534 lines
14 KiB
C
534 lines
14 KiB
C
/* BFD library -- caching of file descriptors.
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Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002,
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2003, 2004, 2005, 2007 Free Software Foundation, Inc.
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Hacked by Steve Chamberlain of Cygnus Support (steve@cygnus.com).
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This file is part of BFD, the Binary File Descriptor library.
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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, write to the Free Software
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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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MA 02110-1301, USA. */
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/*
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SECTION
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File caching
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The file caching mechanism is embedded within BFD and allows
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the application to open as many BFDs as it wants without
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regard to the underlying operating system's file descriptor
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limit (often as low as 20 open files). The module in
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<<cache.c>> maintains a least recently used list of
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<<BFD_CACHE_MAX_OPEN>> files, and exports the name
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<<bfd_cache_lookup>>, which runs around and makes sure that
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the required BFD is open. If not, then it chooses a file to
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close, closes it and opens the one wanted, returning its file
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handle.
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SUBSECTION
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Caching functions
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*/
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#include "sysdep.h"
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#include "bfd.h"
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#include "libbfd.h"
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#include "libiberty.h"
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/* In some cases we can optimize cache operation when reopening files.
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For instance, a flush is entirely unnecessary if the file is already
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closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using
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SEEK_SET or SEEK_END need not first seek to the current position.
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For stat we ignore seek errors, just in case the file has changed
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while we weren't looking. If it has, then it's possible that the
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file is shorter and we don't want a seek error to prevent us doing
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the stat. */
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enum cache_flag {
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CACHE_NORMAL = 0,
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CACHE_NO_OPEN = 1,
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CACHE_NO_SEEK = 2,
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CACHE_NO_SEEK_ERROR = 4
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};
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/* The maximum number of files which the cache will keep open at
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one time. */
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#define BFD_CACHE_MAX_OPEN 10
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/* The number of BFD files we have open. */
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static int open_files;
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/* Zero, or a pointer to the topmost BFD on the chain. This is
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used by the <<bfd_cache_lookup>> macro in @file{libbfd.h} to
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determine when it can avoid a function call. */
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static bfd *bfd_last_cache = NULL;
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/* Insert a BFD into the cache. */
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static void
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insert (bfd *abfd)
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{
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if (bfd_last_cache == NULL)
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{
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abfd->lru_next = abfd;
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abfd->lru_prev = abfd;
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}
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else
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{
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abfd->lru_next = bfd_last_cache;
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abfd->lru_prev = bfd_last_cache->lru_prev;
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abfd->lru_prev->lru_next = abfd;
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abfd->lru_next->lru_prev = abfd;
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}
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bfd_last_cache = abfd;
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}
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/* Remove a BFD from the cache. */
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static void
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snip (bfd *abfd)
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{
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abfd->lru_prev->lru_next = abfd->lru_next;
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abfd->lru_next->lru_prev = abfd->lru_prev;
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if (abfd == bfd_last_cache)
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{
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bfd_last_cache = abfd->lru_next;
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if (abfd == bfd_last_cache)
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bfd_last_cache = NULL;
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}
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}
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/* Close a BFD and remove it from the cache. */
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static bfd_boolean
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bfd_cache_delete (bfd *abfd)
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{
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bfd_boolean ret;
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if (fclose ((FILE *) abfd->iostream) == 0)
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ret = TRUE;
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else
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{
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ret = FALSE;
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bfd_set_error (bfd_error_system_call);
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}
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snip (abfd);
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abfd->iostream = NULL;
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--open_files;
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return ret;
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}
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/* We need to open a new file, and the cache is full. Find the least
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recently used cacheable BFD and close it. */
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static bfd_boolean
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close_one (void)
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{
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register bfd *kill;
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if (bfd_last_cache == NULL)
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kill = NULL;
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else
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{
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for (kill = bfd_last_cache->lru_prev;
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! kill->cacheable;
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kill = kill->lru_prev)
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{
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if (kill == bfd_last_cache)
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{
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kill = NULL;
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break;
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}
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}
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}
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if (kill == NULL)
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{
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/* There are no open cacheable BFD's. */
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return TRUE;
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}
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kill->where = real_ftell ((FILE *) kill->iostream);
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/* Save the file st_mtime. This is a hack so that gdb can detect when
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an executable has been deleted and recreated. The only thing that
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makes this reasonable is that st_mtime doesn't change when a file
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is unlinked, so saving st_mtime makes BFD's file cache operation
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a little more transparent for this particular usage pattern. If we
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hadn't closed the file then we would not have lost the original
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contents, st_mtime etc. Of course, if something is writing to an
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existing file, then this is the wrong thing to do.
