lib: Add misaligned load/store trap handling

We generally don't get misaligned load/store traps from Linux/U-Boot
compiled using GCC 8.2 or higher but this is not true with older
GCC toolchains. To tackle this we add misaligned load/store trap
handling adopted from BBL sources but much more simpler.
(Note: BBL sources can be found at https://github.com/riscv/riscv-pk.git)

Signed-off-by: Anup Patel <anup.patel@wdc.com>

4 files changed, 166 insertions, 1 deletions

diff --git a/include/sbi/sbi_misaligned_ldst.h b/include/sbi/sbi_misaligned_ldst.h
new file mode 100644
index 0000000..1641958
--- /dev/null
+++ b/include/sbi/sbi_misaligned_ldst.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2018 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#ifndef __SBI_MISALIGNED_LDST_H__
+#define __SBI_MISALIGNED_LDST_H__
+
+#include <sbi/sbi_types.h>
+
+struct sbi_trap_regs;
+struct sbi_scratch;
+
+int sbi_misaligned_load_handler(u32 hartid, ulong mcause,
+				struct sbi_trap_regs *regs,
+				struct sbi_scratch *scratch);
+
+int sbi_misaligned_store_handler(u32 hartid, ulong mcause,
+				 struct sbi_trap_regs *regs,
+				 struct sbi_scratch *scratch);
+
+#endif
diff --git a/lib/objects.mk b/lib/objects.mk
index ed14677..b70557d 100644
--- a/lib/objects.mk
+++ b/lib/objects.mk
@@ -18,6 +18,7 @@ lib-objs-y += sbi_hart.o
 lib-objs-y += sbi_illegal_insn.o
 lib-objs-y += sbi_init.o
 lib-objs-y += sbi_ipi.o
+lib-objs-y += sbi_misaligned_ldst.o
 lib-objs-y += sbi_system.o
 lib-objs-y += sbi_timer.o
 lib-objs-y += sbi_trap.o
diff --git a/lib/sbi_misaligned_ldst.c b/lib/sbi_misaligned_ldst.c
new file mode 100644
index 0000000..b35e919
--- /dev/null
+++ b/lib/sbi_misaligned_ldst.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2018 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sbi/riscv_asm.h>
+#include <sbi/riscv_encoding.h>
+#include <sbi/sbi_error.h>
+#include <sbi/sbi_misaligned_ldst.h>
+#include <sbi/sbi_trap.h>
+#include <sbi/sbi_unpriv.h>
+
+union reg_data {
+	u8 data_bytes[8];
+	ulong data_ulong;
+	u64 data_u64;
+};
+
+int sbi_misaligned_load_handler(u32 hartid, ulong mcause,
+				struct sbi_trap_regs *regs,
+				struct sbi_scratch *scratch)
+{
+	union reg_data val;
+	ulong mstatus = csr_read(mstatus);
+	ulong insn = get_insn(regs->mepc, &mstatus);
+	ulong addr = csr_read(mtval);
+	int i, shift = 0, len = 0;
+
+	if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
+		len = 4;
+		shift = 8 * (sizeof(ulong) - len);
+#if __riscv_xlen == 64
+	} else if ((insn & INSN_MASK_LD) == INSN_MATCH_LD) {
+		len = 8;
+		shift = 8 * (sizeof(ulong) - len);
+	} else if ((insn & INSN_MASK_LWU) == INSN_MATCH_LWU) {
+		len = 4;
+#endif
+	} else if ((insn & INSN_MASK_LH) == INSN_MATCH_LH) {
+		len = 2;
+		shift = 8 * (sizeof(ulong) - len);
+	} else if ((insn & INSN_MASK_LHU) == INSN_MATCH_LHU) {
+		len = 2;
+#ifdef __riscv_compressed
+# if __riscv_xlen >= 64
+	} else if ((insn & INSN_MASK_C_LD) == INSN_MATCH_C_LD) {
+		len = 8;
+		shift = 8 * (sizeof(ulong) - len);
+		insn = RVC_RS2S(insn) << SH_RD;
