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8480a37e14
We currently pass frames to function by value, as `frame_info_ptr`.
This is somewhat expensive:
- the size of `frame_info_ptr` is 64 bytes, which is a bit big to pass
by value
- the constructors and destructor link/unlink the object in the global
`frame_info_ptr::frame_list` list. This is an `intrusive_list`, so
it's not so bad: it's just assigning a few points, there's no memory
allocation as if it was `std::list`, but still it's useless to do
that over and over.
As suggested by Tom Tromey, change many function signatures to accept
`const frame_info_ptr &` instead of `frame_info_ptr`.
Some functions reassign their `frame_info_ptr` parameter, like:
void
the_func (frame_info_ptr frame)
{
for (; frame != nullptr; frame = get_prev_frame (frame))
{
...
}
}
I wondered what to do about them, do I leave them as-is or change them
(and need to introduce a separate local variable that can be
re-assigned). I opted for the later for consistency. It might not be
clear why some functions take `const frame_info_ptr &` while others take
`frame_info_ptr`. Also, if a function took a `frame_info_ptr` because
it did re-assign its parameter, I doubt that we would think to change it
to `const frame_info_ptr &` should the implementation change such that
it doesn't need to take `frame_info_ptr` anymore. It seems better to
have a simple rule and apply it everywhere.
Change-Id: I59d10addef687d157f82ccf4d54f5dde9a963fd0
Approved-By: Andrew Burgess <aburgess@redhat.com>
239 lines
9.2 KiB
C++
239 lines
9.2 KiB
C++
/* Definitions for a frame unwinder, for GDB, the GNU debugger.
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Copyright (C) 2003-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#if !defined (FRAME_UNWIND_H)
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#define FRAME_UNWIND_H 1
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struct frame_data;
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class frame_info_ptr;
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struct frame_id;
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struct frame_unwind;
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struct gdbarch;
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struct regcache;
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struct value;
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#include "frame.h"
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/* The following unwind functions assume a chain of frames forming the
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sequence: (outer) prev <-> this <-> next (inner). All the
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functions are called with this frame's `struct frame_info' and
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prologue cache.
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THIS frame's register values can be obtained by unwinding NEXT
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frame's registers (a recursive operation).
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THIS frame's prologue cache can be used to cache information such
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as where this frame's prologue stores the previous frame's
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registers. */
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/* Given THIS frame, take a whiff of its registers (namely
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the PC and attributes) and if SELF is the applicable unwinder,
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return non-zero. Possibly also initialize THIS_PROLOGUE_CACHE; but
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only if returning 1. Initializing THIS_PROLOGUE_CACHE in other
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cases (0 return) is invalid. In case of exception, the caller has
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to set *THIS_PROLOGUE_CACHE to NULL. */
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typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
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const frame_info_ptr &this_frame,
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void **this_prologue_cache);
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typedef unwind_stop_reason (frame_unwind_stop_reason_ftype)
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(const frame_info_ptr &this_frame, void **this_prologue_cache);
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/* A default frame sniffer which always accepts the frame. Used by
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fallback prologue unwinders. */
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int default_frame_sniffer (const struct frame_unwind *self,
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const frame_info_ptr &this_frame,
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void **this_prologue_cache);
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/* A default stop_reason callback which always claims the frame is
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unwindable. */
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enum unwind_stop_reason
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default_frame_unwind_stop_reason (const frame_info_ptr &this_frame,
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void **this_cache);
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/* A default unwind_pc callback that simply unwinds the register identified
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by GDBARCH_PC_REGNUM. */
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extern CORE_ADDR default_unwind_pc (struct gdbarch *gdbarch,
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const frame_info_ptr &next_frame);
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/* A default unwind_sp callback that simply unwinds the register identified
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by GDBARCH_SP_REGNUM. */
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extern CORE_ADDR default_unwind_sp (struct gdbarch *gdbarch,
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const frame_info_ptr &next_frame);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and through it the NEXT frame's register unwind
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method, to determine the frame ID of THIS frame.
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A frame ID provides an invariant that can be used to re-identify an
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instance of a frame. It is a combination of the frame's `base' and
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the frame's function's code address.
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Traditionally, THIS frame's ID was determined by examining THIS
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frame's function's prologue, and identifying the register/offset
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used as THIS frame's base.
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Example: An examination of THIS frame's prologue reveals that, on
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entry, it saves the PC(+12), SP(+8), and R1(+4) registers
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(decrementing the SP by 12). Consequently, the frame ID's base can
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be determined by adding 12 to the THIS frame's stack-pointer, and
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the value of THIS frame's SP can be obtained by unwinding the NEXT
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frame's SP.
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THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
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with the other unwind methods. Memory for that cache should be
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allocated using FRAME_OBSTACK_ZALLOC(). */
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typedef void (frame_this_id_ftype) (const frame_info_ptr &this_frame,
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void **this_prologue_cache,
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struct frame_id *this_id);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and implicitly the NEXT frame's register unwind
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method, to unwind THIS frame's registers (returning the value of
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the specified register REGNUM in the previous frame).
