m68k: Define sigcontext ABI of ColdFire

The following patch defines sigcontext ABI of ColdFire.  Due to ISA
restrictions ColdFire needs different rt_sigreturn trampoline.

And due to ColdFire FP registers being 8-bytes instead of 12-bytes on
m68k, sigcontext and fpregset structures should be updated.

Regarding the sc_fpstate[16+6*8] field, it would've been enough 16
bytes to store ColdFire's FP state.  To accomodate GLIBC's libSegFault
it would'be been enough 6*8 bytes (room for the 6 non-call-clobbered
FP registers).  I set it to 16+6*8 to provide some extra space for any
future changes in the ColdFire FPU.
Signed-off-by: Maxim Kuvyrkov <maxim@codesourcery.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/asm/sigcontext.h

@@ -15,9 +15,15 @@ struct sigcontext {
 	unsigned long  sc_pc;
 	unsigned short sc_formatvec;
 #ifndef __uClinux__
+# ifdef __mcoldfire__
+	unsigned long  sc_fpregs[2][2];	/* room for two fp registers */
+	unsigned long  sc_fpcntl[3];
+	unsigned char  sc_fpstate[16+6*8];
+# else
 	unsigned long  sc_fpregs[2*3];  /* room for two fp registers */
 	unsigned long  sc_fpcntl[3];
 	unsigned char  sc_fpstate[216];
+# endif
 #endif
 };
 

arch/m68k/include/asm/ucontext.h

@@ -7,7 +7,11 @@ typedef greg_t gregset_t[NGREG];
 
 typedef struct fpregset {
 	int f_fpcntl[3];
+#ifdef __mcoldfire__
+	int f_fpregs[8][2];
+#else
 	int f_fpregs[8*3];
+#endif
 } fpregset_t;
 
 struct mcontext {

arch/m68k/kernel/signal.c

@@ -897,10 +897,17 @@ static void setup_rt_frame (int sig, struct k_sigaction *ka, siginfo_t *info,
 
 	/* Set up to return from userspace.  */
 	err |= __put_user(frame->retcode, &frame->pretcode);
+#ifdef __mcoldfire__
+	/* movel #__NR_rt_sigreturn,d0; trap #0 */
+	err |= __put_user(0x203c0000, (long __user *)(frame->retcode + 0));
+	err |= __put_user(0x00004e40 + (__NR_rt_sigreturn << 16),
+			  (long __user *)(frame->retcode + 4));
+#else
 	/* moveq #,d0; notb d0; trap #0 */
 	err |= __put_user(0x70004600 + ((__NR_rt_sigreturn ^ 0xff) << 16),
 			  (long __user *)(frame->retcode + 0));
 	err |= __put_user(0x4e40, (short __user *)(frame->retcode + 4));
+#endif
 
 	if (err)
 		goto give_sigsegv;