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/* Target memory searching
Copyright (C) 2020-2021 Free Software Foundation, Inc.
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 "gdbsupport/common-defs.h"
#include "gdbsupport/search.h"
#include "gdbsupport/byte-vector.h"
/* This implements a basic search of memory, reading target memory and
performing the search here (as opposed to performing the search in on the
target side with, for example, gdbserver). */
(gdb::function_view<target_read_memory_ftype> read_memory,
CORE_ADDR start_addr, ULONGEST search_space_len,
const gdb_byte *pattern, ULONGEST pattern_len,
CORE_ADDR *found_addrp)
const unsigned chunk_size = SEARCH_CHUNK_SIZE;
/* Buffer to hold memory contents for searching. */
unsigned search_buf_size;
search_buf_size = chunk_size + pattern_len - 1;
/* No point in trying to allocate a buffer larger than the search space. */
if (search_space_len < search_buf_size)
search_buf_size = search_space_len;
gdb::byte_vector search_buf (search_buf_size);
/* Prime the search buffer. */
if (!read_memory (start_addr, (), search_buf_size))
warning (_("Unable to access %s bytes of target "
"memory at %s, halting search."),
pulongest (search_buf_size), hex_string (start_addr));
return -1;
/* Perform the search.
The loop is kept simple by allocating [N + pattern-length - 1] bytes.
When we've scanned N bytes we copy the trailing bytes to the start and
read in another N bytes. */
while (search_space_len >= pattern_len)
gdb_byte *found_ptr;
unsigned nr_search_bytes
= std::min (search_space_len, (ULONGEST) search_buf_size);
found_ptr = (gdb_byte *) memmem ( (), nr_search_bytes,
pattern, pattern_len);
if (found_ptr != NULL)
CORE_ADDR found_addr = start_addr + (found_ptr - ());
*found_addrp = found_addr;
return 1;
/* Not found in this chunk, skip to next chunk. */
/* Don't let search_space_len wrap here, it's unsigned. */
if (search_space_len >= chunk_size)
search_space_len -= chunk_size;
search_space_len = 0;
if (search_space_len >= pattern_len)
unsigned keep_len = search_buf_size - chunk_size;
CORE_ADDR read_addr = start_addr + chunk_size + keep_len;
int nr_to_read;
/* Copy the trailing part of the previous iteration to the front
of the buffer for the next iteration. */
gdb_assert (keep_len == pattern_len - 1);
if (keep_len > 0)
memcpy (&search_buf[0], &search_buf[chunk_size], keep_len);
nr_to_read = std::min (search_space_len - keep_len,
(ULONGEST) chunk_size);
if (!read_memory (read_addr, &search_buf[keep_len], nr_to_read))
warning (_("Unable to access %s bytes of target "
"memory at %s, halting search."),
plongest (nr_to_read),
hex_string (read_addr));
return -1;
start_addr += chunk_size;
/* Not found. */
return 0;