-/* Caching code. Typically used by remote back ends for
- caching remote memory.
+/* Caching code for GDB, the GNU debugger.
- Copyright 1992, 1993 Free Software Foundation, Inc.
+ Copyright (C) 1992, 1993, 1995, 1996, 1998, 1999, 2000, 2001, 2003, 2007,
+ 2008, 2009 Free Software Foundation, Inc.
-This file is part of GDB.
+ 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 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
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU General Public License for more details.
+ 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "dcache.h"
#include "gdbcmd.h"
+#include "gdb_string.h"
+#include "gdbcore.h"
+#include "target.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 the nocache
+ memory region attribute 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_INVALID 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_VALID 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.
+ */
+
+/* NOTE: Interaction of dcache and memory region attributes
+
+ As there is no requirement that memory region attributes be aligned
+ to or be a multiple of the dcache page size, dcache_read_line() and
+ dcache_write_line() must break up the page by memory region. If a
+ chunk does not have the cache attribute set, an invalid memory type
+ is set, etc., then the chunk is skipped. Those chunks are handled
+ in target_xfer_memory() (or target_xfer_memory_partial()).
+
+ This doesn't occur very often. The most common occurance is when
+ the last bit of the .text segment and the first bit of the .data
+ segment fall within the same dcache page with a ro/cacheable memory
+ region defined for the .text segment and a rw/non-cacheable memory
+ region defined for the .data segment. */
-#ifdef __STDC__
-/* In case the system header files define a prototype for insque and
- remque that uses a pointer to a struct qelem, silence the warnings */
-struct qelem;
-#define insque(a,b) (insque)((struct qelem *)(a), (struct qelem *)(b))
-#define remque(a) (remque)((struct qelem *)(a))
-#endif
+/* 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 */
-int remote_dcache = 0;
+#define DCACHE_SIZE 64
-/* The data cache records all the data read from the remote machine
- since the last time it stopped.
+/* This value regulates the size of a cache line. Smaller values
+ reduce the time taken to read a single byte, but reduce overall
+ throughput. */
- Each cache block holds LINE_SIZE bytes of data
+#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)) /* eg 7*2+1= 111*/
-#define XFORM(x) (((x) & LINE_SIZE_MASK) >> 2)
+#define LINE_SIZE_MASK ((LINE_SIZE - 1))
+#define XFORM(x) ((x) & LINE_SIZE_MASK)
+#define MASK(x) ((x) & ~LINE_SIZE_MASK)
+
+
+#define ENTRY_INVALID 0 /* data at this byte is wrong */
+#define ENTRY_DIRTY 1 /* data at this byte needs to be written back */
+#define ENTRY_VALID 2 /* data at this byte is same as in memory */
+
+/* For cache state display by "info dcache".
+ The letters I,D,V map to
+ I = ENTRY_INVALID
+ D = ENTRY_DIRTY
+ V = ENTRY_VALID */
+static const char state_chars[3] = { 'I', 'D', 'V' };
+
+struct dcache_block
+ {
+ struct dcache_block *p; /* next in list */
+ CORE_ADDR addr; /* Address for which data is recorded. */
+ gdb_byte 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;
+ };
+
+
+/* FIXME: dcache_struct used to have a cache_has_stuff field that was
+ used to record whether the cache had been accessed. This was used
+ to invalidate the cache whenever caching was (re-)enabled (if the
+ cache was disabled and later re-enabled, it could contain stale
+ data). This was not needed because the cache is write through and
+ the code that enables, disables, and deletes memory region all
+ invalidate the cache.
