1 /* Simulate breakpoints by patching locations in the target system, for GDB. 2 3 Copyright (C) 1990-2017 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 /* Insert a breakpoint on targets that don't have any better 28 breakpoint support. We read the contents of the target location 29 and stash it, then overwrite it with a breakpoint instruction. 30 BP_TGT->placed_address is the target location in the target 31 machine. BP_TGT->shadow_contents is some memory allocated for 32 saving the target contents. It is guaranteed by the caller to be 33 long enough to save BREAKPOINT_LEN bytes (this is accomplished via 34 BREAKPOINT_MAX). */ 35 36 int 37 default_memory_insert_breakpoint (struct gdbarch *gdbarch, 38 struct bp_target_info *bp_tgt) 39 { 40 CORE_ADDR addr = bp_tgt->placed_address; 41 const unsigned char *bp; 42 gdb_byte *readbuf; 43 int bplen; 44 int val; 45 46 /* Determine appropriate breakpoint contents and size for this address. */ 47 bp = gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen); 48 49 /* Save the memory contents in the shadow_contents buffer and then 50 write the breakpoint instruction. */ 51 readbuf = (gdb_byte *) alloca (bplen); 52 val = target_read_memory (addr, readbuf, bplen); 53 if (val == 0) 54 { 55 /* These must be set together, either before or after the shadow 56 read, so that if we're "reinserting" a breakpoint that 57 doesn't have a shadow yet, the breakpoint masking code inside 58 target_read_memory doesn't mask out this breakpoint using an 59 unfilled shadow buffer. The core may be trying to reinsert a 60 permanent breakpoint, for targets that support breakpoint 61 conditions/commands on the target side for some types of 62 breakpoints, such as target remote. */ 63 bp_tgt->shadow_len = bplen; 64 memcpy (bp_tgt->shadow_contents, readbuf, bplen); 65 66 val = target_write_raw_memory (addr, bp, bplen); 67 } 68 69 return val; 70 } 71 72 73 int 74 default_memory_remove_breakpoint (struct gdbarch *gdbarch, 75 struct bp_target_info *bp_tgt) 76 { 77 int bplen; 78 79 gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen); 80 81 return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents, 82 bplen); 83 } 84 85 86 int 87 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch, 88 struct bp_target_info *bp_tgt) 89 { 90 return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt); 91 } 92 93 int 94 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch, 95 struct bp_target_info *bp_tgt, 96 enum remove_bp_reason reason) 97 { 98 return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt); 99 } 100 101 int 102 memory_validate_breakpoint (struct gdbarch *gdbarch, 103 struct bp_target_info *bp_tgt) 104 { 105 CORE_ADDR addr = bp_tgt->placed_address; 106 const gdb_byte *bp; 107 int val; 108 int bplen; 109 gdb_byte cur_contents[BREAKPOINT_MAX]; 110 struct cleanup *cleanup; 111 int ret; 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 cleanup = make_show_memory_breakpoints_cleanup (1); 122 val = target_read_memory (addr, cur_contents, bplen); 123 124 /* If our breakpoint is no longer at the address, this means that 125 the program modified the code on us, so it is wrong to put back 126 the old value. */ 127 ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0); 128 129 do_cleanups (cleanup); 130 return ret; 131 } 132