Linker.c

/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 2000-2004
 *
 * RTS Object Linker
 *
 * ---------------------------------------------------------------------------*/

#if 0
#include "PosixSource.h"
#endif

/* Linux needs _GNU_SOURCE to get RTLD_DEFAULT from <dlfcn.h> and
   MREMAP_MAYMOVE from <sys/mman.h>.
 */
#ifdef __linux__
#define _GNU_SOURCE
#endif

#include "Rts.h"
#include "RtsFlags.h"
#include "HsFFI.h"
#include "Hash.h"
#include "Linker.h"
#include "LinkerInternals.h"
#include "RtsUtils.h"
#include "Schedule.h"
#include "Sparks.h"
#include "RtsGlobals.h"
#include "Timer.h"
#include "Trace.h"

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include <stdlib.h>
#include <string.h>

#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif

#if defined(HAVE_DLFCN_H)
#include <dlfcn.h>
#endif

#if defined(cygwin32_HOST_OS)
#ifdef HAVE_DIRENT_H
#include <dirent.h>
#endif

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <regex.h>
#include <sys/fcntl.h>
#include <sys/termios.h>
#include <sys/utime.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#endif

#if defined(ia64_HOST_ARCH) || defined(linux_HOST_OS) || defined(freebsd_HOST_OS) || defined(netbsd_HOST_OS) || defined(openbsd_HOST_OS)
#define USE_MMAP
#include <fcntl.h>
#include <sys/mman.h>

#if defined(linux_HOST_OS) || defined(freebsd_HOST_OS) || defined(netbsd_HOST_OS) || defined(openbsd_HOST_OS)
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#endif

#endif

#if defined(linux_HOST_OS) || defined(solaris2_HOST_OS) || defined(freebsd_HOST_OS) || defined(netbsd_HOST_OS) || defined(openbsd_HOST_OS)
#  define OBJFORMAT_ELF
#elif defined(cygwin32_HOST_OS) || defined (mingw32_HOST_OS)
#  define OBJFORMAT_PEi386
#  include <windows.h>
#  include <math.h>
#elif defined(darwin_HOST_OS)
#  define OBJFORMAT_MACHO
#  include <mach-o/loader.h>
#  include <mach-o/nlist.h>
#  include <mach-o/reloc.h>
#if !defined(HAVE_DLFCN_H)
#  include <mach-o/dyld.h>
#endif
#if defined(powerpc_HOST_ARCH)
#  include <mach-o/ppc/reloc.h>
#endif
#if defined(x86_64_HOST_ARCH)
#  include <mach-o/x86_64/reloc.h>
#endif
#endif

/* Hash table mapping symbol names to Symbol */
static /*Str*/HashTable *symhash;

/* Hash table mapping symbol names to StgStablePtr */
static /*Str*/HashTable *stablehash;

/* List of currently loaded objects */
ObjectCode *objects = NULL;	/* initially empty */

#if defined(OBJFORMAT_ELF)
static int ocVerifyImage_ELF    ( ObjectCode* oc );
static int ocGetNames_ELF       ( ObjectCode* oc );
static int ocResolve_ELF        ( ObjectCode* oc );
#if defined(powerpc_HOST_ARCH) || defined(x86_64_HOST_ARCH)
static int ocAllocateSymbolExtras_ELF ( ObjectCode* oc );
#endif
#elif defined(OBJFORMAT_PEi386)
static int ocVerifyImage_PEi386 ( ObjectCode* oc );
static int ocGetNames_PEi386    ( ObjectCode* oc );
static int ocResolve_PEi386     ( ObjectCode* oc );
static void *lookupSymbolInDLLs ( unsigned char *lbl );
static void zapTrailingAtSign   ( unsigned char *sym );
#elif defined(OBJFORMAT_MACHO)
static int ocVerifyImage_MachO    ( ObjectCode* oc );
static int ocGetNames_MachO       ( ObjectCode* oc );
static int ocResolve_MachO        ( ObjectCode* oc );

static int machoGetMisalignment( FILE * );
#if defined(powerpc_HOST_ARCH) || defined(x86_64_HOST_ARCH)
static int ocAllocateSymbolExtras_MachO ( ObjectCode* oc );
#endif
#ifdef powerpc_HOST_ARCH
static void machoInitSymbolsWithoutUnderscore( void );
#endif
#endif

/* on x86_64 we have a problem with relocating symbol references in
 * code that was compiled without -fPIC.  By default, the small memory
 * model is used, which assumes that symbol references can fit in a
 * 32-bit slot.  The system dynamic linker makes this work for
 * references to shared libraries by either (a) allocating a jump
 * table slot for code references, or (b) moving the symbol at load
 * time (and copying its contents, if necessary) for data references.
 *
 * We unfortunately can't tell whether symbol references are to code
 * or data.  So for now we assume they are code (the vast majority
 * are), and allocate jump-table slots.  Unfortunately this will
 * SILENTLY generate crashing code for data references.  This hack is
 * enabled by X86_64_ELF_NONPIC_HACK.
 * 
 * One workaround is to use shared Haskell libraries.  This is
 * coming.  Another workaround is to keep the static libraries but
 * compile them with -fPIC, because that will generate PIC references
 * to data which can be relocated.  The PIC code is still too green to
 * do this systematically, though.
 *
 * See bug #781
 * See thread http://www.haskell.org/pipermail/cvs-ghc/2007-September/038458.html
 *
 * Naming Scheme for Symbol Macros
 *
 * SymI_*: symbol is internal to the RTS. It resides in an object
 *         file/library that is statically.
 * SymE_*: symbol is external to the RTS library. It might be linked
 *         dynamically.
 *
 * Sym*_HasProto  : the symbol prototype is imported in an include file
 *                  or defined explicitly
 * Sym*_NeedsProto: the symbol is undefined and we add a dummy
 *                  default proto extern void sym(void);
 */
#define X86_64_ELF_NONPIC_HACK 1

/* Link objects into the lower 2Gb on x86_64.  GHC assumes the
 * small memory model on this architecture (see gcc docs,
 * -mcmodel=small).
 *
 * MAP_32BIT not available on OpenBSD/amd64
 */
#if defined(x86_64_HOST_ARCH) && defined(MAP_32BIT)
#define TRY_MAP_32BIT MAP_32BIT
#else
#define TRY_MAP_32BIT 0
#endif

/*
 * Due to the small memory model (see above), on x86_64 we have to map
 * all our non-PIC object files into the low 2Gb of the address space
 * (why 2Gb and not 4Gb?  Because all addresses must be reachable
 * using a 32-bit signed PC-relative offset). On Linux we can do this
 * using the MAP_32BIT flag to mmap(), however on other OSs
 * (e.g. *BSD, see #2063, and also on Linux inside Xen, see #2512), we
 * can't do this.  So on these systems, we have to pick a base address
 * in the low 2Gb of the address space and try to allocate memory from
 * there.
 *
 * We pick a default address based on the OS, but also make this
 * configurable via an RTS flag (+RTS -xm)
 */
#if defined(x86_64_HOST_ARCH)

#if defined(MAP_32BIT)
// Try to use MAP_32BIT
#define MMAP_32BIT_BASE_DEFAULT 0
#else
// A guess: 1Gb.
#define MMAP_32BIT_BASE_DEFAULT 0x40000000
#endif

static void *mmap_32bit_base = (void *)MMAP_32BIT_BASE_DEFAULT;
#endif

/* MAP_ANONYMOUS is MAP_ANON on some systems, e.g. OpenBSD */
#if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
#define MAP_ANONYMOUS MAP_ANON
#endif

/* -----------------------------------------------------------------------------
 * Built-in symbols from the RTS
 */

typedef struct _RtsSymbolVal {
    char   *lbl;
    void   *addr;
} RtsSymbolVal;

