660 lines
18 KiB
C
660 lines
18 KiB
C
/* Caching code for GDB, the GNU debugger.
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Copyright (C) 1992, 1993, 1995, 1996, 1998, 1999, 2000, 2001, 2003, 2007,
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2008, 2009, 2010, 2011 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "dcache.h"
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#include "gdbcmd.h"
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#include "gdb_string.h"
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#include "gdbcore.h"
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#include "target.h"
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#include "inferior.h"
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#include "splay-tree.h"
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/* The data cache could lead to incorrect results because it doesn't
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know about volatile variables, thus making it impossible to debug
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functions which use memory mapped I/O devices. Set the nocache
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memory region attribute in those cases.
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In general the dcache speeds up performance. Some speed improvement
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comes from the actual caching mechanism, but the major gain is in
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the reduction of the remote protocol overhead; instead of reading
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or writing a large area of memory in 4 byte requests, the cache
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bundles up the requests into LINE_SIZE chunks, reducing overhead
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significantly. This is most useful when accessing a large amount
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of data, such as when performing a backtrace.
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The cache is a splay tree along with a linked list for replacement.
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Each block caches a LINE_SIZE area of memory. Within each line we
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remember the address of the line (which must be a multiple of
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LINE_SIZE) and the actual data block.
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Lines are only allocated as needed, so DCACHE_SIZE really specifies the
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*maximum* number of lines in the cache.
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At present, the cache is write-through rather than writeback: as soon
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as data is written to the cache, it is also immediately written to
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the target. Therefore, cache lines are never "dirty". Whether a given
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line is valid or not depends on where it is stored in the dcache_struct;
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there is no per-block valid flag. */
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/* NOTE: Interaction of dcache and memory region attributes
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As there is no requirement that memory region attributes be aligned
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to or be a multiple of the dcache page size, dcache_read_line() and
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dcache_write_line() must break up the page by memory region. If a
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chunk does not have the cache attribute set, an invalid memory type
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is set, etc., then the chunk is skipped. Those chunks are handled
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in target_xfer_memory() (or target_xfer_memory_partial()).
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This doesn't occur very often. The most common occurance is when
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the last bit of the .text segment and the first bit of the .data
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segment fall within the same dcache page with a ro/cacheable memory
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region defined for the .text segment and a rw/non-cacheable memory
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region defined for the .data segment. */
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/* The maximum number of lines stored. The total size of the cache is
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equal to DCACHE_SIZE times LINE_SIZE. */
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#define DCACHE_SIZE 4096
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/* The size of a cache line. Smaller values reduce the time taken to
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read a single byte and make the cache more granular, but increase
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overhead and reduce the effectiveness of the cache as a prefetcher. */
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#define LINE_SIZE_POWER 6
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#define LINE_SIZE (1 << LINE_SIZE_POWER)
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/* Each cache block holds LINE_SIZE bytes of data
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starting at a multiple-of-LINE_SIZE address. */
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#define LINE_SIZE_MASK ((LINE_SIZE - 1))
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#define XFORM(x) ((x) & LINE_SIZE_MASK)
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#define MASK(x) ((x) & ~LINE_SIZE_MASK)
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struct dcache_block
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{
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/* For least-recently-allocated and free lists. */
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struct dcache_block *prev;
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struct dcache_block *next;
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CORE_ADDR addr; /* address of data */
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gdb_byte data[LINE_SIZE]; /* bytes at given address */
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int refs; /* # hits */
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};
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struct dcache_struct
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{
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splay_tree tree;
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struct dcache_block *oldest; /* least-recently-allocated list. */
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/* The free list is maintained identically to OLDEST to simplify
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the code: we only need one set of accessors. */
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struct dcache_block *freelist;
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/* The number of in-use lines in the cache. */
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int size;
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/* The ptid of last inferior to use cache or null_ptid. */
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ptid_t ptid;
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};
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typedef void (block_func) (struct dcache_block *block, void *param);
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static struct dcache_block *dcache_hit (DCACHE *dcache, CORE_ADDR addr);
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static int dcache_read_line (DCACHE *dcache, struct dcache_block *db);
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static struct dcache_block *dcache_alloc (DCACHE *dcache, CORE_ADDR addr);
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static void dcache_info (char *exp, int tty);
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void _initialize_dcache (void);
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static int dcache_enabled_p = 0; /* OBSOLETE */
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static void
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show_dcache_enabled_p (struct ui_file *file, int from_tty,
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struct cmd_list_element *c, const char *value)
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{
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fprintf_filtered (file, _("Deprecated remotecache flag is %s.\n"), value);
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}
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static DCACHE *last_cache; /* Used by info dcache. */
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/* Add BLOCK to circular block list BLIST, behind the block at *BLIST.
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*BLIST is not updated (unless it was previously NULL of course).
