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i386-tdep.c
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C/C++ Source or Header
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1992-09-11
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12KB
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469 lines
/* Intel 386 target-dependent stuff.
Copyright (C) 1988, 1989, 1991 Free Software Foundation, Inc.
This file is part of GDB.
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 of the License, 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include <stdio.h>
#include "defs.h"
#include "param.h"
#include "frame.h"
#include "inferior.h"
#include "gdbcore.h"
/* helper functions for tm-i386.h */
/* stdio style buffering to minimize calls to ptrace */
static CORE_ADDR codestream_next_addr;
static CORE_ADDR codestream_addr;
static unsigned char codestream_buf[sizeof (int)];
static int codestream_off;
static int codestream_cnt;
#define codestream_tell() (codestream_addr + codestream_off)
#define codestream_peek() (codestream_cnt == 0 ? \
codestream_fill(1): codestream_buf[codestream_off])
#define codestream_get() (codestream_cnt-- == 0 ? \
codestream_fill(0) : codestream_buf[codestream_off++])
static unsigned char
codestream_fill (peek_flag)
{
codestream_addr = codestream_next_addr;
codestream_next_addr += sizeof (int);
codestream_off = 0;
codestream_cnt = sizeof (int);
read_memory (codestream_addr,
(unsigned char *)codestream_buf,
sizeof (int));
if (peek_flag)
return (codestream_peek());
else
return (codestream_get());
}
static void
codestream_seek (place)
{
codestream_next_addr = place & -sizeof (int);
codestream_cnt = 0;
codestream_fill (1);
while (codestream_tell() != place)
codestream_get ();
}
static void
codestream_read (buf, count)
unsigned char *buf;
{
unsigned char *p;
int i;
p = buf;
for (i = 0; i < count; i++)
*p++ = codestream_get ();
}
/* next instruction is a jump, move to target */
static
i386_follow_jump ()
{
int long_delta;
short short_delta;
char byte_delta;
int data16;
int pos;
pos = codestream_tell ();
data16 = 0;
if (codestream_peek () == 0x66)
{
codestream_get ();
data16 = 1;
}
switch (codestream_get ())
{
case 0xe9:
/* relative jump: if data16 == 0, disp32, else disp16 */
if (data16)
{
codestream_read ((unsigned char *)&short_delta, 2);
/* include size of jmp inst (including the 0x66 prefix). */
pos += short_delta + 4;
}
else
{
codestream_read ((unsigned char *)&long_delta, 4);
pos += long_delta + 5;
}
break;
case 0xeb:
/* relative jump, disp8 (ignore data16) */
codestream_read ((unsigned char *)&byte_delta, 1);
pos += byte_delta + 2;
break;
}
codestream_seek (pos);
}
/*
* find & return amound a local space allocated, and advance codestream to
* first register push (if any)
*
* if entry sequence doesn't make sense, return -1, and leave
* codestream pointer random
*/
static long
i386_get_frame_setup (pc)
{
unsigned char op;
codestream_seek (pc);
i386_follow_jump ();
op = codestream_get ();
if (op == 0x58) /* popl %eax */
{
/*
* this function must start with
*
* popl %eax 0x58
* xchgl %eax, (%esp) 0x87 0x04 0x24
* or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00
*
* (the system 5 compiler puts out the second xchg
* inst, and the assembler doesn't try to optimize it,
* so the 'sib' form gets generated)
*
* this sequence is used to get the address of the return
* buffer for a function that returns a structure
*/
int pos;
unsigned char buf[4];
static unsigned char proto1[3] = { 0x87,0x04,0x24 };
static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 };
pos = codestream_tell ();
codestream_read (buf, 4);
if (bcmp (buf, proto1, 3) == 0)
pos += 3;
else if (bcmp (buf, proto2, 4) == 0)
pos += 4;
codestream_seek (pos);
op = codestream_get (); /* update next opcode */
}
if (op == 0x55) /* pushl %ebp */
{
/* check for movl %esp, %ebp - can be written two ways */
switch (codestream_get ())
{
case 0x8b:
if (codestream_get () != 0xec)
return (-1);
break;
case 0x89:
if (codestream_get () != 0xe5)
return (-1);
break;
default:
return (-1);
}
/* check for stack adjustment
*
* subl $XXX, %esp
*
* note: you can't subtract a 16 bit immediate
* from a 32 bit reg, so we don't have to worry
* about a data16 prefix
*/
op = codestream_peek ();
if (op == 0x83)
{
/* subl with 8 bit immed */
codestream_get ();
if (codestream_get () != 0xec)
/* Some instruction starting with 0x83 other than subl. */
{
codestream_seek (codestream_tell () - 2);
return 0;
}
/* subl with signed byte immediate
* (though it wouldn't make sense to be negative)
*/
return (codestream_get());
}
else if (op == 0x81)
{
/* subl with 32 bit immed */
int locals;
codestream_get();
if (codestream_get () != 0xec)
/* Some instruction starting with 0x81 other than subl. */
{
codestream_seek (codestream_tell () - 2);
return 0;
}
/* subl with 32 bit immediate */
codestream_read ((unsigned char *)&locals, 4);
SWAP_TARGET_AND_HOST (&locals, 4);
return (locals);
}
else
{
return (0);
}
}
else if (op == 0xc8)
{
/* enter instruction: arg is 16 bit unsigned immed */
unsigned short slocals;
codestream_read ((unsigned char *)&slocals, 2);
SWAP_TARGET_AND_HOST (&slocals, 2);
codestream_get (); /* flush final byte of enter instruction */
return (slocals);
}
return (-1);
}
/* Return number of args passed to a frame.
