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linux/arch/i386/math-emu/get_address.c
Zachary Amsden 4d37e7e3fd [PATCH] i386: inline assembler: cleanup and encapsulate descriptor and task register management 
i386 inline assembler cleanup.

This change encapsulates descriptor and task register management.  Also,
it is possible to improve assembler generation in two cases; savesegment
may store the value in a register instead of a memory location, which
allows GCC to optimize stack variables into registers, and MOV MEM, SEG
is always a 16-bit write to memory, making the casting in math-emu
unnecessary.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05 00:06:11 -07:00

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/*---------------------------------------------------------------------------+
| get_address.c |
| |
| Get the effective address from an FPU instruction. |
| |
| Copyright (C) 1992,1993,1994,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
| Australia. E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| Note: |
| The file contains code which accesses user memory. |
| Emulator static data may change when user memory is accessed, due to |
| other processes using the emulator while swapping is in progress. |
+---------------------------------------------------------------------------*/
#include <linux/stddef.h>
#include <asm/uaccess.h>
#include <asm/desc.h>
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#define FPU_WRITE_BIT 0x10
static int reg_offset[] = {
offsetof(struct info,___eax),
offsetof(struct info,___ecx),
offsetof(struct info,___edx),
offsetof(struct info,___ebx),
offsetof(struct info,___esp),
offsetof(struct info,___ebp),
offsetof(struct info,___esi),
offsetof(struct info,___edi)
};
#define REG_(x) (*(long *)(reg_offset[(x)]+(u_char *) FPU_info))
static int reg_offset_vm86[] = {
offsetof(struct info,___cs),
offsetof(struct info,___vm86_ds),
offsetof(struct info,___vm86_es),
offsetof(struct info,___vm86_fs),
offsetof(struct info,___vm86_gs),
offsetof(struct info,___ss),
offsetof(struct info,___vm86_ds)
};
#define VM86_REG_(x) (*(unsigned short *) \
(reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
/* These are dummy, fs and gs are not saved on the stack. */
#define ___FS ___ds
#define ___GS ___ds
static int reg_offset_pm[] = {
offsetof(struct info,___cs),
offsetof(struct info,___ds),
offsetof(struct info,___es),
offsetof(struct info,___FS),
offsetof(struct info,___GS),
offsetof(struct info,___ss),
offsetof(struct info,___ds)
};
#define PM_REG_(x) (*(unsigned short *) \
(reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
/* Decode the SIB byte. This function assumes mod != 0 */
static int sib(int mod, unsigned long *fpu_eip)
{
u_char ss,index,base;
long offset;
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(1);
FPU_get_user(base, (u_char __user *) (*fpu_eip)); /* The SIB byte */
RE_ENTRANT_CHECK_ON;
(*fpu_eip)++;
ss = base >> 6;
index = (base >> 3) & 7;
base &= 7;
if ((mod == 0) && (base == 5))
offset = 0; /* No base register */
else
offset = REG_(base);
if (index == 4)
{
/* No index register */
/* A non-zero ss is illegal */
if ( ss )
EXCEPTION(EX_Invalid);
}
else
{
offset += (REG_(index)) << ss;
}
if (mod == 1)
{
/* 8 bit signed displacement */
long displacement;
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(1);
FPU_get_user(displacement, (signed char __user *) (*fpu_eip));
offset += displacement;
RE_ENTRANT_CHECK_ON;
(*fpu_eip)++;
}
else if (mod == 2 || base == 5) /* The second condition also has mod==0 */
{
/* 32 bit displacement */
long displacement;
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(4);
FPU_get_user(displacement, (long __user *) (*fpu_eip));
offset += displacement;
RE_ENTRANT_CHECK_ON;
(*fpu_eip) += 4;
}
return offset;
}
static unsigned long vm86_segment(u_char segment,
struct address *addr)
{
segment--;
#ifdef PARANOID
if ( segment > PREFIX_SS_ )
{
EXCEPTION(EX_INTERNAL|0x130);
math_abort(FPU_info,SIGSEGV);
}
#endif /* PARANOID */
addr->selector = VM86_REG_(segment);
return (unsigned long)VM86_REG_(segment) << 4;
}
/* This should work for 16 and 32 bit protected mode. */
static long pm_address(u_char FPU_modrm, u_char segment,
struct address *addr, long offset)
{
struct desc_struct descriptor;
unsigned long base_address, limit, address, seg_top;
segment--;
#ifdef PARANOID
/* segment is unsigned, so this also detects if segment was 0: */
if ( segment > PREFIX_SS_ )
{
EXCEPTION(EX_INTERNAL|0x132);
math_abort(FPU_info,SIGSEGV);
}
#endif /* PARANOID */
switch ( segment )
{
/* fs and gs aren't used by the kernel, so they still have their
user-space values. */
case PREFIX_FS_-1:
/* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
savesegment(fs, addr->selector);
break;
case PREFIX_GS_-1:
savesegment(gs, addr->selector);
break;
default:
addr->selector = PM_REG_(segment);
}
descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
base_address = SEG_BASE_ADDR(descriptor);
address = base_address + offset;
limit = base_address
+ (SEG_LIMIT(descriptor)+1) * SEG_GRANULARITY(descriptor) - 1;
if ( limit < base_address ) limit = 0xffffffff;
if ( SEG_EXPAND_DOWN(descriptor) )
{
if ( SEG_G_BIT(descriptor) )
seg_top = 0xffffffff;
else
{
seg_top = base_address + (1 << 20);
if ( seg_top < base_address ) seg_top = 0xffffffff;
}
access_limit =
(address <= limit) || (address >= seg_top) ? 0 :
((seg_top-address) >= 255 ? 255 : seg_top-address);
}
else
{
access_limit =
(address > limit) || (address < base_address) ? 0 :
((limit-address) >= 254 ? 255 : limit-address+1);
}
if ( SEG_EXECUTE_ONLY(descriptor) ||
(!SEG_WRITE_PERM(descriptor) && (FPU_modrm & FPU_WRITE_BIT)) )
{
access_limit = 0;
}
return address;
}
/*
MOD R/M byte: MOD == 3 has a special use for the FPU
SIB byte used iff R/M = 100b
7 6 5 4 3 2 1 0
..... ......... .........
