From b9dd0160640adcbb1b5a66247b274bf99a7de705 Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Sun, 12 May 2024 01:26:32 +0200
Subject: First real program running!

---
 emulator/main.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++----------
 main.asm        | 23 ++++++++++++++++++-----
 2 files changed, 66 insertions(+), 15 deletions(-)

diff --git a/emulator/main.c b/emulator/main.c
index d48c049..ed875a3 100644
--- a/emulator/main.c
+++ b/emulator/main.c
@@ -216,6 +216,8 @@ struct Hart
 {
     uint32_t pc;
     uint32_t regs[32];
+    char*    mem;
+    uint32_t mem_size;
 };
 
 void execute_op_imm(struct Hart* hart, uint32_t instruction)
@@ -334,24 +336,61 @@ void execute_branch(struct Hart* hart, uint32_t instruction)
     }
 }
 
-uint32_t load_byte(struct Hart* hart, uint32_t address)
+inline uint32_t load_size(struct Hart* hart, uint32_t address, uint32_t size)
 {
+    if ((address & 0x80000000) == 0)
+    {
+        assert(address + size < hart->mem_size);
+        uint32_t value = 0;
+        memcpy(&value, hart->mem + address, size);
+        return value;
+    }
+    
     return 0;
 }
 
+uint32_t load_byte(struct Hart* hart, uint32_t address)
+{
+    return load_size(hart, address, 1);
+}
+
 uint32_t load_half(struct Hart* hart, uint32_t address)
 {
-    return 0;
+    return load_size(hart, address, 2);
 }
 
 uint32_t load_word(struct Hart* hart, uint32_t address)
 {
-    return 0;
+    return load_size(hart, address, 4);
 }
 
-void store_byte(struct Hart* hart, uint32_t address, uint8_t value) {}
-void store_half(struct Hart* hart, uint32_t address, uint16_t value) {}
-void store_word(struct Hart* hart, uint32_t address, uint32_t value) {}
+inline void store_size(struct Hart* hart, uint32_t address, uint32_t value, uint32_t size)
+{
+    if ((address & 0x80000000) == 0)
+    {
+        assert(address + size < hart->mem_size);
+        memcpy(hart->mem + address, &value, size);
+    }
+    else if (address == 0x80000000)
+    {
+        fwrite(&value, 1, size, stdout);
+    }
+}
+
+void store_byte(struct Hart* hart, uint32_t address, uint8_t value)
+{
+    store_size(hart, address, value, 1);
+}
+
+void store_half(struct Hart* hart, uint32_t address, uint16_t value)
+{
+    store_size(hart, address, value, 2);
+}
+
+void store_word(struct Hart* hart, uint32_t address, uint32_t value)
+{
+    store_size(hart, address, value, 4);
+}
 
 void execute_op_load(struct Hart* hart, uint32_t instruction)
 {
@@ -786,14 +825,13 @@ int main(int argc, char* argv[])
 
     struct Hart hart = {0};
     hart.pc = start_address;
+    hart.mem = mem;
+    hart.mem_size = mem_size;
 
     while (true)
     {
-        uint32_t instruction = *(uint32_t*)(mem + hart.pc);
+        uint32_t instruction = load_word(&hart, hart.pc);
         execute(&hart, instruction);
-        printf("pc=%x x1=%d x2=%d x3=%d x4=%d\n",
-            hart.pc, hart.regs[1], hart.regs[2], hart.regs[3], hart.regs[4]);
-        fgetc(stdout);
     }
     
     return EXIT_SUCCESS;
diff --git a/main.asm b/main.asm
index e90d6a2..2d41e48 100644
--- a/main.asm
+++ b/main.asm
@@ -1,9 +1,22 @@
 .section .text
 .global _main
+
+print:
+    li      t1, 0x80000000
+l0:
+    lb      t0, 0(a0)
+    beqz    t0, l1
+    sb      t0, 0(t1)
+    addi    a0, a0, 1
+    j       l0
+l1:
+    ret
+
 _main:
-    li      x1, 5
-    addi    x2, x1, 45
+    la      a0, my_str
+    call    print
+
+halt: j halt
 
-loop:
-    addi    x2, x2, 1
-    j       loop
+.section .rodata
+my_str: .string "Hello, world!\n"
-- 
cgit