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This is for the least-recently-allocated list's sake:
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BLIST points to the oldest block.
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??? This makes for poor cache usage of the free list,
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but is it measurable? */
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static void
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append_block (struct dcache_block **blist, struct dcache_block *block)
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{
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if (*blist)
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{
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block->next = *blist;
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block->prev = (*blist)->prev;
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block->prev->next = block;
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(*blist)->prev = block;
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/* We don't update *BLIST here to maintain the invariant that for the
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least-recently-allocated list *BLIST points to the oldest block. */
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}
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else
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{
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block->next = block;
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block->prev = block;
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*blist = block;
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}
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}
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/* Remove BLOCK from circular block list BLIST. */
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static void
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remove_block (struct dcache_block **blist, struct dcache_block *block)
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{
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if (block->next == block)
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{
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*blist = NULL;
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}
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else
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{
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block->next->prev = block->prev;
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block->prev->next = block->next;
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/* If we removed the block *BLIST points to, shift it to the next block
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to maintain the invariant that for the least-recently-allocated list
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*BLIST points to the oldest block. */
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if (*blist == block)
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*blist = block->next;
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}
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}
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/* Iterate over all elements in BLIST, calling FUNC.
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PARAM is passed to FUNC.
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FUNC may remove the block it's passed, but only that block. */
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static void
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for_each_block (struct dcache_block **blist, block_func *func, void *param)
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{
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struct dcache_block *db;
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if (*blist == NULL)
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return;
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db = *blist;
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do
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{
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struct dcache_block *next = db->next;
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func (db, param);
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db = next;
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}
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while (*blist && db != *blist);
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}
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/* BLOCK_FUNC function for dcache_invalidate.
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This doesn't remove the block from the oldest list on purpose.
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dcache_invalidate will do it later. */
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static void
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invalidate_block (struct dcache_block *block, void *param)
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{
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DCACHE *dcache = (DCACHE *) param;
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splay_tree_remove (dcache->tree, (splay_tree_key) block->addr);
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append_block (&dcache->freelist, block);
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}
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/* Free all the data cache blocks, thus discarding all cached data. */
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void
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dcache_invalidate (DCACHE *dcache)
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{
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for_each_block (&dcache->oldest, invalidate_block, dcache);
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dcache->oldest = NULL;
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dcache->size = 0;
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dcache->ptid = null_ptid;
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}
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/* Invalidate the line associated with ADDR. */
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static void
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dcache_invalidate_line (DCACHE *dcache, CORE_ADDR addr)
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{
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struct dcache_block *db = dcache_hit (dcache, addr);
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if (db)
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{
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splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
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remove_block (&dcache->oldest, db);
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append_block (&dcache->freelist, db);
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--dcache->size;
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}
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}
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/* If addr is present in the dcache, return the address of the block
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containing it. Otherwise return NULL. */
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static struct dcache_block *
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dcache_hit (DCACHE *dcache, CORE_ADDR addr)
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{
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struct dcache_block *db;
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splay_tree_node node = splay_tree_lookup (dcache->tree,
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(splay_tree_key) MASK (addr));
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if (!node)
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return NULL;
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db = (struct dcache_block *) node->value;
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db->refs++;
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return db;
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}
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/* Fill a cache line from target memory.
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The result is 1 for success, 0 if the (entire) cache line
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wasn't readable. */
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static int
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dcache_read_line (DCACHE *dcache, struct dcache_block *db)
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{
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CORE_ADDR memaddr;
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gdb_byte *myaddr;
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int len;
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int res;
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int reg_len;
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struct mem_region *region;
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len = LINE_SIZE;
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memaddr = db->addr;
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myaddr = db->data;
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while (len > 0)
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{
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/* Don't overrun if this block is right at the end of the region. */
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region = lookup_mem_region (memaddr);
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if (region->hi == 0 || memaddr + len < region->hi)
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reg_len = len;
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else
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reg_len = region->hi - memaddr;
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/* Skip non-readable regions. The cache attribute can be ignored,
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since we may be loading this for a stack access. */
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if (region->attrib.mode == MEM_WO)
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{
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memaddr += reg_len;
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myaddr += reg_len;
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len -= reg_len;
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continue;
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}
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res = target_read (¤t_target, TARGET_OBJECT_RAW_MEMORY,
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NULL, myaddr, memaddr, reg_len);
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if (res < reg_len)
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return 0;
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memaddr += res;
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myaddr += res;
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len -= res;
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}
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return 1;
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}
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/* Get a free cache block, put or keep it on the valid list,
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and return its address. */
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static struct dcache_block *
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dcache_alloc (DCACHE *dcache, CORE_ADDR addr)
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{
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struct dcache_block *db;
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if (dcache->size >= DCACHE_SIZE)
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{
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/* Evict the least recently allocated line. */
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db = dcache->oldest;
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remove_block (&dcache->oldest, db);
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splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
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}
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else
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{
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db = dcache->freelist;
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if (db)
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remove_block (&dcache->freelist, db);
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else
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db = xmalloc (sizeof (struct dcache_block));
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dcache->size++;
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}
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db->addr = MASK (addr);
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db->refs = 0;
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/* Put DB at the end of the list, it's the newest. */
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append_block (&dcache->oldest, db);
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splay_tree_insert (dcache->tree, (splay_tree_key) db->addr,
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(splay_tree_value) db);
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return db;
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}
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/* Using the data cache DCACHE, store in *PTR the contents of the byte at
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address ADDR in the remote machine.
