From 270c3b1dfaf7b4a901aa7082fbeb3456be1a00bc Mon Sep 17 00:00:00 2001 From: Andrew Cagney Date: Wed, 26 Mar 2003 00:00:07 +0000 Subject: [PATCH] 2003-03-25 Andrew Cagney * frame.c (get_prev_frame): Delay validating a frame's ID - non-NULL, didn't go backwards - until an attempt to unwind it to the previous frame. --- gdb/ChangeLog | 6 +++++ gdb/frame.c | 75 +++++++++++++++++++++++++++++---------------------- 2 files changed, 49 insertions(+), 32 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index cb09e2188b1..8bd33598e65 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2003-03-25 Andrew Cagney + + * frame.c (get_prev_frame): Delay validating a frame's ID - + non-NULL, didn't go backwards - until an attempt to unwind it to + the previous frame. + 2003-03-25 Andrew Cagney * gdbarch.sh (DEPRECATED_EXTRA_STACK_ALIGNMENT_NEEDED): Replace diff --git a/gdb/frame.c b/gdb/frame.c index c233193a00a..8609ce194fb 100644 --- a/gdb/frame.c +++ b/gdb/frame.c @@ -1467,6 +1467,38 @@ get_prev_frame (struct frame_info *this_frame) return prev_frame; } + /* Check that this frame's ID was valid. If it wasn't, don't try to + unwind to the prev frame. Be careful to not apply this test to + the sentinel frame. */ + if (this_frame->level >= 0 && !frame_id_p (get_frame_id (this_frame))) + { + if (frame_debug) + fprintf_filtered (gdb_stdlog, + "Outermost frame - this ID is NULL\n"); + return NULL; + } + + /* Check that this frame's ID isn't inner to (younger, below, next) + the next frame. This happens when frame unwind goes backwards. + Since the sentinel frame isn't valid, don't apply this if this + frame is entier the inner-most or sentinel frame. */ + if (this_frame->level > 0 + && frame_id_inner (get_frame_id (this_frame), + get_frame_id (this_frame->next))) + error ("This frame inner-to next frame (corrupt stack?)"); + + /* Check that this and the next frame are different. If they are + not, there is most likely a stack cycle. As with the inner-than + test, avoid the inner-most and sentinel frames. */ + /* FIXME: cagney/2003-03-17: Can't yet enable this this check. The + frame_id_eq() method doesn't yet use function addresses when + comparing frame IDs. */ + if (0 + && this_frame->level > 0 + && frame_id_eq (get_frame_id (this_frame), + get_frame_id (this_frame->next))) + error ("This frame identical to next frame (corrupt stack?)"); + /* Allocate the new frame but do not wire it in to the frame chain. Some (bad) code in INIT_FRAME_EXTRA_INFO tries to look along frame->next to pull some fancy tricks (of course such code is, by @@ -1533,38 +1565,17 @@ get_prev_frame (struct frame_info *this_frame) &prev_frame->prologue_cache, &prev_frame->id); - /* Check that the unwound ID is valid. */ - if (!frame_id_p (prev_frame->id)) - { - if (frame_debug) - fprintf_unfiltered (gdb_stdlog, - "Outermost frame - unwound frame ID invalid\n"); - return NULL; - } - - /* Check that the new frame isn't inner to (younger, below, next) - the old frame. If that happens the frame unwind is going - backwards. */ - /* FIXME: cagney/2003-02-25: Ignore the sentinel frame since that - doesn't have a valid frame ID. Should instead set the sentinel - frame's frame ID to a true `sentinel'. Leave it until after the - switch to storing the frame ID, instead of the frame base, in the - frame object. */ - if (this_frame->level >= 0 - && frame_id_inner (prev_frame->id, get_frame_id (this_frame))) - error ("Unwound frame inner-to selected frame (corrupt stack?)"); - - /* FIXME: cagney/2003-03-14: Should check that this and next frame's - IDs are different (i.e., !frame_id_eq()). Can't yet do that as - the EQ function doesn't yet compare PC values. */ - - /* FIXME: cagney/2003-03-14: Should delay the evaluation of the - frame ID until when it is needed. That way the inner most frame - can be created without needing to do prologue analysis. */ - - /* Note that, due to frameless functions, the stronger test of the - new frame being outer to the old frame can't be used - frameless - functions differ by only their PC value. */ + /* The unwound frame ID is validate at the start of this function, + as part of the logic to decide if that frame should be further + unwound, and not here while the prev frame is being created. + Doing this makes it possible for the user to examine a frame that + has an invalid frame ID. + + The very old VAX frame_args_address_correct() method noted: [...] + For the sake of argument, suppose that the stack is somewhat + trashed (which is one reason that "info frame" exists). So, + return 0 (indicating we don't know the address of the arglist) if + we don't know what frame this frame calls. */ /* FIXME: cagney/2002-12-18: Instead of this hack, should only store the frame ID in PREV_FRAME. Unfortunatly, some architectures -- 2.30.2