanup_after_sniffer, frame_prepare_for_sniffer): New
	functions.
	* frame.h: Update comments.
	(frame_debug, frame_unwind_register_value, get_frame_register_value)
	(frame_prepare_for_sniffer): Declare.
	* frame-unwind.h: Update comments and parameter names.
	(default_frame_sniffer): Declare.
	(frame_prev_register_ftype): Return a struct value *.
	(struct frame_unwind): Remove prev_pc member.
	(frame_unwind_sniffer_ftype, frame_unwind_append_sniffer): Delete.
	(frame_unwind_append_unwinder, frame_unwind_got_optimized)
	(frame_unwind_got_register, frame_unwind_got_memory)
	(frame_unwind_got_constant, frame_unwind_got_address): Declare.
	* frame-base.h: Update comments and parameter names.
	* valops.c (value_fetch_lazy): Use get_frame_register_value.  Iterate
	if necessary.  Add debugging output.
	* sentinel-frame.c (sentinel_frame_prev_register)
	(sentinel_frame_this_id): Update for new signature.
	(sentinel_frame_prev_pc): Delete.
	(sentinel_frame_unwinder): Remove prev_pc.
	* ia64-tdep.c (ia64_libunwind_frame_unwind): Do not initialize
	prev_pc.
	* libunwind-frame.c (libunwind_frame_unwind): Likewise.
	* frame-unwind.c (struct frame_unwind_table_entry): Remove sniffer.
	(frame_unwind_append_sniffer): Delete.
	(frame_unwind_append_unwinder): New function.
	(frame_unwind_find_by_frame): Take this frame.  Only use sniffers
	from unwinders.  Use frame_prepare_for_sniffer.
	(default_frame_sniffer, frame_unwind_got_optimized)
	(frame_unwind_got_register, frame_unwind_got_memory)
	(frame_unwind_got_constant, frame_unwind_got_address): New functions.
	* dummy-frame.c (dummy_frame_sniffer): Use gdbarch_dummy_id.
	(dummy_frame_prev_register, dummy_frame_this_id): Update for new
	signature.
	* gdbarch.sh: Replace unwind_dummy_id with dummy_id.
	* gdbarch.c, gdbarch.c: Regenerated.
	* frame-base.c (default_frame_base_address)
	(default_frame_locals_address, default_frame_args_address): Update
	for new signature.
	(frame_base_find_by_frame): Pass this frame to unwinder routines.
	* infcall.c (call_function_by_hand): Update comments.
	* Makefile.in (frame-unwind.o): Update dependencies.

	* gdbint.texinfo (Stack Frames): New chapter.
	(Algorithms): Move Frames text to the new chapter.
	(Target Conditionals): Delete SAVE_DUMMY_FRAME_TOS.  Document
	gdbarch_dummy_id instead of gdbarch_unwind_dummy_id.
This commit is contained in:
Daniel Jacobowitz
2008-04-30 21:16:46 +00:00
parent 9214ee5f5f
commit 669fac235d
19 changed files with 687 additions and 321 deletions
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172
gdb/doc/gdbint.texinfo
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@@ -76,6 +76,7 @@ as the mechanisms that adapt @value{GDBN} to specific hosts and targets.
* Algorithms::
* User Interface::
* libgdb::
* Stack Frames::
* Symbol Handling::
* Language Support::
* Host Definition::
@@ -273,39 +274,6 @@ cases and real-world issues. This chapter describes the basic
algorithms and mentions some of the specific target definitions that
they use.
@section Frames
@cindex frame
@cindex call stack frame
A frame is a construct that @value{GDBN} uses to keep track of calling
and called functions.
@cindex frame, unwind
@value{GDBN}'s frame model, a fresh design, was implemented with the
need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
the term ``unwind'' is taken directly from that specification.
Developers wishing to learn more about unwinders, are encouraged to
read the @sc{dwarf} specification.
@findex frame_register_unwind
@findex get_frame_register
@value{GDBN}'s model is that you find a frame's registers by
``unwinding'' them from the next younger frame. That is,
@samp{get_frame_register} which returns the value of a register in
frame #1 (the next-to-youngest frame), is implemented by calling frame
#0's @code{frame_register_unwind} (the youngest frame). But then the
obvious question is: how do you access the registers of the youngest
frame itself?
@cindex sentinel frame
@findex get_frame_type
@vindex SENTINEL_FRAME
To answer this question, GDB has the @dfn{sentinel} frame, the
``-1st'' frame. Unwinding registers from the sentinel frame gives you
the current values of the youngest real frame's registers. If @var{f}
is a sentinel frame, then @code{get_frame_type (@var{f}) ==
SENTINEL_FRAME}.
@section Prologue Analysis
@cindex prologue analysis
@@ -1853,6 +1821,127 @@ the query interface. Each function is parameterized by a @code{ui-out}
builder. The result of the query is constructed using that builder
before the query function returns.
@node Stack Frames
@chapter Stack Frames
@cindex frame
@cindex call stack frame
A frame is a construct that @value{GDBN} uses to keep track of calling
and called functions.
@cindex unwind frame
@value{GDBN}'s frame model, a fresh design, was implemented with the
need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
the term ``unwind'' is taken directly from that specification.
Developers wishing to learn more about unwinders, are encouraged to
read the @sc{dwarf} specification, available from
@url{http://www.dwarfstd.org}.
@findex frame_register_unwind
@findex get_frame_register
@value{GDBN}'s model is that you find a frame's registers by
``unwinding'' them from the next younger frame. That is,
@samp{get_frame_register} which returns the value of a register in
frame #1 (the next-to-youngest frame), is implemented by calling frame
#0's @code{frame_register_unwind} (the youngest frame). But then the
obvious question is: how do you access the registers of the youngest
frame itself?
