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unsigned char _cdecl inportb (unsigned short portid) {
#ifdef _MSC_VER
	_asm {
		mov		dx, word ptr [portid]
		in		al, dx
		mov		byte ptr [portid], al
	}
#endif
	return (unsigned char)portid;
}

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unsigned char inportb(unsigned short portid){

	__asm__(
		"movw %[portid],%%dx \n"
		"in %%dx,%%al \n"
		"movb %%al, %[portid] \n"
		: // no output
		: [portid] "m" (portid)  // input
		: "dx","al" //clobbers
	);

	return (unsigned char) portid;
}

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void _cdecl outportb (unsigned short portid, unsigned char value) {
#ifdef _MSC_VER
	_asm {
		mov		al, byte ptr [value]
		mov		dx, word ptr [portid]
		out		dx, al
	}
#endif
}

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void outportb (unsigned short portid, unsigned char value){

	__asm__(
		"movb %[value], %%al \n"
		"movw %[portid], %%dx \n"
		"out %%al,%%dx \n"
		: // no output
		:[value] "m" (value), [portid] "m" (portid)
		: "al","dx"
	);
	
}

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void _cdecl i86_pit_irq () {

	_asm add esp, 12
	_asm pushad

	//! increment tick count
	_pit_ticks++;

	//! tell hal we are done
	interruptdone(0);

	_asm popad
	_asm iretd
}

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void i86_pit_irq(){

	__asm__(
	"addl $12,%esp \n"
	"pusha \n"
	);
	
	_pit_ticks++;

	interruptdone(0);

	__asm__(
	"popa \n"
	"iret \n"
	);

}

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char* i86_cpu_get_vender () {

	static char	vender[32] = {0};

#ifdef _MSC_VER
	_asm {
		mov		eax, 0
		cpuid
		mov		dword ptr [vender], ebx
		mov		dword ptr [vender+4], edx
		mov		dword ptr [vender+8], ecx
	}
#endif

	return vender;
}

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char* i86_cpu_get_vender(){

	static char vendername[50] = {0};

 	__asm__(
		"movl $0,%%eax \n"
		"cpuid \n"
		"movl %%ebx, %[vendername] \n"
		"movl %%edx, %[vendername+$4] \n"
		"movl %%ecx, %[vendername+$8] \n"
		:"=r"(vendername) //user vendername as output
		:[vendername]"m"(vendername) //use vendername as input
		:"eax","ebx","edx","ecx" // clobbers those regs
	);

	return vendername;

}

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 in the function i86_pit_irq(), you have 2 separated block of assembly without side effect, the compiler is free to re-order them or even eliminate them. Furthermore, you should use the attribute hack to tell gcc that you are using iret in inline assembly.

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/* your interrupt handler */

void i86_pit_irq (void) __attribute__ ( ( signal, naked ) );
void i86_pit_irq (void) {
   _pit_ticks++;
   interruptdone(0);
   asm("reti");
}

/* inportb and outportb */

unsigned char _cdecl inportb (unsigned short portid) {
    unsigned char ret;
    asm volatile( "inb %1, %0" : "=a"(ret) : "Nd"(portid) );
    return ret;
}

void _cdecl outportb (unsigned short portid, unsigned char value) {
    asm volatile( "outb %0, %1" : : "a"(value), "Nd"(portid) );
}

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#include <stdfoo.h>

asm (".global foo\n"
       ".type foo, @function\n"
       "foo:\n"
       "	ret\n"
       ".size foo, . - foo");

#if defined(__cplusplus)
extern "C"
#endif
void foo(void);

void bar()
{
    foo();
}

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asm (".global i86_pit_irq\n"
       ".type i86_pit_irq, @function\n"
       "i86_pit_irq:\n"
       "   pusha\n"                        
       "call  i86_pit_irq_from_c\n"
       "popa\n"
       "iret\n"
       ".size i86_pit_irq, . - i86_pit_irq");

void i86_pit_irq();

void i86_pit_irq_from_c(){
	_pit_ticks++;
	interruptdone(0);
}

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global   i86_pit_irq
align 4

extern  i86_pit_irq_from_c

i86_pit_irq:
    pusha
    call     i86_pit_irq_from_c
    popa
    iret

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global _i86_pit_irq
align 4

extern  _i86_pit_irq_from_c

_i86_pit_irq:
    pusha
    call     _i86_pit_irq_from_c
    popa
    iret

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#ifdef __cplusplus
extern "C" { /* don't need if using C. */
#endif

#define CDECL __cdecl

/* define as uint32_t to discourage direct calling. */
extern uint32_t i86_pit_irq;

void PitInitialize (void) {
   /* register interrupt handler. */
   IdtRegisterHandler (i86_pit_irq, 0);
}

void CDECL i86_pit_irq_from_c (void) {
   /* real interrupt handler. */
}

#ifdef __cplusplus
}
#endif

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void PitInitialize (void) {
   /* register interrupt handler. */
   IdtRegisterHandler (i86_pit_irq, 0);
}

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void i86_pit_initialize(){

	setvect(32,i86_pit_irq);
	_pit_isinit = 1;

}