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FIXME: gdb should save these times itself on first opening a file,
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and this hack be removed. */
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if (kill->direction == no_direction || kill->direction == read_direction)
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{
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bfd_get_mtime (kill);
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kill->mtime_set = TRUE;
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}
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return bfd_cache_delete (kill);
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}
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/* Check to see if the required BFD is the same as the last one
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looked up. If so, then it can use the stream in the BFD with
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impunity, since it can't have changed since the last lookup;
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otherwise, it has to perform the complicated lookup function. */
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#define bfd_cache_lookup(x, flag) \
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((x) == bfd_last_cache \
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? (FILE *) (bfd_last_cache->iostream) \
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: bfd_cache_lookup_worker (x, flag))
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/* Called when the macro <<bfd_cache_lookup>> fails to find a
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quick answer. Find a file descriptor for @var{abfd}. If
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necessary, it open it. If there are already more than
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<<BFD_CACHE_MAX_OPEN>> files open, it tries to close one first, to
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avoid running out of file descriptors. It will return NULL
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if it is unable to (re)open the @var{abfd}. */
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static FILE *
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bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag)
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{
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bfd *orig_bfd = abfd;
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if ((abfd->flags & BFD_IN_MEMORY) != 0)
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abort ();
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if (abfd->my_archive)
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abfd = abfd->my_archive;
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if (abfd->iostream != NULL)
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{
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/* Move the file to the start of the cache. */
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if (abfd != bfd_last_cache)
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{
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snip (abfd);
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insert (abfd);
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}
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return (FILE *) abfd->iostream;
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}
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if (flag & CACHE_NO_OPEN)
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return NULL;
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if (bfd_open_file (abfd) == NULL)
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;
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else if (!(flag & CACHE_NO_SEEK)
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&& real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0
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&& !(flag & CACHE_NO_SEEK_ERROR))
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bfd_set_error (bfd_error_system_call);
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else
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return (FILE *) abfd->iostream;
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(*_bfd_error_handler) (_("reopening %B: %s\n"),
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orig_bfd, bfd_errmsg (bfd_get_error ()));
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return NULL;
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}
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static file_ptr
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cache_btell (struct bfd *abfd)
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{
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FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
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if (f == NULL)
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return abfd->where;
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return real_ftell (f);
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}
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static int
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cache_bseek (struct bfd *abfd, file_ptr offset, int whence)
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{
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FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : 0);
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if (f == NULL)
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return -1;
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return real_fseek (f, offset, whence);
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}
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/* Note that archive entries don't have streams; they share their parent's.
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This allows someone to play with the iostream behind BFD's back.
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Also, note that the origin pointer points to the beginning of a file's
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contents (0 for non-archive elements). For archive entries this is the
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first octet in the file, NOT the beginning of the archive header. */
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static file_ptr
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cache_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
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{
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FILE *f;
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file_ptr nread;
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/* FIXME - this looks like an optimization, but it's really to cover
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up for a feature of some OSs (not solaris - sigh) that
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ld/pe-dll.c takes advantage of (apparently) when it creates BFDs
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internally and tries to link against them. BFD seems to be smart
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enough to realize there are no symbol records in the "file" that
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doesn't exist but attempts to read them anyway. On Solaris,
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attempting to read zero bytes from a NULL file results in a core
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dump, but on other platforms it just returns zero bytes read.
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This makes it to something reasonable. - DJ */
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if (nbytes == 0)
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return 0;
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f = bfd_cache_lookup (abfd, 0);
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if (f == NULL)
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return 0;
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#if defined (__VAX) && defined (VMS)
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/* Apparently fread on Vax VMS does not keep the record length
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information. */
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nread = read (fileno (f), buf, nbytes);
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/* Set bfd_error if we did not read as much data as we expected. If
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the read failed due to an error set the bfd_error_system_call,
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else set bfd_error_file_truncated. */
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if (nread == (file_ptr)-1)
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{
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bfd_set_error (bfd_error_system_call);
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return -1;
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}
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#else
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nread = fread (buf, 1, nbytes, f);
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/* Set bfd_error if we did not read as much data as we expected. If
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the read failed due to an error set the bfd_error_system_call,
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else set bfd_error_file_truncated. */
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if (nread < nbytes && ferror (f))
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{
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bfd_set_error (bfd_error_system_call);
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return -1;
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}
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#endif
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return nread;
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}
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static file_ptr
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cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes)
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{
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file_ptr nwrite;
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FILE *f = bfd_cache_lookup (abfd, 0);
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if (f == NULL)
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return 0;
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nwrite = fwrite (where, 1, nbytes, f);
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if (nwrite < nbytes && ferror (f))
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{
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bfd_set_error (bfd_error_system_call);
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return -1;
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}
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return nwrite;
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}
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static int
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cache_bclose (struct bfd *abfd)
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{
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return bfd_cache_close (abfd);
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}
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static int
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cache_bflush (struct bfd *abfd)
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{
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int sts;
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FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
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if (f == NULL)
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return 0;
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sts = fflush (f);
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if (sts < 0)
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bfd_set_error (bfd_error_system_call);
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return sts;
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}
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static int
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cache_bstat (struct bfd *abfd, struct stat *sb)
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{
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int sts;
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FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
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if (f == NULL)
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return -1;
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sts = fstat (fileno (f), sb);
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if (sts < 0)
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bfd_set_error (bfd_error_system_call);
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return sts;
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}
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static const struct bfd_iovec cache_iovec = {
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&cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
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&cache_bclose, &cache_bflush, &cache_bstat
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};
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/*
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INTERNAL_FUNCTION
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bfd_cache_init
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SYNOPSIS
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bfd_boolean bfd_cache_init (bfd *abfd);
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DESCRIPTION
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Add a newly opened BFD to the cache.
