1/* Simulate breakpoints by patching locations in the target system, for GDB. 2 3 Copyright (C) 1990-2020 Free Software Foundation, Inc. 4 5 Contributed by Cygnus Support. Written by John Gilmore. 6 7 This file is part of GDB. 8 9 This program is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3 of the License, or 12 (at your option) any later version. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 21 22#include "defs.h" 23#include "symtab.h" 24#include "breakpoint.h" 25#include "inferior.h" 26#include "target.h" 27#include "gdbarch.h" 28 29/* Insert a breakpoint on targets that don't have any better 30 breakpoint support. We read the contents of the target location 31 and stash it, then overwrite it with a breakpoint instruction. 32 BP_TGT->placed_address is the target location in the target 33 machine. BP_TGT->shadow_contents is some memory allocated for 34 saving the target contents. It is guaranteed by the caller to be 35 long enough to save BREAKPOINT_LEN bytes (this is accomplished via 36 BREAKPOINT_MAX). */ 37 38int 39default_memory_insert_breakpoint (struct gdbarch *gdbarch, 40 struct bp_target_info *bp_tgt) 41{ 42 CORE_ADDR addr = bp_tgt->placed_address; 43 const unsigned char *bp; 44 gdb_byte *readbuf; 45 int bplen; 46 int val; 47 48 /* Determine appropriate breakpoint contents and size for this address. */ 49 bp = gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen); 50 51 /* Save the memory contents in the shadow_contents buffer and then 52 write the breakpoint instruction. */ 53 readbuf = (gdb_byte *) alloca (bplen); 54 val = target_read_memory (addr, readbuf, bplen); 55 if (val == 0) 56 { 57 /* These must be set together, either before or after the shadow 58 read, so that if we're "reinserting" a breakpoint that 59 doesn't have a shadow yet, the breakpoint masking code inside 60 target_read_memory doesn't mask out this breakpoint using an 61 unfilled shadow buffer. The core may be trying to reinsert a 62 permanent breakpoint, for targets that support breakpoint 63 conditions/commands on the target side for some types of 64 breakpoints, such as target remote. */ 65 bp_tgt->shadow_len = bplen; 66 memcpy (bp_tgt->shadow_contents, readbuf, bplen); 67 68 val = target_write_raw_memory (addr, bp, bplen); 69 } 70 71 return val; 72} 73 74 75int 76default_memory_remove_breakpoint (struct gdbarch *gdbarch, 77 struct bp_target_info *bp_tgt) 78{ 79 int bplen; 80 81 gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen); 82 83 return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents, 84 bplen); 85} 86 87 88int 89memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch, 90 struct bp_target_info *bp_tgt) 91{ 92 return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt); 93} 94 95int 96memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch, 97 struct bp_target_info *bp_tgt, 98 enum remove_bp_reason reason) 99{ 100 return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt); 101} 102 103int 104memory_validate_breakpoint (struct gdbarch *gdbarch, 105 struct bp_target_info *bp_tgt) 106{ 107 CORE_ADDR addr = bp_tgt->placed_address; 108 const gdb_byte *bp; 109 int val; 110 int bplen; 111 gdb_byte cur_contents[BREAKPOINT_MAX]; 112 113 /* Determine appropriate breakpoint contents and size for this 114 address. */ 115 bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen); 116 117 if (bp == NULL) 118 return 0; 119 120 /* Make sure we see the memory breakpoints. */ 121 scoped_restore restore_memory 122 = make_scoped_restore_show_memory_breakpoints (1); 123 val = target_read_memory (addr, cur_contents, bplen); 124 125 /* If our breakpoint is no longer at the address, this means that 126 the program modified the code on us, so it is wrong to put back 127 the old value. */ 128 return (val == 0 && memcmp (bp, cur_contents, bplen) == 0); 129} 130