src/avr32/ffi.c

/* -----------------------------------------------------------------------
   ffi.c - Copyright (c) 2011  Anthony Green
           Copyright (c) 2009  Bradley Smith <brad@brad-smith.co.uk>

   AVR32 Foreign Function Interface

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   ``Software''), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   DEALINGS IN THE SOFTWARE.
   ----------------------------------------------------------------------- */

#include <ffi.h>
#include <ffi_common.h>

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <asm/unistd.h>

/* #define DEBUG */

extern void ffi_call_SYSV(void (*)(char *, extended_cif *), extended_cif *,
    unsigned int, unsigned int, unsigned int*, unsigned int,
    void (*fn)(void));
extern void ffi_closure_SYSV (ffi_closure *);

unsigned int pass_struct_on_stack(ffi_type *type)
{
    if(type->type != FFI_TYPE_STRUCT)
        return 0;

    if(type->alignment < type->size &&
        !(type->size == 4 || type->size == 8) &&
        !(type->size == 8 && type->alignment >= 4))
        return 1;

    if(type->size == 3 || type->size == 5 || type->size == 6 ||
        type->size == 7)
        return 1;

    return 0;
}

/* ffi_prep_args is called by the assembly routine once stack space
 * has been allocated for the function's arguments
 *
 * This is annoyingly complex since we need to keep track of used
 * registers.
 */

void ffi_prep_args(char *stack, extended_cif *ecif)
{
    unsigned int i;
    void **p_argv;
    ffi_type **p_arg;
    char *reg_base = stack;
    char *stack_base = stack + 20;
    unsigned int stack_offset = 0;
    unsigned int reg_mask = 0;

    p_argv = ecif->avalue;

    /* If cif->flags is struct then we know it's not passed in registers */
    if(ecif->cif->flags == FFI_TYPE_STRUCT)
    {
        *(void**)reg_base = ecif->rvalue;
        reg_mask |= 1;
    }

    for(i = 0, p_arg = ecif->cif->arg_types; i < ecif->cif->nargs;
        i++, p_arg++)
    {
        size_t z = (*p_arg)->size;
        int alignment = (*p_arg)->alignment;
        int type = (*p_arg)->type;
        char *addr = 0;

        if(z % 4 != 0)
            z += (4 - z % 4);

        if(reg_mask != 0x1f)
        {
            if(pass_struct_on_stack(*p_arg))
            {
                addr = stack_base + stack_offset;
                stack_offset += z;
            }
            else if(z == sizeof(int))
            {
                char index = 0;

                while((reg_mask >> index) & 1)
                    index++;

                addr = reg_base + (index * 4);
                reg_mask |= (1 << index);
            }
            else if(z == 2 * sizeof(int))
            {
                if(!((reg_mask >> 1) & 1))
                {
                    addr = reg_base + 4;
                    reg_mask |= (3 << 1);
                }
                else if(!((reg_mask >> 3) & 1))
                {
                    addr = reg_base + 12;
                    reg_mask |= (3 << 3);
                }
            }
        }

        if(!addr)
        {
            addr = stack_base + stack_offset;
            stack_offset += z;
        }

        if(type == FFI_TYPE_STRUCT && (*p_arg)->elements[1] == NULL)
            type = (*p_arg)->elements[0]->type;

        switch(type)
        {
        case FFI_TYPE_UINT8:
            *(unsigned int *)addr = (unsigned int)*(UINT8 *)(*p_argv);
            break;
        case FFI_TYPE_SINT8:
            *(signed int *)addr = (signed int)*(SINT8 *)(*p_argv);
            break;
        case FFI_TYPE_UINT16:
            *(unsigned int *)addr = (unsigned int)*(UINT16 *)(*p_argv);
            break;
        case FFI_TYPE_SINT16:
            *(signed int *)addr = (signed int)*(SINT16 *)(*p_argv);
            break;
        default:
            memcpy(addr, *p_argv, z);
        }

        p_argv++;
    }

#ifdef DEBUG
    /* Debugging */
    for(i = 0; i < 5; i++)
    {
        if((reg_mask & (1 << i)) == 0)
            printf("r%d: (unused)\n", 12 - i);
        else
            printf("r%d: 0x%08x\n", 12 - i, ((unsigned int*)reg_base)[i]);
    }

    for(i = 0; i < stack_offset / 4; i++)
    {
        printf("sp+%d: 0x%08x\n", i*4, ((unsigned int*)stack_base)[i]);
    }
#endif
}

