[RFC V2 PATCH 5/9] riscv: add support for sysctl unaligned_enabled control

[Clément Léger]

This sysctl tuning option allows the user to disable misaligned access
handling globally on the system. This will also be used by misaligned
detection code to temporarily disable misaligned access handling.

Signed-off-by: Clément Léger <cleger at rivosinc.com>
---
 arch/riscv/Kconfig                   | 1 +
 arch/riscv/kernel/traps_misaligned.c | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c69572fbe613..99fd951def39 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -139,6 +139,7 @@ config RISCV
 	select RISCV_TIMER if RISCV_SBI
 	select SIFIVE_PLIC
 	select SPARSE_IRQ
+	select SYSCTL_ARCH_UNALIGN_ALLOW
 	select SYSCTL_EXCEPTION_TRACE
 	select THREAD_INFO_IN_TASK
 	select TRACE_IRQFLAGS_SUPPORT
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 804f6c5e0e44..39ec6caa6234 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -287,6 +287,9 @@ union reg_data {
 	u64 data_u64;
 };
 
+/* sysctl hooks */
+int unaligned_enabled __read_mostly = 1;	/* Enabled by default */
+
 int handle_misaligned_load(struct pt_regs *regs)
 {
 	union reg_data val;
@@ -297,6 +300,9 @@ int handle_misaligned_load(struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
 
+	if (!unaligned_enabled)
+		return -1;
+
 	if (get_insn(regs, epc, &insn))
 		return -1;
 
@@ -387,6 +393,9 @@ int handle_misaligned_store(struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
 
+	if (!unaligned_enabled)
+		return -1;
+
 	if (get_insn(regs, epc, &insn))
 		return -1;
 
-- 
2.40.1