#define Maybe_Stable_Names      SymI_HasProto(mkWeakzh_fast)			\
      				SymI_HasProto(mkWeakForeignEnvzh_fast)		\
      				SymI_HasProto(makeStableNamezh_fast)		\
      				SymI_HasProto(finalizzeWeakzh_fast)

#if !defined (mingw32_HOST_OS)
#define RTS_POSIX_ONLY_SYMBOLS                  \
      SymI_HasProto(shutdownHaskellAndSignal)	\
      SymI_NeedsProto(lockFile)                 \
      SymI_NeedsProto(unlockFile)               \
      SymI_HasProto(signal_handlers)		\
      SymI_HasProto(stg_sig_install)		\
      SymI_NeedsProto(nocldstop)
#endif

#if defined (cygwin32_HOST_OS)
#define RTS_MINGW_ONLY_SYMBOLS /**/
/* Don't have the ability to read import libs / archives, so
 * we have to stupidly list a lot of what libcygwin.a
 * exports; sigh.
 */
#define RTS_CYGWIN_ONLY_SYMBOLS                          \
      SymI_HasProto(regfree)                             \
      SymI_HasProto(regexec)                             \
      SymI_HasProto(regerror)                            \
      SymI_HasProto(regcomp)                             \
      SymI_HasProto(__errno)                             \
      SymI_HasProto(access)                              \
      SymI_HasProto(chmod)                               \
      SymI_HasProto(chdir)                               \
      SymI_HasProto(close)                               \
      SymI_HasProto(creat)                               \
      SymI_HasProto(dup)                                 \
      SymI_HasProto(dup2)                                \
      SymI_HasProto(fstat)                               \
      SymI_HasProto(fcntl)                               \
      SymI_HasProto(getcwd)                              \
      SymI_HasProto(getenv)                              \
      SymI_HasProto(lseek)                               \
      SymI_HasProto(open)                                \
      SymI_HasProto(fpathconf)                           \
      SymI_HasProto(pathconf)                            \
      SymI_HasProto(stat)                                \
      SymI_HasProto(pow)                                 \
      SymI_HasProto(tanh)                                \
      SymI_HasProto(cosh)                                \
      SymI_HasProto(sinh)                                \
      SymI_HasProto(atan)                                \
      SymI_HasProto(acos)                                \
      SymI_HasProto(asin)                                \
      SymI_HasProto(tan)                                 \
      SymI_HasProto(cos)                                 \
      SymI_HasProto(sin)                                 \
      SymI_HasProto(exp)                                 \
      SymI_HasProto(log)                                 \
      SymI_HasProto(sqrt)                                \
      SymI_HasProto(localtime_r)                         \
      SymI_HasProto(gmtime_r)                            \
      SymI_HasProto(mktime)                              \
      SymI_NeedsProto(_imp___tzname)                     \
      SymI_HasProto(gettimeofday)                        \
      SymI_HasProto(timezone)                            \
      SymI_HasProto(tcgetattr)                           \
      SymI_HasProto(tcsetattr)                           \
      SymI_HasProto(memcpy)                              \
      SymI_HasProto(memmove)                             \
      SymI_HasProto(realloc)                             \
      SymI_HasProto(malloc)                              \
      SymI_HasProto(free)                                \
      SymI_HasProto(fork)                                \
      SymI_HasProto(lstat)                               \
      SymI_HasProto(isatty)                              \
      SymI_HasProto(mkdir)                               \
      SymI_HasProto(opendir)                             \
      SymI_HasProto(readdir)                             \
      SymI_HasProto(rewinddir)                           \
      SymI_HasProto(closedir)                            \
      SymI_HasProto(link)                                \
      SymI_HasProto(mkfifo)                              \
      SymI_HasProto(pipe)                                \
      SymI_HasProto(read)                                \
      SymI_HasProto(rename)                              \
      SymI_HasProto(rmdir)                               \
      SymI_HasProto(select)                              \
      SymI_HasProto(system)                              \
      SymI_HasProto(write)                               \
      SymI_HasProto(strcmp)                              \
      SymI_HasProto(strcpy)                              \
      SymI_HasProto(strncpy)                             \
      SymI_HasProto(strerror)                            \
      SymI_HasProto(sigaddset)                           \
      SymI_HasProto(sigemptyset)                         \
      SymI_HasProto(sigprocmask)                         \
      SymI_HasProto(umask)                               \
      SymI_HasProto(uname)                               \
      SymI_HasProto(unlink)                              \
      SymI_HasProto(utime)                               \
      SymI_HasProto(waitpid)

#elif !defined(mingw32_HOST_OS)
#define RTS_MINGW_ONLY_SYMBOLS /**/
#define RTS_CYGWIN_ONLY_SYMBOLS /**/
#else /* defined(mingw32_HOST_OS) */
#define RTS_POSIX_ONLY_SYMBOLS  /**/
#define RTS_CYGWIN_ONLY_SYMBOLS /**/

/* Extra syms gen'ed by mingw-2's gcc-3.2: */
#if __GNUC__>=3
#define RTS_MINGW_EXTRA_SYMS                    \
      SymI_NeedsProto(_imp____mb_cur_max)       \
      SymI_NeedsProto(_imp___pctype)
#else
#define RTS_MINGW_EXTRA_SYMS
#endif

#if HAVE_GETTIMEOFDAY
#define RTS_MINGW_GETTIMEOFDAY_SYM SymI_NeedsProto(gettimeofday)
#else
#define RTS_MINGW_GETTIMEOFDAY_SYM /**/
#endif

/* These are statically linked from the mingw libraries into the ghc
   executable, so we have to employ this hack. */
#define RTS_MINGW_ONLY_SYMBOLS                           \
      SymI_HasProto(asyncReadzh_fast)			 \
      SymI_HasProto(asyncWritezh_fast)			 \
      SymI_HasProto(asyncDoProczh_fast)			 \
      SymI_HasProto(memset)                              \
      SymI_HasProto(inet_ntoa)                           \
      SymI_HasProto(inet_addr)                           \
      SymI_HasProto(htonl)                               \
      SymI_HasProto(recvfrom)                            \
      SymI_HasProto(listen)                              \
      SymI_HasProto(bind)                                \
      SymI_HasProto(shutdown)                            \
      SymI_HasProto(connect)                             \
      SymI_HasProto(htons)                               \
      SymI_HasProto(ntohs)                               \
      SymI_HasProto(getservbyname)                       \
      SymI_HasProto(getservbyport)                       \
      SymI_HasProto(getprotobynumber)                    \
      SymI_HasProto(getprotobyname)                      \
      SymI_HasProto(gethostbyname)                       \
      SymI_HasProto(gethostbyaddr)                       \
      SymI_HasProto(gethostname)                         \
      SymI_HasProto(strcpy)                              \
      SymI_HasProto(strncpy)                             \
      SymI_HasProto(abort)                               \
      SymI_NeedsProto(_alloca)                           \
      SymI_NeedsProto(isxdigit)                          \
      SymI_NeedsProto(isupper)                           \
      SymI_NeedsProto(ispunct)                           \
      SymI_NeedsProto(islower)                           \
      SymI_NeedsProto(isspace)                           \
      SymI_NeedsProto(isprint)                           \
      SymI_NeedsProto(isdigit)                           \
      SymI_NeedsProto(iscntrl)                           \
      SymI_NeedsProto(isalpha)                           \
      SymI_NeedsProto(isalnum)                           \
      SymI_HasProto(strcmp)                              \
      SymI_HasProto(memmove)                             \
      SymI_HasProto(realloc)                             \
      SymI_HasProto(malloc)                              \
      SymI_HasProto(pow)                                 \
      SymI_HasProto(tanh)                                \
      SymI_HasProto(cosh)                                \
      SymI_HasProto(sinh)                                \
      SymI_HasProto(atan)                                \
      SymI_HasProto(acos)                                \
      SymI_HasProto(asin)                                \
      SymI_HasProto(tan)                                 \
      SymI_HasProto(cos)                                 \
      SymI_HasProto(sin)                                 \
      SymI_HasProto(exp)                                 \
      SymI_HasProto(log)                                 \
      SymI_HasProto(sqrt)                                \
      SymI_HasProto(powf)                                \
      SymI_HasProto(tanhf)                               \
      SymI_HasProto(coshf)                               \
      SymI_HasProto(sinhf)                               \
      SymI_HasProto(atanf)                               \
      SymI_HasProto(acosf)                               \
      SymI_HasProto(asinf)                               \
      SymI_HasProto(tanf)                                \
      SymI_HasProto(cosf)                                \
      SymI_HasProto(sinf)                                \
      SymI_HasProto(expf)                                \
      SymI_HasProto(logf)                                \
      SymI_HasProto(sqrtf)                               \
      SymI_HasProto(memcpy)                              \
      SymI_HasProto(rts_InstallConsoleEvent)             \
      SymI_HasProto(rts_ConsoleHandlerDone)              \
      SymI_NeedsProto(mktime)                            \
      SymI_NeedsProto(_imp___timezone)                   \
      SymI_NeedsProto(_imp___tzname)                     \
      SymI_NeedsProto(_imp__tzname)                      \
      SymI_NeedsProto(_imp___iob)                        \
      SymI_NeedsProto(_imp___osver)                      \
      SymI_NeedsProto(localtime)                         \
      SymI_NeedsProto(gmtime)                            \
      SymI_NeedsProto(opendir)                           \
      SymI_NeedsProto(readdir)                           \
      SymI_NeedsProto(rewinddir)                         \
      RTS_MINGW_EXTRA_SYMS                               \
      RTS_MINGW_GETTIMEOFDAY_SYM		         \
      SymI_NeedsProto(closedir)
#endif

