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misc: if dlopen() is available, use it to load the libmagic library 

This prevents the libmagic library from being a hard dependency; if
it's not there, we can simply do without it.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
crypto
Theodore Ts'o 2014-09-21 01:25:58 -04:00
parent b291c11f08
commit d2e3c0dc60
3 changed files with 55 additions and 7 deletions
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3
configure vendored
View File

@ -13187,6 +13187,9 @@ done
fi
if test "$ac_cv_lib_dl_dlopen" = yes ; then
MAGIC_LIB=$DLOPEN_LIB
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for optreset" >&5
$as_echo_n "checking for optreset... " >&6; }

3
configure.in
View File

@ -1157,6 +1157,9 @@ dnl See if libmagic exists
dnl
AC_CHECK_LIB(magic, magic_file, [MAGIC_LIB=-lmagic
AC_CHECK_HEADERS([magic.h])])
if test "$ac_cv_lib_dl_dlopen" = yes ; then
MAGIC_LIB=$DLOPEN_LIB
fi
AC_SUBST(MAGIC_LIB)
dnl
dnl See if optreset exists

56
misc/plausible.c
View File

@ -36,6 +36,48 @@
#include "nls-enable.h"
#include "blkid/blkid.h"
static magic_t (*dl_magic_open)(int);
static const char *(*dl_magic_file)(magic_t, const char *);
static int (*dl_magic_load)(magic_t, const char *);
static void (*dl_magic_close)(magic_t);
#ifdef HAVE_MAGIC_H
#ifdef HAVE_DLOPEN
#include <dlfcn.h>
static void *magic_handle;
static int magic_library_available(void)
{
if (!magic_handle) {
magic_handle = dlopen("libmagic.so.1", RTLD_NOW);
if (!magic_handle)
return 0;
dl_magic_open = dlsym(magic_handle, "magic_open");
dl_magic_file = dlsym(magic_handle, "magic_file");
dl_magic_load = dlsym(magic_handle, "magic_load");
dl_magic_close = dlsym(magic_handle, "magic_close");
}
if (!dl_magic_open || !dl_magic_file ||
!dl_magic_load || !dl_magic_close)
return 0;
return 1;
}
#else
static int magic_library_available(void)
{
dl_magic_open = magic_open;
dl_magic_file = magic_file;
dl_magic_load = magic_load;
dl_magic_close = magic_close;
return 1;
}
#endif
#endif
static void print_ext2_info(const char *device)
{
@ -198,20 +240,20 @@ int check_plausibility(const char *device, int flags, int *ret_is_dev)
}
#ifdef HAVE_MAGIC_H
if (flags & CHECK_FS_EXIST) {
if ((flags & CHECK_FS_EXIST) && magic_library_available()) {
const char *msg;
magic_t mag;
mag = magic_open(MAGIC_RAW | MAGIC_SYMLINK | MAGIC_DEVICES |
MAGIC_ERROR | MAGIC_NO_CHECK_ELF |
MAGIC_NO_CHECK_COMPRESS);
magic_load(mag, NULL);
mag = dl_magic_open(MAGIC_RAW | MAGIC_SYMLINK | MAGIC_DEVICES |
MAGIC_ERROR | MAGIC_NO_CHECK_ELF |
MAGIC_NO_CHECK_COMPRESS);
dl_magic_load(mag, NULL);
msg = magic_file(mag, device);
msg = dl_magic_file(mag, device);
if (msg && strcmp(msg, "data") && strcmp(msg, "empty"))
printf(_("%s contains a `%s'\n"), device, msg);
magic_close(mag);
dl_magic_close(mag);
return 0;
}
#endif