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