#if defined(darwin_TARGET_OS) && HAVE_PRINTF_LDBLSTUB
#define RTS_DARWIN_ONLY_SYMBOLS			            \
     SymI_NeedsProto(asprintf$LDBLStub)                     \
     SymI_NeedsProto(err$LDBLStub)                          \
     SymI_NeedsProto(errc$LDBLStub)                         \
     SymI_NeedsProto(errx$LDBLStub)                         \
     SymI_NeedsProto(fprintf$LDBLStub)                      \
     SymI_NeedsProto(fscanf$LDBLStub)                       \
     SymI_NeedsProto(fwprintf$LDBLStub)                     \
     SymI_NeedsProto(fwscanf$LDBLStub)                      \
     SymI_NeedsProto(printf$LDBLStub)                       \
     SymI_NeedsProto(scanf$LDBLStub)                        \
     SymI_NeedsProto(snprintf$LDBLStub)                     \
     SymI_NeedsProto(sprintf$LDBLStub)                      \
     SymI_NeedsProto(sscanf$LDBLStub)                       \
     SymI_NeedsProto(strtold$LDBLStub)                      \
     SymI_NeedsProto(swprintf$LDBLStub)                     \
     SymI_NeedsProto(swscanf$LDBLStub)                      \
     SymI_NeedsProto(syslog$LDBLStub)                       \
     SymI_NeedsProto(vasprintf$LDBLStub)                    \
     SymI_NeedsProto(verr$LDBLStub)                         \
     SymI_NeedsProto(verrc$LDBLStub)                        \
     SymI_NeedsProto(verrx$LDBLStub)                        \
     SymI_NeedsProto(vfprintf$LDBLStub)                     \
     SymI_NeedsProto(vfscanf$LDBLStub)                      \
     SymI_NeedsProto(vfwprintf$LDBLStub)                    \
     SymI_NeedsProto(vfwscanf$LDBLStub)                     \
     SymI_NeedsProto(vprintf$LDBLStub)                      \
     SymI_NeedsProto(vscanf$LDBLStub)                       \
     SymI_NeedsProto(vsnprintf$LDBLStub)                    \
     SymI_NeedsProto(vsprintf$LDBLStub)                     \
     SymI_NeedsProto(vsscanf$LDBLStub)                      \
     SymI_NeedsProto(vswprintf$LDBLStub)                    \
     SymI_NeedsProto(vswscanf$LDBLStub)                     \
     SymI_NeedsProto(vsyslog$LDBLStub)                      \
     SymI_NeedsProto(vwarn$LDBLStub)                        \
     SymI_NeedsProto(vwarnc$LDBLStub)                       \
     SymI_NeedsProto(vwarnx$LDBLStub)                       \
     SymI_NeedsProto(vwprintf$LDBLStub)                     \
     SymI_NeedsProto(vwscanf$LDBLStub)                      \
     SymI_NeedsProto(warn$LDBLStub)                         \
     SymI_NeedsProto(warnc$LDBLStub)                        \
     SymI_NeedsProto(warnx$LDBLStub)                        \
     SymI_NeedsProto(wcstold$LDBLStub)                      \
     SymI_NeedsProto(wprintf$LDBLStub)                      \
     SymI_NeedsProto(wscanf$LDBLStub)
#else
#define RTS_DARWIN_ONLY_SYMBOLS
#endif

#ifndef SMP
# define MAIN_CAP_SYM SymI_HasProto(MainCapability)
#else
# define MAIN_CAP_SYM
#endif

#if !defined(mingw32_HOST_OS)
#define RTS_USER_SIGNALS_SYMBOLS \
   SymI_HasProto(setIOManagerPipe) \
   SymI_NeedsProto(blockUserSignals) \
   SymI_NeedsProto(unblockUserSignals)
#else
#define RTS_USER_SIGNALS_SYMBOLS     \
   SymI_HasProto(sendIOManagerEvent) \
   SymI_HasProto(readIOManagerEvent) \
   SymI_HasProto(getIOManagerEvent)  \
   SymI_HasProto(console_handler)
#endif

#define RTS_LIBFFI_SYMBOLS                                  \
     SymE_NeedsProto(ffi_prep_cif)                          \
     SymE_NeedsProto(ffi_call)                              \
     SymE_NeedsProto(ffi_type_void)                         \
     SymE_NeedsProto(ffi_type_float)                        \
     SymE_NeedsProto(ffi_type_double)                       \
     SymE_NeedsProto(ffi_type_sint64)                       \
     SymE_NeedsProto(ffi_type_uint64)                       \
     SymE_NeedsProto(ffi_type_sint32)                       \
     SymE_NeedsProto(ffi_type_uint32)                       \
     SymE_NeedsProto(ffi_type_sint16)                       \
     SymE_NeedsProto(ffi_type_uint16)                       \
     SymE_NeedsProto(ffi_type_sint8)                        \
     SymE_NeedsProto(ffi_type_uint8)                        \
     SymE_NeedsProto(ffi_type_pointer)

#ifdef TABLES_NEXT_TO_CODE
#define RTS_RET_SYMBOLS /* nothing */
#else
#define RTS_RET_SYMBOLS 		                \
      SymI_HasProto(stg_enter_ret)			\
      SymI_HasProto(stg_gc_fun_ret)			\
      SymI_HasProto(stg_ap_v_ret)			\
      SymI_HasProto(stg_ap_f_ret)			\
      SymI_HasProto(stg_ap_d_ret)			\
      SymI_HasProto(stg_ap_l_ret)			\
      SymI_HasProto(stg_ap_n_ret)			\
      SymI_HasProto(stg_ap_p_ret)			\
      SymI_HasProto(stg_ap_pv_ret)			\
      SymI_HasProto(stg_ap_pp_ret)			\
      SymI_HasProto(stg_ap_ppv_ret)			\
      SymI_HasProto(stg_ap_ppp_ret)			\
      SymI_HasProto(stg_ap_pppv_ret)			\
      SymI_HasProto(stg_ap_pppp_ret)			\
      SymI_HasProto(stg_ap_ppppp_ret)			\
      SymI_HasProto(stg_ap_pppppp_ret)
#endif

