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68901c4d43
When we find out that a breakpoint is set on top of a program breakpoint, we mark it as "permanent". E.g.,: ... if (bp_loc_is_permanent (loc)) { loc->inserted = 1; loc->permanent = 1; } ... Note we didn't fill in the breakpoint's shadow (shadow_len remains 0). In case the target claims support for evaluating breakpoint conditions, GDB sometimes reinserts breakpoints that are already inserted (to update the conditions on the target side). Since GDB doesn't know whether the target supports evaluating conditions _of_ software breakpoints (vs hardware breakpoints, etc.) until it actually tries it, if the target doesn't actually support z0 breakpoints, GDB ends up reinserting a GDB-managed software/memory breakpoint (mem-break.c). And that is the case that is buggy: breakpoints that are marked inserted contribute their shadows (if any) to the memory returned by target_read_memory, to mask out breakpoints. Permanent breakpoints are always marked as inserted. So if the permanent breakpoint doesn't have a shadow yet in its shadow buffer, but we set shadow_len before calling target_read_memory, then the still clear shadow_contents buffer will be used by the breakpoint masking code... And then from there on, the permanent breakpoint has a broken shadow buffer, and thus any memory read out of that address will read bogus code, and many random bad things fall out from that. The fix is just to set shadow_len at the same time shadow_contents is set, not one before and another after... Fixes all gdb.base/bp-permanent.exp FAILs on PPC64 GNU/Linux gdbserver and probably any other gdbserver port that doesn't do z0 breakpoints. gdb/ChangeLog: 2015-03-05 Pedro Alves <palves@redhat.com> PR gdb/18002 * mem-break.c (default_memory_insert_breakpoint): Set shadow_len after reading the breakpoint's shadow memory.
132 lines
4.2 KiB
C
132 lines
4.2 KiB
C
/* Simulate breakpoints by patching locations in the target system, for GDB.
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Copyright (C) 1990-2015 Free 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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#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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/* 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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CORE_ADDR addr = bp_tgt->reqstd_address;
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const unsigned char *bp;
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gdb_byte *readbuf;
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int bplen;
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int val;
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/* Determine appropriate breakpoint contents and size for this address. */
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bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
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if (bp == NULL)
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error (_("Software breakpoints not implemented for this target."));
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bp_tgt->placed_address = addr;
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bp_tgt->placed_size = bplen;
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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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readbuf = alloca (bplen);
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val = target_read_memory (addr, readbuf, bplen);
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if (val == 0)
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{
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/* These must be set together, either before or after the shadow
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read, so that if we're "reinserting" a breakpoint that
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doesn't have a shadow yet, the breakpoint masking code inside
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target_read_memory doesn't mask out this breakpoint using an
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unfilled shadow buffer. The core may be trying to reinsert a
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permanent breakpoint, for targets that support breakpoint
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conditions/commands on the target side for some types of
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breakpoints, such as target remote. */
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bp_tgt->shadow_len = bplen;
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memcpy (bp_tgt->shadow_contents, readbuf, bplen);
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val = target_write_raw_memory (addr, bp, bplen);
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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 target_ops *ops, 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 target_ops *ops, 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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int
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memory_validate_breakpoint (struct gdbarch *gdbarch,
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struct bp_target_info *bp_tgt)
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{
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CORE_ADDR addr = bp_tgt->placed_address;
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const gdb_byte *bp;
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int val;
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int bplen;
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gdb_byte cur_contents[BREAKPOINT_MAX];
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struct cleanup *cleanup;
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int ret;
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/* Determine appropriate breakpoint contents and size for this
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address. */
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bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
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if (bp == NULL || bp_tgt->placed_size != bplen)
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return 0;
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/* Make sure we see the memory breakpoints. */
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cleanup = make_show_memory_breakpoints_cleanup (1);
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val = target_read_memory (addr, cur_contents, bplen);
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/* If our breakpoint is no longer at the address, this means that
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the program modified the code on us, so it is wrong to put back
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the old value. */
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ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
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do_cleanups (cleanup);
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return ret;
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}
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