(timer): basic start

src/boot/traps.S

@@ -4,10 +4,10 @@
 .global trap_entry
 
 trap_entry:
-    # Allocate stack space for GPRs (256 bytes) + FPU registers (512 bytes)
-    addi sp, sp, -768  # Total: 256 (GPRs) + 512 (FPU)
+    # Create space on the stack for 32 registers (32 * 8 = 256 bytes)
+    addi sp, sp, -256
 
-    # --- Save GPRs ---
+    # Save all General Purpose Registers (GPRs)
     sd ra, 0(sp)
     sd gp, 8(sp)
     sd tp, 16(sp)
@@ -39,112 +39,19 @@ trap_entry:
     sd t5, 224(sp)
     sd t6, 232(sp)
 
-    # --- Save mepc/mcause/mstatus ---
+    # Save mepc to the stack (using offset 240)
     csrr t0, mepc
     sd t0, 240(sp)
-    csrr t0, mcause
-    sd t0, 248(sp) 
-    csrr t0, mstatus
-    sd t0, 256(sp)
 
-    # --- Check FPU Status (mstatus.FS) ---
-    csrr t1, mstatus
-    li t2, 0x6000
-    and t1, t1, t2
-    bnez t1, save_fpu
-
-    # If no FPU, skip to handler
-    j call_handler
-
-save_fpu:
-    # Save FPU registers (f0-f31) starting at offset 256
-    fsd f0, 256(sp)
-    fsd f1, 264(sp)
-    fsd f2, 272(sp)
-    fsd f3, 280(sp)
-    fsd f4, 288(sp)
-    fsd f5, 296(sp)
-    fsd f6, 304(sp)
-    fsd f7, 312(sp)
-    fsd f8, 320(sp)
-    fsd f9, 328(sp)
-    fsd f10, 336(sp)
-    fsd f11, 344(sp)
-    fsd f12, 352(sp)
-    fsd f13, 360(sp)
-    fsd f14, 368(sp)
-    fsd f15, 376(sp)
-    fsd f16, 384(sp)
-    fsd f17, 392(sp)
-    fsd f18, 400(sp)
-    fsd f19, 408(sp)
-    fsd f20, 416(sp)
-    fsd f21, 424(sp)
-    fsd f22, 432(sp)
-    fsd f23, 440(sp)
-    fsd f24, 448(sp)
-    fsd f25, 456(sp)
-    fsd f26, 464(sp)
-    fsd f27, 472(sp)
-    fsd f28, 480(sp)
-    fsd f29, 488(sp)
-    fsd f30, 496(sp)
-    fsd f31, 504(sp)
-
-call_handler:
-    # Pass stack pointer to C handler
-    mv a0, sp
+    # Call trap handler
+    mv a0, sp # put the stack pointer to the first arg
     call handle_trap
 
-    # --- Restore mepc ---
+    # restore mepc
     ld t0, 240(sp)
     csrw mepc, t0
 
-    # --- Restore FPU (if it was saved) ---
-    csrr t1, mstatus
-    li t2, 0x6000
-    and t1, t1, t2
-    bnez t1, restore_fpu
-
-    j restore_gpr
-
-restore_fpu:
-    # Restore FPU registers
-    fld f0, 256(sp)
-    fld f1, 264(sp)
-    fld f2, 272(sp)
-    fld f3, 280(sp)
-    fld f4, 288(sp)
-    fld f5, 296(sp)
-    fld f6, 304(sp)
-    fld f7, 312(sp)
-    fld f8, 320(sp)
-    fld f9, 328(sp)
-    fld f10, 336(sp)
-    fld f11, 344(sp)
-    fld f12, 352(sp)
-    fld f13, 360(sp)
-    fld f14, 368(sp)
-    fld f15, 376(sp)
-    fld f16, 384(sp)
-    fld f17, 392(sp)
-    fld f18, 400(sp)
-    fld f19, 408(sp)
-    fld f20, 416(sp)
-    fld f21, 424(sp)
-    fld f22, 432(sp)
-    fld f23, 440(sp)
-    fld f24, 448(sp)
-    fld f25, 456(sp)
-    fld f26, 464(sp)
-    fld f27, 472(sp)
-    fld f28, 480(sp)
-    fld f29, 488(sp)
-    fld f30, 496(sp)
-    fld f31, 504(sp)
-
-restore_gpr:
-    # Restore GPRs
+    # Restore all GPRs
     ld ra, 0(sp)
     ld gp, 8(sp)
     ld tp, 16(sp)
@@ -176,6 +83,8 @@ restore_gpr:
     ld t5, 224(sp)
     ld t6, 232(sp)
 
