83 lines
3.3 KiB
C
83 lines
3.3 KiB
C
/* autoload.h: Define functions for auto-loading symbols from a DLL.
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Copyright 1999, 2000 Cygnus Solutions.
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Written by Christopher Faylor <cgf@cygnus.com>
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#define LoadDLLinitfunc(dllname) \
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HANDLE NO_COPY dllname ## _handle = NULL; \
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static int dllname ## _init () __asm__ (#dllname "_init") __attribute__ ((unused)); \
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static int dllname ## _init ()
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#define LoadDLLinitnow(dllname) \
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({__asm__ ("movl $cygwin_dll_func_load, " #dllname "_init_holder"); dllname##_init ();})
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#define _LoadDLLinitnow(dllname) \
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__asm__ ("movl $cygwin_dll_func_load, " #dllname "_init_holder"); \
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__asm__ ("call " #dllname "_init"); \
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#define LoadDLLinit(dllname) \
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__asm__ (".section .data_cygwin_nocopy,\"w\""); \
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__asm__ (#dllname "_init_holder: .long " #dllname "_init_and_load"); \
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__asm__ (".text"); \
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__asm__ (#dllname "_init_and_load:"); \
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_LoadDLLinitnow (dllname); \
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__asm__ ("jmp cygwin_dll_func_load");
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/* Macro for defining "auto-load" functions.
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* Note that this is self-modifying code *gasp*.
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* The first invocation of a routine will trigger the loading of
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* the DLL. This will then be followed by the discovery of
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* the procedure's entry point, which is placed into the location
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* pointed to by the stack pointer. This code then changes
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* the "call" operand which invoked it to a "jmp" which will
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* transfer directly to the DLL function on the next invocation.
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*
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* Subsequent calls to routines whose transfer address has not been
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* determined will skip the "load the dll" step, starting at the
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* "discovery of the DLL" step.
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*
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* So, immediately following the the call to one of the above routines
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* we have:
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* foojmp (4 bytes) Pointer to a word containing the routine used
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* to eventually invoke the function. Initially
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* points to an init function which loads the
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* DLL, gets the process's load address,
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* changes the contents here to point to the
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* function address, and changes the call *(%eax)
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* to a jmp %eax. If the initialization has been
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* done, only the load part is done.
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* DLL handle (4 bytes) The handle to use when loading the DLL.
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* flag (4 bytes) If "TRUE" then it is not a fatal error if this
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* function cannot be found. Instead, error is set
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* to ERROR_PROC_NOT_FOUND and 0 is returned.
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* func name (n bytes) asciz string containing the name of the function
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* to be loaded.
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*/
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#define LoadDLLmangle(name, n) #name "@" #n
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#define LoadDLLfunc(name, n, dllname) LoadDLLfuncEx (name, n, dllname, 0)
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#define LoadDLLfuncEx(name, n, dllname, notimp) \
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__asm__ (".section .data_cygwin_nocopy,\"w\""); \
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__asm__ (".global _" LoadDLLmangle (name, n)); \
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__asm__ (".global _win32_" LoadDLLmangle (name, n)); \
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__asm__ (".align 8"); \
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__asm__ ("_" LoadDLLmangle (name, n) ":"); \
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__asm__ ("_win32_" LoadDLLmangle (name, n) ":"); \
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__asm__ ("movl (" #name "jump),%eax"); \
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__asm__ ("call *(%eax)"); \
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__asm__ (#name "jump: .long " #dllname "_init_holder"); \
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__asm__ (" .long _" #dllname "_handle"); \
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__asm__ (" .long " #n "+" #notimp); \
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__asm__ (".asciz \"" #name "\""); \
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__asm__ (".text");
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extern "C" void cygwin_dll_func_load () __asm__ ("cygwin_dll_func_load");
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