@cindex sentinel frame
@findex get_frame_type
@vindex SENTINEL_FRAME
To answer this question, GDB has the @dfn{sentinel} frame, the
``-1st'' frame. Unwinding registers from the sentinel frame gives you
the current values of the youngest real frame's registers. If @var{f}
is a sentinel frame, then @code{get_frame_type (@var{f}) @equiv{}
SENTINEL_FRAME}.
@section Selecting an Unwinder
@findex frame_unwind_prepend_unwinder
@findex frame_unwind_append_unwinder
The architecture registers a list of frame unwinders (@code{struct
frame_unwind}), using the functions
@code{frame_unwind_prepend_unwinder} and
@code{frame_unwind_append_unwinder}. Each unwinder includes a
sniffer. Whenever @value{GDBN} needs to unwind a frame (to fetch the
previous frame's registers or the current frame's ID), it calls
registered sniffers in order to find one which recognizes the frame.
The first time a sniffer returns non-zero, the corresponding unwinder
is assigned to the frame.
@section Unwinding the Frame ID
@cindex frame ID
Every frame has an associated ID, of type @code{struct frame_id}.
The ID includes the stack base and function start address for
the frame. The ID persists through the entire life of the frame,
including while other called frames are running; it is used to
locate an appropriate @code{struct frame_info} from the cache.
Every time the inferior stops, and at various other times, the frame
cache is flushed. Because of this, parts of @value{GDBN} which need
to keep track of individual frames cannot use pointers to @code{struct
frame_info}. A frame ID provides a stable reference to a frame, even
when the unwinder must be run again to generate a new @code{struct
frame_info} for the same frame.
The frame's unwinder's @code{this_id} method is called to find the ID.
Note that this is different from register unwinding, where the next
frame's @code{prev_register} is called to unwind this frame's
registers.
Both stack base and function address are required to identify the
frame, because a recursive function has the same function address for
two consecutive frames and a leaf function may have the same stack
address as its caller. On some platforms, a third address is part of
the ID to further disambiguate frames---for instance, on IA-64
the separate register stack address is included in the ID.
An invalid frame ID (@code{null_frame_id}) returned from the
@code{this_id} method means to stop unwinding after this frame.
@section Unwinding Registers
Each unwinder includes a @code{prev_register} method. This method
takes a frame, an associated cache pointer, and a register number.
It returns a @code{struct value *} describing the requested register,
as saved by this frame. This is the value of the register that is
current in this frame's caller.
The returned value must have the same type as the register. It may
have any lvalue type. In most circumstances one of these routines
will generate the appropriate value:
@table @code
@item frame_unwind_got_optimized
@findex frame_unwind_got_optimized
This register was not saved.
@item frame_unwind_got_register
@findex frame_unwind_got_register
This register was copied into another register in this frame. This
is also used for unchanged registers; they are ``copied'' into the
same register.
@item frame_unwind_got_memory
@findex frame_unwind_got_memory
This register was saved in memory.
@item frame_unwind_got_constant
@findex frame_unwind_got_constant
This register was not saved, but the unwinder can compute the previous
value some other way.
@item frame_unwind_got_address
@findex frame_unwind_got_address
Same as @code{frame_unwind_got_constant}, except that the value is a target
address. This is frequently used for the stack pointer, which is not
explicitly saved but has a known offset from this frame's stack
pointer. For architectures with a flat unified address space, this is
generally the same as @code{frame_unwind_got_constant}.
@end table
@node Symbol Handling
@chapter Symbol Handling
@@ -3943,14 +4032,6 @@ This method replaces @w{@code{gdbarch_call_dummy_location (@var{gdbarch})}} and
Return the name of register @var{regnr} as a string. May return @code{NULL}
to indicate that @var{regnr} is not a valid register.
@item SAVE_DUMMY_FRAME_TOS (@var{sp})
@findex SAVE_DUMMY_FRAME_TOS
@anchor{SAVE_DUMMY_FRAME_TOS} Used in @samp{call_function_by_hand} to
notify the target dependent code of the top-of-stack value that will be
passed to the inferior code. This is the value of the @code{SP}
after both the dummy frame and space for parameters/results have been
allocated on the stack. @xref{gdbarch_unwind_dummy_id}.
@item int gdbarch_sdb_reg_to_regnum (@var{gdbarch}, @var{sdb_regnr})
@findex gdbarch_sdb_reg_to_regnum
Use this function to convert sdb register @var{sdb_regnr} into @value{GDBN}
@@ -4132,13 +4213,12 @@ the @code{opcodes} library (@pxref{Support Libraries, ,Opcodes}).
@file{include/dis-asm.h} used to pass information to the instruction
decoding routine.
@item frame_id gdbarch_unwind_dummy_id (@var{gdbarch}, @var{frame})
@findex gdbarch_unwind_dummy_id
@anchor{gdbarch_unwind_dummy_id} Given @var{frame} return a @w{@code{struct
@item frame_id gdbarch_dummy_id (@var{gdbarch}, @var{frame})
@findex gdbarch_dummy_id
@anchor{gdbarch_dummy_id} Given @var{frame} return a @w{@code{struct
frame_id}} that uniquely identifies an inferior function call's dummy
frame. The value returned must match the dummy frame stack value
previously saved using @code{SAVE_DUMMY_FRAME_TOS}.
@xref{SAVE_DUMMY_FRAME_TOS}.
previously saved by @code{call_function_by_hand}.
@item DEPRECATED_USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
@findex DEPRECATED_USE_STRUCT_CONVENTION