From e62d49f1a8b27002871f712e80b1785442e23393 Mon Sep 17 00:00:00 2001
From: Lee Lup Yuen <luppy@appkaki.com>
Date: Fri, 19 Jan 2024 21:06:38 +0800
Subject: [PATCH] MRET to Supervisor Mode

---
 riscv_cpu.c     | 4 ++--
 riscv_machine.c | 8 +++++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/riscv_cpu.c b/riscv_cpu.c
index ab9ae6d..214f223 100644
--- a/riscv_cpu.c
+++ b/riscv_cpu.c
@@ -47,7 +47,7 @@ void print_console(void *machine0, const char *buf, int len);
 #define DUMP_INTERRUPTS
 #define DUMP_INVALID_CSR
 #define DUMP_EXCEPTIONS
-//#define DUMP_CSR
+#define DUMP_CSR
 #define CONFIG_LOGFILE
  
 #include "riscv_cpu_priv.h"
@@ -1141,7 +1141,7 @@ static void raise_exception2(RISCVCPUState *s, uint32_t cause,
         s->pc = s->mtvec;
     }
     //// Begin Test: Quit if cause=2, otherwise it will loop forever
-    if (cause == 2) { puts("tinyemu: Unknown mcause 2, quitting"); exit(1); }
+    // if (cause == 2) { puts("tinyemu: Unknown mcause 2, quitting"); exit(1); }
     //// End Test
 }
 
diff --git a/riscv_machine.c b/riscv_machine.c
index d5afcb8..6657a60 100644
--- a/riscv_machine.c
+++ b/riscv_machine.c
@@ -867,7 +867,13 @@ static void copy_bios(RISCVMachine *s, const uint8_t *buf, int buf_len,
     q[1] = 0x597; /* auipc a1, dtb */
     q[2] = 0x58593 + ((fdt_addr - 4) << 20); /* addi a1, a1, dtb */
     q[3] = 0xf1402573; /* csrr a0, mhartid */
-    q[4] = 0x00028067; /* jalr zero, t0, jump_addr */
+
+    //// Previously: Jump to RAM_BASE_ADDR in Machine Mode
+    // q[4] = 0x00028067; /* jalr zero, t0, jump_addr */
+
+    //// Jump to RAM_BASE_ADDR in Supervisor Mode
+    q[4] = 0x34129073;  // csrw mepc, t0
+    q[5] = 0x30200073;  // mret
 }
 
 static void riscv_flush_tlb_write_range(void *opaque, uint8_t *ram_addr,