MIPS: unaligned: Add DSP lwx & lhx missaligned access support

Add handling of missaligned access for DSP load instructions
lwx & lhx.

Since DSP instructions share SPECIAL3 opcode with other non-DSP
instructions, necessary logic was inserted for distinguishing
between instructions with SPECIAL3 opcode. For that purpose,
the instruction format for DSP instructions is added to
arch/mips/include/uapi/asm/inst.h.
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtech.com>
Cc: James.Hogan@imgtec.com
Cc: Paul.Burton@imgtec.com
Cc: Raghu.Gandham@imgtec.com
Cc: Leonid.Yegoshin@imgtec.com
Cc: Douglas.Leung@imgtec.com
Cc: Petar.Jovanovic@imgtec.com
Cc: Goran.Ferenc@imgtec.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16511/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/uapi/asm/inst.h

@@ -762,6 +762,16 @@ struct msa_mi10_format {		/* MSA MI10 */
 	;))))))
 };
 
+struct dsp_format {		/* SPEC3 DSP format instructions */
+	__BITFIELD_FIELD(unsigned int opcode : 6,
+	__BITFIELD_FIELD(unsigned int base : 5,
+	__BITFIELD_FIELD(unsigned int index : 5,
+	__BITFIELD_FIELD(unsigned int rd : 5,
+	__BITFIELD_FIELD(unsigned int op : 5,
+	__BITFIELD_FIELD(unsigned int func : 6,
+	;))))))
+};
+
 struct spec3_format {   /* SPEC3 */
 	__BITFIELD_FIELD(unsigned int opcode:6,
 	__BITFIELD_FIELD(unsigned int rs:5,
@@ -1053,6 +1063,7 @@ union mips_instruction {
 	struct b_format b_format;
 	struct ps_format ps_format;
 	struct v_format v_format;
+	struct dsp_format dsp_format;
 	struct spec3_format spec3_format;
 	struct fb_format fb_format;
 	struct fp0_format fp0_format;

arch/mips/kernel/unaligned.c

@@ -939,12 +939,37 @@ static void emulate_load_store_insn(struct pt_regs *regs,
 		 * The remaining opcodes are the ones that are really of
 		 * interest.
 		 */
-#ifdef CONFIG_EVA
 	case spec3_op:
+		if (insn.dsp_format.func == lx_op) {
+			switch (insn.dsp_format.op) {
+			case lwx_op:
+				if (!access_ok(VERIFY_READ, addr, 4))
+					goto sigbus;
+				LoadW(addr, value, res);
+				if (res)
+					goto fault;
+				compute_return_epc(regs);
+				regs->regs[insn.dsp_format.rd] = value;
+				break;
+			case lhx_op:
+				if (!access_ok(VERIFY_READ, addr, 2))
+					goto sigbus;
+				LoadHW(addr, value, res);
+				if (res)
+					goto fault;
+				compute_return_epc(regs);
+				regs->regs[insn.dsp_format.rd] = value;
+				break;
+			default:
+				goto sigill;
+			}
+		}
+#ifdef CONFIG_EVA
+		else {
 			/*
-		 * we can land here only from kernel accessing user memory,
-		 * so we need to "switch" the address limit to user space, so
-		 * address check can work properly.
+			 * we can land here only from kernel accessing user
+			 * memory, so we need to "switch" the address limit to
+			 * user space, so that address check can work properly.
 			 */
 			seg = get_fs();
 			set_fs(USER_DS);
@@ -1019,8 +1044,9 @@ static void emulate_load_store_insn(struct pt_regs *regs,
 				goto sigill;
 			}
 			set_fs(seg);
-		break;
+		}
 #endif
+		break;
 	case lh_op:
 		if (!access_ok(VERIFY_READ, addr, 2))
 			goto sigbus;