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1 files changed, 558 insertions, 0 deletions

diff --git a/gdb/dcache.c b/gdb/dcache.c
new file mode 100644
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--- /dev/null
+++ b/gdb/dcache.c
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+/* Caching code.  Typically used by remote back ends for
+   caching remote memory.
+
+   Copyright 1992, 1993, 1995, 1998 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 2 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
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+#include "defs.h"
+#include "dcache.h"
+#include "gdbcmd.h"
+#include "gdb_string.h"
+#include "gdbcore.h"
+
+/* 
+   The data cache could lead to incorrect results because it doesn't know
+   about volatile variables, thus making it impossible to debug
+   functions which use memory mapped I/O devices.
+
+   set remotecache 0
+
+   In those cases.
+
+   In general the dcache speeds up performance, some speed improvement
+   comes from the actual caching mechanism, but the major gain is in
+   the reduction of the remote protocol overhead; instead of reading
+   or writing a large area of memory in 4 byte requests, the cache
+   bundles up the requests into 32 byte (actually LINE_SIZE) chunks.
+   Reducing the overhead to an eighth of what it was.  This is very
+   obvious when displaying a large amount of data,
+
+   eg, x/200x 0 
+
+   caching     |   no    yes 
+   ---------------------------- 
+   first time  |   4 sec  2 sec improvement due to chunking 
+   second time |   4 sec  0 sec improvement due to caching
+
+   The cache structure is unusual, we keep a number of cache blocks
+   (DCACHE_SIZE) and each one caches a LINE_SIZEed area of memory.
+   Within each line we remember the address of the line (always a
+   multiple of the LINE_SIZE) and a vector of bytes over the range.
+   There's another vector which contains the state of the bytes.
+
+   ENTRY_BAD means that the byte is just plain wrong, and has no
+   correspondence with anything else (as it would when the cache is
+   turned on, but nothing has been done to it.
+
+   ENTRY_DIRTY means that the byte has some data in it which should be
+   written out to the remote target one day, but contains correct
+   data.  ENTRY_OK means that the data is the same in the cache as it
+   is in remote memory.
+
+
+   The ENTRY_DIRTY state is necessary because GDB likes to write large
+   lumps of memory in small bits.  If the caching mechanism didn't
+   maintain the DIRTY information, then something like a two byte
+   write would mean that the entire cache line would have to be read,
+   the two bytes modified and then written out again.  The alternative
+   would be to not read in the cache line in the first place, and just
+   write the two bytes directly into target memory.  The trouble with
+   that is that it really nails performance, because of the remote
+   protocol overhead.  This way, all those little writes are bundled
+   up into an entire cache line write in one go, without having to
+   read the cache line in the first place.
+
+
+  */
+
+
+/* This value regulates the number of cache blocks stored.
+   Smaller values reduce the time spent searching for a cache
+   line, and reduce memory requirements, but increase the risk
+   of a line not being in memory */
+
+#define DCACHE_SIZE 64 
+
+/* This value regulates the size of a cache line.  Smaller values
+   reduce the time taken to read a single byte, but reduce overall
+   throughput.  */
+
+#define LINE_SIZE_POWER (5) 
+#define LINE_SIZE (1 << LINE_SIZE_POWER)
+
+/* Each cache block holds LINE_SIZE bytes of data