+
+ This is overkill, since it also invalidates cache lines from
+ unrelated regions. One way this could be addressed by adding a
+ new function that takes an address and a length and invalidates
+ only those cache lines that match. */
+
+struct dcache_struct
+ {
+ /* 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;
+ };
+
+static struct dcache_block *dcache_hit (DCACHE *dcache, CORE_ADDR addr);
+
+static int dcache_write_line (DCACHE *dcache, struct dcache_block *db);
+
+static int dcache_read_line (DCACHE *dcache, struct dcache_block *db);
+
+static struct dcache_block *dcache_alloc (DCACHE *dcache, CORE_ADDR addr);
+
+static int dcache_writeback (DCACHE *dcache);
+
+static void dcache_info (char *exp, int tty);
+
+void _initialize_dcache (void);
+
+static int dcache_enabled_p = 0;
+
+static void
+show_dcache_enabled_p (struct ui_file *file, int from_tty,
+ struct cmd_list_element *c, const char *value)
+{
+ fprintf_filtered (file, _("Cache use for remote targets is %s.\n"), value);
+}
+
+
+DCACHE *last_cache; /* Used by info dcache */
+
/* Free all the data cache blocks, thus discarding all cached data. */
+
void
-dcache_flush (dcache)
- DCACHE *dcache;
+dcache_invalidate (DCACHE *dcache)
{
- register struct dcache_block *db;
+ int i;
+ dcache->valid_head = 0;
+ dcache->valid_tail = 0;
- if (remote_dcache > 0)
- while ((db = dcache->dcache_valid.next) != &dcache->dcache_valid)
- {
- remque (db);
- insque (db, &dcache->dcache_free);
- }
+ 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;
+ }
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;
- unsigned int addr;
-{
- register struct dcache_block *db;
+/* If addr is present in the dcache, return the address of the block
+ containing it. */
- if (addr & 3
- || remote_dcache == 0)
- abort ();
+static struct dcache_block *
+dcache_hit (DCACHE *dcache, CORE_ADDR addr)
+{
+ struct dcache_block *db;
/* Search all cache blocks for one that is at this address. */
- db = dcache->dcache_valid.next;
- while (db != &dcache->dcache_valid)
+ db = dcache->valid_head;
+
+ while (db)
{
- if ((addr & ~LINE_SIZE_MASK) == db->addr)
- return db;
- db = db->next;
+ if (MASK (addr) == db->addr)
+ {
+ db->refs++;
+ return db;
+ }
+ db = db->p;
}
return NULL;
}
-/* Return the int data at address ADDR in dcache block DC. */
-static
-int
-dcache_value (db, addr)
- struct dcache_block *db;
- unsigned int addr;
+/* Make sure that anything in this line which needs to
+ be written is. */
+
+static int
+dcache_write_line (DCACHE *dcache, struct dcache_block *db)
{
- if (addr & 3
- || remote_dcache == 0)
- abort ();
- return (db->data[XFORM (addr)]);
+ CORE_ADDR memaddr;
+ gdb_byte *myaddr;
+ int len;
+ int res;
+ int reg_len;
+ struct mem_region *region;
+
+ if (!db->anydirty)
+ return 1;
+
+ len = LINE_SIZE;
+ memaddr = db->addr;
+ myaddr = db->data;
+
+ while (len > 0)
+ {
+ int s;
+ int e;
+ int dirty_len;
+
+ region = lookup_mem_region(memaddr);
+ if (memaddr + len < region->hi)
+ reg_len = len;
+ else
+ reg_len = region->hi - memaddr;
+
+ if (!region->attrib.cache || region->attrib.mode == MEM_RO)
+ {
+ memaddr += reg_len;
+ myaddr += reg_len;
+ len -= reg_len;
+ continue;
+ }
+
+ while (reg_len > 0)
+ {
+ s = XFORM(memaddr);
+ while (reg_len > 0) {
+ if (db->state[s] == ENTRY_DIRTY)
+ break;
+ s++;
+ reg_len--;
+
+ memaddr++;
+ myaddr++;
+ len--;
+ }
+
+ e = s;
+ while (reg_len > 0) {
+ if (db->state[e] != ENTRY_DIRTY)
+ break;
+ e++;
+ reg_len--;
+ }
+
+ dirty_len = e - s;
+ res = target_write (¤t_target, TARGET_OBJECT_RAW_MEMORY,
+ NULL, myaddr, memaddr, dirty_len);
+ if (res < dirty_len)
+ return 0;
+
+ memset (&db->state[XFORM(memaddr)], ENTRY_VALID, res);
+ memaddr += res;
+ myaddr += res;
+ len -= res;
+ }
+ }
+
+ 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;
+/* Read cache line */
+static int
+dcache_read_line (DCACHE *dcache, struct dcache_block *db)
{
- register struct dcache_block *db;
-
- if (remote_dcache == 0)
- abort();
