resolve merge conflict

.gdbinit

@@ -0,0 +1,4 @@
+file build/boot/sys/core
+target remote :3117
+b _start
+c

.gitignore

@@ -1,3 +1,5 @@
 config.mk
 build/
 drive.img
+/compile_commands.json
+/opt

Makefile

@@ -2,6 +2,8 @@
 
 include config.mk
 
+CFLAGS += -ggdb
+
 # Kernel sources which are specific to the x86_64 architecture.
 # Add new source files (C or Assembler) here,
 # preferentially in alphabetical order.
@@ -16,7 +18,6 @@ KERNEL_SOURCES_x86_64 := \
 # preferentially in alphabetical order.
 KERNEL_SOURCES := \
 	src/kernel.c \
-	src/output.c \
 	src/pci.c    \
 	src/tar.c    \
 	src/std.c    \

debug-run-qemu.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+qemu-system-x86_64 -drive if=ide,format=raw,file=build/disk.img -drive if=virtio,media=disk,format=raw,file=drive.img "$@" -S -gdb tcp::3117

include/output.h

@@ -1,17 +0,0 @@
-#ifndef KARLOS_OUTPUT_H
-#define KARLOS_OUTPUT_H
-
-#include <stdbool.h>
-#include <stdint.h>
-
-void putc(char c);
-void puts(const char *s);
-void println(const char *s);
-__attribute__((noreturn))
-void panic(const char *msg);
-void assert(bool cond, const char *msg);
-void print_u8x(uint8_t value);
-void print_u16x(uint16_t value);
-void print_u32x(uint32_t value);
-
-#endif

include/pci.h

@@ -1,6 +1,8 @@
 #ifndef KARLOS_PCI_H
 #define KARLOS_PCI_H
 
+#include <stdint.h>
+
 uint16_t pci_bdf_make(uint8_t bus, uint8_t dev, uint8_t fun);
 uint32_t pci_config_read_u32(uint16_t bdf, uint8_t offset);
 uint16_t pci_config_read_u16(uint16_t bdf, uint8_t offset);
@@ -9,14 +11,14 @@ void pci_config_write_u32(uint16_t bdf, uint8_t offset, uint32_t value);
 struct pci_bar_desc {
 #define PCI_BAR_TYPE_MEM 0
 #define PCI_BAR_TYPE_IO 1
-    uint8_t type;
+  uint8_t type;
 #define PCI_BAR_LOCATABLE_32 0
 #define PCI_BAR_LOCATABLE_SMALL 1
 #define PCI_BAR_LOCATABLE_64 2
-    uint8_t locatable;
-    uint8_t prefetchable;
-    uint32_t address;
-    uint32_t length;
+  uint8_t locatable;
+  uint8_t prefetchable;
+  uint32_t address;
+  uint32_t length;
 };
 
 struct pci_bar_desc pci_bar_desc_read(uint16_t bdf, uint8_t barnum);

include/std.h

@@ -2,8 +2,52 @@
 #define KARLOS_STD_H
 
 #include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
 
+// Memory functions
+void *memset(void *ptr, int value, size_t num);
+void *memcpy(void *dest, const void *src, size_t n);
+int memcmp(const void *ptr, const void *ptr2, size_t num);
+void *memmove(void *dest, const void *src, size_t num);
+
+// String functions
+unsigned int strlen(const char *s);
 bool streq(const char *a, const char *b);
-void memcpy(void *dst, const void *src, unsigned int n);
+bool strcontains(const char *s, char c);
 
-#endif
+// Low-level output functions
+void putc(char c);
+void putln(void);
+void puts(const char *s);
+void putsln(const char *s);
+void put_charbuf(const char *buf, unsigned int len);
+void putu8x(uint8_t value);
+void putu16x(uint16_t value);
+void putu32x(uint32_t value);
+void putu64x(uint64_t value);
+
+// String and conversion utilities
+void itoa(int value, unsigned int base, char *buffer);
+void utoa(unsigned int value, unsigned int base, char *buffer);
+void itoa_ll(long long value, unsigned int base, char *buffer);
+void utoa_ll(unsigned long long value, unsigned int base, char *buffer);
+unsigned int toa_buf_size(unsigned int bits, unsigned int base);
+
+// Formatted output
+void printf(const char *format, ...);
+
+// Debug helpers
+#define PANIC(msg) panic(__FILE__, __LINE__, msg)
+#define ASSERT(cond) do {\
+  if (!(cond)) {\
+    PANIC("assertion failed: " #cond);\
+  }\
+} while (0)
+#define TODO() PANIC("not implemented")
+#define UNREACHABLE() PANIC("unreachable")
+// don't use this directly, use the macros above
+__attribute__ ((noreturn))
+void panic(const char *file, unsigned int line, const char *msg);
+
+#endif // KARLOS_UTILITY_H

src/kernel.c

@@ -28,26 +28,27 @@
 
 #include <stdbool.h>
 #include <stdint.h>
-#include "bootboot.h"
-#include "output.h"
+
 #include "x86_64/mem.h"
 #include "x86_64/asm.h"
+#include "bootboot.h"
 #include "pci.h"
+#include "std.h"
 #include "tar.h"
 