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Traditionally, THIS frame's registers were unwound by examining
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THIS frame's function's prologue and identifying which registers
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that prolog code saved on the stack.
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Example: An examination of THIS frame's prologue reveals that, on
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entry, it saves the PC(+12), SP(+8), and R1(+4) registers
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(decrementing the SP by 12). Consequently, the value of the PC
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register in the previous frame is found in memory at SP+12, and
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THIS frame's SP can be obtained by unwinding the NEXT frame's SP.
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This function takes THIS_FRAME as an argument. It can find the
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values of registers in THIS frame by calling get_frame_register
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(THIS_FRAME), and reinvoke itself to find other registers in the
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PREVIOUS frame by calling frame_unwind_register (THIS_FRAME).
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The result is a GDB value object describing the register value. It
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may be a lazy reference to memory, a lazy reference to the value of
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a register in THIS frame, or a non-lvalue.
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If the previous frame's register was not saved by THIS_FRAME and is
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therefore undefined, return a wholly optimized-out not_lval value.
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THIS_PROLOGUE_CACHE can be used to share any prolog analysis data
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with the other unwind methods. Memory for that cache should be
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allocated using FRAME_OBSTACK_ZALLOC(). */
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typedef value *(frame_prev_register_ftype) (const frame_info_ptr &this_frame,
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void **this_prologue_cache,
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int regnum);
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/* Deallocate extra memory associated with the frame cache if any. */
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typedef void (frame_dealloc_cache_ftype) (frame_info *self,
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void *this_cache);
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/* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
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use THIS frame, and implicitly the NEXT frame's register unwind
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method, return PREV frame's architecture. */
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typedef gdbarch *(frame_prev_arch_ftype) (const frame_info_ptr &this_frame,
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void **this_prologue_cache);
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struct frame_unwind
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{
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const char *name;
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/* The frame's type. Should this instead be a collection of
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predicates that test the frame for various attributes? */
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enum frame_type type;
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/* Should an attribute indicating the frame's address-in-block go
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here? */
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frame_unwind_stop_reason_ftype *stop_reason;
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frame_this_id_ftype *this_id;
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frame_prev_register_ftype *prev_register;
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const struct frame_data *unwind_data;
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frame_sniffer_ftype *sniffer;
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frame_dealloc_cache_ftype *dealloc_cache;
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frame_prev_arch_ftype *prev_arch;
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};
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/* Register a frame unwinder, _prepending_ it to the front of the
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search list (so it is sniffed before previously registered
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unwinders). By using a prepend, later calls can install unwinders
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that override earlier calls. This allows, for instance, an OSABI
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to install a more specific sigtramp unwinder that overrides the
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traditional brute-force unwinder. */
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extern void frame_unwind_prepend_unwinder (struct gdbarch *,
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const struct frame_unwind *);
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/* Add a frame sniffer to the list. The predicates are polled in the
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order that they are appended. The initial list contains the dummy
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frame sniffer. */
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extern void frame_unwind_append_unwinder (struct gdbarch *gdbarch,
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const struct frame_unwind *unwinder);
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/* Iterate through sniffers for THIS_FRAME frame until one returns with an
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unwinder implementation. THIS_FRAME->UNWIND must be NULL, it will get set
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by this function. Possibly initialize THIS_CACHE. */
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extern void frame_unwind_find_by_frame (const frame_info_ptr &this_frame,
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void **this_cache);
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/* Helper functions for value-based register unwinding. These return
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a (possibly lazy) value of the appropriate type. */
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/* Return a value which indicates that FRAME did not save REGNUM. */
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value *frame_unwind_got_optimized (const frame_info_ptr &frame, int regnum);
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/* Return a value which indicates that FRAME copied REGNUM into
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register NEW_REGNUM. */
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value *frame_unwind_got_register (const frame_info_ptr &frame, int regnum,
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int new_regnum);
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/* Return a value which indicates that FRAME saved REGNUM in memory at
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ADDR. */
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value *frame_unwind_got_memory (const frame_info_ptr &frame, int regnum,
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CORE_ADDR addr);
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/* Return a value which indicates that FRAME's saved version of
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REGNUM has a known constant (computed) value of VAL. */
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value *frame_unwind_got_constant (const frame_info_ptr &frame, int regnum,
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ULONGEST val);
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/* Return a value which indicates that FRAME's saved version of
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REGNUM has a known constant (computed) value which is stored
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inside BUF. */
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value *frame_unwind_got_bytes (const frame_info_ptr &frame, int regnum,
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const gdb_byte *buf);
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/* Return a value which indicates that FRAME's saved version of REGNUM
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has a known constant (computed) value of ADDR. Convert the
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CORE_ADDR to a target address if necessary. */
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value *frame_unwind_got_address (const frame_info_ptr &frame, int regnum,
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CORE_ADDR addr);
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#endif
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