gdbsupport/search.cc

   1 /* Target memory searching
   2
   3    Copyright (C) 2020-2022 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "gdbsupport/common-defs.h"
  21
  22 #include "gdbsupport/search.h"
  23 #include "gdbsupport/byte-vector.h"
  24
  25 /* This implements a basic search of memory, reading target memory and
  26    performing the search here (as opposed to performing the search in on the
  27    target side with, for example, gdbserver).  */
  28
  29 int
  30 simple_search_memory
  31   (gdb::function_view<target_read_memory_ftype> read_memory,
  32    CORE_ADDR start_addr, ULONGEST search_space_len,
  33    const gdb_byte *pattern, ULONGEST pattern_len,
  34    CORE_ADDR *found_addrp)
  35 {
  36   const unsigned chunk_size = SEARCH_CHUNK_SIZE;
  37   /* Buffer to hold memory contents for searching.  */
  38   unsigned search_buf_size;
  39
  40   search_buf_size = chunk_size + pattern_len - 1;
  41
  42   /* No point in trying to allocate a buffer larger than the search space.  */
  43   if (search_space_len < search_buf_size)
  44     search_buf_size = search_space_len;
  45
  46   gdb::byte_vector search_buf (search_buf_size);
  47
  48   /* Prime the search buffer.  */
  49
  50   if (!read_memory (start_addr, search_buf.data (), search_buf_size))
  51     {
  52       warning (_("Unable to access %s bytes of target "
  53                  "memory at %s, halting search."),
  54                pulongest (search_buf_size), hex_string (start_addr));
  55       return -1;
  56     }
  57
  58   /* Perform the search.
  59
  60      The loop is kept simple by allocating [N + pattern-length - 1] bytes.
  61      When we've scanned N bytes we copy the trailing bytes to the start and
  62      read in another N bytes.  */
  63
  64   while (search_space_len >= pattern_len)
  65     {
  66       gdb_byte *found_ptr;
  67       unsigned nr_search_bytes
  68         = std::min (search_space_len, (ULONGEST) search_buf_size);
  69
  70       found_ptr = (gdb_byte *) memmem (search_buf.data (), nr_search_bytes,
  71                                        pattern, pattern_len);
  72
  73       if (found_ptr != NULL)
  74         {
  75           CORE_ADDR found_addr = start_addr + (found_ptr - search_buf.data ());
  76
  77           *found_addrp = found_addr;
  78           return 1;
  79         }
  80
  81       /* Not found in this chunk, skip to next chunk.  */
  82
  83       /* Don't let search_space_len wrap here, it's unsigned.  */
  84       if (search_space_len >= chunk_size)
  85         search_space_len -= chunk_size;
  86       else
  87         search_space_len = 0;
  88
  89       if (search_space_len >= pattern_len)
  90         {
  91           unsigned keep_len = search_buf_size - chunk_size;
  92           CORE_ADDR read_addr = start_addr + chunk_size + keep_len;
  93           int nr_to_read;
  94
  95           /* Copy the trailing part of the previous iteration to the front
  96              of the buffer for the next iteration.  */
  97           gdb_assert (keep_len == pattern_len - 1);
  98           if (keep_len > 0)
  99             memcpy (&search_buf[0], &search_buf[chunk_size], keep_len);
 100
 101           nr_to_read = std::min (search_space_len - keep_len,
 102                                  (ULONGEST) chunk_size);
 103
 104           if (!read_memory (read_addr, &search_buf[keep_len], nr_to_read))
 105             {
 106               warning (_("Unable to access %s bytes of target "
 107                          "memory at %s, halting search."),
 108                        plongest (nr_to_read),
 109                        hex_string (read_addr));
 110               return -1;
 111             }
 112
 113           start_addr += chunk_size;
 114         }
 115     }
 116
 117   /* Not found.  */
 118
 119   return 0;
 120 }