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When debugging on Windows with GDBserver, the debugger starts
failing after hitting a breakpoint. For instance:
(gdb) b foo
Breakpoint 1 at 0x40177e: file foo.adb, line 5.
(gdb) cont
Continuing.
Breakpoint 1, foo () at foo.adb:5
5 Put_Line ("Hello World."); -- STOP
(gdb) n
Program received signal SIGSEGV, Segmentation fault.
0x00401782 in foo () at foo.adb:5
5 Put_Line ("Hello World."); -- STOP
There are two issues:
1. While trying to re-insert a breakpoint that is still inserted
in memory, insert_bp_location wipes out the breakpoint location's
shadow_contents. As a consequence, we cannot restore the proper
instruction when removing the breakpoint anymore. That's why
the inferior's behavior changes when trying to resume after
the breakpoint was hit.
2. mem-break.c:default_memory_insert_breakpoint passes a breakpoint
location's shadow_contents as the buffer for a memory read.
This reveals a limitation of the various memory-read target
functions. This patch documents this limitation and adjust
the two calls that seem to hit that limitation.
gdb/ChangeLog:
* breakpoint.c (breakpoint_xfer_memory): Add assertion.
Update function description.
(insert_bp_location): Do not wipe bl->target_info out.
* mem-break.c: #include "gdb_string.h".
(default_memory_insert_breakpoint): Do not call target_read_memory
with a pointer to the breakpoint's shadow_contents buffer. Use
a local buffer instead.
* m32r-tdep.c (m32r_memory_insert_breakpoint): Ditto.
97 lines
3.0 KiB
C
97 lines
3.0 KiB
C
/* Simulate breakpoints by patching locations in the target system, for GDB.
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Copyright (C) 1990-1993, 1995, 1997-2000, 2002, 2007-2012 Free
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Software Foundation, Inc.
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Contributed by Cygnus Support. Written by John Gilmore.
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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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#include "defs.h"
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/* This file is only useful if BREAKPOINT_FROM_PC is set. If not, we
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punt. */
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#include "symtab.h"
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#include "breakpoint.h"
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#include "inferior.h"
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#include "target.h"
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#include "gdb_string.h"
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/* Insert a breakpoint on targets that don't have any better
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breakpoint support. We read the contents of the target location
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and stash it, then overwrite it with a breakpoint instruction.
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BP_TGT->placed_address is the target location in the target
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machine. BP_TGT->shadow_contents is some memory allocated for
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saving the target contents. It is guaranteed by the caller to be
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long enough to save BREAKPOINT_LEN bytes (this is accomplished via
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BREAKPOINT_MAX). */
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int
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default_memory_insert_breakpoint (struct gdbarch *gdbarch,
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struct bp_target_info *bp_tgt)
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{
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int val;
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const unsigned char *bp;
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gdb_byte *readbuf;
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/* Determine appropriate breakpoint contents and size for this address. */
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bp = gdbarch_breakpoint_from_pc
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(gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
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if (bp == NULL)
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error (_("Software breakpoints not implemented for this target."));
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/* Save the memory contents in the shadow_contents buffer and then
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write the breakpoint instruction. */
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bp_tgt->shadow_len = bp_tgt->placed_size;
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readbuf = alloca (bp_tgt->placed_size);
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val = target_read_memory (bp_tgt->placed_address, readbuf,
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bp_tgt->placed_size);
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if (val == 0)
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{
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memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
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val = target_write_raw_memory (bp_tgt->placed_address, bp,
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bp_tgt->placed_size);
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}
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return val;
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}
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int
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default_memory_remove_breakpoint (struct gdbarch *gdbarch,
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struct bp_target_info *bp_tgt)
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{
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return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
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bp_tgt->placed_size);
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}
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int
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memory_insert_breakpoint (struct gdbarch *gdbarch,
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struct bp_target_info *bp_tgt)
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{
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return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
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}
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int
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memory_remove_breakpoint (struct gdbarch *gdbarch,
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struct bp_target_info *bp_tgt)
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{
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return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
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}
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