 /* imported virtual addresses, see linker script */
-extern BOOTBOOT bootboot;               // see bootboot.h
+extern BOOTBOOT bootboot; // see bootboot.h
 extern unsigned char environment[4096]; // configuration, UTF-8 text key=value pairs
 extern uint8_t fb;                      // linear framebuffer mapped
 
 void print_virtio_blk_bars() {
     uint16_t bdf;
     if (pci_search(0x1AF4, 0x1001, &bdf) && pci_search(0x1AF4, 0x1042, &bdf)) {
-        panic("couldn't find virtio_blk device!");
+        PANIC("couldn't find virtio_blk device!");
     }
     puts("found virtio_blk device at bdf ");
-    print_u16x(bdf);
-    println(".");
+    putu16x(bdf);
+    printf(".\n");
     // read BARs
     for (int i = 0; i < 6; i++) {
         struct pci_bar_desc desc = pci_bar_desc_read(bdf, i);
@@ -56,65 +57,77 @@ void print_virtio_blk_bars() {
 }
 
 void check_initrd() {
-    println("");
+    putln();
     uint64_t printed_in_line = 0;
     for (uint64_t off = 0; off < bootboot.initrd_size; off++) {
         uint8_t byte = ((uint8_t*)bootboot.initrd_ptr)[off];
 
-        print_u8x(byte);
+        putu8x(byte);
         putc(' ');
 
         if (++printed_in_line % 32 == 0) {
             printed_in_line = 0;
-            println("");
+            putln();
         }
     }
-    println("");
+    putln();
 }
 
 /******************************************
  * Entry point, called by BOOTBOOT Loader *
  ******************************************/
-void _start()
-{
+void _start() {
     /*** NOTE: this code runs on all cores in parallel ***/
-    int x, y, s=bootboot.fb_scanline, w=bootboot.fb_width, h=bootboot.fb_height;
+    int x, y, s = bootboot.fb_scanline, w = bootboot.fb_width, h = bootboot.fb_height;
 
-    if(s) {
+    if (s) {
         // cross-hair to see screen dimension detected correctly
-        for(y=0;y<h;y++) { *((uint32_t*)(&fb + s*y + (w*2)))=0x00FFFFFF; }
-        for(x=0;x<w;x++) { *((uint32_t*)(&fb + s*(h/2)+x*4))=0x00FFFFFF; }
+        for (y = 0; y < h; y++) {
+            *((uint32_t *)(&fb + s * y + (w * 2))) = 0x000FFFFF;
+        }
+        for (x = 0; x < w; x++) {
+            *((uint32_t *)(&fb + s * (h / 2) + x * 4)) = 0x00FFFFFF;
+        }
 
         // red, green, blue boxes in order
-        for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+20)*4))=0x00FF0000; } }
-        for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+50)*4))=0x0000FF00; } }
-        for(y=0;y<20;y++) { for(x=0;x<20;x++) { *((uint32_t*)(&fb + s*(y+20) + (x+80)*4))=0x000000FF; } }
-
-        // say hello
-        println("Hello from a simple BOOTBOOT kernel");
+        for (y = 0; y < 20; y++) {
+            for (x = 0; x < 20; x++) {
+                *((uint32_t *)(&fb + s * (y + 20) + (x + 20) * 4)) = 0x00FF0000;
+            }
+        }
+        for (y = 0; y < 20; y++) {
+            for (x = 0; x < 20; x++) {
+                *((uint32_t *)(&fb + s * (y + 20) + (x + 50) * 4)) = 0x0000FF00;
+            }
+        }
+        for (y = 0; y < 20; y++) {
+            for (x = 0; x < 20; x++) {
+                *((uint32_t *)(&fb + s * (y + 20) + (x + 80) * 4)) = 0x000000FF;
+            }
+        }
     }
 
     // memory stuff
     init_gdt();
     init_idt();
 
-    println("Test after init");
+    printf("Test after init\n");
 
     // __asm__("int $0x80" :: );
 
     struct tar_header hd;
     int res = tar_get_file("hello.txt", &hd);
-    assert(res == 1, "file not found");
-    println(hd.name);
-    print_u32x(hd.size);
-    println("");
+    ASSERT(res == 1);
+    puts(hd.name);
+    putu32x(hd.size);
+    putln();
     for (uint64_t i = 0; i < hd.size; i++) {
         putc(((char *)hd.data)[i]);
     }
-    println("");
+    putln();
 
