[PATCH v2 3/6] Use simple_search_memory in gdbserver

[Tom Tromey]

This replaces gdbserver's memory-searching function with
simple_search_memory.

gdbserver/ChangeLog
2020-09-25  Tom Tromey  <tromey@adacore.com>

	* server.cc (handle_search_memory_1): Remove.
	(handle_search_memory): Use simple_search_memory.
---
 gdbserver/ChangeLog |   5 ++
 gdbserver/server.cc | 113 +++-----------------------------------------
 2 files changed, 11 insertions(+), 107 deletions(-)

diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index d45154d1f54..1c21660027e 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -49,6 +49,7 @@
 #include "gdbsupport/scope-exit.h"
 #include "gdbsupport/gdb_select.h"
 #include "gdbsupport/scoped_restore.h"
+#include "gdbsupport/search.h"
 
 #define require_running_or_return(BUF)		\
   if (!target_running ())			\
@@ -1038,89 +1039,6 @@ gdb_write_memory (CORE_ADDR memaddr, const unsigned char *myaddr, int len)
     }
 }
 
-/* Subroutine of handle_search_memory to simplify it.  */
-
-static int
-handle_search_memory_1 (CORE_ADDR start_addr, CORE_ADDR search_space_len,
-			gdb_byte *pattern, unsigned pattern_len,
-			gdb_byte *search_buf,
-			unsigned chunk_size, unsigned search_buf_size,
-			CORE_ADDR *found_addrp)
-{
-  /* Prime the search buffer.  */
-
-  if (gdb_read_memory (start_addr, search_buf, search_buf_size)
-      != search_buf_size)
-    {
-      warning ("Unable to access %ld bytes of target "
-	       "memory at 0x%lx, halting search.",
-	       (long) search_buf_size, (long) 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 = (search_space_len < search_buf_size
-				  ? search_space_len
-				  : search_buf_size);
-
-      found_ptr = (gdb_byte *) memmem (search_buf, nr_search_bytes, pattern,
-				       pattern_len);
-
-      if (found_ptr != NULL)
-	{
-	  CORE_ADDR found_addr = start_addr + (found_ptr - search_buf);
-	  *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;
-      else
-	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.  */
-	  memcpy (search_buf, search_buf + chunk_size, keep_len);
-
-	  nr_to_read = (search_space_len - keep_len < chunk_size
-			? search_space_len - keep_len
-			: chunk_size);
-
-	  if (gdb_read_memory (read_addr, search_buf + keep_len,
-			       nr_to_read) != nr_to_read)
-	    {
-	      warning ("Unable to access %ld bytes of target memory "
-		       "at 0x%lx, halting search.",
-		       (long) nr_to_read, (long) read_addr);
-	      return -1;
-	    }
-
-	  start_addr += chunk_size;
-	}
-    }
-
-  /* Not found.  */
-
-  return 0;
-}
-
 /* Handle qSearch:memory packets.  */
 
 static void
@@ -1130,12 +1048,6 @@ handle_search_memory (char *own_buf, int packet_len)
   CORE_ADDR search_space_len;
   gdb_byte *pattern;
   unsigned int pattern_len;
-  /* NOTE: also defined in find.c testcase.  */
-#define SEARCH_CHUNK_SIZE 16000
-  const unsigned chunk_size = SEARCH_CHUNK_SIZE;
-  /* Buffer to hold memory contents for searching.  */
-  gdb_byte *search_buf;
-  unsigned search_buf_size;
   int found;
   CORE_ADDR found_addr;
   int cmd_name_len = sizeof ("qSearch:memory:") - 1;
@@ -1158,25 +1070,13 @@ handle_search_memory (char *own_buf, int packet_len)
       return;
     }
 
-  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;
-
-  search_buf = (gdb_byte *) malloc (search_buf_size);
-  if (search_buf == NULL)
+  auto read_memory = [] (CORE_ADDR addr, gdb_byte *result, size_t len)
     {
-      free (pattern);
-      error ("Unable to allocate memory to perform the search");
-      strcpy (own_buf, "E00");
-      return;
-    }
+      return gdb_read_memory (addr, result, len) == len;
+    };
 
-  found = handle_search_memory_1 (start_addr, search_space_len,
-				  pattern, pattern_len,
-				  search_buf, chunk_size, search_buf_size,
-				  &found_addr);
+  found = simple_search_memory (read_memory, start_addr, search_space_len,
+				pattern, pattern_len, &found_addr);
 
   if (found > 0)
     sprintf (own_buf, "1,%lx", (long) found_addr);
@@ -1185,7 +1085,6 @@ handle_search_memory (char *own_buf, int packet_len)
   else
     strcpy (own_buf, "E00");
 
-  free (search_buf);
   free (pattern);
 }
 
-- 
2.26.2