-    # Restore stack pointer
-    addi sp, sp, 768
+    # Shrink the stack back
+    addi sp, sp, 256
+
+    # Return from Machine-mode trap
     mret

src/drivers/uart.c

@@ -137,8 +137,7 @@ void kprintf_internal(const char *format, va_list args)
 		if (*p == '%')
 		{
 			p++;
-			if (*p == '\0')
-				break;
+			if(*p == '\0') break;
 			switch (*p)
 			{
 			case 'c':
@@ -150,8 +149,7 @@ void kprintf_internal(const char *format, va_list args)
 			case 's':
 			{
 				char *s = va_arg(args, char *);
-				if (!s)
-					s = "(null)";
+				if (!s) s = "(null)";
 				kprint(s);
 				break;
 			}
@@ -161,12 +159,12 @@ void kprintf_internal(const char *format, va_list args)
 				kprint_int(d);
 				break;
 			}
-			case 'u':
-			{
+	        case 'u':
+			{ 
 				unsigned int u = va_arg(args, unsigned int);
 				kprint_int((int)u);
 				break;
-			}
+        	}
 			case 'f':
 			{
 				double f = va_arg(args, double);
@@ -176,11 +174,11 @@ void kprintf_internal(const char *format, va_list args)
 			case 'x': // Hex
 			case 'p': // Pointer
 			{
-#if UINTPTR_MAX == 0xffffffffULL
-				unsigned int x = va_arg(args, unsigned int);
-#else
-				uint64_t x = va_arg(args, uint64_t);
-#endif
+				#if UINTPTR_MAX == 0xffffffffULL
+					unsigned int x = va_arg(args, unsigned int);
+				#else
+					uint64_t x = va_arg(args, uint64_t);
+				#endif
 				kprint_hex(x);
 				break;
 			}

src/kernel/interrupts.c

@@ -8,7 +8,6 @@
 #include <kernel/memory.h>
 #include <kernel/timer.h>
 
-
 void interrupt_init()
 {
     kprint("Initialising Interrupts...");
@@ -23,17 +22,6 @@ void interrupt_init()
     mie_val |= (1 << MIE_BIT_MEIE) | (1 << MIE_BIT_MTIE);
     asm volatile("csrw mie, %0" ::"r"(mie_val));
     kputs("OK");
-
-    uint32_t mie, sie, mstatus;
-    asm volatile ("csrr %0, mie" : "=r"(mie));
-    asm volatile ("csrr %0, sie" : "=r"(sie));
-    asm volatile ("csrr %0, mstatus" : "=r"(mstatus));
-    kprintf("mie: 0x%X, sie: 0x%X, mstatus: 0x%X\n", mie, sie, mstatus);
-
-    // Enable timer and global interrupts
-    asm volatile ("csrs mie, %0" : : "r"(mie | (1 << 7) | (1 << 3)));  // Enable timer and global
-    asm volatile ("csrs sie, %0" : : "r"(sie | (1 << 7) | (1 << 3)));  // Enable timer and global
-    asm volatile ("csrs mstatus, %0" : : "r"(mstatus | (1 << 3)));     // Set MIE bit
 }
 
 void kpanic(const char *reason, ...)
@@ -67,11 +55,15 @@ void kpanic_force()
 
 void handle_trap(trap_frame_t *registers)
 {
+    // Read the 'mcause' register to see WHY we trapped
+    unsigned long cause;
+    __asm__ volatile("csrr %0, mcause" : "=r"(cause));
+
     // Check if the top bit is 1 (Interrupt) or 0 (Exception)
     // For 64-bit RISC-V, the bit is 63
-    int is_interrupt = (registers->mcause >> 63) & 1;
+    int is_interrupt = (cause >> 63) & 1;
 