+   starting at a multiple-of-LINE_SIZE address.  */
+
+#define LINE_SIZE_MASK  ((LINE_SIZE - 1))	
+#define XFORM(x) 	((x) & LINE_SIZE_MASK)
+#define MASK(x)         ((x) & ~LINE_SIZE_MASK)
+
+
+#define ENTRY_BAD   0  /* data at this byte is wrong */
+#define ENTRY_DIRTY 1  /* data at this byte needs to be written back */
+#define ENTRY_OK    2  /* data at this byte is same as in memory */
+
+
+struct dcache_block
+{
+  struct dcache_block *p;	/* next in list */
+  CORE_ADDR addr;		/* Address for which data is recorded.  */
+  char data[LINE_SIZE];		/* bytes at given address */
+  unsigned char state[LINE_SIZE]; /* what state the data is in */
+
+  /* whether anything in state is dirty - used to speed up the 
+     dirty scan. */
+  int anydirty;			
+
+  int refs;
+};
+
+
+struct dcache_struct 
+{
+  /* Function to actually read the target memory. */
+  memxferfunc read_memory;
+
+  /* Function to actually write the target memory */
+  memxferfunc write_memory;
+
+  /* free list */
+  struct dcache_block *free_head;
+  struct dcache_block *free_tail;
+
+  /* in use list */
+  struct dcache_block *valid_head;
+  struct dcache_block *valid_tail;
+
+  /* The cache itself. */
+  struct dcache_block *the_cache;
+
+  /* potentially, if the cache was enabled, and then turned off, and
+     then turned on again, the stuff in it could be stale, so this is
+     used to mark it */
+  int cache_has_stuff;
+} ;
+
+static int dcache_poke_byte PARAMS ((DCACHE *dcache, CORE_ADDR addr, 
+                                     char *ptr));
+
+static int dcache_peek_byte PARAMS ((DCACHE *dcache, CORE_ADDR addr, 
+                                     char *ptr));
+
+static struct dcache_block *dcache_hit PARAMS ((DCACHE *dcache, 
+                                                CORE_ADDR addr));
+
+static int dcache_write_line PARAMS ((DCACHE *dcache,struct dcache_block *db));
+
+static struct dcache_block *dcache_alloc PARAMS ((DCACHE *dcache));
+
+static int dcache_writeback PARAMS ((DCACHE *dcache));
+
+static void dcache_info PARAMS ((char *exp, int tty));
+
+void _initialize_dcache PARAMS ((void));
+
+int remote_dcache = 0;
+
+DCACHE *last_cache; /* Used by info dcache */
+
+
+/* Free all the data cache blocks, thus discarding all cached data.  */
+
+void
+dcache_flush (dcache)
+     DCACHE *dcache;
+{
+  int i;
+  dcache->valid_head = 0;
+  dcache->valid_tail = 0;
+
+  dcache->free_head = 0;
+  dcache->free_tail = 0;
+
+  for (i = 0; i < DCACHE_SIZE; i++)
+    {
+      struct dcache_block *db = dcache->the_cache + i;
+
+      if (!dcache->free_head)
+	dcache->free_head = db;
+      else
+	dcache->free_tail->p = db;
+      dcache->free_tail = db;
+      db->p = 0;
+    }
+
+  dcache->cache_has_stuff = 0;
+
+  return;
+}
+
+/* If addr is present in the dcache, return the address of the block
+   containing it. */
+
+static struct dcache_block *
+dcache_hit (dcache, addr)
+     DCACHE *dcache;
+     CORE_ADDR addr;
+{
+  register struct dcache_block *db;
+
+  /* Search all cache blocks for one that is at this address.  */
+  db = dcache->valid_head;
+
+  while (db)
+    {
+      if (MASK(addr) == db->addr)
+	{
+	  db->refs++;
+	  return db;
+	}
+      db = db->p;
+    }
+
+  return NULL;
+}
+
+/* Make sure that anything in this line which needs to
+   be written is. */
+
+static int
+dcache_write_line (dcache, db)
+     DCACHE *dcache;
+     register struct dcache_block *db;
+{
+  int s;
+  int e;
+  s = 0;
+  if (db->anydirty)
+    {
+      for (s = 0; s < LINE_SIZE; s++)
+	{
+	  if (db->state[s] == ENTRY_DIRTY)
+	    {
+	      int len = 0;
+	      for (e = s ; e < LINE_SIZE; e++, len++)
+		if (db->state[e] != ENTRY_DIRTY)
+		  break;
+	      {
+		/* all bytes from s..s+len-1 need to
