ghelpers.c

The Valgrind distribution has multiple tools. The most popular is the memory checking tool (called M

/*---------------------------------------------------------------*/
/*---                                                         ---*/
/*--- This file (guest-arm/ghelpers.c) is                     ---*/
/*--- Copyright (C) OpenWorks LLP.  All rights reserved.      ---*/
/*---                                                         ---*/
/*---------------------------------------------------------------*/

/*
   This file is part of LibVEX, a library for dynamic binary
   instrumentation and translation.

   Copyright (C) 2004-2006 OpenWorks LLP.  All rights reserved.

   This library is made available under a dual licensing scheme.

   If you link LibVEX against other code all of which is itself
   licensed under the GNU General Public License, version 2 dated June
   1991 ("GPL v2"), then you may use LibVEX under the terms of the GPL
   v2, as appearing in the file LICENSE.GPL.  If the file LICENSE.GPL
   is missing, you can obtain a copy of the GPL v2 from the Free
   Software Foundation Inc., 51 Franklin St, Fifth Floor, Boston, MA
   02110-1301, USA.

   For any other uses of LibVEX, you must first obtain a commercial
   license from OpenWorks LLP.  Please contact [e-mail]
   for information about commercial licensing.

   This software is provided by OpenWorks LLP "as is" and any express
   or implied warranties, including, but not limited to, the implied
   warranties of merchantability and fitness for a particular purpose
   are disclaimed.  In no event shall OpenWorks LLP be liable for any
   direct, indirect, incidental, special, exemplary, or consequential
   damages (including, but not limited to, procurement of substitute
   goods or services; loss of use, data, or profits; or business
   interruption) however caused and on any theory of liability,
   whether in contract, strict liability, or tort (including
   negligence or otherwise) arising in any way out of the use of this
   software, even if advised of the possibility of such damage.

   Neither the names of the U.S. Department of Energy nor the
   University of California nor the names of its contributors may be
   used to endorse or promote products derived from this software
   without prior written permission.
*/

#include "libvex_basictypes.h"
#include "libvex_guest_arm.h"
#include "libvex_ir.h"
#include "libvex.h"

#include "main/vex_util.h"
#include "guest-arm/gdefs.h"


/* This file contains helper functions for arm guest code.
   Calls to these functions are generated by the back end.
   These calls are of course in the host machine code and 
   this file will be compiled to host machine code, so that
   all makes sense.  

   Only change the signatures of these helper functions very
   carefully.  If you change the signature here, you'll have to change
   the parameters passed to it in the IR calls constructed by
   guest-arm/toIR.c.
*/







#define BORROWFROM() \
{ \
}
#define OVERFLOWFROM() \
{ \
}


/*-------------------------------------------------------------*/
/*
  LOGIC: EOR, AND, TST, TEQ, MOV, ORR, MVN, BIC
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: shifter_carry_out
  v: unaffected
*/
#define ACTIONS_LOGIC()                                          \
{                                                                \
   { Int nf, zf, cf, vf;                                         \
     Int oldV=0;    /* CAB: vf unaffected: what todo? */         \
     nf = cc_dep1_formal & ARMG_CC_MASK_N;                       \
     zf = cc_dep1_formal == 0 ? 1 : 0;                           \
     cf = (cc_dep2_formal << ARMG_CC_SHIFT_C) & ARMG_CC_MASK_C;  \
     vf = oldV & ARMG_CC_MASK_V;                                 \
     return nf | zf | cf | vf;                                   \
   }                                                             \
}