/* On Windows, we link libgmp.a statically into libHSrts.dll */
#ifdef mingw32_HOST_OS
#define GMP_SYMS				        \
      SymI_HasProto(__gmpz_cmp)				\
      SymI_HasProto(__gmpz_cmp_si)			\
      SymI_HasProto(__gmpz_cmp_ui)			\
      SymI_HasProto(__gmpz_get_si)			\
      SymI_HasProto(__gmpz_get_ui)
#else
#define GMP_SYMS				        \
      SymE_HasProto(__gmpz_cmp)			        \
      SymE_HasProto(__gmpz_cmp_si)			\
      SymE_HasProto(__gmpz_cmp_ui)			\
      SymE_HasProto(__gmpz_get_si)			\
      SymE_HasProto(__gmpz_get_ui)
#endif

#define RTS_SYMBOLS				        \
      Maybe_Stable_Names			        \
      SymI_HasProto(StgReturn)				\
      SymI_HasProto(stg_enter_info)			\
      SymI_HasProto(stg_gc_void_info)			\
      SymI_HasProto(__stg_gc_enter_1)			\
      SymI_HasProto(stg_gc_noregs)			\
      SymI_HasProto(stg_gc_unpt_r1_info)		\
      SymI_HasProto(stg_gc_unpt_r1)			\
      SymI_HasProto(stg_gc_unbx_r1_info)		\
      SymI_HasProto(stg_gc_unbx_r1)			\
      SymI_HasProto(stg_gc_f1_info)			\
      SymI_HasProto(stg_gc_f1)				\
      SymI_HasProto(stg_gc_d1_info)			\
      SymI_HasProto(stg_gc_d1)				\
      SymI_HasProto(stg_gc_l1_info)			\
      SymI_HasProto(stg_gc_l1)				\
      SymI_HasProto(__stg_gc_fun)			\
      SymI_HasProto(stg_gc_fun_info)			\
      SymI_HasProto(stg_gc_gen)				\
      SymI_HasProto(stg_gc_gen_info)			\
      SymI_HasProto(stg_gc_gen_hp)			\
      SymI_HasProto(stg_gc_ut)				\
      SymI_HasProto(stg_gen_yield)			\
      SymI_HasProto(stg_yield_noregs)			\
      SymI_HasProto(stg_yield_to_interpreter)		\
      SymI_HasProto(stg_gen_block)			\
      SymI_HasProto(stg_block_noregs)			\
      SymI_HasProto(stg_block_1)			\
      SymI_HasProto(stg_block_takemvar)			\
      SymI_HasProto(stg_block_putmvar)			\
      MAIN_CAP_SYM                                      \
      SymI_HasProto(MallocFailHook)			\
      SymI_HasProto(OnExitHook)				\
      SymI_HasProto(OutOfHeapHook)			\
      SymI_HasProto(StackOverflowHook)			\
      SymI_HasProto(__encodeDouble)			\
      SymI_HasProto(__encodeFloat)			\
      SymI_HasProto(addDLL)               		\
      GMP_SYMS					        \
      SymI_HasProto(__int_encodeDouble)			\
      SymI_HasProto(__word_encodeDouble)		\
      SymI_HasProto(__2Int_encodeDouble)		\
      SymI_HasProto(__int_encodeFloat)			\
      SymI_HasProto(__word_encodeFloat)			\
      SymI_HasProto(andIntegerzh_fast)			\
      SymI_HasProto(atomicallyzh_fast)			\
      SymI_HasProto(barf)				\
      SymI_HasProto(debugBelch)				\
      SymI_HasProto(errorBelch)				\
      SymI_HasProto(sysErrorBelch)                      \
      SymI_HasProto(asyncExceptionsBlockedzh_fast)	\
      SymI_HasProto(blockAsyncExceptionszh_fast)	\
      SymI_HasProto(catchzh_fast)			\
      SymI_HasProto(catchRetryzh_fast)			\
      SymI_HasProto(catchSTMzh_fast)			\
      SymI_HasProto(checkzh_fast)                       \
      SymI_HasProto(closure_flags)                      \
      SymI_HasProto(cmp_thread)				\
      SymI_HasProto(cmpIntegerzh_fast)	        	\
      SymI_HasProto(cmpIntegerIntzh_fast)	      	\
      SymI_HasProto(complementIntegerzh_fast)		\
      SymI_HasProto(createAdjustor)			\
      SymI_HasProto(decodeDoublezh_fast)		\
      SymI_HasProto(decodeDoublezu2Intzh_fast)		\
      SymI_HasProto(decodeFloatzuIntzh_fast)		\
      SymI_HasProto(defaultsHook)			\
      SymI_HasProto(delayzh_fast)			\
      SymI_HasProto(deRefWeakzh_fast)			\
      SymI_HasProto(deRefStablePtrzh_fast)		\
      SymI_HasProto(dirty_MUT_VAR)			\
      SymI_HasProto(divExactIntegerzh_fast)		\
      SymI_HasProto(divModIntegerzh_fast)		\
      SymI_HasProto(forkzh_fast)			\
      SymI_HasProto(forkOnzh_fast)			\
      SymI_HasProto(forkProcess)			\
      SymI_HasProto(forkOS_createThread)		\
      SymI_HasProto(freeHaskellFunctionPtr)		\
      SymI_HasProto(freeStablePtr)		        \
      SymI_HasProto(getOrSetTypeableStore)		\
      SymI_HasProto(getOrSetSignalHandlerStore)		\
      SymI_HasProto(gcdIntegerzh_fast)			\
      SymI_HasProto(gcdIntegerIntzh_fast)		\
      SymI_HasProto(gcdIntzh_fast)			\
      SymI_HasProto(genSymZh)				\
      SymI_HasProto(genericRaise)			\
      SymI_HasProto(getProgArgv)			\
      SymI_HasProto(getFullProgArgv)			\
      SymI_HasProto(getStablePtr)			\
      SymI_HasProto(hs_init)				\
      SymI_HasProto(hs_exit)				\
      SymI_HasProto(hs_set_argv)			\
      SymI_HasProto(hs_add_root)			\
      SymI_HasProto(hs_perform_gc)			\
      SymI_HasProto(hs_free_stable_ptr)			\
      SymI_HasProto(hs_free_fun_ptr)			\
      SymI_HasProto(hs_hpc_rootModule)		        \
      SymI_HasProto(hs_hpc_module)		        \
      SymI_HasProto(initLinker)				\
      SymI_HasProto(unpackClosurezh_fast)               \
      SymI_HasProto(getApStackValzh_fast)               \
      SymI_HasProto(getSparkzh_fast)                    \
      SymI_HasProto(int2Integerzh_fast)			\
      SymI_HasProto(integer2Intzh_fast)			\
      SymI_HasProto(integer2Wordzh_fast)		\
      SymI_HasProto(isCurrentThreadBoundzh_fast)	\
      SymI_HasProto(isDoubleDenormalized)		\
      SymI_HasProto(isDoubleInfinite)			\
      SymI_HasProto(isDoubleNaN)			\
      SymI_HasProto(isDoubleNegativeZero)		\
      SymI_HasProto(isEmptyMVarzh_fast)			\
      SymI_HasProto(isFloatDenormalized)		\
      SymI_HasProto(isFloatInfinite)			\
      SymI_HasProto(isFloatNaN)				\
      SymI_HasProto(isFloatNegativeZero)		\
      SymI_HasProto(killThreadzh_fast)			\
      SymI_HasProto(loadObj)          			\
      SymI_HasProto(insertStableSymbol) 		\
      SymI_HasProto(insertSymbol)     			\
      SymI_HasProto(lookupSymbol)     			\
      SymI_HasProto(makeStablePtrzh_fast)		\
      SymI_HasProto(minusIntegerzh_fast)		\
      SymI_HasProto(mkApUpd0zh_fast)			\
      SymI_HasProto(myThreadIdzh_fast)			\
      SymI_HasProto(labelThreadzh_fast)                 \
      SymI_HasProto(newArrayzh_fast)			\
      SymI_HasProto(newBCOzh_fast)			\
      SymI_HasProto(newByteArrayzh_fast)		\
      SymI_HasProto_redirect(newCAF, newDynCAF)		\
      SymI_HasProto(newMVarzh_fast)			\
      SymI_HasProto(newMutVarzh_fast)			\
      SymI_HasProto(newTVarzh_fast)			\
      SymI_HasProto(noDuplicatezh_fast)			\
      SymI_HasProto(atomicModifyMutVarzh_fast)		\
      SymI_HasProto(newPinnedByteArrayzh_fast)		\
      SymI_HasProto(newAlignedPinnedByteArrayzh_fast)	\
      SymI_HasProto(newSpark)				\
      SymI_HasProto(orIntegerzh_fast)			\
      SymI_HasProto(performGC)				\
      SymI_HasProto(performMajorGC)			\
      SymI_HasProto(plusIntegerzh_fast)			\
      SymI_HasProto(prog_argc)				\
      SymI_HasProto(prog_argv)				\
      SymI_HasProto(putMVarzh_fast)			\
      SymI_HasProto(quotIntegerzh_fast)			\
      SymI_HasProto(quotRemIntegerzh_fast)		\