+		   be written out */
+		int done = 0;
+		while (done < len) {
+		  int t = dcache->write_memory (db->addr + s + done,
+						db->data + s + done,
+						len - done);
+		  if (t == 0)
+		    return 0;
+		  done += t;
+		}
+		memset (db->state + s, ENTRY_OK, len);
+		s = e;
+	      }
+	    }
+	}
+      db->anydirty = 0;
+    }
+  return 1;
+}
+
+
+/* Get a free cache block, put or keep it on the valid list,
+   and return its address.  The caller should store into the block
+   the address and data that it describes, then remque it from the
+   free list and insert it into the valid list.  This procedure
+   prevents errors from creeping in if a memory retrieval is
+   interrupted (which used to put garbage blocks in the valid
+   list...).  */
+
+static struct dcache_block *
+dcache_alloc (dcache)
+     DCACHE *dcache;
+{
+  register struct dcache_block *db;
+
+  if (remote_dcache == 0)
+    abort ();
+
+  /* Take something from the free list */
+  db = dcache->free_head;
+  if (db)
+    {
+      dcache->free_head = db->p;
+    }
+  else
+    {
+      /* Nothing left on free list, so grab one from the valid list */
+      db = dcache->valid_head;
+      dcache->valid_head = db->p;
+
+      dcache_write_line (dcache, db);
+    }
+
+  /* append this line to end of valid list */
+  if (!dcache->valid_head)
+    dcache->valid_head = db;
+  else
+    dcache->valid_tail->p = db;
+  dcache->valid_tail = db;
+  db->p = 0;
+
+  return db;
+}
+
+/* Using the data cache DCACHE return the contents of the byte at
+   address ADDR in the remote machine.  
+
+   Returns 0 on error. */
+
+static int
+dcache_peek_byte (dcache, addr, ptr)
+     DCACHE *dcache;
+     CORE_ADDR addr;
+     char *ptr;
+{
+  register struct dcache_block *db = dcache_hit (dcache, addr);
+  int ok=1;
+  int done = 0;
+  if (db == 0
+      || db->state[XFORM (addr)] == ENTRY_BAD)
+    {
+      if (db)
+	{
+	  dcache_write_line (dcache, db);
+	}
+    else
+      db = dcache_alloc (dcache);
+      immediate_quit++;
+      db->addr = MASK (addr);
+      while (done < LINE_SIZE) 
+	{
+	  int try =
+	    (*dcache->read_memory)
+	      (db->addr + done,
+	       db->data + done,
+	       LINE_SIZE - done);
+	  if (try == 0)
+	    return 0;
+	  done += try;
+	}
+      immediate_quit--;
+     
+      memset (db->state, ENTRY_OK, sizeof (db->data));
+      db->anydirty = 0;
+    }
+  *ptr = db->data[XFORM (addr)];
+  return ok;
+}
+
+/* Writeback any dirty lines to the remote. */
+static int
+dcache_writeback (dcache)
+     DCACHE *dcache;
+{
+  struct dcache_block *db;
+
+  db = dcache->valid_head;
+
+  while (db)
+    {
+      if (!dcache_write_line (dcache, db))
+	return 0;
+      db = db->p;
+    }
+  return 1;
+}
+
+
+/* Using the data cache DCACHE return the contents of the word at
+   address ADDR in the remote machine.  */
+int
+dcache_fetch (dcache, addr)
+     DCACHE *dcache;
+     CORE_ADDR addr;
+{
+  int res;
+
+  if (dcache_xfer_memory (dcache, addr, (char *)&res, sizeof res, 0) != sizeof res)
+    memory_error (EIO, addr);
+
+  return res;
+}
+
+
+/* Write the byte at PTR into ADDR in the data cache.
+   Return zero on write error.
+ */
+
+static int
+dcache_poke_byte (dcache, addr, ptr)
+     DCACHE *dcache;
+     CORE_ADDR addr;
+     char *ptr;
+{
+  register struct dcache_block *db = dcache_hit (dcache, addr);
+
+  if (!db)
+    {
+      db = dcache_alloc (dcache);
+      db->addr = MASK (addr);
+      memset (db->state, ENTRY_BAD, sizeof (db->data));
+    }
+
+  db->data[XFORM (addr)] = *ptr;
+  db->state[XFORM (addr)] = ENTRY_DIRTY;
+  db->anydirty = 1;
+  return 1;
+}
+
+/* Write the word at ADDR both in the data cache and in the remote machine.  
