src/farptr.h

// Code to access multiple segments within gcc.
//
// Copyright (C) 2008  Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#ifndef __FARPTR_H
#define __FARPTR_H

#include "ioport.h" // insb

// Low level macros for reading/writing memory via a segment selector.
#define READ8_SEG(SEG, var) ({                                          \
    u8 __value;                                                         \
    __asm__ __volatile__("movb %%" #SEG ":%1, %b0"                      \
                         : "=Qi"(__value) : "m"(var));                  \
    __value; })
#define READ16_SEG(SEG, var) ({                                         \
    u16 __value;                                                        \
    __asm__ __volatile__("movw %%" #SEG ":%1, %w0"                      \
                         : "=ri"(__value) : "m"(var));                  \
    __value; })
#define READ32_SEG(SEG, var) ({                                         \
    u32 __value;                                                        \
    __asm__ __volatile__("movl %%" #SEG ":%1, %0"                       \
                         : "=ri"(__value) : "m"(var));                  \
    __value; })
#define WRITE8_SEG(SEG, var, value)                     \
    __asm__ __volatile__("movb %b0, %%" #SEG ":%1"      \
                         : : "Q"(value), "m"(var))
#define WRITE16_SEG(SEG, var, value)                    \
    __asm__ __volatile__("movw %w0, %%" #SEG ":%1"      \
                         : : "r"(value), "m"(var))
#define WRITE32_SEG(SEG, var, value)                    \
    __asm__ __volatile__("movl %0, %%" #SEG ":%1"       \
                         : : "r"(value), "m"(var))

// Low level macros for getting/setting a segment register.
#define __SET_SEG(SEG, value)                                   \
    __asm__ __volatile__("movw %w0, %%" #SEG : : "r"(value))
#define __GET_SEG(SEG) ({                                       \
    u16 __seg;                                                  \
    __asm__ __volatile__("movw %%" #SEG ", %w0" : "=r"(__seg)); \
    __seg;})

// Macros for automatically choosing the appropriate memory size
// access method.
extern void __force_link_error__unknown_type();

#define __GET_VAR(seg, var) ({                                  \
    typeof(var) __val;                                          \
    if (__builtin_types_compatible_p(typeof(__val), u8))        \
        __val = READ8_SEG(seg, var);                            \
    else if (__builtin_types_compatible_p(typeof(__val), u16))  \
        __val = READ16_SEG(seg, var);                           \
    else if (__builtin_types_compatible_p(typeof(__val), u32))  \
        __val = READ32_SEG(seg, var);                           \
    else                                                        \
        __force_link_error__unknown_type();                     \
    __val; })

#define __SET_VAR(seg, var, val) do {                             \
        if (__builtin_types_compatible_p(typeof(var), u8))        \
            WRITE8_SEG(seg, var, (val));                          \
        else if (__builtin_types_compatible_p(typeof(var), u16))  \
            WRITE16_SEG(seg, var, (val));                         \
        else if (__builtin_types_compatible_p(typeof(var), u32))  \
            WRITE32_SEG(seg, var, (val));                         \
        else                                                      \
            __force_link_error__unknown_type();                   \
    } while (0)

// Macros for accessing a variable in another segment.  (They
// automatically update the %es segment and then make the appropriate
// access.)
#define __GET_FARVAR(seg, var) ({               \
    SET_SEG(ES, (seg));                         \
    GET_VAR(ES, (var)); })
#define __SET_FARVAR(seg, var, val) do {        \
        typeof(var) __sfv_val = (val);          \
        SET_SEG(ES, (seg));                     \
        SET_VAR(ES, (var), __sfv_val);          \
    } while (0)

// Macros for accesssing a 32bit pointer from 16bit mode.  (They
// automatically update the %es segment, break the pointer into
// segment/offset, and then make the access.)
#define __GET_FARPTR(ptr) ({                                            \
    typeof (&(ptr)) __ptr = (ptr);                                      \
    GET_FARVAR(PTR_TO_SEG(__ptr), *(typeof __ptr)PTR_TO_OFFSET(__ptr)); })
#define __SET_FARPTR(ptr, val) do {                                     \
        typeof (&(ptr)) __ptr = (ptr);                                  \
        SET_FARVAR(PTR_TO_SEG(__ptr), *(typeof __ptr)PTR_TO_OFFSET(__ptr) \
                   , (val));                                            \
    } while (0)

// Macros for converting to/from 32bit style pointers to their
// equivalent 16bit segment/offset values.
#define PTR_TO_SEG(p) (((u32)(p)) >> 4)
#define PTR_TO_OFFSET(p) (((u32)(p)) & 0xf)
#define MAKE_32_PTR(seg,off) ((void*)(((seg)<<4)+(off)))


#ifdef MODE16

// Definitions when in 16 bit mode.
#define GET_FARVAR(seg, var) __GET_FARVAR((seg), (var))
#define SET_FARVAR(seg, var, val) __SET_FARVAR((seg), (var), (val))
#define GET_VAR(seg, var) __GET_VAR(seg, (var))
#define SET_VAR(seg, var, val) __SET_VAR(seg, (var), (val))
#define SET_SEG(SEG, value) __SET_SEG(SEG, (value))
#define GET_SEG(SEG) __GET_SEG(SEG)
#define GET_FARPTR(ptr) __GET_FARPTR(ptr)
#define SET_FARPTR(ptr, val) __SET_FARPTR((ptr), (val))

static inline void insb_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    insb(port, (u8*)PTR_TO_OFFSET(farptr), count);
}
static inline void insw_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    insw(port, (u16*)PTR_TO_OFFSET(farptr), count);
}
static inline void insl_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    insl(port, (u32*)PTR_TO_OFFSET(farptr), count);
}
static inline void outsb_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    outsb(port, (u8*)PTR_TO_OFFSET(farptr), count);
}
static inline void outsw_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    outsw(port, (u16*)PTR_TO_OFFSET(farptr), count);
}
static inline void outsl_far(u16 port, void *farptr, u16 count) {
    SET_SEG(ES, PTR_TO_SEG(farptr));
    outsl(port, (u32*)PTR_TO_OFFSET(farptr), count);
}

#else

// In 32-bit mode there is no need to mess with the segments.
#define GET_FARVAR(seg, var) \
    (*((typeof(&(var)))MAKE_32_PTR((seg), (u32)&(var))))
#define SET_FARVAR(seg, var, val) \
    do { GET_FARVAR((seg), (var)) = (val); } while (0)
#define GET_VAR(seg, var) (var)
#define SET_VAR(seg, var, val) do { (var) = (val); } while (0)
#define SET_SEG(SEG, value) ((void)(value))
#define GET_SEG(SEG) 0
#define GET_FARPTR(ptr) (ptr)
#define SET_FARPTR(ptr, val) do { (var) = (val); } while (0)

#define insb_far(port, farptr, count) insb(port, farptr, count)
#define insw_far(port, farptr, count) insw(port, farptr, count)
#define insl_far(port, farptr, count) insl(port, farptr, count)
#define outsb_far(port, farptr, count) outsb(port, farptr, count)
#define outsw_far(port, farptr, count) outsw(port, farptr, count)
#define outsl_far(port, farptr, count) outsl(port, farptr, count)

#endif

#endif // farptr.h