      SymI_HasProto(raisezh_fast)			\
      SymI_HasProto(raiseIOzh_fast)			\
      SymI_HasProto(readTVarzh_fast)			\
      SymI_HasProto(readTVarIOzh_fast)			\
      SymI_HasProto(remIntegerzh_fast)			\
      SymI_HasProto(resetNonBlockingFd)			\
      SymI_HasProto(resumeThread)			\
      SymI_HasProto(resolveObjs)                        \
      SymI_HasProto(retryzh_fast)                       \
      SymI_HasProto(rts_apply)				\
      SymI_HasProto(rts_checkSchedStatus)		\
      SymI_HasProto(rts_eval)				\
      SymI_HasProto(rts_evalIO)				\
      SymI_HasProto(rts_evalLazyIO)			\
      SymI_HasProto(rts_evalStableIO)			\
      SymI_HasProto(rts_eval_)				\
      SymI_HasProto(rts_getBool)			\
      SymI_HasProto(rts_getChar)			\
      SymI_HasProto(rts_getDouble)			\
      SymI_HasProto(rts_getFloat)			\
      SymI_HasProto(rts_getInt)				\
      SymI_HasProto(rts_getInt8)			\
      SymI_HasProto(rts_getInt16)			\
      SymI_HasProto(rts_getInt32)			\
      SymI_HasProto(rts_getInt64)			\
      SymI_HasProto(rts_getPtr)				\
      SymI_HasProto(rts_getFunPtr)			\
      SymI_HasProto(rts_getStablePtr)			\
      SymI_HasProto(rts_getThreadId)			\
      SymI_HasProto(rts_getWord)			\
      SymI_HasProto(rts_getWord8)			\
      SymI_HasProto(rts_getWord16)			\
      SymI_HasProto(rts_getWord32)			\
      SymI_HasProto(rts_getWord64)			\
      SymI_HasProto(rts_lock)				\
      SymI_HasProto(rts_mkBool)				\
      SymI_HasProto(rts_mkChar)				\
      SymI_HasProto(rts_mkDouble)			\
      SymI_HasProto(rts_mkFloat)			\
      SymI_HasProto(rts_mkInt)				\
      SymI_HasProto(rts_mkInt8)				\
      SymI_HasProto(rts_mkInt16)			\
      SymI_HasProto(rts_mkInt32)			\
      SymI_HasProto(rts_mkInt64)			\
      SymI_HasProto(rts_mkPtr)				\
      SymI_HasProto(rts_mkFunPtr)			\
      SymI_HasProto(rts_mkStablePtr)			\
      SymI_HasProto(rts_mkString)			\
      SymI_HasProto(rts_mkWord)				\
      SymI_HasProto(rts_mkWord8)			\
      SymI_HasProto(rts_mkWord16)			\
      SymI_HasProto(rts_mkWord32)			\
      SymI_HasProto(rts_mkWord64)			\
      SymI_HasProto(rts_unlock)				\
      SymI_HasProto(rtsSupportsBoundThreads)		\
      SymI_HasProto(__hscore_get_saved_termios)		\
      SymI_HasProto(__hscore_set_saved_termios)		\
      SymI_HasProto(setProgArgv)			\
      SymI_HasProto(startupHaskell)			\
      SymI_HasProto(shutdownHaskell)			\
      SymI_HasProto(shutdownHaskellAndExit)		\
      SymI_HasProto(stable_ptr_table)			\
      SymI_HasProto(stackOverflow)			\
      SymI_HasProto(stg_CAF_BLACKHOLE_info)		\
      SymI_HasProto(__stg_EAGER_BLACKHOLE_info)		\
      SymI_HasProto(awakenBlockedQueue)			\
      SymI_HasProto(startTimer)                         \
      SymI_HasProto(stg_CHARLIKE_closure)		\
      SymI_HasProto(stg_MVAR_CLEAN_info)		\
      SymI_HasProto(stg_MVAR_DIRTY_info)		\
      SymI_HasProto(stg_IND_STATIC_info)		\
      SymI_HasProto(stg_INTLIKE_closure)		\
      SymI_HasProto(stg_MUT_ARR_PTRS_DIRTY_info)	\
      SymI_HasProto(stg_MUT_ARR_PTRS_FROZEN_info)	\
      SymI_HasProto(stg_MUT_ARR_PTRS_FROZEN0_info)	\
      SymI_HasProto(stg_WEAK_info)                      \
      SymI_HasProto(stg_ap_v_info)			\
      SymI_HasProto(stg_ap_f_info)			\
      SymI_HasProto(stg_ap_d_info)			\
      SymI_HasProto(stg_ap_l_info)			\
      SymI_HasProto(stg_ap_n_info)			\
      SymI_HasProto(stg_ap_p_info)			\
      SymI_HasProto(stg_ap_pv_info)			\
      SymI_HasProto(stg_ap_pp_info)			\
      SymI_HasProto(stg_ap_ppv_info)			\
      SymI_HasProto(stg_ap_ppp_info)			\
      SymI_HasProto(stg_ap_pppv_info)			\
      SymI_HasProto(stg_ap_pppp_info)			\
      SymI_HasProto(stg_ap_ppppp_info)			\
      SymI_HasProto(stg_ap_pppppp_info)			\
      SymI_HasProto(stg_ap_0_fast)			\
      SymI_HasProto(stg_ap_v_fast)			\
      SymI_HasProto(stg_ap_f_fast)			\
      SymI_HasProto(stg_ap_d_fast)			\
      SymI_HasProto(stg_ap_l_fast)			\
      SymI_HasProto(stg_ap_n_fast)			\
      SymI_HasProto(stg_ap_p_fast)			\
      SymI_HasProto(stg_ap_pv_fast)			\
      SymI_HasProto(stg_ap_pp_fast)			\
      SymI_HasProto(stg_ap_ppv_fast)			\
      SymI_HasProto(stg_ap_ppp_fast)			\
      SymI_HasProto(stg_ap_pppv_fast)			\
      SymI_HasProto(stg_ap_pppp_fast)			\
      SymI_HasProto(stg_ap_ppppp_fast)			\
      SymI_HasProto(stg_ap_pppppp_fast)			\
      SymI_HasProto(stg_ap_1_upd_info)			\
      SymI_HasProto(stg_ap_2_upd_info)			\
      SymI_HasProto(stg_ap_3_upd_info)			\
      SymI_HasProto(stg_ap_4_upd_info)			\
      SymI_HasProto(stg_ap_5_upd_info)			\
      SymI_HasProto(stg_ap_6_upd_info)			\
      SymI_HasProto(stg_ap_7_upd_info)			\
      SymI_HasProto(stg_exit)				\
      SymI_HasProto(stg_sel_0_upd_info)			\
      SymI_HasProto(stg_sel_10_upd_info)		\
      SymI_HasProto(stg_sel_11_upd_info)		\
      SymI_HasProto(stg_sel_12_upd_info)		\
      SymI_HasProto(stg_sel_13_upd_info)		\
      SymI_HasProto(stg_sel_14_upd_info)		\
      SymI_HasProto(stg_sel_15_upd_info)		\
      SymI_HasProto(stg_sel_1_upd_info)			\
      SymI_HasProto(stg_sel_2_upd_info)			\
      SymI_HasProto(stg_sel_3_upd_info)			\
      SymI_HasProto(stg_sel_4_upd_info)			\
      SymI_HasProto(stg_sel_5_upd_info)			\
      SymI_HasProto(stg_sel_6_upd_info)			\
      SymI_HasProto(stg_sel_7_upd_info)			\
      SymI_HasProto(stg_sel_8_upd_info)			\
      SymI_HasProto(stg_sel_9_upd_info)			\
      SymI_HasProto(stg_upd_frame_info)			\
      SymI_HasProto(suspendThread)			\
      SymI_HasProto(takeMVarzh_fast)			\
      SymI_HasProto(threadStatuszh_fast)		\
      SymI_HasProto(timesIntegerzh_fast)		\
      SymI_HasProto(tryPutMVarzh_fast)			\
      SymI_HasProto(tryTakeMVarzh_fast)			\
      SymI_HasProto(unblockAsyncExceptionszh_fast)	\
      SymI_HasProto(unloadObj)                          \
      SymI_HasProto(unsafeThawArrayzh_fast)		\
      SymI_HasProto(waitReadzh_fast)			\
      SymI_HasProto(waitWritezh_fast)			\
      SymI_HasProto(word2Integerzh_fast)		\
      SymI_HasProto(writeTVarzh_fast)			\
      SymI_HasProto(xorIntegerzh_fast)			\
      SymI_HasProto(yieldzh_fast)                       \
      SymI_NeedsProto(stg_interp_constr_entry)          \
      SymI_HasProto(allocateExec)	                \
      SymI_HasProto(freeExec)		                \
      SymI_HasProto(getAllocations)                     \
      SymI_HasProto(revertCAFs)                         \
      SymI_HasProto(RtsFlags)                           \
      SymI_NeedsProto(rts_breakpoint_io_action)		\
      SymI_NeedsProto(rts_stop_next_breakpoint)		\
      SymI_NeedsProto(rts_stop_on_exception)		\
      SymI_HasProto(stopTimer)				\
      SymI_HasProto(n_capabilities)			\
      SymI_HasProto(traceCcszh_fast)                    \
      RTS_USER_SIGNALS_SYMBOLS

