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btrace, frame: fix crash in get_frame_type

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In skip_artificial_frames we repeatedly call get_prev_frame_always until we get
a non-inline and non-tailcall frame assuming that there must be such a frame
eventually.

For record targets, however, we may have a frame chain that consists only of
artificial frames.  This leads to a crash in get_frame_type when dereferencing a
NULL frame pointer.

Change skip_artificial_frames and skip_tailcall_frames to return NULL in such a
case and modify each caller to cope with a NULL return.

In frame_unwind_caller_pc and frame_unwind_caller_arch, we simply assert that
the returned value is not NULL.  Their caller was supposed to check
frame_unwind_caller_id before calling those functions.

In other cases, we thrown an error.

In infcmd further move the skip_tailcall_frames call to the forward-stepping
case since we don't need a frame for reverse execution and we don't want to fail
because of that.  Reverse-finish does make sense for a tailcall frame.

gdb/
	* frame.h (skip_tailcall_frames): Update comment.
	* frame.c (skip_artificial_frames, skip_tailcall_frames): Return NULL
	if only	artificial frames are found.  Update comment.
	(frame_unwind_caller_id): Handle NULL return.
	(frame_unwind_caller_pc, frame_unwind_caller_arch): Assert that
	skip_artificial_frames does not return NULL.
	(frame_pop): Add an error if only tailcall frames are found.
	* infcmd.c (finish_command): Move skip_tailcall_frames call into forward-
	execution case.  Add an error if only tailcall frames are found.

testsuite/
	* gdb.btrace/tailcall-only.exp: New.
	* gdb.btrace/tailcall-only.c: New.
	* gdb.btrace/x86_64-tailcall-only.S: New.
	* gdb.btrace/i686-tailcall-only.S: New.
This commit is contained in:
Markus Metzger 2016-01-26 14:58:44 +01:00
parent a038fa3e14
commit 33b4777ca1
9 changed files with 1115 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

48
gdb/frame.c
View file

@ -420,7 +420,8 @@ fprint_frame (struct ui_file *file, struct frame_info *fi)
/* Given FRAME, return the enclosing frame as found in real frames read-in from
inferior memory. Skip any previous frames which were made up by GDB.
Return the original frame if no immediate previous frames exist. */
Return FRAME if FRAME is a non-artificial frame.
Return NULL if FRAME is the start of an artificial-only chain. */
static struct frame_info *
skip_artificial_frames (struct frame_info *frame)
@ -428,12 +429,17 @@ skip_artificial_frames (struct frame_info *frame)
/* Note we use get_prev_frame_always, and not get_prev_frame. The
latter will truncate the frame chain, leading to this function
unintentionally returning a null_frame_id (e.g., when the user
sets a backtrace limit). This is safe, because as these frames
are made up by GDB, there must be a real frame in the chain
below. */
sets a backtrace limit).
Note that for record targets we may get a frame chain that consists
of artificial frames only. */
while (get_frame_type (frame) == INLINE_FRAME
|| get_frame_type (frame) == TAILCALL_FRAME)
frame = get_prev_frame_always (frame);
{
frame = get_prev_frame_always (frame);
if (frame == NULL)
break;
}
return frame;
}
@ -444,7 +450,13 @@ struct frame_info *
skip_tailcall_frames (struct frame_info *frame)
{
while (get_frame_type (frame) == TAILCALL_FRAME)
frame = get_prev_frame (frame);
{
/* Note that for record targets we may get a frame chain that consists of
tailcall frames only. */
frame = get_prev_frame (frame);
if (frame == NULL)
break;
}
return frame;
}
@ -507,6 +519,9 @@ frame_unwind_caller_id (struct frame_info *next_frame)
requests the frame ID of "main()"s caller. */
next_frame = skip_artificial_frames (next_frame);
if (next_frame == NULL)
return null_frame_id;
this_frame = get_prev_frame_always (next_frame);
if (this_frame)
return get_frame_id (skip_artificial_frames (this_frame));
@ -880,7 +895,14 @@ frame_unwind_pc (struct frame_info *this_frame)
CORE_ADDR
frame_unwind_caller_pc (struct frame_info *this_frame)
{
return frame_unwind_pc (skip_artificial_frames (this_frame));
this_frame = skip_artificial_frames (this_frame);
/* We must have a non-artificial frame. The caller is supposed to check
the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID
in this case. */
gdb_assert (this_frame != NULL);
return frame_unwind_pc (this_frame);
}
int
@ -985,6 +1007,9 @@ frame_pop (struct frame_info *this_frame)
entering THISFRAME. */
prev_frame = skip_tailcall_frames (prev_frame);
if (prev_frame == NULL)
error (_("Cannot find the caller frame."));
/* Make a copy of all the register values unwound from this frame.
Save them in a scratch buffer so that there isn't a race between
trying to extract the old values from the current regcache while
@ -2571,7 +2596,14 @@ frame_unwind_arch (struct frame_info *next_frame)
struct gdbarch *
frame_unwind_caller_arch (struct frame_info *next_frame)
{
return frame_unwind_arch (skip_artificial_frames (next_frame));
next_frame = skip_artificial_frames (next_frame);
/* We must have a non-artificial frame. The caller is supposed to check
the result of frame_unwind_caller_id (), which returns NULL_FRAME_ID
in this case. */
gdb_assert (next_frame != NULL);
return frame_unwind_arch (next_frame);
}
/* Gets the language of FRAME. */