+ CORE_ADDR memaddr;
+ gdb_byte *myaddr;
+ int len;
+ int res;
+ int reg_len;
+ struct mem_region *region;
+
+ /* If there are any dirty bytes in the line, it must be written
+ before a new line can be read */
+ if (db->anydirty)
+ {
+ if (!dcache_write_line (dcache, db))
+ return 0;
+ }
+
+ len = LINE_SIZE;
+ memaddr = db->addr;
+ myaddr = db->data;
- if ((db = dcache->dcache_free.next) == &dcache->dcache_free)
+ while (len > 0)
{
- /* If we can't get one from the free list, take last valid and put
- it on the free list. */
- db = dcache->dcache_valid.last;
- remque (db);
- insque (db, &dcache->dcache_free);
+ region = lookup_mem_region(memaddr);
+ if (memaddr + len < region->hi)
+ reg_len = len;
+ else
+ reg_len = region->hi - memaddr;
+
+ if (!region->attrib.cache || region->attrib.mode == MEM_WO)
+ {
+ memaddr += reg_len;
+ myaddr += reg_len;
+ len -= reg_len;
+ continue;
+ }
+
+ res = target_read (¤t_target, TARGET_OBJECT_RAW_MEMORY,
+ NULL, myaddr, memaddr, reg_len);
+ if (res < reg_len)
+ return 0;
+
+ memaddr += res;
+ myaddr += res;
+ len -= res;
}
- remque (db);
- insque (db, &dcache->dcache_valid);
- return (db);
+ memset (db->state, ENTRY_VALID, sizeof (db->data));
+ db->anydirty = 0;
+
+ 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;
+/* Get a free cache block, put or keep it on the valid list,
+ and return its address. */
+
+static struct dcache_block *
+dcache_alloc (DCACHE *dcache, CORE_ADDR addr)
{
- register struct dcache_block *db;
+ struct dcache_block *db;
- if (remote_dcache == 0)
+ /* Take something from the free list */
+ db = dcache->free_head;
+ if (db)
{
- int i;
+ dcache->free_head = db->p;
+ }
+ else
+ {
+ /* Nothing left on free list, so grab one from the valid list */
+ db = dcache->valid_head;
- (*dcache->read_memory) (addr, (unsigned char *) &i, 4);
- return(i);
+ if (!dcache_write_line (dcache, db))
+ return NULL;
+
+ dcache->valid_head = db->p;
}
- db = dcache_hit (dcache, addr);
- if (db == 0)
+ db->addr = MASK(addr);
+ db->refs = 0;
+ db->anydirty = 0;
+ memset (db->state, ENTRY_INVALID, sizeof (db->data));
+
+ /* 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;
+}
+
+/* Writeback any dirty lines. */
+static int
+dcache_writeback (DCACHE *dcache)
+{
+ struct dcache_block *db;
+
+ db = dcache->valid_head;
+
+ while (db)
{
- db = dcache_alloc (dcache);
- immediate_quit++;
- (*dcache->read_memory) (addr & ~LINE_SIZE_MASK, (unsigned char *) db->data, LINE_SIZE);
- immediate_quit--;
- db->addr = addr & ~LINE_SIZE_MASK;
- remque (db); /* Off the free list */
- insque (db, &dcache->dcache_valid); /* On the valid list */
+ if (!dcache_write_line (dcache, db))
+ return 0;
+ db = db->p;
}
- return (dcache_value (db, addr));
+ return 1;
}
-/* Write the word at ADDR both in the data cache and in the remote machine. */
-void
-dcache_poke (dcache, addr, data)
- DCACHE *dcache;
- CORE_ADDR addr;
- int data;
+
+/* 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 *dcache, CORE_ADDR addr, gdb_byte *ptr)
{
- register struct dcache_block *db;
+ struct dcache_block *db = dcache_hit (dcache, addr);
- if (remote_dcache == 0)
+ if (!db)
{
- (*dcache->write_memory) (addr, (unsigned char *) &data, 4);
- return;
+ db = dcache_alloc (dcache, addr);
+ if (!db)
+ return 0;
}
-
- /* First make sure the word is IN the cache. DB is its cache block. */
- db = dcache_hit (dcache, addr);
- if (db == 0)
+
+ if (db->state[XFORM (addr)] == ENTRY_INVALID)
{
- db = dcache_alloc (dcache);
- immediate_quit++;
- (*dcache->write_memory) (addr & ~LINE_SIZE_MASK, (unsigned char *) db->data, LINE_SIZE);
- immediate_quit--;
- db->addr = addr & ~LINE_SIZE_MASK;
- remque (db); /* Off the free list */
- insque (db, &dcache->dcache_valid); /* On the valid list */
+ if (!dcache_read_line(dcache, db))
+ return 0;
}
- /* Modify the word in the cache. */
- db->data[XFORM (addr)] = data;
+ *ptr = db->data[XFORM (addr)];
+ return 1;
+}
+
+
+/* Write the byte at PTR into ADDR in the data cache.