#ifdef SUPPORT_LONG_LONGS
#define RTS_LONG_LONG_SYMS			        \
      SymI_HasProto(int64ToIntegerzh_fast)		\
      SymI_HasProto(word64ToIntegerzh_fast)
#else
#define RTS_LONG_LONG_SYMS /* nothing */
#endif

// 64-bit support functions in libgcc.a
#if defined(__GNUC__) && SIZEOF_VOID_P <= 4
#define RTS_LIBGCC_SYMBOLS			       \
      SymI_NeedsProto(__divdi3)                        \
      SymI_NeedsProto(__udivdi3)                       \
      SymI_NeedsProto(__moddi3)                        \
      SymI_NeedsProto(__umoddi3)		       \
      SymI_NeedsProto(__muldi3)			       \
      SymI_NeedsProto(__ashldi3)		       \
      SymI_NeedsProto(__ashrdi3)		       \
      SymI_NeedsProto(__lshrdi3)		       \
      SymI_NeedsProto(__eprintf)
#elif defined(ia64_HOST_ARCH)
#define RTS_LIBGCC_SYMBOLS			        \
      SymI_NeedsProto(__divdi3)				\
      SymI_NeedsProto(__udivdi3)                        \
      SymI_NeedsProto(__moddi3)				\
      SymI_NeedsProto(__umoddi3)			\
      SymI_NeedsProto(__divsf3)				\
      SymI_NeedsProto(__divdf3)
#else
#define RTS_LIBGCC_SYMBOLS
#endif

#if defined(darwin_HOST_OS) && defined(powerpc_HOST_ARCH)
      // Symbols that don't have a leading underscore
      // on Mac OS X. They have to receive special treatment,
      // see machoInitSymbolsWithoutUnderscore()
#define RTS_MACHO_NOUNDERLINE_SYMBOLS		\
      SymI_NeedsProto(saveFP)				\
      SymI_NeedsProto(restFP)
#endif

/* entirely bogus claims about types of these symbols */
#define SymI_NeedsProto(vvv)  extern void vvv(void);
#if defined(__PIC__) && defined(mingw32_TARGET_OS)
#define SymE_HasProto(vvv)    SymE_HasProto(vvv);
#define SymE_NeedsProto(vvv)    extern void _imp__ ## vvv (void);
#else
#define SymE_NeedsProto(vvv)  SymI_NeedsProto(vvv);
#define SymE_HasProto(vvv)    SymI_HasProto(vvv)
#endif
#define SymI_HasProto(vvv) /**/
#define SymI_HasProto_redirect(vvv,xxx) /**/
RTS_SYMBOLS
RTS_RET_SYMBOLS
RTS_LONG_LONG_SYMS
RTS_POSIX_ONLY_SYMBOLS
RTS_MINGW_ONLY_SYMBOLS
RTS_CYGWIN_ONLY_SYMBOLS
RTS_DARWIN_ONLY_SYMBOLS
RTS_LIBGCC_SYMBOLS
RTS_LIBFFI_SYMBOLS
#undef SymI_NeedsProto
#undef SymI_HasProto
#undef SymI_HasProto_redirect
#undef SymE_HasProto
#undef SymE_NeedsProto

#ifdef LEADING_UNDERSCORE
#define MAYBE_LEADING_UNDERSCORE_STR(s) ("_" s)
#else
#define MAYBE_LEADING_UNDERSCORE_STR(s) (s)
#endif

#define SymI_HasProto(vvv) { MAYBE_LEADING_UNDERSCORE_STR(#vvv), \
                    (void*)(&(vvv)) },
#define SymE_HasProto(vvv) { MAYBE_LEADING_UNDERSCORE_STR(#vvv), \
	    (void*)DLL_IMPORT_DATA_REF(vvv) },

#define SymI_NeedsProto(vvv) SymI_HasProto(vvv)
#define SymE_NeedsProto(vvv) SymE_HasProto(vvv)

