From 2d33e50074135b9a64d298aa677b0c307b726171 Mon Sep 17 00:00:00 2001
From: vhaudiquet <vhaudiquet343@hotmail.fr>
Date: Tue, 24 Oct 2023 00:19:10 +0200
Subject: [PATCH] Define CSR STATUS bits, std functions on exception

---
 src/cpu/csr.h       | 36 ++++++++++++++++++++++++++++++++++++
 src/cpu/exception.c | 18 ++++++++++--------
 src/cpu/rv32cpu.c   |  7 +++----
 3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/src/cpu/csr.h b/src/cpu/csr.h
index 317398d..df1f3a5 100644
--- a/src/cpu/csr.h
+++ b/src/cpu/csr.h
@@ -61,4 +61,40 @@
 /* Machine Memory Protection */
 #define CSR_PMPCFG0 0x3A0
 
+// CSR STATUS
+// SIE: Supervisor Interrupt Enable
+#define STATUS_SIE 0x2
+// MIE: Machine Interrupt Enable
+#define STATUS_MIE 0x8
+// SPIE: Supervisor Previous Interrupt Enable
+#define STATUS_SPIE 0x20
+// MPIE: Machine Previous Interrupt Enable
+#define STATUS_MPIE 0x80
+// UBE : User Big Endian (always 0 for us, we are little endian)
+#define STATUS_UBE 0x40
+// SPP : Supervisor Previous Privilege
+#define STATUS_SPP 0x100
+// VS (2bits) : for extensions
+#define STATUS_VS 0x600
+// MPP (2bits) : Machine Previous Privilege
+#define STATUS_MPP 0x1800
+// FS (2bits) : for extensions
+#define STATUS_FS 0x6000
+// XS (2bits) : for extensions
+#define STATUS_XS 0x18000
+// MPRV : Modify PRiVilege
+#define STATUS_MPRV 0x20000
+// SUM : permit Supervisor User Memory access
+#define STATUS_SUM 0x40000
+// MXR : Make eXecutable Readable
+#define STATUS_MXR 0x80000
+// TVM : Trap Virtual Memory (virtualization support)
+#define STATUS_TVM 0x100000
+// TW : Timeout Wait (virtualization support)
+#define STATUS_TW 0x200000
+// TSR : Trap SRET (virtualization support)
+#define STATUS_TSR 0x400000
+// SD : for extensions
+#define STATUS_SD 0x80000000
+
 #endif
diff --git a/src/cpu/exception.c b/src/cpu/exception.c
index 9d0677f..f2db177 100644
--- a/src/cpu/exception.c
+++ b/src/cpu/exception.c
@@ -16,10 +16,10 @@ __attribute__((noreturn)) void exception_trigger(rv32_cpu_t* cpu, uint32_t scaus
 	// Exceptions cannot be disabled
 
 	// Unset SIE (interrupt enable) bit
-	cpu->csr[CSR_SSTATUS] &= ~0b10U;
+	csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) & (~STATUS_SIE));
 
 	// Set xCAUSE : exception cause, with interrupt bit set to null
-	cpu->csr[CSR_SCAUSE] = scause;
+	csr_write(cpu, CSR_SCAUSE, scause);
 	if(gdbstub && scause == SCAUSE_BREAKPOINT)
 	{
 		cpu->sim_ticks_left = 0;
@@ -31,26 +31,28 @@ __attribute__((noreturn)) void exception_trigger(rv32_cpu_t* cpu, uint32_t scaus
 	}
 
 	// Save previous interrupt enable in xSTATUS.xPIE
-	if(cpu->csr[CSR_SSTATUS] & 0b10U)
-		cpu->csr[CSR_SSTATUS] |= 0x80;
+	if(csr_read(cpu, CSR_SSTATUS) & STATUS_SIE)
+		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SPIE);
+	else
+		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) & (~STATUS_SPIE));
 
 	// Set previous privilege mode in xSTATUS.xPP
 	// TODO : Allow user mode exceptions (by not setting this)
-	cpu->csr[CSR_SSTATUS] |= 0x100;
+	csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SPP);
 
 	// Set privilege mode for exception handling, checking for delegation
 	// TODO
 
 	// Set xTVAL, exception-specific information related to xCAUSE
-	cpu->csr[CSR_STVAL] = tval;
+	csr_write(cpu, CSR_STVAL, tval);
 
 	// Set SEPC to instruction that caused exception
-	cpu->csr[CSR_SEPC] = cpu->pc;
+	csr_write(cpu, CSR_SEPC, cpu->pc);
 
 	// Set PC to xTVEC : exception handling code
 	// xTVEC: [Base(30bits) Mode(2 bits)], address 4-byte aligned in base
 	// Exceptions are not vectored (we can safely ignore mode)
-	cpu->pc = cpu->csr[CSR_STVEC] & 0xFFFFFFFC;
+	cpu->pc = csr_read(cpu, CSR_STVEC) & 0xFFFFFFFC;
 
 	// Unlock cpu mutex, cpu_loop will lock it just after
 	pthread_mutex_unlock(&cpu->mutex);
diff --git a/src/cpu/rv32cpu.c b/src/cpu/rv32cpu.c
index 0a3226c..a28c51a 100644
--- a/src/cpu/rv32cpu.c
+++ b/src/cpu/rv32cpu.c
@@ -529,15 +529,14 @@ static void cpu_execute(rv32_cpu_t* cpu, instruction_t* instruction)
 						case IMM_SRET:
 							// SRET: Return from supervisor interrupt
 							// Restore Interrupt Enable from Previous Interrupt Enable
-							uint32_t sstatus = csr_read(cpu, CSR_SSTATUS);
-							if(sstatus & 0x80)
-								csr_write(cpu, CSR_SSTATUS, sstatus | 0b10);
+							if(csr_read(cpu, CSR_SSTATUS) & STATUS_SPIE)
+								csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SIE);
 
 							// Restore privilege mode from Previous Privilege
 							// TODO
 
 							// Set Previous Interrupt Enable to 1
-							csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | 0x80);
+							csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SPIE);
 
 							// Set Previous Privilege to 0
 							// TODO