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*/
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bfd_boolean
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bfd_cache_init (bfd *abfd)
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{
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BFD_ASSERT (abfd->iostream != NULL);
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if (open_files >= BFD_CACHE_MAX_OPEN)
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{
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if (! close_one ())
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return FALSE;
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}
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abfd->iovec = &cache_iovec;
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insert (abfd);
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++open_files;
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return TRUE;
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}
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/*
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INTERNAL_FUNCTION
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bfd_cache_close
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SYNOPSIS
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bfd_boolean bfd_cache_close (bfd *abfd);
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DESCRIPTION
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Remove the BFD @var{abfd} from the cache. If the attached file is open,
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then close it too.
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RETURNS
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<<FALSE>> is returned if closing the file fails, <<TRUE>> is
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returned if all is well.
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*/
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bfd_boolean
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bfd_cache_close (bfd *abfd)
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{
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if (abfd->iovec != &cache_iovec)
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return TRUE;
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if (abfd->iostream == NULL)
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/* Previously closed. */
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return TRUE;
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return bfd_cache_delete (abfd);
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}
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/*
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FUNCTION
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bfd_cache_close_all
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SYNOPSIS
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bfd_boolean bfd_cache_close_all (void);
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DESCRIPTION
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Remove all BFDs from the cache. If the attached file is open,
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then close it too.
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RETURNS
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<<FALSE>> is returned if closing one of the file fails, <<TRUE>> is
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returned if all is well.
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*/
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bfd_boolean
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bfd_cache_close_all ()
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{
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bfd_boolean ret = TRUE;
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while (bfd_last_cache != NULL)
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ret &= bfd_cache_close (bfd_last_cache);
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return ret;
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}
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/*
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INTERNAL_FUNCTION
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bfd_open_file
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SYNOPSIS
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FILE* bfd_open_file (bfd *abfd);
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DESCRIPTION
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Call the OS to open a file for @var{abfd}. Return the <<FILE *>>
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(possibly <<NULL>>) that results from this operation. Set up the
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BFD so that future accesses know the file is open. If the <<FILE *>>
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returned is <<NULL>>, then it won't have been put in the
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cache, so it won't have to be removed from it.
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*/
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FILE *
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bfd_open_file (bfd *abfd)
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{
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abfd->cacheable = TRUE; /* Allow it to be closed later. */
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if (open_files >= BFD_CACHE_MAX_OPEN)
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{
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if (! close_one ())
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return NULL;
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}
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switch (abfd->direction)
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{
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case read_direction:
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case no_direction:
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abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB);
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break;
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case both_direction:
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case write_direction:
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if (abfd->opened_once)
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{
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abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB);
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if (abfd->iostream == NULL)
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abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
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}
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else
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{
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/* Create the file.
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Some operating systems won't let us overwrite a running
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binary. For them, we want to unlink the file first.
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However, gcc 2.95 will create temporary files using
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O_EXCL and tight permissions to prevent other users from
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substituting other .o files during the compilation. gcc
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will then tell the assembler to use the newly created
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file as an output file. If we unlink the file here, we
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open a brief window when another user could still
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substitute a file.
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So we unlink the output file if and only if it has
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non-zero size. */
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#ifndef __MSDOS__
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/* Don't do this for MSDOS: it doesn't care about overwriting
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a running binary, but if this file is already open by
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another BFD, we will be in deep trouble if we delete an
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open file. In fact, objdump does just that if invoked with
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the --info option. */
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struct stat s;
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if (stat (abfd->filename, &s) == 0 && s.st_size != 0)
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unlink_if_ordinary (abfd->filename);
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#endif
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abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_WUB);
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abfd->opened_once = TRUE;
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}
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break;
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}
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if (abfd->iostream == NULL)
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bfd_set_error (bfd_error_system_call);
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else
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{
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if (! bfd_cache_init (abfd))
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return NULL;
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}
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return (FILE *) abfd->iostream;
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}
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