/**
 * \file
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 * Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
 * Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
 * -->
 *
 * \author Bernie Innocenti <bernie@codewiz.org>
 *
 * \brief i386 context switch
 *
 * x86 function calling convention:
 * --------------------------------
 *  arguments         | callee-saved        | extra caller-saved | return
 * [callee-clobbered] |                     | [callee-clobbered] |
 * -------------------------------------------------------------------------
 * eax edx ecx        | ebx edi esi ebp [*] | <none>             | eax, edx
 *
 *  [*]  In the frame-pointers case rbp must hold a base address for the
 *       current stack frame.
 *
 * asm_switch_context() can be considered as a normal function call, so we need
 * to save all the callee-clobbered registers minus the return registers.
 */

#ifdef __APPLE__
    // This workaround is necessary to compile under OS X assembler.
    #define SWITCH_CONTEXT _asm_switch_context
#else
    #define SWITCH_CONTEXT asm_switch_context
#endif

/* void asm_switch_context(void ** new_sp [sp+4], void ** save_sp [sp+8]) */
.globl SWITCH_CONTEXT
SWITCH_CONTEXT:
	pushl	%ebp
	pushl	%ecx
	movl	0x10(%esp),%ebp         /* ebp = save_sp */
	movl	%esp,(%ebp)             /* *save_sp = esp */
	movl	0x0c(%esp),%ebp         /* ebp = new_sp */
	movl	(%ebp),%esp             /* esp = *new_sp */
	popl	%ecx
	popl	%ebp
	ret