From 5c12f756189373fb25220fe8824d4df785e61742 Mon Sep 17 00:00:00 2001
From: Nathan Lee <me@nwlee.tech>
Date: Sun, 26 Jul 2026 15:25:22 -0500
Subject: create ringbuffer for logging

---
 kernel/log.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 kernel/log.c

(limited to 'kernel/log.c')

diff --git a/kernel/log.c b/kernel/log.c
new file mode 100644
index 0000000..3392223
--- /dev/null
+++ b/kernel/log.c
@@ -0,0 +1,96 @@
+#include <log.h>
+#include <types.h>
+__attribute__((section(".ringbuf"), aligned(64)))
+volatile char log_ring[RINGBUF_SIZE];
+static int pos = 0;
+
+void put_char(char c) {
+    log_ring[pos++] = c;
+    if (pos >= RINGBUF_SIZE)
+        pos = 0;
+}
+
+void put_string(const char *s) {
+    while (*s)
+        put_char(*s++);
+}
+
+void put_uint(unsigned int value, unsigned int radix) {
+    char tmp[16];
+    const char digits[] = "0123456789abcdef";
+    int i = 0;
+
+    if (value == 0) {
+        put_char('0');
+        return;
+    }
+
+    while (value) {
+        tmp[i++] = digits[value % radix];
+        value /= radix;
+    }
+
+    while (i--)
+        put_char(tmp[i]);
+}
+
+void put_int(int value) {
+    if (value < 0) {
+        put_char('-');
+        put_uint((unsigned int)(-value), 10);
+    } else {
+        put_uint((unsigned int)value, 10);
+    }
+}
+
+void vprintk(const char *fmt, __builtin_va_list args) {
+    while (*fmt) {
+        if (*fmt != '%') {
+            put_char(*fmt++);
+            continue;
+        }
+
+        fmt++;
+
+        switch (*fmt) {
+        case '%':
+            put_char('%');
+            break;
+
+        case 'c':
+            put_char((char)__builtin_va_arg(args, int));
+            break;
+
+        case 's':
+            put_string(__builtin_va_arg(args, const char *));
+            break;
+
+        case 'd':
+        case 'i':
+            put_int(__builtin_va_arg(args, int));
+            break;
+
+        case 'u':
+            put_uint(__builtin_va_arg(args, unsigned int), 10);
+            break;
+
+        case 'x':
+            put_uint(__builtin_va_arg(args, unsigned int), 16);
+            break;
+
+        default:
+            put_char('%');
+            put_char(*fmt);
+            break;
+        }
+
+        fmt++;
+    }
+}
+
+void printk(const char *fmt, ...) {
+    __builtin_va_list args;
+    __builtin_va_start(args, fmt);
+    vprintk(fmt, args);
+    __builtin_va_end(args);
+}
-- 
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