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/*-
* Copyright (c) 2005
* Bill Paul <wpaul@windriver.com>. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Bill Paul.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL Bill Paul OR THE VOICES IN HIS HEAD
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD: release/9.1.0/sys/compat/ndis/winx32_wrap.S 187948 2009-01-31 11:37:21Z obrien $
*/
/* The 'ret' macro doesn't work in this file if GPROF is enabled. */
#ifdef GPROF
#undef GPROF
#endif
#include <machine/asmacros.h>
/*
* This file contains assembly language wrappers for the different
* calling conventions supported by Windows on the i386 architecture.
* In FreeBSD, the whole OS typically use same C calling convention
* everywhere, namely _cdecl. Windows, on the other hand, uses several
* different C calling conventions depending on the circumstances:
*
* _stdcall: Used for most ordinary Windows APIs. With _stdcall,
* arguments are passed on the stack, and the callee unwinds the stack
* before returning control to the caller. Not suitable for variadic
* functions.
*
* _fastcall: Used for some APIs that may be invoked frequently and
* where speed is a critical factor (e.g. KeAcquireSpinLock() and
* KeReleaseSpinLock()) Similar to _stdcall, except the first 2 32-bit
* or smaller arguments are passed in the %ecx and %edx registers
* instead of on the stack. Not suitable for variadic functions.
*
* _cdecl: Used for standard C library routines and for variadic
* functions.
*
* _regparm(3): Used for certain assembly routines. All arguments
* passed in %eax, %ecx and %edx.
*
* Furthermore, there is an additional wrinkle that's not obvious
* with all code: Microsoft supports the use of exceptions in C
* (__try/__except) both in user _and_ kernel mode. Sadly, Windows
* structured exception handling uses machine-specific features
* that conflict rather badly with FreeBSD. (See utility routines
* at the end of this module for more details.)
*
* We want to support these calling conventions in as portable a manner
* as possible. The trick is doing it not only with different versions
* of GNU C, but with compilers other than GNU C (e.g. the Solaris
* SunOne C compiler). The only sure fire method is with assembly
* language trampoline code which both fixes up the argument passing,
* stack unwinding and exception/thread context all at once.
*
* You'll notice that we call the thunk/unthunk routines in the
* *_wrap() functions in an awkward way. Rather than branching
* directly to the address, we load the address into a register
* first as a literal value, then we branch to it. This is done
* to insure that the assembler doesn't translate the branch into
* a relative branch. We use the *_wrap() routines here as templates
* and create the actual trampolines at run time, at which point
* we only know the absolute addresses of the thunk and unthunk
* routines. So we need to make sure the templates have enough
* room in them for the full address.
*
* Also note that when we call the a thunk/unthunk routine after
* invoking a wrapped function, we have to make sure to preserve
* the value returned from that function. Most functions return
* a 32-bit value in %eax, however some routines return 64-bit
* values, which span both %eax and %edx. Consequently, we have
* to preserve both registers.
*/
/*
* Handle _stdcall going from Windows to UNIX.
* This is frustrating, because to do it right you have to
* know how many arguments the called function takes, and there's
* no way to figure this out on the fly: you just have to be told
* ahead of time. We assume there will be 16 arguments. I don't
* think there are any Windows APIs that require this many.
*/
.globl x86_stdcall_wrap_call
.globl x86_stdcall_wrap_arg
.globl x86_stdcall_wrap_end
ENTRY(x86_stdcall_wrap)
push %esi
push %edi
sub $64,%esp
mov %esp,%esi
add $64+8+4,%esi
mov %esp,%edi
mov $16,%ecx # handle up to 16 args
rep
movsl
movl $ctxsw_wtou, %eax
call *%eax # unthunk
x86_stdcall_wrap_call:
movl $0,%eax
call *%eax # jump to routine
push %eax # preserve return val
push %edx
movl $ctxsw_utow, %eax
call *%eax # thunk
pop %edx
pop %eax # restore return val
add $64,%esp # clean the stack
pop %edi
pop %esi
x86_stdcall_wrap_arg:
ret $0xFF
x86_stdcall_wrap_end:
/*
* Handle _stdcall going from UNIX to Windows. This routine
* expects to be passed the function to be called, number of
* args and the arguments for the Windows function on the stack.
*/
ENTRY(x86_stdcall_call)
push %esi # must preserve %esi
push %edi # and %edi
mov 16(%esp),%eax # get arg cnt
mov %eax,%ecx # save as copy count
mov %esp,%esi # Set source address register to point to
add $20,%esi # first agument to be forwarded.
shl $2,%eax # turn arg cnt into offset
sub %eax,%esp # shift stack to new location
mov %esp,%edi # store dest copy addr
rep # do the copy
movsl
call ctxsw_utow # thunk
call *12(%edi) # branch to stdcall routine
push %eax # preserve return val
push %edx
call ctxsw_wtou # unthunk
pop %edx
pop %eax # restore return val
mov %edi,%esp # restore stack
pop %edi # restore %edi
pop %esi # and %esi
ret
/*
* Fastcall support. Similar to _stdcall, except the first
* two arguments are passed in %ecx and %edx. It happens we
* only support a small number of _fastcall APIs, none of them
* take more than three arguments. So to keep the code size
* and complexity down, we only handle 3 arguments here.
