uml: floating point signal delivery fixes

Handle floating point state in across signals correctly.  UML/i386 needs to
know whether the host does PTRACE_[GS]ETFPXREGS, so an arch_init_registers
hook is added, which on x86_64 does nothing.

UML doesn't save and restore floating point registers on kernel entry and
exit, so they need to be copied between the host process and the sigcontext.
save_fpx_registers and restore_fpx_registers are added for this purpose.
save_fp_registers and restore_fp_registers already exist.

There was a bunch of floating point state conversion code in
arch/um/sys-i386/ptrace.c which isn't needed there, but is needed in signal.c,
so it is moved over.

The i386 code now distinguishes between fp and fpx state and handles them
correctly.  The x86_64 code just needs to copy state as-is between the host
process and the stack.  There are also some fixes there to pass the correct
address of the floating point state around.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/sys-i386/ptrace.c

@@ -144,85 +144,6 @@ int peek_user(struct task_struct *child, long addr, long data)
 	return put_user(tmp, (unsigned long __user *) data);
 }
 
-struct i387_fxsave_struct {
-	unsigned short	cwd;
-	unsigned short	swd;
-	unsigned short	twd;
-	unsigned short	fop;
-	long	fip;
-	long	fcs;
-	long	foo;
-	long	fos;
-	long	mxcsr;
-	long	reserved;
-	long	st_space[32];	/* 8*16 bytes for each FP-reg = 128 bytes */
-	long	xmm_space[32];	/* 8*16 bytes for each XMM-reg = 128 bytes */
-	long	padding[56];
-};
-
-/*
- * FPU tag word conversions.
- */
-
-static inline unsigned short twd_i387_to_fxsr( unsigned short twd )
-{
-	unsigned int tmp; /* to avoid 16 bit prefixes in the code */
-
-	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
-	tmp = ~twd;
-	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
-	/* and move the valid bits to the lower byte. */
-	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
-	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
-	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
-	return tmp;
-}
-
-static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct *fxsave )
-{
-	struct _fpxreg *st = NULL;
-	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);
-
-	for ( i = 0 ; i < 8 ; i++ ) {
-		if ( twd & 0x1 ) {
-			st = (struct _fpxreg *) FPREG_ADDR( fxsave, i );
-
-			switch ( st->exponent & 0x7fff ) {
-			case 0x7fff:
-				tag = 2;		/* Special */
-				break;
-			case 0x0000:
-				if ( !st->significand[0] &&
-				     !st->significand[1] &&
-				     !st->significand[2] &&
-				     !st->significand[3] ) {
-					tag = 1;	/* Zero */
-				} else {
-					tag = 2;	/* Special */
-				}
-				break;
-			default:
-				if ( st->significand[3] & 0x8000 ) {
-					tag = 0;	/* Valid */
-				} else {
-					tag = 2;	/* Special */
-				}
-				break;
-			}
-		} else {
-			tag = 3;			/* Empty */
-		}
-		ret |= (tag << (2 * i));
-		twd = twd >> 1;
-	}
-	return ret;
-}
-
 static inline int convert_fxsr_to_user(struct _fpstate __user *buf,
 				       struct pt_regs *regs)
 {