53e8a631a0
https://sourceware.org/ml/gdb-patches/2014-05/msg00737.html Currently a MEMORY_ERROR raised during unwinding a frame will cause the unwind to stop with an error message, for example: (gdb) bt #0 breakpt () at amd64-invalid-stack-middle.c:27 #1 0x00000000004008f0 in func5 () at amd64-invalid-stack-middle.c:32 #2 0x0000000000400900 in func4 () at amd64-invalid-stack-middle.c:38 #3 0x0000000000400910 in func3 () at amd64-invalid-stack-middle.c:44 #4 0x0000000000400928 in func2 () at amd64-invalid-stack-middle.c:50 Cannot access memory at address 0x2aaaaaab0000 However, frame #4 is marked as being the end of the stack unwind, so a subsequent request for the backtrace looses the error message, such as: (gdb) bt #0 breakpt () at amd64-invalid-stack-middle.c:27 #1 0x00000000004008f0 in func5 () at amd64-invalid-stack-middle.c:32 #2 0x0000000000400900 in func4 () at amd64-invalid-stack-middle.c:38 #3 0x0000000000400910 in func3 () at amd64-invalid-stack-middle.c:44 #4 0x0000000000400928 in func2 () at amd64-invalid-stack-middle.c:50 When fetching the backtrace, or requesting the stack depth using the MI interface the situation is even worse, the first time a request is made we encounter the memory error and so the MI returns an error instead of the correct result, for example: (gdb) -stack-info-depth ^error,msg="Cannot access memory at address 0x2aaaaaab0000" Or, (gdb) -stack-list-frames ^error,msg="Cannot access memory at address 0x2aaaaaab0000" However, once one of these commands has been used gdb has, internally, walked the stack and figured that out that frame #4 is the bottom of the stack, so the second time an MI command is tried you'll get the "expected" result: (gdb) -stack-info-depth ^done,depth="5" Or, (gdb) -stack-list-frames ^done,stack=[frame={level="0", .. snip lots .. }] After this patch the MEMORY_ERROR encountered during the frame unwind is attached to frame #4 as the stop reason, and is displayed in the CLI each time the backtrace is requested. In the MI, catching the error means that the "expected" result is returned the first time the MI command is issued. So, from the CLI the results of the backtrace will be: (gdb) bt #0 breakpt () at amd64-invalid-stack-middle.c:27 #1 0x00000000004008f0 in func5 () at amd64-invalid-stack-middle.c:32 #2 0x0000000000400900 in func4 () at amd64-invalid-stack-middle.c:38 #3 0x0000000000400910 in func3 () at amd64-invalid-stack-middle.c:44 #4 0x0000000000400928 in func2 () at amd64-invalid-stack-middle.c:50 Backtrace stopped: Cannot access memory at address 0x2aaaaaab0000 Each and every time that the backtrace is requested, while the MI output will similarly be consistently: (gdb) -stack-info-depth ^done,depth="5" Or, (gdb) -stack-list-frames ^done,stack=[frame={level="0", .. snip lots .. }] gdb/ChangeLog: * frame.c (struct frame_info): Add stop_string field. (get_prev_frame_always_1): Renamed from get_prev_frame_always. (get_prev_frame_always): Old content moved into get_prev_frame_always_1. Call get_prev_frame_always_1 inside TRY_CATCH, handle MEMORY_ERROR exceptions. (frame_stop_reason_string): New function definition. * frame.h (unwind_stop_reason_to_string): Extend comment to mention frame_stop_reason_string. (frame_stop_reason_string): New function declaration. * stack.c (frame_info): Switch to frame_stop_reason_string. (backtrace_command_1): Switch to frame_stop_reason_string. * unwind_stop_reason.def: Add UNWIND_MEMORY_ERROR. (LAST_ENTRY): Changed to UNWIND_MEMORY_ERROR. * guile/lib/gdb.scm: Add FRAME_UNWIND_MEMORY_ERROR to export list. gdb/doc/ChangeLog: * guile.texi (Frames In Guile): Mention FRAME_UNWIND_MEMORY_ERROR. * python.texi (Frames In Python): Mention gdb.FRAME_UNWIND_MEMORY_ERROR. gdb/testsuite/ChangeLog: * gdb.arch/amd64-invalid-stack-middle.exp: Update expected results. * gdb.arch/amd64-invalid-stack-top.exp: Likewise.
80 lines
2.8 KiB
Modula-2
80 lines
2.8 KiB
Modula-2
/* Copyright (C) 2011-2014 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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/* Reasons why frames could not be further unwound
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SET (name, description)
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After this reason name, all reasons should be considered errors;
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i.e.: abnormal stack termination.
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FIRST_ERROR (name)
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First and Last reason defined
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FIRST_ENTRY (name)
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LAST_ENTRY (name) */
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#ifdef SET
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/* No particular reason; either we haven't tried unwinding yet,
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or we didn't fail. */
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SET (UNWIND_NO_REASON, "no reason")
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/* This is no longer used anywhere, but it's kept because it's exposed
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to Python. This is how GDB used to indicate end of stack. We've
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now migrated to a model where frames always have a valid ID. */
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SET (UNWIND_NULL_ID, "unwinder did not report frame ID")
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/* This frame is the outermost. */
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SET (UNWIND_OUTERMOST, "outermost")
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/* Can't unwind further, because that would require knowing the
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values of registers or memory that haven't been collected. */
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SET (UNWIND_UNAVAILABLE, \
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"not enough registers or memory available to unwind further")
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/* This frame ID looks like it ought to belong to a NEXT frame,
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but we got it for a PREV frame. Normally, this is a sign of
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unwinder failure. It could also indicate stack corruption. */
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SET (UNWIND_INNER_ID, "previous frame inner to this frame (corrupt stack?)")
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/* This frame has the same ID as the previous one. That means
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that unwinding further would almost certainly give us another
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frame with exactly the same ID, so break the chain. Normally,
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this is a sign of unwinder failure. It could also indicate
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stack corruption. */
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SET (UNWIND_SAME_ID, "previous frame identical to this frame (corrupt stack?)")
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/* The frame unwinder didn't find any saved PC, but we needed
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one to unwind further. */
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SET (UNWIND_NO_SAVED_PC, "frame did not save the PC")
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/* There was an error accessing memory while unwinding this frame. */
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SET (UNWIND_MEMORY_ERROR, "memory error while unwinding")
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#endif /* SET */
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#ifdef FIRST_ERROR
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FIRST_ERROR (UNWIND_UNAVAILABLE)
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#endif
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#ifdef FIRST_ENTRY
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FIRST_ENTRY (UNWIND_NO_REASON)
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#endif
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#ifdef LAST_ENTRY
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LAST_ENTRY (UNWIND_MEMORY_ERROR)
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#endif
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