On Sun, 16 Jan 2005, Roland McGrath wrote:
>
> Note, this code is identical in 2.4 so this fix applies there as well.
Uhh.. "(i + 8 - tos) & 7" makes no sense.
It's not only mathematically the same as "(i - tos) & 7", but I don't even
see how you got to the "+ 8" in the first place..
Also, we're not using C++, so we don't do the "const" part of
const unsigned int tos = ...
thing. So suggested version with trivial fixes appended (technically, you
don't need the "& 7" on the tos calculation either, but hey, at least that
one I see why it's there, and agree with - the compiler may well be able
to optimize both of these things away, so keeping the source in its
"logical" format makes sense). Does this still work for you?
> Fortunately, only the manuals differ and all the chips actually agree.
Hmm.
What happens if it was in MMX mode? If I remember correctly, different
CPU's do different things for MMX (some rotate them so that "mmx0" is
always the same as "st(0)", some don't, and/or have separate hw registers
altogether for it)? I realize we don't probably care, I'm just wondering
if somebody knows...
Linus
----
===== arch/i386/kernel/i387.c 1.22 vs edited =====
--- 1.22/arch/i386/kernel/i387.c 2004-10-28 00:39:55 -07:00
+++ edited/arch/i386/kernel/i387.c 2005-01-16 19:38:28 -08:00
@@ -111,16 +111,17 @@
static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct
*fxsave )
{
struct _fpxreg *st = NULL;
+ unsigned int tos = (fxsave->swd >> 11) & 7;
unsigned long twd = (unsigned long) fxsave->twd;
unsigned long tag;
unsigned long ret = 0xffff0000u;
int i;
-#define FPREG_ADDR(f, n) ((char *)&(f)->st_space + (n) * 16);
+#define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16);
for ( i = 0 ; i < 8 ; i++ ) {
if ( twd & 0x1 ) {
- st = (struct _fpxreg *) FPREG_ADDR( fxsave, i );
+ st = FPREG_ADDR( fxsave, (i - tos) & 7 );
switch ( st->exponent & 0x7fff ) {
case 0x7fff:
===== arch/x86_64/ia32/fpu32.c 1.8 vs edited =====
--- 1.8/arch/x86_64/ia32/fpu32.c 2004-05-30 12:49:35 -07:00
+++ edited/arch/x86_64/ia32/fpu32.c 2005-01-16 19:39:20 -08:00
@@ -28,16 +28,17 @@
static inline unsigned long twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
{
struct _fpxreg *st = NULL;
+ unsigned long tos = (fxsave->swd >> 11) & 7;
unsigned long twd = (unsigned long) fxsave->twd;
unsigned long tag;
unsigned long ret = 0xffff0000;
int i;
-#define FPREG_ADDR(f, n) ((char *)&(f)->st_space + (n) * 16);
+#define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16);
for (i = 0 ; i < 8 ; i++) {
if (twd & 0x1) {
- st = (struct _fpxreg *) FPREG_ADDR( fxsave, i );
+ st = FPREG_ADDR( fxsave, (i - tos) & 7 );
switch (st->exponent & 0x7fff) {
case 0x7fff:
-
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