md.cpp

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/* src/vm/jit/alpha/md.cpp - machine dependent Alpha functions

   Copyright (C) 1996-2013
   CACAOVM - Verein zur Foerderung der freien virtuellen Maschine CACAO
   Copyright (C) 2009 Theobroma Systems Ltd.

   This file is part of CACAO.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301, USA.

*/


#include "config.h"

#include <stdint.h>
#include <ucontext.h>

#if defined(__LINUX__)
# include <asm/fpu.h>

extern "C" unsigned long ieee_get_fp_control();
extern "C" void          ieee_set_fp_control(unsigned long fp_control);
#endif

#include "vm/jit/alpha/codegen.hpp"
#include "vm/jit/alpha/md.hpp"

#include "vm/jit/asmpart.hpp"
#include "vm/jit/jit.hpp"
#include "vm/jit/trap.hpp"


/* global variables ***********************************************************/

bool has_ext_instr_set = false;             /* has instruction set extensions */


/* md_init *********************************************************************

   Do some machine dependent initialization.

*******************************************************************************/

void md_init(void)
{
#if defined(__LINUX__)
    unsigned long int fpcw;
#endif

    /* check for extended instruction set */

    has_ext_instr_set = !asm_md_init();

#if defined(__LINUX__)
    /* Linux on Digital Alpha needs an initialisation of the ieee
       floating point control for IEEE compliant arithmetic (option
       -mieee of GCC). Under Digital Unix this is done
       automatically. */

    /* initialize floating point control */

    fpcw = ieee_get_fp_control();

    fpcw = fpcw
        & ~IEEE_TRAP_ENABLE_INV
        & ~IEEE_TRAP_ENABLE_DZE
        /* We dont want underflow. */
/*      & ~IEEE_TRAP_ENABLE_UNF */
        & ~IEEE_TRAP_ENABLE_OVF;

/*  fpcw = fpcw */
/*      | IEEE_TRAP_ENABLE_INV */
/*      | IEEE_TRAP_ENABLE_DZE */
/*      | IEEE_TRAP_ENABLE_OVF */
/*      | IEEE_TRAP_ENABLE_UNF */
/*      | IEEE_TRAP_ENABLE_INE */
/*      | IEEE_TRAP_ENABLE_DNO; */

    ieee_set_fp_control(fpcw);
#endif
}


/* md_jit_method_patch_address *************************************************

   Gets the patch address of the currently compiled method. The offset
   is extracted from the load instruction(s) before the jump and added
   to the right base address (PV or REG_METHODPTR).

   INVOKESTATIC/SPECIAL:

   a77bffb8    ldq     pv,-72(pv)
   6b5b4000    jsr     (pv)

   INVOKEVIRTUAL:

   a7900000    ldq     at,0(a0)
   a77c0000    ldq     pv,0(at)
   6b5b4000    jsr     (pv)

   INVOKEINTERFACE:

   a7900000    ldq     at,0(a0)
   a79cff98    ldq     at,-104(at)
   a77c0018    ldq     pv,24(at)
   6b5b4000    jsr     (pv)

*******************************************************************************/

void *md_jit_method_patch_address(void *pv, void *ra, void *mptr)
{
    uint32_t *pc;
    uint32_t  mcode;
    int       opcode;
    int       base;
    int32_t   disp;
    void     *pa;                       /* patch address                      */

    /* Go back to the load instruction (2 instructions). */

    pc = ((uint32_t *) ra) - 2;

    /* Get first instruction word. */

    mcode = pc[0];

    /* Get opcode, base register and displacement. */

    opcode = M_MEM_GET_Opcode(mcode);
    base   = M_MEM_GET_Rb(mcode);
    disp   = M_MEM_GET_Memory_disp(mcode);

    /* Check for short or long load (2 instructions). */

    switch (opcode) {
    case 0x29: /* LDQ: TODO use define */
        switch (base) {
        case REG_PV:
            /* Calculate the data segment address. */

            pa = ((uint8_t *) pv) + disp;
            break;

        case REG_METHODPTR:
            /* Return NULL if no mptr was specified (used for
               replacement). */

            if (mptr == NULL)
                return NULL;

            /* Calculate the address in the vftbl. */

            pa = ((uint8_t *) mptr) + disp;
            break;

        default:
            vm_abort_disassemble(pc, 2, "md_jit_method_patch_address: unknown instruction %x", mcode);
            return NULL;
        }
        break;

    case 0x09: /* LDAH: TODO use define */
        /* XXX write a regression for this */

        vm_abort("md_jit_method_patch_address: IMPLEMENT ME!");

        pa = NULL;
        break;

    default:
        vm_abort_disassemble(pc, 2, "md_jit_method_patch_address: unknown instruction %x", mcode);
        return NULL;
    }

    return pa;
}


/**
 * Decode the trap instruction at the given PC.
 *
 * @param trp information about trap to be filled
 * @param sig signal number
 * @param xpc exception PC
 * @param es execution state of the machine
 * @return true if trap was decoded successfully, false otherwise.
 */
bool md_trap_decode(trapinfo_t* trp, int sig, void* xpc, executionstate_t* es)
{
    // Get the exception-throwing instruction.
    uint32_t mcode = *((uint32_t*) xpc);

    switch (sig) {
    case TRAP_SIGILL:
        // Check for valid trap instruction.
        // TODO Check the whole instruction.
        if (M_OP3_GET_Opcode(mcode) == 0x4) {
            trp->type  = TRAP_PATCHER;
            trp->value = 0;
            return true;
        }
        return false;

    case TRAP_SIGSEGV:
    {
        // Retrieve base address of instruction.
        int32_t   s1   = M_MEM_GET_Rb(mcode);
        uintptr_t addr = es->intregs[s1];

        // Check for special-load.
        if (s1 == REG_ZERO) {
            int32_t d    = M_MEM_GET_Ra(mcode);
            int32_t disp = M_MEM_GET_Memory_disp(mcode);

            // We use the exception type as load displacement.
            trp->type  = disp;
            trp->value = es->intregs[d];
            return true;
        }

        // Check for implicit NullPointerException.
        if (addr == 0) {
            trp->type  = TRAP_NullPointerException;
            trp->value = 0;
            return true;
        }

        return false;
    }

    default:
        return false;
    }
}


/* md_patch_replacement_point **************************************************

   Patch the given replacement point.

*******************************************************************************/

#if defined(ENABLE_REPLACEMENT)
void md_patch_replacement_point(u1 *pc, u1 *savedmcode, bool revert)
{
    u4 mcode;

    if (revert) {
        /* restore the patched-over instruction */
        *(u4*)(pc) = *(u4*)(savedmcode);
    }
    else {
        /* save the current machine code */
        *(u4*)(savedmcode) = *(u4*)(pc);

        /* build the machine code for the patch */
        mcode = (0xa41f0000 | (TRAP_PATCHER));

        /* write the new machine code */
        *(u4*)(pc) = mcode;
    }
    
    /* flush instruction cache */
    md_icacheflush(pc,4);
}
#endif /* defined(ENABLE_REPLACEMENT) */


/*
 * These are local overrides for various environment variables in Emacs.
 * Please do not remove this and leave it at the end of the file, where
 * Emacs will automagically detect them.
 * ---------------------------------------------------------------------
 * Local variables:
 * mode: c++
 * indent-tabs-mode: t
 * c-basic-offset: 4
 * tab-width: 4
 * End:
 * vim:noexpandtab:sw=4:ts=4:
 */