+ Return zero on write error.
+ */
+
+static int
+dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, gdb_byte *ptr)
+{
+ struct dcache_block *db = dcache_hit (dcache, addr);
+
+ if (!db)
+ {
+ db = dcache_alloc (dcache, addr);
+ if (!db)
+ return 0;
+ }
- /* Send the changed word. */
- immediate_quit++;
- (*dcache->write_memory) (addr, (unsigned char *) &data, 4);
- immediate_quit--;
+ db->data[XFORM (addr)] = *ptr;
+ db->state[XFORM (addr)] = ENTRY_DIRTY;
+ db->anydirty = 1;
+ return 1;
}
/* Initialize the data cache. */
DCACHE *
-dcache_init (reading, writing)
- memxferfunc reading;
- memxferfunc writing;
+dcache_init (void)
{
- register i;
- register struct dcache_block *db;
+ 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 (sizeof (*dcache->the_cache) * DCACHE_SIZE);
- dcache->dcache_free.next = dcache->dcache_free.last = &dcache->dcache_free;
- dcache->dcache_valid.next = dcache->dcache_valid.last = &dcache->dcache_valid;
- for (db = dcache->the_cache, i = 0; i < DCACHE_SIZE; i++, db++)
- insque (db, &dcache->dcache_free);
+ dcache->the_cache = (struct dcache_block *) xmalloc (csize);
+ memset (dcache->the_cache, 0, csize);
+
+ dcache_invalidate (dcache);
+
+ last_cache = dcache;
+ return dcache;
+}
+
+/* Free a data cache */
+void
+dcache_free (DCACHE *dcache)
+{
+ if (last_cache == dcache)
+ last_cache = NULL;
- return(dcache);
+ xfree (dcache->the_cache);
+ xfree (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 *dcache, CORE_ADDR memaddr, gdb_byte *myaddr,
+ int len, int should_write)
+{
+ int i;
+ int (*xfunc) (DCACHE *dcache, CORE_ADDR addr, gdb_byte *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;
+ }
+
+ /* FIXME: There may be some benefit from moving the cache writeback
+ to a higher layer, as it could occur after a sequence of smaller
+ writes have been completed (as when a stack frame is constructed
+ for an inferior function call). Note that only moving it up one
+ level to target_xfer_memory() (also target_xfer_memory_partial())
+ is not sufficent, since we want to coalesce memory transfers that
+ are "logically" connected but not actually a single call to one
+ of the memory transfer functions. */
+
+ if (should_write)
+ dcache_writeback (dcache);
+
+ return len;
+}
+
+static void
+dcache_info (char *exp, int tty)
+{
+ struct dcache_block *p;
+
+ printf_filtered (_("Dcache line width %d, depth %d\n"),
+ LINE_SIZE, DCACHE_SIZE);
+
+ if (last_cache)
+ {
+ printf_filtered (_("Cache state:\n"));
+
+ for (p = last_cache->valid_head; p; p = p->p)
+ {
+ int j;
+ printf_filtered (_("Line at %s, referenced %d times\n"),
+ paddr (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 (" %c", state_chars[p->state[j]]);
+ printf_filtered ("\n");
+ }
+ }
}
void
-_initialitize_dcache ()
+_initialize_dcache (void)
{
- add_show_from_set
- (add_set_cmd ("remotecache", class_support, var_boolean,
- (char *) &remote_dcache,
- "\
-Set cache use for remote targets.\n\
+ add_setshow_boolean_cmd ("remotecache", class_support,
+ &dcache_enabled_p, _("\
+Set cache use for remote targets."), _("\
+Show cache use for remote targets."), _("\
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 off.",
- &setlist),
- &showlist);
+volatile registers are in use. By default, this option is off."),
+ NULL,
+ show_dcache_enabled_p,
+ &setlist, &showlist);
+
+ add_info ("dcache", dcache_info,
+ _("\
+Print information on the dcache performance.\n\
+The state of each cached byte is represented by a letter:\n\
+ I = invalid\n\
+ D = dirty\n\
+ V = valid"));
}
projects / external / binutils.git / blobdiff