/* Perform machine dependent cif processing */
ffi_status ffi_prep_cif_machdep(ffi_cif *cif)
{
    /* Round the stack up to a multiple of 8 bytes.  This isn't needed
     * everywhere, but it is on some platforms, and it doesn't harm
     * anything when it isn't needed. */
    cif->bytes = (cif->bytes + 7) & ~7;

    /* Flag to indicate that he return value is in fact a struct */
    cif->rstruct_flag = 0;

    /* Set the return type flag */
    switch(cif->rtype->type)
    {
    case FFI_TYPE_SINT8:
    case FFI_TYPE_UINT8:
        cif->flags = (unsigned)FFI_TYPE_UINT8;
        break;
    case FFI_TYPE_SINT16:
    case FFI_TYPE_UINT16:
        cif->flags = (unsigned)FFI_TYPE_UINT16;
        break;
    case FFI_TYPE_FLOAT:
    case FFI_TYPE_SINT32:
    case FFI_TYPE_UINT32:
    case FFI_TYPE_POINTER:
        cif->flags = (unsigned)FFI_TYPE_UINT32;
        break;
    case FFI_TYPE_DOUBLE:
    case FFI_TYPE_SINT64:
    case FFI_TYPE_UINT64:
        cif->flags = (unsigned)FFI_TYPE_UINT64;
        break;
    case FFI_TYPE_STRUCT:
        cif->rstruct_flag = 1;
        if(!pass_struct_on_stack(cif->rtype))
        {
            if(cif->rtype->size <= 1)
                cif->flags = (unsigned)FFI_TYPE_UINT8;
            else if(cif->rtype->size <= 2)
                cif->flags = (unsigned)FFI_TYPE_UINT16;
            else if(cif->rtype->size <= 4)
                cif->flags = (unsigned)FFI_TYPE_UINT32;
            else if(cif->rtype->size <= 8)
                cif->flags = (unsigned)FFI_TYPE_UINT64;
            else
                cif->flags = (unsigned)cif->rtype->type;
        }
        else
            cif->flags = (unsigned)cif->rtype->type;
        break;
    default:
        cif->flags = (unsigned)cif->rtype->type;
        break;
    }

    return FFI_OK;
}

void ffi_call(ffi_cif *cif, void (*fn)(void), void *rvalue, void **avalue)
{
    extended_cif ecif;

    unsigned int size = 0, i = 0;
    ffi_type **p_arg;

    ecif.cif = cif;
    ecif.avalue = avalue;

    for(i = 0, p_arg = cif->arg_types; i < cif->nargs; i++, p_arg++)
        size += (*p_arg)->size + (4 - (*p_arg)->size % 4);

    /* If the return value is a struct and we don't have a return value
     * address then we need to make one */

    /* If cif->flags is struct then it's not suitable for registers */
    if((rvalue == NULL) && (cif->flags == FFI_TYPE_STRUCT))
        ecif.rvalue = alloca(cif->rtype->size);
    else
        ecif.rvalue = rvalue;

    switch(cif->abi)
    {
    case FFI_SYSV:
        ffi_call_SYSV(ffi_prep_args, &ecif, size, cif->flags,
            ecif.rvalue, cif->rstruct_flag, fn);
        break;
    default:
        FFI_ASSERT(0);
        break;
    }
}

static void ffi_prep_incoming_args_SYSV(char *stack, void **rvalue,
    void **avalue, ffi_cif *cif)
{
    register unsigned int i, reg_mask = 0;
    register void **p_argv;
    register ffi_type **p_arg;
    register char *reg_base = stack;
    register char *stack_base = stack + 20;
    register unsigned int stack_offset = 0;

#ifdef DEBUG
    /* Debugging */
    for(i = 0; i < cif->nargs + 7; i++)
    {
        printf("sp+%d: 0x%08x\n", i*4, ((unsigned int*)stack)[i]);
    }
#endif

    /* If cif->flags is struct then we know it's not passed in registers */
    if(cif->flags == FFI_TYPE_STRUCT)
    {
        *rvalue = *(void **)reg_base;
        reg_mask |= 1;
    }

    p_argv = avalue;

    for(i = 0, p_arg = cif->arg_types; i < cif->nargs; i++, p_arg++)
    {
        size_t z = (*p_arg)->size;
        int alignment = (*p_arg)->alignment;