/*-------------------------------------------------------------*/
/*
  ADD: ADD, CMN
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: CarryFrom(Rn + shifter_op)
  v: OverflowFrom(Rn + shifter_op)
*/
#define ACTIONS_ADD()                                            \
{                                                                \
   { Int nf, zf, cf, vf;                                         \
     Int argL, argR, res;                                        \
     argL = cc_dep1_formal;                                      \
     argR = cc_dep2_formal;                                      \
     res  = argL + argR;                                         \
     nf = res & ARMG_CC_MASK_N;                                  \
     zf = (res == 0) << ARMG_CC_SHIFT_Z;                         \
     cf = ((UInt)argL < (UInt)argR) << ARMG_CC_SHIFT_C;          \
     vf = (((argL ^ argR ^ -1) & (argL ^ res)) >>                \
           (32 - ARMG_CC_SHIFT_V)) & ARMG_CC_MASK_V;             \
     return nf | zf | cf | vf;                                   \
   }                                                             \
}

/*-------------------------------------------------------------*/
/*
  SUB: SUB, CMP, RSB
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: NOT BorrowFrom(Rn - shifter_op)
  v: OverflowFrom(Rn - shifter_op)
*/
// CAB: cf right? ARM ARM A4-99
#define ACTIONS_SUB()                                            \
{                                                                \
   { Int nf, zf, cf, vf;                                         \
     Int argL, argR, res;                                        \
     argL = cc_dep1_formal;                                      \
     argR = cc_dep2_formal;                                      \
     res  = argL - argR;                                         \
     nf = res & ARMG_CC_MASK_N;                                  \
     zf = (res == 0) << ARMG_CC_SHIFT_Z;                         \
     cf = (~((UInt)argL < (UInt)argR) <<                         \
           ARMG_CC_SHIFT_C) & ARMG_CC_MASK_C;                    \
     vf = (((argL ^ argR ^ -1) & (argL ^ res)) >>                \
           (32 - ARMG_CC_SHIFT_V)) & ARMG_CC_MASK_V;             \
     return nf | zf | cf | vf;                                   \
   }                                                             \
}


/*-------------------------------------------------------------*/
/*
  ADC
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: CarryFrom(Rn + shifter_op + C Flag)
  v: OverflowFrom(Rn + shifter_op + C Flag)
*/

/*-------------------------------------------------------------*/
/*
  RSC
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: NOT BorrowFrom(shifter_op - Rn - NOT(C Flag))
  v: OverflowFrom(shifter_op - Rn - NOT(C Flag))
*/

/*-------------------------------------------------------------*/
/*
  SBC
  ----------------
  n: Rd[31]
  z: Rd==0 ? 1:0
  c: NOT BorrowFrom(Rn - shifter_op - NOT(C Flag))
  v: OverflowFrom(Rn - shifter_op - NOT(C Flag))
*/









/* CALLED FROM GENERATED CODE: CLEAN HELPER */
/* Calculate all the 4 flags from the supplied thunk parameters. */
UInt armg_calculate_flags_all ( UInt cc_op, 
                                UInt cc_dep1_formal, 
                                UInt cc_dep2_formal )
{
   switch (cc_op) {
   case ARMG_CC_OP_LOGIC:  ACTIONS_LOGIC();
   case ARMG_CC_OP_ADD:  ACTIONS_ADD();
   case ARMG_CC_OP_SUB:  ACTIONS_SUB();

   default:
      /* shouldn't really make these calls from generated code */
      vex_printf("armg_calculate_flags_all(ARM)( %u, 0x%x, 0x%x )\n",
                 cc_op, cc_dep1_formal, cc_dep2_formal );
      vpanic("armg_calculate_flags_all(ARM)");
   }
}

/* CALLED FROM GENERATED CODE: CLEAN HELPER */
/* Calculate just the carry flag from the supplied thunk parameters. */
UInt armg_calculate_flags_c ( UInt cc_op, 
                              UInt cc_dep1, 
                              UInt cc_dep2 )
{
   /* Fast-case some common ones. */
   switch (cc_op) {
   default: 
      break;
   }
   return armg_calculate_flags_all(cc_op,cc_dep1,cc_dep2) & ARMG_CC_MASK_C;
}



/* CALLED FROM GENERATED CODE: CLEAN HELPER */
/* returns 1 or 0 */
/*static*/
UInt armg_calculate_condition ( UInt/*ARMCondcode*/ cond, 
                                UInt cc_op, 
                                UInt cc_dep1, 
                                UInt cc_dep2 )
{
   UInt nf,zf,vf,cf;
   UInt inv = cond & 1;

