| /* 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."); |
| |
| } |