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/* $OpenBSD: db_sstep.c,v 1.4 1999/02/09 06:36:25 smurph Exp $ */
/*
* Mach Operating System
* Copyright (c) 1993-1991 Carnegie Mellon University
* Copyright (c) 1991 OMRON Corporation
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON AND OMRON ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON AND OMRON DISCLAIM ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
#include <machine/db_machdep.h>
#include <ddb/db_access.h> /* db_get_value() */
/*
* Support routines for software single step.
*
* Author: Daniel Stodolsky (danner@cs.cmu.edu)
*
*/
/* is the instruction a branch or jump instruction (br, bb0, bb1, bcnd, jmp)
but not a function call (bsr or jsr) */
boolean_t
inst_branch(unsigned ins)
{
/* check high five bits */
switch (ins >> (32-5))
{
case 0x18: /* br */
case 0x1a: /* bb0 */
case 0x1b: /* bb1 */
case 0x1d: /* bcnd */
return TRUE;
break;
case 0x1e: /* could be jmp */
if ((ins & 0xfffffbe0U) == 0xf400c000U)
return TRUE;
}
return FALSE;
}
/* inst_load(ins) - returns the number of words the instruction loads. byte,
half and word count as 1; double word as 2 */
unsigned
inst_load(unsigned ins)
{
/* look at the top six bits, for starters */
switch (ins >> (32-6))
{
case 0x0: /* xmem byte imm */
case 0x1: /* xmem word imm */
case 0x2: /* unsigned half-word load imm */
case 0x3: /* unsigned byte load imm */
case 0x5: /* signed word load imm */
case 0x6: /* signed half-word load imm */
case 0x7: /* signed byte load imm */
return 1;
case 0x4: /* signed double word load imm */
return 2;
case 0x3d: /* load/store/xmem scaled/unscaled instruction */
if ((ins & 0xf400c0e0U) == 0xf4000000U) /* is load/xmem */
switch ((ins & 0x0000fce0)>>5) /* look at bits 15-5, but mask bits 8-9 */
{
case 0x0: /* xmem byte */
case 0x1: /* xmem word */
case 0x2: /* unsigned half word */
case 0x3: /* unsigned byte load */
case 0x5: /* signed word load */
case 0x6: /* signed half-word load */
case 0x7: /* signed byte load */
return 1;
case 0x4: /* signed double word load */
return 2;
} /* end switch load/xmem */
break;
} /* end switch 32-6 */
return 0;
}
/* inst_store - like inst_load, except for store instructions. */
unsigned
inst_store(unsigned ins)
{
/* decode top 6 bits again */
switch (ins >> (32-6))
{
case 0x0: /* xmem byte imm */
case 0x1: /* xmem word imm */
case 0x9: /* store word imm */
case 0xa: /* store half-word imm */
case 0xb: /* store byte imm */
return 1;
case 0x8: /* store double word */
return 2;
case 0x3d: /* load/store/xmem scaled/unscaled instruction */
/* check bits 15,14,12,7,6,5 are all 0 */
if ((ins & 0x0000d0e0U) == 0)
switch ((ins & 0x00003c00U) >> 10 ) /* decode bits 10-13 */
{
case 0x0: /* xmem byte imm */
case 0x1: /* xmem word imm */
case 0x9: /* store word */
case 0xa: /* store half-word */
case 0xb: /* store byte */
return 1;
case 0x8: /* store double word */
return 2;
} /* end switch store/xmem */
break;
} /* end switch 32-6 */
return 0;
}
/* inst_delayed - this instruction is followed by a delay slot. Could be
br.n, bsr.n bb0.n, bb1.n, bcnd.n or jmp.n or jsr.n */
boolean_t
inst_delayed(unsigned ins)
{
/* check the br, bsr, bb0, bb1, bcnd cases */
switch ((ins & 0xfc000000U)>>(32-6))
{
case 0x31: /* br */
case 0x33: /* bsr */
case 0x35: /* bb0 */
case 0x37: /* bb1 */
case 0x3b: /* bcnd */
return TRUE;
}
/* check the jmp, jsr cases */
/* mask out bits 0-4, bit 11 */
return ((ins & 0xfffff7e0U) == 0xf400c400U) ? TRUE : FALSE;
}
/*
* next_instr_address(pc,delay_slot,task) has the following semantics.
* Let inst be the instruction at pc.
* If delay_slot = 1, next_instr_address should return
* the address of the instruction in the delay slot; if this instruction
* does not have a delay slot, it should return pc.
* If delay_slot = 0, next_instr_address should return the
* address of next sequential instruction, or pc if the instruction is
* followed by a delay slot.
*
* 91-11-28 jfriedl: I think the above is wrong. I think it should be:
* if delay_slot true, return address of the delay slot if there is one,
* return pc otherwise.
* if delay_slot false, return (pc + 4) regardless.
*
*/
db_addr_t
next_instr_address(db_addr_t pc, unsigned delay_slot)
{
if (delay_slot == 0)
return pc + 4;
else
{
if (inst_delayed(db_get_value(pc,sizeof(int),FALSE)))
return pc + 4;
else
return pc;
}
}
/*
* branch_taken(instruction, program counter, func, func_data)
*
* instruction will be a control flow instruction location at address pc.
* Branch taken is supposed to return the address to which the instruction
* would jump if the branch is taken. Func can be used to get the current
* register values when invoked with a register number and func_data as
* arguments.
*
* If the instruction is not a control flow instruction, panic.
*/
unsigned
branch_taken(
unsigned inst,
unsigned pc,
db_expr_t (*func)(unsigned int, db_regs_t *),
db_regs_t *func_data) /* 'opaque' */
{
/* check if br/bsr */
if ((inst & 0xf0000000U) == 0xc0000000U)
{
/* signed 26 bit pc relative displacement, shift left two bits */
inst = (inst & 0x03ffffffU)<<2;
/* check if sign extension is needed */
if (inst & 0x08000000U)
inst |= 0xf0000000U;
return pc + inst;
}
/* check if bb0/bb1/bcnd case */
switch ((inst & 0xf8000000U))
{
case 0xd0000000U: /* bb0 */
case 0xd8000000U: /* bb1 */
case 0xe8000000U: /* bcnd */
/* signed 16 bit pc relative displacement, shift left two bits */
inst = (inst & 0x0000ffffU)<<2;
/* check if sign extension is needed */
if (inst & 0x00020000U)
inst |= 0xfffc0000U;
return pc + inst;
}
/* check jmp/jsr case */
/* check bits 5-31, skipping 10 & 11 */
if ((inst & 0xfffff3e0U) == 0xf400c000U)
return (*func)(inst & 0x1f, func_data); /* the register value */
panic("branch_taken");
return 0; /* keeps compiler happy */
}
/*
* getreg_val - handed a register number and an exception frame.
* Returns the value of the register in the specified
* frame. Only makes sense for general registers.
*/
db_expr_t
getreg_val(unsigned regno, db_regs_t *frame)
{
if (regno == 0)
return 0;
else if (regno < 31)
return frame->r[regno];
else {
panic("bad register number to getreg_val.");
return 0;/*to make compiler happy */
}
}
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