   UInt nzvc = armg_calculate_flags_all(cc_op, cc_dep1, cc_dep2);

   switch (cond) {
   case ARMCondEQ:    // Z=1         => z
   case ARMCondNE:    // Z=0
      zf = nzvc >> ARMG_CC_SHIFT_Z;
      return 1 & (inv ^ zf);

   case ARMCondHS:    // C=1         => c
   case ARMCondLO:    // C=0
      cf = nzvc >> ARMG_CC_SHIFT_C;
      return 1 & (inv ^ cf);

   case ARMCondMI:    // N=1         => n
   case ARMCondPL:    // N=0
      nf = nzvc >> ARMG_CC_SHIFT_N;
      return 1 & (inv ^ nf);

   case ARMCondVS:    // V=1         => v
   case ARMCondVC:    // V=0
      vf = nzvc >> ARMG_CC_SHIFT_V;
      return 1 & (inv ^ vf);

   case ARMCondHI:    // C=1 && Z=0   => c & ~z
   case ARMCondLS:    // C=0 || Z=1
      cf = nzvc >> ARMG_CC_SHIFT_C;
      zf = nzvc >> ARMG_CC_SHIFT_Z;
      return 1 & (inv ^ (cf & ~zf));

   case ARMCondGE:    // N=V          => ~(n^v)
   case ARMCondLT:    // N!=V
      nf = nzvc >> ARMG_CC_SHIFT_N;
      vf = nzvc >> ARMG_CC_SHIFT_V;
      return 1 & (inv ^ ~(nf ^ vf));

   case ARMCondGT:    // Z=0 && N=V   => (~z & ~(n^v)  =>  ~(z | (n^v)
   case ARMCondLE:    // Z=1 || N!=V
      nf = nzvc >> ARMG_CC_SHIFT_N;
      vf = nzvc >> ARMG_CC_SHIFT_V;
      zf = nzvc >> ARMG_CC_SHIFT_Z;
       return 1 & (inv ^ ~(zf | (nf ^ vf)));

   case ARMCondAL:   // should never get here: Always => no flags to calc
   case ARMCondNV:   // should never get here: Illegal instr
   default:
      /* shouldn't really make these calls from generated code */
      vex_printf("armg_calculate_condition(ARM)( %u, %u, 0x%x, 0x%x )\n",
                 cond, cc_op, cc_dep1, cc_dep2 );
      vpanic("armg_calculate_condition(ARM)");
   }
}


/* Used by the optimiser to try specialisations.  Returns an
   equivalent expression, or NULL if none. */

#if 0
/* temporarily unused */
static Bool isU32 ( IRExpr* e, UInt n )
{
   return (e->tag == Iex_Const
           && e->Iex.Const.con->tag == Ico_U32
           && e->Iex.Const.con->Ico.U32 == n);
}
#endif
IRExpr* guest_arm_spechelper ( HChar* function_name,
                               IRExpr** args )
{
   return NULL;
}


/*----------------------------------------------*/
/*--- The exported fns ..                    ---*/
/*----------------------------------------------*/

/* VISIBLE TO LIBVEX CLIENT */
#if 0
void LibVEX_GuestARM_put_flags ( UInt flags_native,
                                 /*OUT*/VexGuestARMState* vex_state )
{
   vassert(0); // FIXME

   /* Mask out everything except N Z V C. */
   flags_native
      &= (ARMG_CC_MASK_N | ARMG_CC_MASK_Z | ARMG_CC_MASK_V | ARMG_CC_MASK_C);
   
   vex_state->guest_CC_OP   = ARMG_CC_OP_COPY;
   vex_state->guest_CC_DEP1 = flags_native;
   vex_state->guest_CC_DEP2 = 0;
}
#endif

