riscv: Unaligned load/store handling for M_MODE

Add handlers for unaligned load and store traps that may be generated
by applications. Code heavily inspired from the OpenSBI project.
Handling of the unaligned access traps is suitable for applications
compiled with or without compressed instructions and is independent of
the kernel CONFIG_RISCV_ISA_C option value.

Signed-off-by: Damien Le Moal <[email protected]>
Signed-off-by: Anup Patel <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: damien-lemoal

arch/riscv/kernel/Makefile

@@ -30,7 +30,7 @@ obj-y	+= cacheinfo.o
 obj-y	+= patch.o
 obj-$(CONFIG_MMU) += vdso.o vdso/
 
-obj-$(CONFIG_RISCV_M_MODE)	+= clint.o
+obj-$(CONFIG_RISCV_M_MODE)	+= clint.o traps_misaligned.o
 obj-$(CONFIG_FPU)		+= fpu.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o

arch/riscv/kernel/traps.c

@@ -97,12 +97,33 @@ DO_ERROR_INFO(do_trap_insn_fault,
 	SIGSEGV, SEGV_ACCERR, "instruction access fault");
 DO_ERROR_INFO(do_trap_insn_illegal,
 	SIGILL, ILL_ILLOPC, "illegal instruction");
-DO_ERROR_INFO(do_trap_load_misaligned,
-	SIGBUS, BUS_ADRALN, "load address misaligned");
 DO_ERROR_INFO(do_trap_load_fault,
 	SIGSEGV, SEGV_ACCERR, "load access fault");
+#ifndef CONFIG_RISCV_M_MODE
+DO_ERROR_INFO(do_trap_load_misaligned,
+	SIGBUS, BUS_ADRALN, "Oops - load address misaligned");
 DO_ERROR_INFO(do_trap_store_misaligned,
-	SIGBUS, BUS_ADRALN, "store (or AMO) address misaligned");
+	SIGBUS, BUS_ADRALN, "Oops - store (or AMO) address misaligned");
+#else
+int handle_misaligned_load(struct pt_regs *regs);
+int handle_misaligned_store(struct pt_regs *regs);
+
+asmlinkage void do_trap_load_misaligned(struct pt_regs *regs)
+{
+	if (!handle_misaligned_load(regs))
+		return;
+	do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
+		      "Oops - load address misaligned");
+}
+
+asmlinkage void do_trap_store_misaligned(struct pt_regs *regs)
+{
+	if (!handle_misaligned_store(regs))
+		return;
+	do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
+		      "Oops - store (or AMO) address misaligned");
+}
+#endif
 DO_ERROR_INFO(do_trap_store_fault,
 	SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
 DO_ERROR_INFO(do_trap_ecall_u,