*/
/* Call _fastcall function going from Windows to UNIX. */
.globl x86_fastcall_wrap_call
.globl x86_fastcall_wrap_arg
.globl x86_fastcall_wrap_end
ENTRY(x86_fastcall_wrap)
mov 4(%esp),%eax
push %eax
push %edx
push %ecx
movl $ctxsw_wtou, %eax
call *%eax # unthunk
x86_fastcall_wrap_call:
mov $0,%eax
call *%eax # branch to fastcall routine
push %eax # preserve return val
push %edx
movl $ctxsw_utow, %eax
call *%eax # thunk
pop %edx
pop %eax # restore return val
add $12,%esp # clean the stack
x86_fastcall_wrap_arg:
ret $0xFF
x86_fastcall_wrap_end:
/*
* Call _fastcall function going from UNIX to Windows.
* This routine isn't normally used since NDIS miniport drivers
* only have _stdcall entry points, but it's provided anyway
* to round out the API, and for testing purposes.
*/
ENTRY(x86_fastcall_call)
mov 4(%esp),%eax
push 16(%esp)
call ctxsw_utow # thunk
mov 12(%esp),%ecx
mov 16(%esp),%edx
call *8(%esp) # branch to fastcall routine
push %eax # preserve return val
push %edx
call ctxsw_wtou # unthunk
pop %edx
pop %eax # restore return val
add $4,%esp # clean the stack
ret
/*
* Call regparm(3) function going from Windows to UNIX. Arguments
* are passed in %eax, %edx and %ecx. Note that while additional
* arguments are passed on the stack, we never bother when them,
* since the only regparm(3) routines we need to wrap never take
* more than 3 arguments.
*/
.globl x86_regparm_wrap_call
.globl x86_regparm_wrap_end
ENTRY(x86_regparm_wrap)
push %ecx
push %edx
push %eax
movl $ctxsw_wtou, %eax
call *%eax # unthunk
x86_regparm_wrap_call:
movl $0,%eax
call *%eax # jump to routine
push %eax # preserve return val
push %edx # preserve return val
movl $ctxsw_utow, %eax
call *%eax # thunk
pop %edx # restore return val
pop %eax # restore return val
add $12,%esp # restore stack
ret
x86_regparm_wrap_end:
/*
* Call regparm(3) function going from UNIX to Windows.
* This routine isn't normally used since NDIS miniport drivers
* only have _stdcall entry points, but it's provided anyway
* to round out the API, and for testing purposes.
*/
ENTRY(x86_regparm_call)
call ctxsw_utow # thunk
mov 8(%esp),%eax
mov 12(%esp),%edx
mov 16(%esp),%ecx
call *4(%esp) # branch to fastcall routine
push %eax # preserve return val
push %edx # preserve return val
call ctxsw_wtou # unthunk
pop %edx # restore return val
pop %eax # restore return val
ret
/*
* Ugly hack alert:
*
* On Win32/i386, using __try/__except results in code that tries to
* manipulate what's supposed to be the Windows Threada Environment
* Block (TEB), which one accesses via the %fs register. In particular,
* %fs:0 (the first DWORD in the TEB) points to the exception
* registration list. Unfortunately, FreeBSD uses %fs for the
* per-cpu data structure (pcpu), and we can't allow Windows code
* to muck with that. I don't even know what Solaris uses %fs for
* (or if it even uses it at all).
*
* Even worse, in 32-bit protected mode, %fs is a selector that
* refers to an entry in either the GDT or the LDT. Ideally, we would
* like to be able to temporarily point it at another descriptor
* while Windows code executes, but to do that we need a separate
* descriptor entry of our own to play with.
*
* Therefore, we go to some trouble to learn the existing layout of
* the GDT and update it to include an extra entry that we can use.
* We need the following utility routines to help us do that. On
* FreeBSD, index #7 in the GDT happens to be unused, so we turn
* this into our own data segment descriptor. It would be better
* if we could use a private LDT entry, but there's no easy way to
* do that in SMP mode because of the way FreeBSD handles user LDTs.
*
* Once we have a custom descriptor, we have to thunk/unthunk whenever
* we cross between FreeBSD code and Windows code. The thunking is
* based on the premise that when executing instructions in the
* Windows binary itself, we won't go to sleep. This is because in
* order to yield the CPU, the code has to call back out to a FreeBSD
* routine first, and when that happens we can unthunk in order to
* restore FreeBSD context. What we're desperately trying to avoid is
* being involuntarily pre-empted with the %fs register still pointing
* to our fake TIB: if FreeBSD code runs with %fs pointing at our
* Windows TIB instead of pcpu, we'll panic the kernel. Fortunately,
* the only way involuntary preemption can occur is if an interrupt
* fires, and the trap handler saves/restores %fs for us.
*
* The thunking routines themselves, ctxsw_utow() (Context SWitch UNIX
* to Windows) and ctxsw_wtou() (Context SWitch Windows to UNIX), are
* external to this module. This is done simply because it's easier
* to manipulate data structures in C rather than assembly.
*/
ENTRY(x86_getldt)
movl 4(%esp),%eax
sgdtl (%eax)
movl 8(%esp),%eax
sldt (%eax)
xor %eax,%eax
ret
ENTRY(x86_setldt)
movl 4(%esp),%eax
lgdt (%eax)
jmp 1f
nop
1:
movl 8(%esp),%eax
lldt %ax
xor %eax,%eax
ret
ENTRY(x86_getfs)
mov %fs,%ax
ret
ENTRY(x86_setfs)
mov 4(%esp),%fs
ret
ENTRY(x86_gettid)
mov %fs:12,%eax
ret
ENTRY(x86_critical_enter)
cli
ret
ENTRY(x86_critical_exit)
sti
ret