+	} else if ((insn & INSN_MASK_C_LDSP) == INSN_MATCH_C_LDSP &&
+		   ((insn >> SH_RD) & 0x1f)) {
+		len = 8;
+		shift = 8 * (sizeof(ulong) - len);
+# endif
+	} else if ((insn & INSN_MASK_C_LW) ==INSN_MATCH_C_LW) {
+		len = 4;
+		shift = 8 * (sizeof(ulong) - len);
+		insn = RVC_RS2S(insn) << SH_RD;
+	} else if ((insn & INSN_MASK_C_LWSP) == INSN_MATCH_C_LWSP &&
+		   ((insn >> SH_RD) & 0x1f)) {
+		len = 4;
+		shift = 8 * (sizeof(ulong) - len);
+#endif
+	} else
+		return SBI_EILL;
+
+	val.data_u64 = 0;
+	for (i = 0; i < len; i++)
+		val.data_bytes[i] = load_u8((void *)(addr + i), regs->mepc);
+
+	SET_RD(insn, regs, val.data_ulong << shift >> shift);
+
+	regs->mepc += INSN_LEN(insn);
+
+	return 0;
+}
+
+int sbi_misaligned_store_handler(u32 hartid, ulong mcause,
+				 struct sbi_trap_regs *regs,
+				 struct sbi_scratch *scratch)
+{
+	union reg_data val;
+	ulong mstatus = csr_read(mstatus);
+	ulong insn = get_insn(regs->mepc, &mstatus);
+	ulong addr = csr_read(mtval);
+	int i, len = 0;
+
+	val.data_ulong = GET_RS2(insn, regs);
+
+	if ((insn & INSN_MASK_SW) == INSN_MATCH_SW) {
+		len = 4;
+#if __riscv_xlen == 64
+	} else if ((insn & INSN_MASK_SD) == INSN_MATCH_SD) {
+		len = 8;
+#endif
+	} else if ((insn & INSN_MASK_SH) == INSN_MATCH_SH) {
+		len = 2;
+#ifdef __riscv_compressed
+# if __riscv_xlen >= 64
+	} else if ((insn & INSN_MASK_C_SD) == INSN_MATCH_C_SD) {
+		len = 8;
+		val.data_ulong = GET_RS2S(insn, regs);
+	} else if ((insn & INSN_MASK_C_SDSP) == INSN_MATCH_C_SDSP &&
+		   ((insn >> SH_RD) & 0x1f)) {
+		len = 8;
+		val.data_ulong = GET_RS2C(insn, regs);
+# endif
+	} else if ((insn & INSN_MASK_C_SW) == INSN_MATCH_C_SW) {
+		len = 4;
+		val.data_ulong = GET_RS2S(insn, regs);
+	} else if ((insn & INSN_MASK_C_SWSP) == INSN_MATCH_C_SWSP &&
+		   ((insn >> SH_RD) & 0x1f)) {
+		len = 4;
+		val.data_ulong = GET_RS2C(insn, regs);
+#endif
+	} else
+		return SBI_EILL;
+
+	for (i = 0; i < len; i++)
+		store_u8((void *)(addr + i), val.data_bytes[i], regs->mepc);
+
+	regs->mepc += INSN_LEN(insn);
+
+	return 0;
+}
diff --git a/lib/sbi_trap.c b/lib/sbi_trap.c
index 284bb74..012a9a0 100644
--- a/lib/sbi_trap.c
+++ b/lib/sbi_trap.c
@@ -12,9 +12,10 @@
 #include <sbi/sbi_console.h>
 #include <sbi/sbi_ecall.h>
 #include <sbi/sbi_error.h>
-#include <sbi/sbi_illegal_insn.h>
 #include <sbi/sbi_hart.h>
+#include <sbi/sbi_illegal_insn.h>
 #include <sbi/sbi_ipi.h>
+#include <sbi/sbi_misaligned_ldst.h>
 #include <sbi/sbi_timer.h>
 #include <sbi/sbi_trap.h>
 
@@ -95,6 +96,14 @@ void sbi_trap_handler(struct sbi_trap_regs *regs,
 		rc = sbi_illegal_insn_handler(hartid, mcause, regs, scratch);
 		msg = "illegal instruction handler failed";
 		break;
+	case CAUSE_MISALIGNED_LOAD:
+		rc = sbi_misaligned_load_handler(hartid, mcause, regs, scratch);
+		msg = "misaligned load handler failed";
+		break;
+	case CAUSE_MISALIGNED_STORE:
+		rc = sbi_misaligned_store_handler(hartid, mcause, regs, scratch);
+		msg = "misaligned store handler failed";
+		break;
 	case CAUSE_SUPERVISOR_ECALL:
 	case CAUSE_HYPERVISOR_ECALL:
 		rc = sbi_ecall_handler(hartid, mcause, regs, scratch);