ia16.h

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/*
 * Copyright (c) 2022, 2023 Adrian "asie" Siekierka
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 *
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 *
 * 3. This notice may not be removed or altered from any source distribution.
 */

 
#ifndef IA16_H_
#define IA16_H_


#define IA16_INT_DIV    0
#define IA16_INT_STEP   1
#define IA16_INT_NMI    2
#define IA16_INT_BREAK  3
#define IA16_INT_INTO   4
#define IA16_INT_BOUNDS 5

#define IA16_FLAG_CF 0x0001
#define IA16_FLAG_PF 0x0004
#define IA16_FLAG_AF 0x0010
#define IA16_FLAG_ZF 0x0040
#define IA16_FLAG_SF 0x0080
#define IA16_FLAG_TF 0x0100
#define IA16_FLAG_IF 0x0200
#define IA16_FLAG_DF 0x0400
#define IA16_FLAG_OF 0x0800
#define IA16_FLAG_MD 0x8000
 
#ifdef __ASSEMBLER__
 
#ifdef __IA16_CMODEL_IS_FAR_TEXT
#define IA16_RET retf
#define IA16_CALL_STACK_OFFSET(n) ((n)+4)

.macro IA16_CALL tgt:req
    .reloc  .+3, R_386_SEG16, "\tgt\‍()!"
    call 0:\tgt
.endm
.macro IA16_CALL_LOCAL tgt:req
    push cs
    call \tgt
.endm
.macro IA16_JMP tgt:req
    .reloc  .+3, R_386_SEG16, "\tgt\‍()!"
    jmp 0:\tgt
.endm
#else
#define IA16_RET ret
#define IA16_CALL_STACK_OFFSET(n) ((n)+2)

.macro IA16_CALL tgt:req
    call \tgt
.endm
.macro IA16_CALL_LOCAL tgt:req
    call \tgt
.endm
.macro IA16_JMP tgt:req
    jmp \tgt
.endm
#endif
 
#else
 
#include <stdbool.h>
#include <stdint.h>

#define FP_SEG(x) __builtin_ia16_selector ((uint16_t) (((uint32_t) ((void __far*) (x))) >> 16))

#define FP_OFF(x) __builtin_ia16_FP_OFF ((x))

#define MK_FP(seg, ofs) ((void __far*) (((uint16_t) ofs) | (((uint32_t) ((uint16_t) seg)) << 16)))
#define _CS ia16_get_cs()
#define _DS ia16_get_ds()
#define _ES ia16_get_es()
#define _SS ia16_get_ss()

static inline __segment ia16_get_cs() {
    __segment result;
    __asm (
        "mov %%cs, %0"
        : "=r" (result)
    );
    return result;
}

#define ia16_get_ds __builtin_ia16_near_data_segment

static inline __segment ia16_get_es() {
    __segment result;
    __asm (
        "mov %%es, %0"
        : "=r" (result)
    );
    return result;
}

#define ia16_get_ss __builtin_ia16_ss

static inline uint16_t ia16_get_sp() {
    uint16_t result;
    __asm (
        "mov %%sp, %0"
        : "=r" (result)
    );
    return result;
}

static inline uint16_t ia16_get_flags() {
    uint16_t result;
    __asm volatile (
        "pushf\npop %0"
        : "=r" (result)
    );
    return result;
}

static inline void ia16_set_flags(uint16_t flags) {
    __asm volatile (
        "push %0\npopf"
        : : "r" (flags)
        : "cc"
    );
}

static inline uint8_t inportb(uint8_t port) {
    uint8_t result;
    __asm volatile (
        "inb %1, %0"
        : "=Ral" (result)
        : "Nd" ((uint16_t) port)
    );
    return result;
}

static inline uint16_t inportw(uint8_t port) {
    uint16_t result;
    __asm volatile (
        "inw %1, %0"
        : "=a" (result)
        : "Nd" ((uint16_t) port)
    );
    return result;
}

static inline void outportb(uint8_t port, uint8_t value) {
    __asm volatile (
        "outb %0, %1"
        :
        : "Ral" (value), "Nd" ((uint16_t) port)
    );
}

static inline void outportw(uint8_t port, uint16_t value) {
    __asm volatile (
        "outw %0, %1"
        :
        : "a" (value), "Nd" ((uint16_t) port)
    );
}
 
#define ia16_port_inb(port) inportb(port)
#define ia16_port_inw(port) inportw(port)
#define ia16_port_outb(value, port) outportb(port, value)
#define ia16_port_outw(value, port) outportw(port, value)

static inline void ia16_halt(void) {
    __asm volatile ("hlt");
}

static inline void ia16_enable_irq(void) {
    __asm volatile ("sti");
}

static inline void ia16_disable_irq(void) {
    __asm volatile ("cli");
}

#define ia16_critical(...) \
    do { \
        ia16_disable_irq(); \
        __VA_ARGS__; \
        ia16_enable_irq(); \
    } while(0)
 
typedef __attribute__((interrupt)) void __far (*ia16_int_handler_t)(void);

void ia16_int_set_handler(uint8_t idx, ia16_int_handler_t handler);
 
#endif

 
#endif /* IA16_H_ */