-    unsigned long code = registers->mcause & 0xfff;
+    unsigned long code = cause & 0xfff;
 
     if (is_interrupt)
     {
@@ -86,7 +78,7 @@ void handle_trap(trap_frame_t *registers)
 
         kprintf("\n[EXCEPTION] Code: %d | Instruction: %x | Fault Address: %x\n", code, registers->mepc, mtval);
 
-        switch (registers->mcause)
+        switch (cause)
         {
         case 0:
             kpanic("Reason: Instruction Address Misaligned\n");
@@ -113,7 +105,7 @@ void handle_trap(trap_frame_t *registers)
             kpanic("Reason: Store/AMO Access Fault\n");
             break;
         default:
-            kpanic("Reason: Unknown Exception Code %d\n", registers->mcause);
+            kpanic("Reason: Unknown Exception Code %d\n", cause);
             break;
         }
     }
@@ -124,7 +116,8 @@ void handle_interrupt(unsigned long code)
     switch (code)
     {
     case 7:
-        timer_tick();
+        timer_handle_interrupt();
+
         break;
     case 11:
         volatile uint32_t *claim_reg = (uint32_t *)PLIC_CLAIM(0);

src/kernel/interrupts.h

@@ -3,8 +3,6 @@
 
 #define MSTATUS 0x300
 #define MIE 0x304
-#define MCAUSE 0x342
-#define MEPC 0x341
 #define MSTATUS_BIT_MIE 3
 #define MIE_BIT_MTIE 7
 #define MIE_BIT_MEIE 11
@@ -58,10 +56,8 @@ typedef struct {
     uint64_t t5;      // x30
     uint64_t t6;      // x31
 
-    // Control and Status Register state (Saved in traps.S)
-    uint64_t mepc;    // offset 240 
-    uint64_t mcause;  // offset 248
-    uint64_t mstatus; // offset 256
+    // Control and Status Register state
+    uint64_t mepc;    // offset 240 (Saved in traps.S)
 } trap_frame_t;
 
 void interrupt_init();

src/kernel/kernel.c

@@ -5,13 +5,11 @@
 #include <kernel/plic.h>
 #include <kernel/interrupts.h>
 #include <kernel/memory.h>
-#include <kernel/timer.h>
 
 void kmain()
 {
     zero_bss();
     plic_init();
-    timer_init();
     uart_init();
     page_init();
     interrupt_init();
@@ -19,12 +17,4 @@ void kmain()
     kprintf("Hello, from %s!", "SquidgeOS");
     kputs("----------------------");
     knewline();
-    while (1) {
-        uint64_t ticks = timer_get_ms();
-        kputchar('T');
-        kputchar(':');  // Print "T:1234" every second
-        kprint_int(ticks);
-        knewline();
-        delay_ms(1000);
-    }
 }

src/kernel/plic.c

@@ -13,13 +13,7 @@ void plic_init()
     // This is a bitmask, so we shift 1 by the IRQ number.
     *PLIC_ENABLE(hart) = (1 << UART_IRQ);
 
-    // Set priority for CLINT timer interrupt (IRQ 7)
-    *PLIC_PRIORITY(TIMER_IRQ) = 1;  // Lowest priority
-
-    // Enable CLINT timer interrupt for Hart 0
-    *PLIC_ENABLE(hart) |= (1 << TIMER_IRQ);
-
     // 3. Set the priority threshold for Hart 0
     // We set this to 0 so that ANY interrupt with priority > 0 gets through.
     *PLIC_THRESHOLD(hart) = 0;
-}
+}

src/kernel/plic.h

@@ -16,7 +16,6 @@
 #define PLIC_CLAIM(hart) ((volatile uint32_t *)(PLIC_BASE + 0x200004 + (hart) * 0x1000))
 