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Returns 1 for success, 0 for error. */
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static int
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dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, gdb_byte *ptr)
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{
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struct dcache_block *db = dcache_hit (dcache, addr);
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if (!db)
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{
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db = dcache_alloc (dcache, addr);
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if (!dcache_read_line (dcache, db))
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return 0;
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}
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*ptr = db->data[XFORM (addr)];
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return 1;
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}
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/* Write the byte at PTR into ADDR in the data cache.
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The caller is responsible for also promptly writing the data
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through to target memory.
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If addr is not in cache, this function does nothing; writing to
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an area of memory which wasn't present in the cache doesn't cause
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it to be loaded in.
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Always return 1 (meaning success) to simplify dcache_xfer_memory. */
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static int
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dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, gdb_byte *ptr)
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{
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struct dcache_block *db = dcache_hit (dcache, addr);
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if (db)
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db->data[XFORM (addr)] = *ptr;
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return 1;
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}
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static int
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dcache_splay_tree_compare (splay_tree_key a, splay_tree_key b)
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{
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if (a > b)
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return 1;
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else if (a == b)
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return 0;
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else
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return -1;
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}
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/* Allocate and initialize a data cache. */
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DCACHE *
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dcache_init (void)
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{
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DCACHE *dcache;
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dcache = (DCACHE *) xmalloc (sizeof (*dcache));
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dcache->tree = splay_tree_new (dcache_splay_tree_compare,
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NULL,
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NULL);
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dcache->oldest = NULL;
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dcache->freelist = NULL;
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dcache->size = 0;
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dcache->ptid = null_ptid;
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last_cache = dcache;
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return dcache;
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}
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/* BLOCK_FUNC routine for dcache_free. */
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static void
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free_block (struct dcache_block *block, void *param)
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{
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free (block);
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}
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/* Free a data cache. */
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void
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dcache_free (DCACHE *dcache)
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{
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if (last_cache == dcache)
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last_cache = NULL;
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splay_tree_delete (dcache->tree);
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for_each_block (&dcache->oldest, free_block, NULL);
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for_each_block (&dcache->freelist, free_block, NULL);
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xfree (dcache);
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}
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/* Read or write LEN bytes from inferior memory at MEMADDR, transferring
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to or from debugger address MYADDR. Write to inferior if SHOULD_WRITE is
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nonzero.
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Return the number of bytes actually transfered, or -1 if the
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transfer is not supported or otherwise fails. Return of a non-negative
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value less than LEN indicates that no further transfer is possible.
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NOTE: This is different than the to_xfer_partial interface, in which
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positive values less than LEN mean further transfers may be possible. */
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int
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dcache_xfer_memory (struct target_ops *ops, DCACHE *dcache,
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CORE_ADDR memaddr, gdb_byte *myaddr,
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int len, int should_write)
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{
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int i;
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int res;
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int (*xfunc) (DCACHE *dcache, CORE_ADDR addr, gdb_byte *ptr);
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xfunc = should_write ? dcache_poke_byte : dcache_peek_byte;
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/* If this is a different inferior from what we've recorded,
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flush the cache. */
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if (! ptid_equal (inferior_ptid, dcache->ptid))
