/* BFD library -- caching of file descriptors.
Copyright (C) 1990-2015 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"
#include "bfd_stdint.h"
#ifdef HAVE_MMAP
#include <sys/mman.h>
#endif
/* 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. When needed call bfd_cache_max_open to initialize. */
static int max_open_files = 0;
/* Set max_open_files, if not already set, to 12.5% of the allowed open
file descriptors, but at least 10, and return the value. */
static int
bfd_cache_max_open (void)
{
max_open_files = 16;
return max_open_files;
}
/* 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 *to_kill;
if (bfd_last_cache == NULL)
to_kill = NULL;
else
{
for (to_kill = bfd_last_cache->lru_prev;
! to_kill->cacheable;
to_kill = to_kill->lru_prev)
{
if (to_kill == bfd_last_cache)
{
to_kill = NULL;
break;
}
}
}
if (to_kill == NULL)
{
/* There are no open cacheable BFD's. */
return TRUE;
}
to_kill->where = real_ftell ((FILE *) to_kill->iostream);
return bfd_cache_delete (to_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)
while (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 : CACHE_NORMAL);
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_1 (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, CACHE_NORMAL);
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 nread;
}
#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 nread;
}
#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_bread (struct bfd *abfd, void *buf, file_ptr nbytes)
{
file_ptr nread = 0;
/* Some filesystems are unable to handle reads that are too large
(for instance, NetApp shares with oplocks turned off). To avoid
hitting this limitation, we read the buffer in chunks of 8MB max. */
while (nread < nbytes)
{
const file_ptr max_chunk_size = 0x800000;
file_ptr chunk_size = nbytes - nread;
file_ptr chunk_nread;
if (chunk_size > max_chunk_size)
chunk_size = max_chunk_size;
chunk_nread = cache_bread_1 (abfd, (char *) buf + nread, chunk_size);
/* Update the nread count.
We just have to be careful of the case when cache_bread_1 returns
a negative count: If this is our first read, then set nread to
that negative count in order to return that negative value to the
caller. Otherwise, don't add it to our total count, or we would
end up returning a smaller number of bytes read than we actually
did. */
if (nread == 0 || chunk_nread > 0)
nread += chunk_nread;
if (chunk_nread < chunk_size)
break;
}
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, CACHE_NORMAL);
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) - 1;
}
static int
cache_bflush (struct bfd *abfd)
{
int sts;
FILE *f = bfd_cache_lookup (abfd, CACHE_NO_OPEN);
if (f == NULL)
return 0;
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 void *
cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
void *addr ATTRIBUTE_UNUSED,
bfd_size_type len ATTRIBUTE_UNUSED,
int prot ATTRIBUTE_UNUSED,
int flags ATTRIBUTE_UNUSED,
file_ptr offset ATTRIBUTE_UNUSED,
void **map_addr ATTRIBUTE_UNUSED,
bfd_size_type *map_len ATTRIBUTE_UNUSED)
{
void *ret = (void *) -1;
if ((abfd->flags & BFD_IN_MEMORY) != 0)
#ifdef HAVE_MMAP
else
{
static uintptr_t pagesize_m1;
FILE *f;
file_ptr pg_offset;
bfd_size_type pg_len;
f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
if (f == NULL)
return ret;
if (pagesize_m1 == 0)
pagesize_m1 = getpagesize () - 1;
/* Handle archive members. */
if (abfd->my_archive != NULL)
offset += abfd->origin;
/* Align. */
pg_offset = offset & ~pagesize_m1;
pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;
ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
if (ret == (void *) -1)
bfd_set_error (bfd_error_system_call);
else
{
*map_addr = ret;
*map_len = pg_len;
ret = (char *) ret + (offset & pagesize_m1);
}
}
#endif
return ret;
}
static const struct bfd_iovec cache_iovec =
{
&cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
&cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
};
/*
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 = real_fopen (abfd->filename, FOPEN_RB);
break;
case both_direction:
case write_direction:
if (abfd->opened_once)
{
abfd->iostream = real_fopen (abfd->filename, FOPEN_RUB);
if (abfd->iostream == NULL)
abfd->iostream = 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 = 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;
}