Can return -1, meaning no way to tell. */
/* on the 386, the instruction following the call could be:
* popl %ecx - one arg
* addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits
* anything else - zero args
*/
int
i386_frame_num_args (fi)
struct frame_info fi;
{
int retpc;
unsigned char op;
struct frame_info *pfi;
int frameless;
FRAMELESS_FUNCTION_INVOCATION (fi, frameless);
if (frameless)
/* In the absence of a frame pointer, GDB doesn't get correct values
for nameless arguments. Return -1, so it doesn't print any
nameless arguments. */
return -1;
pfi = get_prev_frame_info ((fi));
if (pfi == 0)
{
/* Note: this can happen if we are looking at the frame for
main, because FRAME_CHAIN_VALID won't let us go into
start. If we have debugging symbols, that's not really
a big deal; it just means it will only show as many arguments
to main as are declared. */
return -1;
}
else
{
retpc = pfi->pc;
op = read_memory_integer (retpc, 1);
if (op == 0x59)
/* pop %ecx */
return 1;
else if (op == 0x83)
{
op = read_memory_integer (retpc+1, 1);
if (op == 0xc4)
/* addl $<signed imm 8 bits>, %esp */
return (read_memory_integer (retpc+2,1)&0xff)/4;
else
return 0;
}
else if (op == 0x81)
{ /* add with 32 bit immediate */
op = read_memory_integer (retpc+1, 1);
if (op == 0xc4)
/* addl $<imm 32>, %esp */
return read_memory_integer (retpc+2, 4) / 4;
else
return 0;
}
else
{
return 0;
}
}
}
/*
* parse the first few instructions of the function to see
* what registers were stored.
*
* We handle these cases:
*
* The startup sequence can be at the start of the function,
* or the function can start with a branch to startup code at the end.
*
* %ebp can be set up with either the 'enter' instruction, or
* 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful,
* but was once used in the sys5 compiler)
*
* Local space is allocated just below the saved %ebp by either the
* 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has
* a 16 bit unsigned argument for space to allocate, and the
* 'addl' instruction could have either a signed byte, or
* 32 bit immediate.
*
* Next, the registers used by this function are pushed. In
* the sys5 compiler they will always be in the order: %edi, %esi, %ebx
* (and sometimes a harmless bug causes it to also save but not restore %eax);
* however, the code below is willing to see the pushes in any order,
* and will handle up to 8 of them.
*
* If the setup sequence is at the end of the function, then the
* next instruction will be a branch back to the start.
*/
i386_frame_find_saved_regs (fip, fsrp)
struct frame_info *fip;
struct frame_saved_regs *fsrp;
{
long locals;
unsigned char *p;
unsigned char op;
CORE_ADDR dummy_bottom;
CORE_ADDR adr;
int i;
bzero (fsrp, sizeof *fsrp);
/* if frame is the end of a dummy, compute where the
* beginning would be
*/
dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH;
/* check if the PC is in the stack, in a dummy frame */
if (dummy_bottom <= fip->pc && fip->pc <= fip->frame)
{
/* all regs were saved by push_call_dummy () */
adr = fip->frame;
for (i = 0; i < NUM_REGS; i++)
{
adr -= REGISTER_RAW_SIZE (i);
fsrp->regs[i] = adr;
}
return;
}
locals = i386_get_frame_setup (get_pc_function_start (fip->pc));
if (locals >= 0)
{
adr = fip->frame - 4 - locals;
for (i = 0; i < 8; i++)
{
op = codestream_get ();
if (op < 0x50 || op > 0x57)
break;
fsrp->regs[op - 0x50] = adr;
adr -= 4;
}
}
fsrp->regs[PC_REGNUM] = fip->frame + 4;
fsrp->regs[FP_REGNUM] = fip->frame;
}
/* return pc of first real instruction */
i386_skip_prologue (pc)
{
unsigned char op;
int i;
if (i386_get_frame_setup (pc) < 0)
return (pc);
/* found valid frame setup - codestream now points to
* start of push instructions for saving registers
*/
/* skip over register saves */
for (i = 0; i < 8; i++)
{
op = codestream_peek ();
/* break if not pushl inst */
if (op < 0x50 || op > 0x57)
break;
codestream_get ();
}
i386_follow_jump ();
return (codestream_tell ());
}
i386_push_dummy_frame ()
{
CORE_ADDR sp = read_register (SP_REGNUM);
int regnum;
char regbuf[MAX_REGISTER_RAW_SIZE];
sp = push_word (sp, read_register (PC_REGNUM));
sp = push_word (sp, read_register (FP_REGNUM));
write_register (FP_REGNUM, sp);
for (regnum = 0; regnum < NUM_REGS; regnum++)
{
read_register_gen (regnum, regbuf);
sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum));
}
write_register (SP_REGNUM, sp);
}
i386_pop_frame ()
{
FRAME frame = get_current_frame ();
CORE_ADDR fp;
int regnum;
struct frame_saved_regs fsr;
struct frame_info *fi;
char regbuf[MAX_REGISTER_RAW_SIZE];
fi = get_frame_info (frame);
fp = fi->frame;
get_frame_saved_regs (fi, &fsr);
for (regnum = 0; regnum < NUM_REGS; regnum++)
{
CORE_ADDR adr;
adr = fsr.regs[regnum];
if (adr)
{
read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum));
write_register_bytes (REGISTER_BYTE (regnum), regbuf,
REGISTER_RAW_SIZE (regnum));
}
}
write_register (FP_REGNUM, read_memory_integer (fp, 4));
write_register (PC_REGNUM, read_memory_integer (fp + 4, 4));
write_register (SP_REGNUM, fp + 8);
flush_cached_frames ();
set_current_frame ( create_new_frame (read_register (FP_REGNUM),
read_pc ()));
}