| /* BFD library -- caching of file descriptors. |
| |
| Copyright 1990, 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002, |
| 2003, 2004, 2005, 2007 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 3 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. |
| |
| SUBSECTION |
| Caching functions |
| */ |
| |
| #include "sysdep.h" |
| #include "bfd.h" |
| #include "libbfd.h" |
| #include "libiberty.h" |
| |
| /* In some cases we can optimize cache operation when reopening files. |
| For instance, a flush is entirely unnecessary if the file is already |
| closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using |
| SEEK_SET or SEEK_END need not first seek to the current position. |
| For stat we ignore seek errors, just in case the file has changed |
| while we weren't looking. If it has, then it's possible that the |
| file is shorter and we don't want a seek error to prevent us doing |
| the stat. */ |
| enum cache_flag { |
| CACHE_NORMAL = 0, |
| CACHE_NO_OPEN = 1, |
| CACHE_NO_SEEK = 2, |
| CACHE_NO_SEEK_ERROR = 4 |
| }; |
| |
| /* 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 int open_files; |
| |
| /* 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. */ |
| |
| static bfd *bfd_last_cache = NULL; |
| |
| /* Insert a BFD into the cache. */ |
| |
| static void |
| insert (bfd *abfd) |
| { |
| 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; |
| } |
| } |
| |
| /* Close a BFD and remove it from the cache. */ |
| |
| static bfd_boolean |
| bfd_cache_delete (bfd *abfd) |
| { |
| bfd_boolean ret; |
| |
| 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; |
| } |
| |
| /* 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) |
| { |
| register bfd *kill; |
| |
| if (bfd_last_cache == NULL) |
| kill = NULL; |
| else |
| { |
| for (kill = bfd_last_cache->lru_prev; |
| ! kill->cacheable; |
| kill = kill->lru_prev) |
| { |
| if (kill == bfd_last_cache) |
| { |
| kill = NULL; |
| break; |
| } |
| } |
| } |
| |
| if (kill == NULL) |
| { |
| /* There are no open cacheable BFD's. */ |
| return TRUE; |
| } |
| |
| kill->where = real_ftell ((FILE *) kill->iostream); |
| |
| /* Save the file st_mtime. This is a hack so that gdb can detect when |
| an executable has been deleted and recreated. The only thing that |
| makes this reasonable is that st_mtime doesn't change when a file |
| is unlinked, so saving st_mtime makes BFD's file cache operation |
| a little more transparent for this particular usage pattern. If we |
| hadn't closed the file then we would not have lost the original |
| contents, st_mtime etc. Of course, if something is writing to an |
| existing file, then this is the wrong thing to do. |
| FIXME: gdb should save these times itself on first opening a file, |
| and this hack be removed. */ |
| if (kill->direction == no_direction || kill->direction == read_direction) |
| { |
| bfd_get_mtime (kill); |
| kill->mtime_set = TRUE; |
| } |
| |
| return bfd_cache_delete (kill); |
| } |
| |
| /* 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(x, flag) \ |
| ((x) == bfd_last_cache \ |
| ? (FILE *) (bfd_last_cache->iostream) \ |
| : bfd_cache_lookup_worker (x, flag)) |
| |
| /* 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 return NULL |
| if it is unable to (re)open the @var{abfd}. */ |
| |
| static FILE * |
| bfd_cache_lookup_worker (bfd *abfd, enum cache_flag flag) |
| { |
| bfd *orig_bfd = abfd; |
| if ((abfd->flags & BFD_IN_MEMORY) != 0) |
| abort (); |
| |
| if (abfd->my_archive) |
| abfd = abfd->my_archive; |
| |
| if (abfd->iostream != NULL) |
| { |
| /* Move the file to the start of the cache. */ |
| if (abfd != bfd_last_cache) |
| { |
| snip (abfd); |
| insert (abfd); |
| } |
| return (FILE *) abfd->iostream; |
| } |
| |
| if (flag & CACHE_NO_OPEN) |
| return NULL; |
| |
| if (bfd_open_file (abfd) == NULL) |
| ; |
| else if (!(flag & CACHE_NO_SEEK) |
| && real_fseek ((FILE *) abfd->iostream, abfd->where, SEEK_SET) != 0 |
| && !(flag & CACHE_NO_SEEK_ERROR)) |
| bfd_set_error (bfd_error_system_call); |
| else |
| return (FILE *) abfd->iostream; |
| |
| (*_bfd_error_handler) (_("reopening %B: %s\n"), |
| orig_bfd, bfd_errmsg (bfd_get_error ())); |
| return NULL; |
| } |
| |
| static file_ptr |
| cache_btell (struct bfd *abfd) |
| { |
| FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); |
| if (f == NULL) |
| return abfd->where; |
| return real_ftell (f); |
| } |
| |
| static int |
| cache_bseek (struct bfd *abfd, file_ptr offset, int whence) |
| { |
| FILE *f = bfd_cache_lookup (abfd, whence != SEEK_CUR ? CACHE_NO_SEEK : 0); |
| if (f == NULL) |
| return -1; |
| return real_fseek (f, 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 *f; |
| 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; |
| |
| f = bfd_cache_lookup (abfd, 0); |
| if (f == NULL) |
| return 0; |
| |
| #if defined (__VAX) && defined (VMS) |
| /* Apparently fread on Vax VMS does not keep the record length |
| information. */ |
| nread = read (fileno (f), 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, f); |
| /* 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 (f)) |
| { |
| bfd_set_error (bfd_error_system_call); |
| return -1; |
| } |
| #endif |
| if (nread < nbytes) |
| /* This may or may not be an error, but in case the calling code |
| bails out because of it, set the right error code. */ |
| bfd_set_error (bfd_error_file_truncated); |
| return nread; |
| } |
| |
| static file_ptr |
| cache_bwrite (struct bfd *abfd, const void *where, file_ptr nbytes) |
| { |
| file_ptr nwrite; |
| FILE *f = bfd_cache_lookup (abfd, 0); |
| if (f == NULL) |
| return 0; |
| nwrite = fwrite (where, 1, nbytes, f); |
| if (nwrite < nbytes && ferror (f)) |
| { |
| 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; |
| FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN); |
| if (f == NULL) |
| return 0; |
| sts = fflush (f); |
| if (sts < 0) |
| bfd_set_error (bfd_error_system_call); |
| return sts; |
| } |
| |
| static int |
| cache_bstat (struct bfd *abfd, struct stat *sb) |
| { |
| int sts; |
| FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR); |
| if (f == NULL) |
| return -1; |
| sts = fstat (fileno (f), 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_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); |
| if (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. */ |
| |
| if (open_files >= BFD_CACHE_MAX_OPEN) |
| { |
| if (! close_one ()) |
| return NULL; |
| } |
| |
| switch (abfd->direction) |
| { |
| case read_direction: |
| case no_direction: |
| abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RB); |
| break; |
| case both_direction: |
| case write_direction: |
| if (abfd->opened_once) |
| { |
| abfd->iostream = (PTR) real_fopen (abfd->filename, FOPEN_RUB); |
| if (abfd->iostream == NULL) |
| abfd->iostream = (PTR) real_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) real_fopen (abfd->filename, FOPEN_WUB); |
| abfd->opened_once = TRUE; |
| } |
| break; |
| } |
| |
| if (abfd->iostream == NULL) |
| bfd_set_error (bfd_error_system_call); |
| else |
| { |
| if (! bfd_cache_init (abfd)) |
| return NULL; |
| } |
| |
| return (FILE *) abfd->iostream; |
| } |