| /* Caching code for GDB, the GNU debugger. |
| |
| Copyright 1992, 1993, 1995, 1996, 1998, 1999, 2000, 2001, 2003 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" |
| #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_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. |
| */ |
| |
| /* 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. */ |
| |
| /* 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; |
| }; |
| |
| |
| /* 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 int dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr); |
| |
| static int dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr); |
| |
| 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; |
| |
| DCACHE *last_cache; /* Used by info dcache */ |
| |
| |
| /* Free all the data cache blocks, thus discarding all cached data. */ |
| |
| void |
| dcache_invalidate (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; |
| } |
| |
| return; |
| } |
| |
| /* If addr is present in the dcache, return the address of the block |
| containing it. */ |
| |
| 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->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 *dcache, struct dcache_block *db) |
| { |
| CORE_ADDR memaddr; |
| char *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; |
| while (dirty_len > 0) |
| { |
| res = do_xfer_memory(memaddr, myaddr, dirty_len, 1, |
| ®ion->attrib); |
| if (res <= 0) |
| return 0; |
| |
| memset (&db->state[XFORM(memaddr)], ENTRY_OK, res); |
| memaddr += res; |
| myaddr += res; |
| len -= res; |
| dirty_len -= res; |
| } |
| } |
| } |
| |
| db->anydirty = 0; |
| return 1; |
| } |
| |
| /* Read cache line */ |
| static int |
| dcache_read_line (DCACHE *dcache, struct dcache_block *db) |
| { |
| CORE_ADDR memaddr; |
| char *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; |
| |
| while (len > 0) |
| { |
| 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; |
| } |
| |
| while (reg_len > 0) |
| { |
| res = do_xfer_memory (memaddr, myaddr, reg_len, 0, |
| ®ion->attrib); |
| if (res <= 0) |
| return 0; |
| |
| memaddr += res; |
| myaddr += res; |
| len -= res; |
| reg_len -= res; |
| } |
| } |
| |
| memset (db->state, ENTRY_OK, sizeof (db->data)); |
| db->anydirty = 0; |
| |
| return 1; |
| } |
| |
| /* 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) |
| { |
| struct dcache_block *db; |
| |
| /* 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; |
| |
| if (!dcache_write_line (dcache, db)) |
| return NULL; |
| |
| dcache->valid_head = db->p; |
| } |
| |
| db->addr = MASK(addr); |
| db->refs = 0; |
| db->anydirty = 0; |
| memset (db->state, ENTRY_BAD, 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) |
| { |
| if (!dcache_write_line (dcache, db)) |
| return 0; |
| db = db->p; |
| } |
| return 1; |
| } |
| |
| |
| /* 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, char *ptr) |
| { |
| struct dcache_block *db = dcache_hit (dcache, addr); |
| |
| if (!db) |
| { |
| db = dcache_alloc (dcache, addr); |
| if (!db) |
| return 0; |
| } |
| |
| if (db->state[XFORM (addr)] == ENTRY_BAD) |
| { |
| if (!dcache_read_line(dcache, db)) |
| return 0; |
| } |
| |
| *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, char *ptr) |
| { |
| struct dcache_block *db = dcache_hit (dcache, addr); |
| |
| if (!db) |
| { |
| db = dcache_alloc (dcache, addr); |
| if (!db) |
| return 0; |
| } |
| |
| db->data[XFORM (addr)] = *ptr; |
| db->state[XFORM (addr)] = ENTRY_DIRTY; |
| db->anydirty = 1; |
| return 1; |
| } |
| |
| /* Initialize the data cache. */ |
| DCACHE * |
| dcache_init (void) |
| { |
| int csize = sizeof (struct dcache_block) * DCACHE_SIZE; |
| DCACHE *dcache; |
| |
| dcache = (DCACHE *) xmalloc (sizeof (*dcache)); |
| |
| 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; |
| |
| 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, char *myaddr, int len, |
| int should_write) |
| { |
| int i; |
| int (*xfunc) (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; |
| } |
| |
| /* 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 ("%2x", p->state[j]); |
| printf_filtered ("\n"); |
| } |
| } |
| } |
| |
| void |
| _initialize_dcache (void) |
| { |
| deprecated_add_show_from_set |
| (add_set_cmd ("remotecache", class_support, var_boolean, |
| (char *) &dcache_enabled_p, |
| "\ |
| 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 off.", |
| &setlist), |
| &showlist); |
| |
| add_info ("dcache", dcache_info, |
| "Print information on the dcache performance."); |
| |
| } |