MIPS: Dumb MSA FP exception handler

This patch adds a simple handler for MSA FP exceptions which delivers a
SIGFPE to the running task. In the future it should probably be extended
to re-execute the instruction with the MSACSR.NX bit set in order to
generate results for any elements which did not cause an exception
before delivering the SIGFPE signal.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6432/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/genex.S

@@ -475,6 +475,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	BUILD_HANDLER cpu cpu sti silent		/* #11 */
 	BUILD_HANDLER ov ov sti silent			/* #12 */
 	BUILD_HANDLER tr tr sti silent			/* #13 */
+	BUILD_HANDLER msa_fpe msa_fpe sti silent	/* #14 */
 	BUILD_HANDLER fpe fpe fpe silent		/* #15 */
 	BUILD_HANDLER ftlb ftlb none silent		/* #16 */
 	BUILD_HANDLER msa msa sti silent		/* #21 */

arch/mips/kernel/traps.c

@@ -78,6 +78,7 @@ extern asmlinkage void handle_ri_rdhwr(void);
 extern asmlinkage void handle_cpu(void);
 extern asmlinkage void handle_ov(void);
 extern asmlinkage void handle_tr(void);
+extern asmlinkage void handle_msa_fpe(void);
 extern asmlinkage void handle_fpe(void);
 extern asmlinkage void handle_ftlb(void);
 extern asmlinkage void handle_msa(void);
@@ -1250,6 +1251,16 @@ out:
 	exception_exit(prev_state);
 }
 
+asmlinkage void do_msa_fpe(struct pt_regs *regs)
+{
+	enum ctx_state prev_state;
+
+	prev_state = exception_enter();
+	die_if_kernel("do_msa_fpe invoked from kernel context!", regs);
+	force_sig(SIGFPE, current);
+	exception_exit(prev_state);
+}
+
 asmlinkage void do_msa(struct pt_regs *regs)
 {
 	enum ctx_state prev_state;
@@ -2106,6 +2117,7 @@ void __init trap_init(void)
 	set_except_vector(11, handle_cpu);
 	set_except_vector(12, handle_ov);
 	set_except_vector(13, handle_tr);
+	set_except_vector(14, handle_msa_fpe);
 
 	if (current_cpu_type() == CPU_R6000 ||
 	    current_cpu_type() == CPU_R6000A) {