+   Return zero on write error.
+ */
+
+int
+dcache_poke (dcache, addr, data)
+     DCACHE *dcache;
+     CORE_ADDR addr;
+     int data;
+{
+  if (dcache_xfer_memory (dcache, addr, (char *)&data, sizeof data, 1) != sizeof data)
+    return 0;
+
+  return dcache_writeback (dcache);
+}
+
+
+/* Initialize the data cache.  */
+DCACHE *
+dcache_init (reading, writing)
+     memxferfunc reading;
+     memxferfunc writing;
+{
+  int csize = sizeof (struct dcache_block) * DCACHE_SIZE;
+  DCACHE *dcache;
+
+  dcache = (DCACHE *) xmalloc (sizeof (*dcache));
+  dcache->read_memory = reading;
+  dcache->write_memory = writing;
+
+  dcache->the_cache = (struct dcache_block *) xmalloc (csize);
+  memset (dcache->the_cache, 0, csize);
+
+  dcache_flush (dcache);
+
+  last_cache = dcache;
+  return dcache;
+}
+
+/* Read or write LEN bytes from inferior memory at MEMADDR, transferring
+   to or from debugger address MYADDR.  Write to inferior if SHOULD_WRITE is
+   nonzero. 
+
+   Returns length of data written or read; 0 for error.  
+
+   This routine is indended to be called by remote_xfer_ functions. */
+
+int
+dcache_xfer_memory (dcache, memaddr, myaddr, len, should_write)
+     DCACHE *dcache;
+     CORE_ADDR memaddr;
+     char *myaddr;
+     int len;
+     int should_write;
+{
+  int i;
+
+  if (remote_dcache) 
+    {
+      int (*xfunc) PARAMS ((DCACHE *dcache, CORE_ADDR addr, char *ptr));
+      xfunc = should_write ? dcache_poke_byte : dcache_peek_byte;
+
+      for (i = 0; i < len; i++)
+	{
+	  if (!xfunc (dcache, memaddr + i, myaddr + i))
+	    return 0;
+	}
+      dcache->cache_has_stuff = 1;
+      dcache_writeback (dcache);
+    }
+  else 
+    {
+      memxferfunc xfunc;
+      xfunc = should_write ? dcache->write_memory : dcache->read_memory;
+
+      if (dcache->cache_has_stuff)
+	dcache_flush (dcache);
+
+      len = xfunc (memaddr, myaddr, len);
+    }
+  return len;
+}
+
+static void 
+dcache_info (exp, tty)
+     char *exp;
+     int tty;
+{
+  struct dcache_block *p;
+
+  if (!remote_dcache)
+    {
+      printf_filtered ("Dcache not enabled\n");
+      return;
+    }
+  printf_filtered ("Dcache enabled, line width %d, depth %d\n",
+		   LINE_SIZE, DCACHE_SIZE);
+
+  printf_filtered ("Cache state:\n");
+
+  for (p = last_cache->valid_head; p; p = p->p)
+    {
+      int j;
+      printf_filtered ("Line at %08xd, referenced %d times\n",
+		       p->addr, p->refs);
+
+      for (j = 0; j < LINE_SIZE; j++)
+	printf_filtered ("%02x", p->data[j] & 0xFF);
+      printf_filtered ("\n");
+
+      for (j = 0; j < LINE_SIZE; j++)
+	printf_filtered (" %2x", p->state[j]);
+      printf_filtered ("\n");
+    }
+}
+
+void
+_initialize_dcache ()
+{
+  add_show_from_set
+    (add_set_cmd ("remotecache", class_support, var_boolean,
+		  (char *) &remote_dcache,
+		  "\
+Set cache use for remote targets.\n\
+When on, use data caching for remote targets.  For many remote targets\n\
+this option can offer better throughput for reading target memory.\n\
+Unfortunately, gdb does not currently know anything about volatile\n\
+registers and thus data caching will produce incorrect results with\n\
+volatile registers are in use.  By default, this option is on.",
+		  &setlist),
+     &showlist);
+
+  add_info ("dcache", dcache_info,
+	    "Print information on the dcache performance.");
+
+}