/* VISIBLE TO LIBVEX CLIENT */
UInt LibVEX_GuestARM_get_flags ( /*IN*/VexGuestARMState* vex_state )
{
   UInt flags;
   vassert(0); // FIXME

   flags = armg_calculate_flags_all(
              vex_state->guest_CC_OP,
              vex_state->guest_CC_DEP1,
              vex_state->guest_CC_DEP2
           );
   return flags;
}

/* VISIBLE TO LIBVEX CLIENT */
void LibVEX_GuestARM_initialise ( /*OUT*/VexGuestARMState* vex_state )
{
   vex_state->guest_R0  = 0;
   vex_state->guest_R1  = 0;
   vex_state->guest_R2  = 0;
   vex_state->guest_R3  = 0;
   vex_state->guest_R4  = 0;
   vex_state->guest_R5  = 0;
   vex_state->guest_R6  = 0;
   vex_state->guest_R7  = 0;
   vex_state->guest_R8  = 0;
   vex_state->guest_R9  = 0;
   vex_state->guest_R10 = 0;
   vex_state->guest_R11 = 0;
   vex_state->guest_R12 = 0;
   vex_state->guest_R13 = 0;
   vex_state->guest_R14 = 0;
   vex_state->guest_R15 = 0;

   // CAB: Want this?
   //vex_state->guest_SYSCALLNO = 0;

   vex_state->guest_CC_OP   = 0;// CAB: ? ARMG_CC_OP_COPY;
   vex_state->guest_CC_DEP1 = 0;
   vex_state->guest_CC_DEP2 = 0;

   // CAB: Want this?   
   //vex_state->guest_EMWARN = 0;

   vex_state->guest_SYSCALLNO = 0;
}


/*-----------------------------------------------------------*/
/*--- Describing the arm guest state, for the benefit     ---*/
/*--- of iropt and instrumenters.                         ---*/
/*-----------------------------------------------------------*/

/* Figure out if any part of the guest state contained in minoff
   .. maxoff requires precise memory exceptions.  If in doubt return
   True (but this is generates significantly slower code).  

   We enforce precise exns for guest %ESP and %EIP only.
*/
Bool guest_arm_state_requires_precise_mem_exns ( Int minoff, 
                                                 Int maxoff)
{
   return True; // FIXME (also comment above)
#if 0
   Int esp_min = offsetof(VexGuestX86State, guest_ESP);
   Int esp_max = esp_min + 4 - 1;
   Int eip_min = offsetof(VexGuestX86State, guest_EIP);
   Int eip_max = eip_min + 4 - 1;

   if (maxoff < esp_min || minoff > esp_max) {
      /* no overlap with esp */
   } else {
      return True;
   }

   if (maxoff < eip_min || minoff > eip_max) {
      /* no overlap with eip */
   } else {
      return True;
   }

   return False;
#endif
}



#define ALWAYSDEFD(field)                           \
    { offsetof(VexGuestARMState, field),            \
      (sizeof ((VexGuestARMState*)0)->field) }

VexGuestLayout
   armGuest_layout 
      = { 
          /* Total size of the guest state, in bytes. */
          .total_sizeB = sizeof(VexGuestARMState),

          /* Describe the stack pointer. */
          .offset_SP = offsetof(VexGuestARMState,guest_R13),
          .sizeof_SP = 4,

          /* Describe the instruction pointer. */
          .offset_IP = offsetof(VexGuestARMState,guest_R15),
          .sizeof_IP = 4,

          /* Describe any sections to be regarded by Memcheck as
             'always-defined'. */
          .n_alwaysDefd = 2,
          /* flags thunk: OP is always defd, whereas DEP1 and DEP2
             have to be tracked.  See detailed comment in gdefs.h on
             meaning of thunk fields. */

          .alwaysDefd 
             = { /*  0 */ ALWAYSDEFD(guest_CC_OP),
                 /*  1 */ ALWAYSDEFD(guest_SYSCALLNO)
               }
        };


/*---------------------------------------------------------------*/
/*--- end                                guest-arm/ghelpers.c ---*/
/*---------------------------------------------------------------*/