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{
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dcache_invalidate (dcache);
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dcache->ptid = inferior_ptid;
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}
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/* Do write-through first, so that if it fails, we don't write to
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the cache at all. */
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if (should_write)
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{
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res = target_write (ops, TARGET_OBJECT_RAW_MEMORY,
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NULL, myaddr, memaddr, len);
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if (res <= 0)
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return res;
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/* Update LEN to what was actually written. */
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len = res;
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}
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for (i = 0; i < len; i++)
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{
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if (!xfunc (dcache, memaddr + i, myaddr + i))
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{
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/* That failed. Discard its cache line so we don't have a
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partially read line. */
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dcache_invalidate_line (dcache, memaddr + i);
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/* If we're writing, we still wrote LEN bytes. */
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if (should_write)
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return len;
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else
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return i;
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}
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}
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return len;
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}
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/* FIXME: There would be some benefit to making the cache write-back and
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moving the writeback operation to a higher layer, as it could occur
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after a sequence of smaller writes have been completed (as when a stack
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frame is constructed for an inferior function call). Note that only
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moving it up one level to target_xfer_memory[_partial]() is not
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sufficient since we want to coalesce memory transfers that are
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"logically" connected but not actually a single call to one of the
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memory transfer functions. */
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/* Just update any cache lines which are already present. This is called
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by memory_xfer_partial in cases where the access would otherwise not go
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through the cache. */
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void
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dcache_update (DCACHE *dcache, CORE_ADDR memaddr, gdb_byte *myaddr, int len)
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{
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int i;
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for (i = 0; i < len; i++)
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dcache_poke_byte (dcache, memaddr + i, myaddr + i);
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}
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static void
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dcache_print_line (int index)
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{
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splay_tree_node n;
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struct dcache_block *db;
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int i, j;
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if (!last_cache)
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{
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|
printf_filtered (_("No data cache available.\n"));
|
|
return;
|
|
}
|
|
|
|
n = splay_tree_min (last_cache->tree);
|
|
|
|
for (i = index; i > 0; --i)
|
|
{
|
|
if (!n)
|
|
break;
|
|
n = splay_tree_successor (last_cache->tree, n->key);
|
|
}
|
|
|
|
if (!n)
|
|
{
|
|
printf_filtered (_("No such cache line exists.\n"));
|
|
return;
|
|
}
|
|
|
|
db = (struct dcache_block *) n->value;
|
|
|
|
printf_filtered (_("Line %d: address %s [%d hits]\n"),
|
|
index, paddress (target_gdbarch, db->addr), db->refs);
|
|
|
|
for (j = 0; j < LINE_SIZE; j++)
|
|
{
|
|
printf_filtered ("%02x ", db->data[j]);
|
|
|
|
/* Print a newline every 16 bytes (48 characters). */
|
|
if ((j % 16 == 15) && (j != LINE_SIZE - 1))
|
|
printf_filtered ("\n");
|
|
}
|
|
printf_filtered ("\n");
|
|
}
|
|
|
|
static void
|
|
dcache_info (char *exp, int tty)
|
|
{
|
|
splay_tree_node n;
|
|
int i, refcount;
|
|
|
|
if (exp)
|
|
{
|
|
char *linestart;
|
|
|
|
i = strtol (exp, &linestart, 10);
|
|
if (linestart == exp || i < 0)
|
|
{
|
|
printf_filtered (_("Usage: info dcache [linenumber]\n"));
|
|
return;
|
|
}
|
|
|
|
dcache_print_line (i);
|
|
return;
|
|
}
|
|
|
|
printf_filtered (_("Dcache line width %d, maximum size %d\n"),
|
|
LINE_SIZE, DCACHE_SIZE);
|
|
|
|
if (!last_cache || ptid_equal (last_cache->ptid, null_ptid))
|
|
{
|
|
printf_filtered (_("No data cache available.\n"));
|
|
return;
|
|
}
|
|
|
|
printf_filtered (_("Contains data for %s\n"),
|
|
target_pid_to_str (last_cache->ptid));
|
|
|
|
refcount = 0;
|
|
|
|
n = splay_tree_min (last_cache->tree);
|
|
i = 0;
|
|
|
|
while (n)
|
|
{
|
|
struct dcache_block *db = (struct dcache_block *) n->value;
|
|
|
|
printf_filtered (_("Line %d: address %s [%d hits]\n"),
|
|
i, paddress (target_gdbarch, db->addr), db->refs);
|
|
i++;
|
|
refcount += db->refs;
|
|
|
|
n = splay_tree_successor (last_cache->tree, n->key);
|
|
}
|
|
|
|
printf_filtered (_("Cache state: %d active lines, %d hits\n"), i, refcount);
|
|
}
|
|
|
|
void
|
|
_initialize_dcache (void)
|
|
{
|
|
add_setshow_boolean_cmd ("remotecache", class_support,
|
|
&dcache_enabled_p, _("\
|
|
Set cache use for remote targets."), _("\
|
|
Show cache use for remote targets."), _("\
|
|
This used to enable the data cache for remote targets. The cache\n\
|
|
functionality is now controlled by the memory region system and the\n\
|
|
\"stack-cache\" flag; \"remotecache\" now does nothing and\n\
|
|
exists only for compatibility reasons."),
|
|
NULL,
|
|
show_dcache_enabled_p,
|
|
&setlist, &showlist);
|
|
|
|
add_info ("dcache", dcache_info,
|
|
_("\
|
|
Print information on the dcache performance.\n\
|
|
With no arguments, this command prints the cache configuration and a\n\
|
|
summary of each line in the cache. Use \"info dcache <lineno> to dump\"\n\
|
|
the contents of a given line."));
|
|
}
|