// SymI_HasProto_redirect allows us to redirect references to one symbol to
// another symbol.  See newCAF/newDynCAF for an example.
#define SymI_HasProto_redirect(vvv,xxx) \
    { MAYBE_LEADING_UNDERSCORE_STR(#vvv), \
      (void*)(&(xxx)) },

static RtsSymbolVal rtsSyms[] = {
      RTS_SYMBOLS
      RTS_RET_SYMBOLS
      RTS_LONG_LONG_SYMS
      RTS_POSIX_ONLY_SYMBOLS
      RTS_MINGW_ONLY_SYMBOLS
      RTS_CYGWIN_ONLY_SYMBOLS
      RTS_DARWIN_ONLY_SYMBOLS
      RTS_LIBGCC_SYMBOLS
      RTS_LIBFFI_SYMBOLS
#if defined(darwin_HOST_OS) && defined(i386_HOST_ARCH)
      // dyld stub code contains references to this,
      // but it should never be called because we treat
      // lazy pointers as nonlazy.
      { "dyld_stub_binding_helper", (void*)0xDEADBEEF },
#endif
      { 0, 0 } /* sentinel */
};



/* -----------------------------------------------------------------------------
 * Insert symbols into hash tables, checking for duplicates.
 */

static void ghciInsertStrHashTable ( char* obj_name,
                                     HashTable *table,
                                     char* key,
                                     void *data
				   )
{
   if (lookupHashTable(table, (StgWord)key) == NULL)
   {
      insertStrHashTable(table, (StgWord)key, data);
      return;
   }
   debugBelch(
      "\n\n"
      "GHCi runtime linker: fatal error: I found a duplicate definition for symbol\n"
      "   %s\n"
      "whilst processing object file\n"
      "   %s\n"
      "This could be caused by:\n"
      "   * Loading two different object files which export the same symbol\n"
      "   * Specifying the same object file twice on the GHCi command line\n"
      "   * An incorrect `package.conf' entry, causing some object to be\n"
      "     loaded twice.\n"
      "GHCi cannot safely continue in this situation.  Exiting now.  Sorry.\n"
      "\n",
      (char*)key,
      obj_name
   );
   exit(1);
}
/* -----------------------------------------------------------------------------
 * initialize the object linker
 */


static int linker_init_done = 0 ;

#if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
static void *dl_prog_handle;
#endif

void
initLinker( void )
{
    RtsSymbolVal *sym;

    /* Make initLinker idempotent, so we can call it
       before evey relevant operation; that means we
       don't need to initialise the linker separately */
    if (linker_init_done == 1) { return; } else {
      linker_init_done = 1;
    }

    stablehash = allocStrHashTable();
    symhash = allocStrHashTable();

    /* populate the symbol table with stuff from the RTS */
    for (sym = rtsSyms; sym->lbl != NULL; sym++) {
	ghciInsertStrHashTable("(GHCi built-in symbols)",
                               symhash, sym->lbl, sym->addr);
    }
#   if defined(OBJFORMAT_MACHO) && defined(powerpc_HOST_ARCH)
    machoInitSymbolsWithoutUnderscore();
#   endif

#   if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
#   if defined(RTLD_DEFAULT)
    dl_prog_handle = RTLD_DEFAULT;
#   else
    dl_prog_handle = dlopen(NULL, RTLD_LAZY);
#   endif /* RTLD_DEFAULT */
#   endif

#if defined(x86_64_HOST_ARCH)
    if (RtsFlags.MiscFlags.linkerMemBase != 0) {
        // User-override for mmap_32bit_base
        mmap_32bit_base = (void*)RtsFlags.MiscFlags.linkerMemBase;
    }
#endif

#if defined(mingw32_HOST_OS)
    /*
     * These two libraries cause problems when added to the static link,
     * but are necessary for resolving symbols in GHCi, hence we load
     * them manually here.
     */
    addDLL("msvcrt");
    addDLL("kernel32");
#endif
}

/* -----------------------------------------------------------------------------
 *                  Loading DLL or .so dynamic libraries
 * -----------------------------------------------------------------------------
 *
 * Add a DLL from which symbols may be found.  In the ELF case, just
 * do RTLD_GLOBAL-style add, so no further messing around needs to
 * happen in order that symbols in the loaded .so are findable --
 * lookupSymbol() will subsequently see them by dlsym on the program's
 * dl-handle.  Returns NULL if success, otherwise ptr to an err msg.
 *
 * In the PEi386 case, open the DLLs and put handles to them in a
 * linked list.  When looking for a symbol, try all handles in the
 * list.  This means that we need to load even DLLs that are guaranteed
 * to be in the ghc.exe image already, just so we can get a handle
 * to give to loadSymbol, so that we can find the symbols.  For such
 * libraries, the LoadLibrary call should be a no-op except for returning
 * the handle.
 *
 */

#if defined(OBJFORMAT_PEi386)
/* A record for storing handles into DLLs. */

typedef
   struct _OpenedDLL {
      char*              name;
      struct _OpenedDLL* next;
      HINSTANCE instance;
   }
   OpenedDLL;

/* A list thereof. */
static OpenedDLL* opened_dlls = NULL;
#endif

const char *
addDLL( char *dll_name )
{
#  if defined(OBJFORMAT_ELF) || defined(OBJFORMAT_MACHO)
   /* ------------------- ELF DLL loader ------------------- */
   void *hdl;
   const char *errmsg;

   initLinker();

   // omitted: RTLD_NOW
   // see http://www.haskell.org/pipermail/cvs-ghc/2007-September/038570.html
   hdl= dlopen(dll_name, RTLD_LAZY | RTLD_GLOBAL);

   if (hdl == NULL) {
      /* dlopen failed; return a ptr to the error msg. */
      errmsg = dlerror();
      if (errmsg == NULL) errmsg = "addDLL: unknown error";
      return errmsg;
   } else {
      return NULL;
   }
   /*NOTREACHED*/

#  elif defined(OBJFORMAT_PEi386)
   /* ------------------- Win32 DLL loader ------------------- */

   char*      buf;
   OpenedDLL* o_dll;
   HINSTANCE  instance;

   initLinker();

   /* debugBelch("\naddDLL; dll_name = `%s'\n", dll_name); */

   /* See if we've already got it, and ignore if so. */
   for (o_dll = opened_dlls; o_dll != NULL; o_dll = o_dll->next) {
      if (0 == strcmp(o_dll->name, dll_name))
         return NULL;
   }

   /* The file name has no suffix (yet) so that we can try
      both foo.dll and foo.drv

      The documentation for LoadLibrary says:
      	If no file name extension is specified in the lpFileName
      	parameter, the default library extension .dll is
      	appended. However, the file name string can include a trailing
      	point character (.) to indicate that the module name has no
      	extension. */

   buf = stgMallocBytes(strlen(dll_name) + 10, "addDLL");
   sprintf(buf, "%s.DLL", dll_name);
   instance = LoadLibrary(buf);
   if (instance == NULL) {
       if (GetLastError() != ERROR_MOD_NOT_FOUND) goto error;
       // KAA: allow loading of drivers (like winspool.drv)
       sprintf(buf, "%s.DRV", dll_name);
       instance = LoadLibrary(buf);
       if (instance == NULL) {
           if (GetLastError() != ERROR_MOD_NOT_FOUND) goto error;
           // #1883: allow loading of unix-style libfoo.dll DLLs
           sprintf(buf, "lib%s.DLL", dll_name);
           instance = LoadLibrary(buf);
           if (instance == NULL) {
               goto error;
           }
       }
   }
   stgFree(buf);

   /* Add this DLL to the list of DLLs in which to search for symbols. */
   o_dll = stgMallocBytes( sizeof(OpenedDLL), "addDLL" );
   o_dll->name     = stgMallocBytes(1+strlen(dll_name), "addDLL");
   strcpy(o_dll->name, dll_name);
   o_dll->instance = instance;
   o_dll->next     = opened_dlls;
   opened_dlls     = o_dll;

   return NULL;

error:
   stgFree(buf);
   sysErrorBelch(dll_name);

   /* LoadLibrary failed; return a ptr to the error msg. */
   return "addDLL: could not load DLL";

#  else
   barf("addDLL: not implemented on this platform");
#  endif
}

/* -----------------------------------------------------------------------------
 * insert a stable symbol in the hash table
 */

void
insertStableSymbol(char* obj_name, char* key, StgPtr p)
{
  ghciInsertStrHashTable(obj_name, stablehash, key, getStablePtr(p));
}


/* -----------------------------------------------------------------------------
 * insert a symbol in the hash table
 */
void
insertSymbol(char* obj_name, char* key, void* data)
{
  ghciInsertStrHashTable(obj_name, symhash, key, data);
}

/* -----------------------------------------------------------------------------
 * lookup a symbol in the hash table
 */
void *
lookupSymbol( char *lbl )
{
    void *val;
    initLinker() ;
    ASSERT(symhash != NULL);
    val = lookupStrHashTable(symhash, lbl);

    if (val == NULL) {
#       if defined(OBJFORMAT_ELF)
	return dlsym(dl_prog_handle, lbl);
#       elif defined(OBJFORMAT_MACHO)
#       if HAVE_DLFCN_H
        /* On OS X 10.3 and later, we use dlsym instead of the old legacy
           interface.

