gdbsupport/search.cc

   1 /* Target memory searching
   2
   3    Copyright (C) 2020-2024 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
  21 #include "gdbsupport/search.h"
  22 #include "gdbsupport/byte-vector.h"
  23
  24 /* This implements a basic search of memory, reading target memory and
  25    performing the search here (as opposed to performing the search in on the
  26    target side with, for example, gdbserver).  */
  27
  28 int
  29 simple_search_memory
  30   (gdb::function_view<target_read_memory_ftype> read_memory,
  31    CORE_ADDR start_addr, ULONGEST search_space_len,
  32    const gdb_byte *pattern, ULONGEST pattern_len,
  33    CORE_ADDR *found_addrp)
  34 {
  35   const unsigned chunk_size = SEARCH_CHUNK_SIZE;
  36   /* Buffer to hold memory contents for searching.  */
  37   unsigned search_buf_size;
  38
  39   search_buf_size = chunk_size + pattern_len - 1;
  40
  41   /* No point in trying to allocate a buffer larger than the search space.  */
  42   if (search_space_len < search_buf_size)
  43     search_buf_size = search_space_len;
  44
  45   gdb::byte_vector search_buf (search_buf_size);
  46
  47   /* Prime the search buffer.  */
  48
  49   if (!read_memory (start_addr, search_buf.data (), search_buf_size))
  50     {
  51       warning (_("Unable to access %s bytes of target "
  52                  "memory at %s, halting search."),
  53                pulongest (search_buf_size), hex_string (start_addr));
  54       return -1;
  55     }
  56
  57   /* Perform the search.
  58
  59      The loop is kept simple by allocating [N + pattern-length - 1] bytes.
  60      When we've scanned N bytes we copy the trailing bytes to the start and
  61      read in another N bytes.  */
  62
  63   while (search_space_len >= pattern_len)
  64     {
  65       gdb_byte *found_ptr;
  66       unsigned nr_search_bytes
  67         = std::min (search_space_len, (ULONGEST) search_buf_size);
  68
  69       found_ptr = (gdb_byte *) memmem (search_buf.data (), nr_search_bytes,
  70                                        pattern, pattern_len);
  71
  72       if (found_ptr != NULL)
  73         {
  74           CORE_ADDR found_addr = start_addr + (found_ptr - search_buf.data ());
  75
  76           *found_addrp = found_addr;
  77           return 1;
  78         }
  79
  80       /* Not found in this chunk, skip to next chunk.  */
  81
  82       /* Don't let search_space_len wrap here, it's unsigned.  */
  83       if (search_space_len >= chunk_size)
  84         search_space_len -= chunk_size;
  85       else
  86         search_space_len = 0;
  87
  88       if (search_space_len >= pattern_len)
  89         {
  90           unsigned keep_len = search_buf_size - chunk_size;
  91           CORE_ADDR read_addr = start_addr + chunk_size + keep_len;
  92           int nr_to_read;
  93
  94           /* Copy the trailing part of the previous iteration to the front
  95              of the buffer for the next iteration.  */
  96           gdb_assert (keep_len == pattern_len - 1);
  97           if (keep_len > 0)
  98             memcpy (&search_buf[0], &search_buf[chunk_size], keep_len);
  99
 100           nr_to_read = std::min (search_space_len - keep_len,
 101                                  (ULONGEST) chunk_size);
 102
 103           if (!read_memory (read_addr, &search_buf[keep_len], nr_to_read))
 104             {
 105               warning (_("Unable to access %s bytes of target "
 106                          "memory at %s, halting search."),
 107                        plongest (nr_to_read),
 108                        hex_string (read_addr));
 109               return -1;
 110             }
 111
 112           start_addr += chunk_size;
 113         }
 114     }
 115
 116   /* Not found.  */
 117
 118   return 0;
 119 }