linux/arch/x86/math-emu/fpu_aux.c
Daniel Glöckner ab9e18587f x86, math-emu: fix init_fpu for task != current
Impact: fix math-emu related crash while using GDB/ptrace

init_fpu() calls finit to initialize a task's xstate, while finit always
works on the current task. If we use PTRACE_GETFPREGS on another
process and both processes did not already use floating point, we get
a null pointer exception in finit.

This patch creates a new function finit_task that takes a task_struct
parameter. finit becomes a wrapper that simply calls finit_task with
current. On the plus side this avoids many calls to get_current which
would each resolve to an inline assembler mov instruction.

An empty finit_task has been added to i387.h to avoid linker errors in
case the compiler still emits the call in init_fpu when
CONFIG_MATH_EMULATION is not defined.

The declaration of finit in i387.h has been removed as the remaining
code using this function gets its prototype from fpu_proto.h.

Signed-off-by: Daniel Glöckner <dg@emlix.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Bill Metzenthen <billm@melbpc.org.au>
LKML-Reference: <E1Lew31-0004il-Fg@mailer.emlix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-04 20:33:16 +01:00

197 lines
4.3 KiB
C

/*---------------------------------------------------------------------------+
| fpu_aux.c |
| |
| Code to implement some of the FPU auxiliary instructions. |
| |
| Copyright (C) 1992,1993,1994,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "status_w.h"
#include "control_w.h"
static void fnop(void)
{
}
static void fclex(void)
{
partial_status &=
~(SW_Backward | SW_Summary | SW_Stack_Fault | SW_Precision |
SW_Underflow | SW_Overflow | SW_Zero_Div | SW_Denorm_Op |
SW_Invalid);
no_ip_update = 1;
}
/* Needs to be externally visible */
void finit_task(struct task_struct *tsk)
{
struct i387_soft_struct *soft = &tsk->thread.xstate->soft;
struct address *oaddr, *iaddr;
soft->cwd = 0x037f;
soft->swd = 0;
soft->ftop = 0; /* We don't keep top in the status word internally. */
soft->twd = 0xffff;
/* The behaviour is different from that detailed in
Section 15.1.6 of the Intel manual */
oaddr = (struct address *)&soft->foo;
oaddr->offset = 0;
oaddr->selector = 0;
iaddr = (struct address *)&soft->fip;
iaddr->offset = 0;
iaddr->selector = 0;
iaddr->opcode = 0;
soft->no_update = 1;
}
void finit(void)
{
finit_task(current);
}
/*
* These are nops on the i387..
*/
#define feni fnop
#define fdisi fnop
#define fsetpm fnop
static FUNC const finit_table[] = {
feni, fdisi, fclex, finit,
fsetpm, FPU_illegal, FPU_illegal, FPU_illegal
};
void finit_(void)
{
(finit_table[FPU_rm]) ();
}
static void fstsw_ax(void)
{
*(short *)&FPU_EAX = status_word();
no_ip_update = 1;
}
static FUNC const fstsw_table[] = {
fstsw_ax, FPU_illegal, FPU_illegal, FPU_illegal,
FPU_illegal, FPU_illegal, FPU_illegal, FPU_illegal
};
void fstsw_(void)
{
(fstsw_table[FPU_rm]) ();
}
static FUNC const fp_nop_table[] = {
fnop, FPU_illegal, FPU_illegal, FPU_illegal,
FPU_illegal, FPU_illegal, FPU_illegal, FPU_illegal
};
void fp_nop(void)
{
(fp_nop_table[FPU_rm]) ();
}
void fld_i_(void)
{
FPU_REG *st_new_ptr;
int i;
u_char tag;
if (STACK_OVERFLOW) {
FPU_stack_overflow();
return;
}
/* fld st(i) */
i = FPU_rm;
if (NOT_EMPTY(i)) {
reg_copy(&st(i), st_new_ptr);
tag = FPU_gettagi(i);
push();
FPU_settag0(tag);
} else {
if (control_word & CW_Invalid) {
/* The masked response */
FPU_stack_underflow();
} else
EXCEPTION(EX_StackUnder);
}
}
void fxch_i(void)
{
/* fxch st(i) */
FPU_REG t;
int i = FPU_rm;
FPU_REG *st0_ptr = &st(0), *sti_ptr = &st(i);
long tag_word = fpu_tag_word;
int regnr = top & 7, regnri = ((regnr + i) & 7);
u_char st0_tag = (tag_word >> (regnr * 2)) & 3;
u_char sti_tag = (tag_word >> (regnri * 2)) & 3;
if (st0_tag == TAG_Empty) {
if (sti_tag == TAG_Empty) {
FPU_stack_underflow();
FPU_stack_underflow_i(i);
return;
}
if (control_word & CW_Invalid) {
/* Masked response */
FPU_copy_to_reg0(sti_ptr, sti_tag);
}
FPU_stack_underflow_i(i);
return;
}
if (sti_tag == TAG_Empty) {
if (control_word & CW_Invalid) {
/* Masked response */
FPU_copy_to_regi(st0_ptr, st0_tag, i);
}
FPU_stack_underflow();
return;
}
clear_C1();
reg_copy(st0_ptr, &t);
reg_copy(sti_ptr, st0_ptr);
reg_copy(&t, sti_ptr);
tag_word &= ~(3 << (regnr * 2)) & ~(3 << (regnri * 2));
tag_word |= (sti_tag << (regnr * 2)) | (st0_tag << (regnri * 2));
fpu_tag_word = tag_word;
}
void ffree_(void)
{
/* ffree st(i) */
FPU_settagi(FPU_rm, TAG_Empty);
}
void ffreep(void)
{
/* ffree st(i) + pop - unofficial code */
FPU_settagi(FPU_rm, TAG_Empty);
FPU_pop();
}
void fst_i_(void)
{
/* fst st(i) */
FPU_copy_to_regi(&st(0), FPU_gettag0(), FPU_rm);
}
void fstp_i(void)
{
/* fstp st(i) */
FPU_copy_to_regi(&st(0), FPU_gettag0(), FPU_rm);
FPU_pop();
}