           HACK: On OS X, global symbols are prefixed with an underscore.
                 However, dlsym wants us to omit the leading underscore from the
                 symbol name. For now, we simply strip it off here (and ONLY
                 here).
        */
        ASSERT(lbl[0] == '_');
        return dlsym(dl_prog_handle, lbl+1);
#       else
	if(NSIsSymbolNameDefined(lbl)) {
	    NSSymbol symbol = NSLookupAndBindSymbol(lbl);
	    return NSAddressOfSymbol(symbol);
	} else {
	    return NULL;
	}
#       endif /* HAVE_DLFCN_H */
#       elif defined(OBJFORMAT_PEi386)
        void* sym;

        sym = lookupSymbolInDLLs(lbl);
        if (sym != NULL) { return sym; };

        // Also try looking up the symbol without the @N suffix.  Some
        // DLLs have the suffixes on their symbols, some don't.
        zapTrailingAtSign ( lbl );
        sym = lookupSymbolInDLLs(lbl);
        if (sym != NULL) { return sym; };
        return NULL;

#       else
        ASSERT(2+2 == 5);
        return NULL;
#       endif
    } else {
	return val;
    }
}

/* -----------------------------------------------------------------------------
 * Debugging aid: look in GHCi's object symbol tables for symbols
 * within DELTA bytes of the specified address, and show their names.
 */
#ifdef DEBUG
void ghci_enquire ( char* addr );

void ghci_enquire ( char* addr )
{
   int   i;
   char* sym;
   char* a;
   const int DELTA = 64;
   ObjectCode* oc;

   initLinker();

   for (oc = objects; oc; oc = oc->next) {
      for (i = 0; i < oc->n_symbols; i++) {
         sym = oc->symbols[i];
         if (sym == NULL) continue;
         a = NULL;
         if (a == NULL) {
            a = lookupStrHashTable(symhash, sym);
	 }
         if (a == NULL) {
	     // debugBelch("ghci_enquire: can't find %s\n", sym);
         }
         else if (addr-DELTA <= a && a <= addr+DELTA) {
            debugBelch("%p + %3d  ==  `%s'\n", addr, (int)(a - addr), sym);
         }
      }
   }
}
#endif

#ifdef ia64_HOST_ARCH
static unsigned int PLTSize(void);
#endif

#ifdef USE_MMAP
#define ROUND_UP(x,size) ((x + size - 1) & ~(size - 1))

static void *
mmapForLinker (size_t bytes, nat flags, int fd)
{
   void *map_addr = NULL;
   void *result;
   int pagesize, size;
   static nat fixed = 0;

   pagesize = getpagesize();
   size = ROUND_UP(bytes, pagesize);

#if defined(x86_64_HOST_ARCH)
mmap_again:

   if (mmap_32bit_base != 0) {
       map_addr = mmap_32bit_base;
   }
#endif

   result = mmap(map_addr, size, PROT_EXEC|PROT_READ|PROT_WRITE,
		    MAP_PRIVATE|TRY_MAP_32BIT|fixed|flags, fd, 0);

   if (result == MAP_FAILED) {
       sysErrorBelch("mmap %lu bytes at %p",(lnat)size,map_addr);
       errorBelch("Try specifying an address with +RTS -xm<addr> -RTS");
       stg_exit(EXIT_FAILURE);
   }
   
#if defined(x86_64_HOST_ARCH)
   if (mmap_32bit_base != 0) {
       if (result == map_addr) {
           mmap_32bit_base = map_addr + size;
       } else {
           if ((W_)result > 0x80000000) {
               // oops, we were given memory over 2Gb
#if defined(freebsd_HOST_OS)
               // Some platforms require MAP_FIXED.  This is normally
               // a bad idea, because MAP_FIXED will overwrite
               // existing mappings.
               munmap(result,size);
               fixed = MAP_FIXED;
               goto mmap_again;
#else
               barf("loadObj: failed to mmap() memory below 2Gb; asked for %lu bytes at %p.  Try specifying an address with +RTS -xm<addr> -RTS", size, map_addr, result);
#endif
           } else {
               // hmm, we were given memory somewhere else, but it's
               // still under 2Gb so we can use it.  Next time, ask
               // for memory right after the place we just got some
               mmap_32bit_base = (void*)result + size;
           }
       }
   } else {
       if ((W_)result > 0x80000000) {
           // oops, we were given memory over 2Gb
           // ... try allocating memory somewhere else?;
           debugTrace(DEBUG_linker,"MAP_32BIT didn't work; gave us %lu bytes at 0x%p", bytes, result);
           munmap(result, size);
           
           // Set a base address and try again... (guess: 1Gb)
           mmap_32bit_base = (void*)0x40000000;
           goto mmap_again;
       }
   }
#endif

   return result;
}
#endif // USE_MMAP

/* -----------------------------------------------------------------------------
 * Load an obj (populate the global symbol table, but don't resolve yet)
 *
 * Returns: 1 if ok, 0 on error.
 */
HsInt
loadObj( char *path )
{
   ObjectCode* oc;
   struct stat st;
   int r;
#ifdef USE_MMAP
   int fd;
#else
   FILE *f;
#endif
   initLinker();

   /* debugBelch("loadObj %s\n", path ); */

   /* Check that we haven't already loaded this object.
      Ignore requests to load multiple times */
   {
       ObjectCode *o;
       int is_dup = 0;
       for (o = objects; o; o = o->next) {
          if (0 == strcmp(o->fileName, path)) {
             is_dup = 1;
             break; /* don't need to search further */
          }
       }
       if (is_dup) {
          IF_DEBUG(linker, debugBelch(
            "GHCi runtime linker: warning: looks like you're trying to load the\n"
            "same object file twice:\n"
            "   %s\n"
            "GHCi will ignore this, but be warned.\n"
            , path));
          return 1; /* success */
       }
   }

   oc = stgMallocBytes(sizeof(ObjectCode), "loadObj(oc)");

#  if defined(OBJFORMAT_ELF)
   oc->formatName = "ELF";
#  elif defined(OBJFORMAT_PEi386)
   oc->formatName = "PEi386";
#  elif defined(OBJFORMAT_MACHO)
   oc->formatName = "Mach-O";
#  else
   stgFree(oc);
   barf("loadObj: not implemented on this platform");
#  endif

   r = stat(path, &st);
   if (r == -1) { return 0; }

   /* sigh, strdup() isn't a POSIX function, so do it the long way */
   oc->fileName = stgMallocBytes( strlen(path)+1, "loadObj" );
   strcpy(oc->fileName, path);

   oc->fileSize          = st.st_size;
   oc->symbols           = NULL;
   oc->sections          = NULL;
   oc->proddables        = NULL;

   /* chain it onto the list of objects */
   oc->next              =