        *p_argv = 0;

        if(z % 4 != 0)
            z += (4 - z % 4);

        if(reg_mask != 0x1f)
        {
            if(pass_struct_on_stack(*p_arg))
            {
                *p_argv = (void*)stack_base + stack_offset;
                stack_offset += z;
            }
            else if(z <= sizeof(int))
            {
                char index = 0;

                while((reg_mask >> index) & 1)
                    index++;

                *p_argv = (void*)reg_base + (index * 4);
                reg_mask |= (1 << index);
            }
            else if(z == 2 * sizeof(int))
            {
                if(!((reg_mask >> 1) & 1))
                {
                    *p_argv = (void*)reg_base + 4;
                    reg_mask |= (3 << 1);
                }
                else if(!((reg_mask >> 3) & 1))
                {
                    *p_argv = (void*)reg_base + 12;
                    reg_mask |= (3 << 3);
                }
            }
        }

        if(!*p_argv)
        {
            *p_argv = (void*)stack_base + stack_offset;
            stack_offset += z;
        }

        if((*p_arg)->type != FFI_TYPE_STRUCT ||
            (*p_arg)->elements[1] == NULL)
        {
            if(alignment == 1)
                **(unsigned int**)p_argv <<= 24;
            else if(alignment == 2)
                **(unsigned int**)p_argv <<= 16;
        }

        p_argv++;
    }

#ifdef DEBUG
    /* Debugging */
    for(i = 0; i < cif->nargs; i++)
    {
        printf("sp+%d: 0x%08x\n", i*4, *(((unsigned int**)avalue)[i]));
    }
#endif
}

/* This function is jumped to by the trampoline */

unsigned int ffi_closure_SYSV_inner(ffi_closure *closure, void **respp,
    void *args)
{
    ffi_cif *cif;
    void **arg_area;
    unsigned int i, size = 0;
    ffi_type **p_arg;

    cif = closure->cif;

    for(i = 0, p_arg = cif->arg_types; i < cif->nargs; i++, p_arg++)
        size += (*p_arg)->size + (4 - (*p_arg)->size % 4);

    arg_area = (void **)alloca(size);

    /* this call will initialize ARG_AREA, such that each element in that
     * array points to the corresponding value on the stack; and if the
     * function returns a structure, it will re-set RESP to point to the
     * structure return address. */

    ffi_prep_incoming_args_SYSV(args, respp, arg_area, cif);

    (closure->fun)(cif, *respp, arg_area, closure->user_data);

    return cif->flags;
}

ffi_status ffi_prep_closure_loc(ffi_closure* closure, ffi_cif* cif,
    void (*fun)(ffi_cif*, void*, void**, void*), void *user_data,
    void *codeloc)
{
    if (cif->abi != FFI_SYSV)
      return FFI_BAD_ABI;

    unsigned char *__tramp = (unsigned char*)(&closure->tramp[0]);
    unsigned int  __fun = (unsigned int)(&ffi_closure_SYSV);
    unsigned int  __ctx = (unsigned int)(codeloc);
    unsigned int  __rstruct_flag = (unsigned int)(cif->rstruct_flag);
    unsigned int  __inner = (unsigned int)(&ffi_closure_SYSV_inner);
    *(unsigned int*) &__tramp[0] = 0xebcd1f00;    /* pushm  r8-r12 */
    *(unsigned int*) &__tramp[4] = 0xfefc0010;    /* ld.w   r12, pc[16] */
    *(unsigned int*) &__tramp[8] = 0xfefb0010;    /* ld.w   r11, pc[16] */
    *(unsigned int*) &__tramp[12] = 0xfefa0010;   /* ld.w   r10, pc[16] */
    *(unsigned int*) &__tramp[16] = 0xfeff0010;   /* ld.w   pc, pc[16] */
    *(unsigned int*) &__tramp[20] = __ctx;
    *(unsigned int*) &__tramp[24] = __rstruct_flag;
    *(unsigned int*) &__tramp[28] = __inner;
    *(unsigned int*) &__tramp[32] = __fun;
    syscall(__NR_cacheflush, 0, (&__tramp[0]), 36);

    closure->cif = cif;
    closure->user_data = user_data;
    closure->fun  = fun;

    return FFI_OK;
}