MOD OPCODE(2) R/M
SIB byte
7 6 5 4 3 2 1 0
..... ......... .........
SS INDEX BASE
*/
void __user *FPU_get_address(u_char FPU_modrm, unsigned long *fpu_eip,
struct address *addr,
fpu_addr_modes addr_modes)
{
u_char mod;
unsigned rm = FPU_modrm & 7;
long *cpu_reg_ptr;
int address = 0; /* Initialized just to stop compiler warnings. */
/* Memory accessed via the cs selector is write protected
in `non-segmented' 32 bit protected mode. */
if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
&& (addr_modes.override.segment == PREFIX_CS_) )
{
math_abort(FPU_info,SIGSEGV);
}
addr->selector = FPU_DS; /* Default, for 32 bit non-segmented mode. */
mod = (FPU_modrm >> 6) & 3;
if (rm == 4 && mod != 3)
{
address = sib(mod, fpu_eip);
}
else
{
cpu_reg_ptr = & REG_(rm);
switch (mod)
{
case 0:
if (rm == 5)
{
/* Special case: disp32 */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(4);
FPU_get_user(address, (unsigned long __user *) (*fpu_eip));
(*fpu_eip) += 4;
RE_ENTRANT_CHECK_ON;
addr->offset = address;
return (void __user *) address;
}
else
{
address = *cpu_reg_ptr; /* Just return the contents
of the cpu register */
addr->offset = address;
return (void __user *) address;
}
case 1:
/* 8 bit signed displacement */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(1);
FPU_get_user(address, (signed char __user *) (*fpu_eip));
RE_ENTRANT_CHECK_ON;
(*fpu_eip)++;
break;
case 2:
/* 32 bit displacement */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(4);
FPU_get_user(address, (long __user *) (*fpu_eip));
(*fpu_eip) += 4;
RE_ENTRANT_CHECK_ON;
break;
case 3:
/* Not legal for the FPU */
EXCEPTION(EX_Invalid);
}
address += *cpu_reg_ptr;
}
addr->offset = address;
switch ( addr_modes.default_mode )
{
case 0:
break;
case VM86:
address += vm86_segment(addr_modes.override.segment, addr);
break;
case PM16:
case SEG32:
address = pm_address(FPU_modrm, addr_modes.override.segment,
addr, address);
break;
default:
EXCEPTION(EX_INTERNAL|0x133);
}
return (void __user *)address;
}
void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
struct address *addr,
fpu_addr_modes addr_modes)
{
u_char mod;
unsigned rm = FPU_modrm & 7;
int address = 0; /* Default used for mod == 0 */
/* Memory accessed via the cs selector is write protected
in `non-segmented' 32 bit protected mode. */
if ( !addr_modes.default_mode && (FPU_modrm & FPU_WRITE_BIT)
&& (addr_modes.override.segment == PREFIX_CS_) )
{
math_abort(FPU_info,SIGSEGV);
}
addr->selector = FPU_DS; /* Default, for 32 bit non-segmented mode. */
mod = (FPU_modrm >> 6) & 3;
switch (mod)
{
case 0:
if (rm == 6)
{
/* Special case: disp16 */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(2);
FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
(*fpu_eip) += 2;
RE_ENTRANT_CHECK_ON;
goto add_segment;
}
break;
case 1:
/* 8 bit signed displacement */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(1);
FPU_get_user(address, (signed char __user *) (*fpu_eip));
RE_ENTRANT_CHECK_ON;
(*fpu_eip)++;
break;
case 2:
/* 16 bit displacement */
RE_ENTRANT_CHECK_OFF;
FPU_code_access_ok(2);
FPU_get_user(address, (unsigned short __user *) (*fpu_eip));
(*fpu_eip) += 2;
RE_ENTRANT_CHECK_ON;
break;
case 3:
/* Not legal for the FPU */
EXCEPTION(EX_Invalid);
break;
}
switch ( rm )
{
case 0:
address += FPU_info->___ebx + FPU_info->___esi;
break;
case 1:
address += FPU_info->___ebx + FPU_info->___edi;
break;
case 2:
address += FPU_info->___ebp + FPU_info->___esi;
if ( addr_modes.override.segment == PREFIX_DEFAULT )
addr_modes.override.segment = PREFIX_SS_;
break;
case 3:
address += FPU_info->___ebp + FPU_info->___edi;
if ( addr_modes.override.segment == PREFIX_DEFAULT )
addr_modes.override.segment = PREFIX_SS_;
break;
case 4:
address += FPU_info->___esi;
break;
case 5:
address += FPU_info->___edi;
break;
case 6:
address += FPU_info->___ebp;
if ( addr_modes.override.segment == PREFIX_DEFAULT )
addr_modes.override.segment = PREFIX_SS_;
break;
case 7:
address += FPU_info->___ebx;
break;
}
add_segment:
address &= 0xffff;
addr->offset = address;
switch ( addr_modes.default_mode )
{
case 0:
break;
case VM86:
address += vm86_segment(addr_modes.override.segment, addr);
break;
case PM16:
case SEG32:
address = pm_address(FPU_modrm, addr_modes.override.segment,
addr, address);
break;
default:
EXCEPTION(EX_INTERNAL|0x131);
}
return (void __user *)address ;
}
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