 #define UART_IRQ 10
-#define TIMER_IRQ 7
 
 void plic_init();
 

src/kernel/timer.c

@@ -1,43 +1,12 @@
 #include <stdint.h>
-#include <stddef.h>
-#include "timer.h"
-#include "plic.h"
-#include "interrupts.h"
-#include "drivers/uart.h"
+#include <kernel/interrupts.h>
+#include <kernel/plic.h>
+#include <kernel/timer.h>
 
-_Atomic uint64_t sys_ticks = 0;
-const uint64_t tick_delta = TICKS_PER_MS;
+void timer_handle_interrupt()
+{
+	static volatile uint64_t *mtime = (uint64_t *)CLINT_MTIME;
+	static volatile uint64_t *mtimecmp = (uint64_t *)CLINT_MTIMECMP(0);
 
-void timer_init() {
-    timer_tick();
-}
-
-void timer_tick() {
-    static volatile uint64_t *mtime = (uint64_t *)CLINT_MTIME;
-    static volatile uint64_t *mtimecmp = (uint64_t *)CLINT_MTIMECMP(0);
-    uint64_t current_mtime = *mtime;
-    uint64_t new_mtimecmp = current_mtime + tick_delta;
-    *mtimecmp = new_mtimecmp;
-    //kprintf("Set mtimecmp: %u (mtime: %u, delta: %u)\n", new_mtimecmp, current_mtime, tick_delta);
-    sys_ticks++;
-}
-
-// Get current time in milliseconds
-uint64_t timer_get_ms() {
-    return sys_ticks;
-}
-
-// Delay for 'ms' milliseconds (blocking)
-void delay_ms(uint64_t ms) {
-    if (ms == 0) return;
-    uint64_t end = sys_ticks + ms;
-    while (sys_ticks < end) {
-        asm volatile("wfi");
-    }
-}
-
-// Sleep for 'ms' milliseconds (non-blocking, if possible)
-// For now, just call delay_ms (can be improved later)
-void sleep_ms(uint64_t ms) {
-    delay_ms(ms);
+    *mtimecmp = *mtime + TIMER_FREQ;
 }

src/kernel/timer.h

@@ -1,30 +1,8 @@
-#ifndef TIMER_H
-#define TIMER_H
-#include <stdint.h>
+#ifndef KTIMER_H
+#define KTIMER_H
 
-/* Define your clock frequency here based on your hardware */
-/* Example: 12.5 MHz for QEMU virt machine */
-#define CLOCK_FREQ_HZ 12500000 
+#define TIMER_FREQ 100000
 
-/* Calculate ticks per millisecond */
-#define TICKS_PER_MS (CLOCK_FREQ_HZ / 1000) 
-
-extern _Atomic uint64_t sys_ticks;
-extern const uint64_t tick_delta;
-
-// Initialize timer (1ms ticks)
-void timer_init();
-
-// Increment the system tick counter
-void timer_tick();
-
-// Get current time in milliseconds
-uint64_t timer_get_ms();
-
-// Delay for 'ms' milliseconds (blocking)
-void delay_ms(uint64_t ms);
-
-// Sleep for 'ms' milliseconds (non-blocking, if possible)
-void sleep_ms(uint64_t ms);
+void timer_handle_interrupt();
 
 #endif

src/lib/string.h

@@ -2,8 +2,5 @@
 #define STRING_H
 
 void *memset(void *s, int c, size_t n);
-void *memcpy(void *dest, const void *src, size_t n);
-int strcmp(const char *str1, const char *str2);
-size_t strlen(const char *s);
 
 #endif