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/* Simulate breakpoints by patching locations in the target system, for GDB.
Copyright (C) 1990-2021 Free Software Foundation, Inc.
Contributed by Cygnus Support. Written by John Gilmore.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>. */
#include "defs.h"
#include "symtab.h"
#include "breakpoint.h"
#include "inferior.h"
#include "target.h"
#include "gdbarch.h"
/* Insert a breakpoint on targets that don't have any better
breakpoint support. We read the contents of the target location
and stash it, then overwrite it with a breakpoint instruction.
BP_TGT->placed_address is the target location in the target
machine. BP_TGT->shadow_contents is some memory allocated for
saving the target contents. It is guaranteed by the caller to be
long enough to save BREAKPOINT_LEN bytes (this is accomplished via
default_memory_insert_breakpoint (struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
CORE_ADDR addr = bp_tgt->placed_address;
const unsigned char *bp;
gdb_byte *readbuf;
int bplen;
int val;
/* Determine appropriate breakpoint contents and size for this address. */
bp = gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
/* Save the memory contents in the shadow_contents buffer and then
write the breakpoint instruction. */
readbuf = (gdb_byte *) alloca (bplen);
val = target_read_memory (addr, readbuf, bplen);
if (val == 0)
/* These must be set together, either before or after the shadow
read, so that if we're "reinserting" a breakpoint that
doesn't have a shadow yet, the breakpoint masking code inside
target_read_memory doesn't mask out this breakpoint using an
unfilled shadow buffer. The core may be trying to reinsert a
permanent breakpoint, for targets that support breakpoint
conditions/commands on the target side for some types of
breakpoints, such as target remote. */
bp_tgt->shadow_len = bplen;
memcpy (bp_tgt->shadow_contents, readbuf, bplen);
val = target_write_raw_memory (addr, bp, bplen);
return val;
default_memory_remove_breakpoint (struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
int bplen;
gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt,
enum remove_bp_reason reason)
return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
memory_validate_breakpoint (struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
CORE_ADDR addr = bp_tgt->placed_address;
const gdb_byte *bp;
int val;
int bplen;
gdb_byte cur_contents[BREAKPOINT_MAX];
/* Determine appropriate breakpoint contents and size for this
address. */
bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
if (bp == NULL)
return 0;
/* Make sure we see the memory breakpoints. */
scoped_restore restore_memory
= make_scoped_restore_show_memory_breakpoints (1);
val = target_read_memory (addr, cur_contents, bplen);
/* If our breakpoint is no longer at the address, this means that
the program modified the code on us, so it is wrong to put back
the old value. */
return (val == 0 && memcmp (bp, cur_contents, bplen) == 0);