// SPDX-License-Identifier: GPL-2.0
/*---------------------------------------------------------------------------+
| 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 <linux/uaccess.h>
#include <asm/vm86.h>
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#define FPU_WRITE_BIT 0x10
static int reg_offset[] = {
offsetof(struct pt_regs, ax),
offsetof(struct pt_regs, cx),
offsetof(struct pt_regs, dx),
offsetof(struct pt_regs, bx),
offsetof(struct pt_regs, sp),
offsetof(struct pt_regs, bp),
offsetof(struct pt_regs, si),
offsetof(struct pt_regs, di)
};
#define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))
static int reg_offset_vm86[] = {
offsetof(struct pt_regs, cs),
offsetof(struct kernel_vm86_regs, ds),
offsetof(struct kernel_vm86_regs, es),
offsetof(struct kernel_vm86_regs, fs),
offsetof(struct kernel_vm86_regs, gs),
offsetof(struct pt_regs, ss),
offsetof(struct kernel_vm86_regs, ds)
};
#define VM86_REG_(x) (*(unsigned short *) \
(reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))
static int reg_offset_pm[] = {
offsetof(struct pt_regs, cs),
offsetof(struct pt_regs, ds),
offsetof(struct pt_regs, es),
offsetof(struct pt_regs, fs),
offsetof(struct pt_regs, ds), /* dummy, not saved on stack */
offsetof(struct pt_regs, ss),
offsetof(struct pt_regs, ds)
};
#define PM_REG_(x) (*(unsigned short *) \
(reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))
/* 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) {
case PREFIX_GS_ - 1:
/* user gs handling can be lazy, use special accessors */
savesegment(gs, addr->selector);
break;
default:
addr->selector = PM_REG_(segment);
}
descriptor = FPU_get_ldt_descriptor(addr->selector);
base_address = seg_get_base(&descriptor);
address = base_address + offset;
limit = seg_get_limit(&descriptor) + 1;
limit *= seg_get_granularity(&descriptor);
limit += base_address - 1;
if (limit < base_address)
limit = 0xffffffff;
if (seg_expands_down(&descriptor)) {
if (descriptor.g) {
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_writable(&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 = ®_(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->regs->bx + FPU_info->regs->si;
break;
case 1:
address += FPU_info->regs->bx + FPU_info->regs->di;
break;
case 2:
address += FPU_info->regs->bp + FPU_info->regs->si;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 3:
address += FPU_info->regs->bp + FPU_info->regs->di;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 4:
address += FPU_info->regs->si;
break;
case 5:
address += FPU_info->regs->di;
break;
case 6:
address += FPU_info->regs->bp;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 7:
address += FPU_info->regs->bx;
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;
}