     // hang for now
-    panic("end of kernel");
+    PANIC("end of kernel");
 }
 
 /**************************
@@ -131,4 +144,5 @@ typedef struct {
     uint32_t width;
     uint8_t glyphs;
 } __attribute__((packed)) psf2_t;
+
 extern volatile unsigned char _binary_font_psf_start;

src/output.c

@@ -1,61 +0,0 @@
-#include "x86_64/uart.h"
-#include "output.h"
-
-void putc(char c) {
-    uart_write_char(c);
-}
-
-void puts(const char *s) {
-    for (const char *c = s; *c != '\0'; c++) {
-        uart_write_char(*c);
-    }
-}
-
-void println(const char *s) {
-    puts(s);
-    puts("\r\n");
-}
-
-__attribute__((noreturn))
-void panic(const char *msg) {
-    puts("PANIC: ");
-    println(msg);
-
-    // hang for now
-    while (1);
-}
-
-void assert(bool cond, const char *msg) {
-    if (!cond) {
-        panic(msg);
-    }
-}
-
-#define TO_HEX(n) (((n) < 10) ? '0' + (n) : 'a' + (n) - 10)
-
-void print_u8x(uint8_t value) {
-    putc('0');
-    putc('x');
-    putc(TO_HEX((value >> 4) & 0xf));
-    putc(TO_HEX(value & 0xf));
-}
-
-void print_u16x(uint16_t value) {
-    putc('0');
-    putc('x');
-    for (int i = 0; i < 4; i++) {
-        // 12 8 4 0
-        uint8_t hexval = (value >> ((3 - i) << 2)) & 0xf;
-        putc(TO_HEX(hexval));
-    }
-}
-
-void print_u32x(uint32_t value) {
-    putc('0');
-    putc('x');
-    for (int i = 0; i < 8; i++) {
-        uint8_t hexval = (value >> ((7 - i) << 2)) & 0xf;
-        putc(TO_HEX(hexval));
-    }
-}
-

src/pci.c

@@ -1,21 +1,18 @@
-#include "output.h"
 #include "pci.h"
+
 #include "x86_64/asm.h"
+#include "std.h"
 
 #define PCI_CONFIG_ADDR_PORT 0xCF8
 #define PCI_CONFIG_DATA_PORT 0xCFC
 
 uint16_t pci_bdf_make(uint8_t bus, uint8_t dev, uint8_t fun) {
-    if (dev >= 32 || fun >= 8) {
-        panic("pci_bdf_make");
-    }
+    ASSERT(dev < 32 && fun < 8);
     return ((uint16_t)bus << 8) | ((uint16_t)dev << 3) | (uint16_t)fun;
 }
 
 static uint32_t pci_address(uint16_t bdf, uint8_t offset) {
-    return ((uint32_t)bdf << 8)
-         | ((uint32_t)offset & 0xfc)
-         | ((uint32_t)0x80000000);
+    return ((uint32_t)bdf << 8) | ((uint32_t)offset & 0xfc) | ((uint32_t)0x80000000);
 }
 
 uint32_t pci_config_read_u32(uint16_t bdf, uint8_t offset) {
@@ -34,29 +31,25 @@ void pci_config_write_u32(uint16_t bdf, uint8_t offset, uint32_t value) {
 }
 
 struct pci_bar_desc pci_bar_desc_read(uint16_t bdf, uint8_t barnum) {
-    if (barnum >= 6) {
-        panic("pci_config_read_bar");
-    }
+    ASSERT(barnum < 6);
 
-    // get basic information
-    // https://en.wikipedia.org/wiki/PCI_configuration_space
+  // get basic information
+  // https://en.wikipedia.org/wiki/PCI_configuration_space
     uint8_t offset = 0x10 + (barnum << 2);
     uint32_t bar = pci_config_read_u32(bdf, offset);
     struct pci_bar_desc desc;
     desc.type = bar & 0x1;
     if (desc.type == PCI_BAR_TYPE_MEM) {
         desc.locatable = (bar >> 1) & 0x3;
-        if (desc.locatable == 3) {
-            panic("pci_config_read_bar");
-        }
+        ASSERT(desc.locatable != 3);
         desc.prefetchable = (bar >> 3) & 0x1;
         desc.address = bar & 0xfffffff0;
     } else {
         desc.address = bar & 0xfffffffc;
     }
 
-    // get length
-    // https://stackoverflow.com/questions/19006632/how-is-a-pci-pcie-bar-size-determined
+  // get length
+  // https://stackoverflow.com/questions/19006632/how-is-a-pci-pcie-bar-size-determined
     pci_config_write_u32(bdf, offset, 0xffffffff);
     bar = pci_config_read_u32(bdf, offset);
     desc.length = (~(bar & 0xfffffff0)) + 1;
@@ -65,34 +58,26 @@ struct pci_bar_desc pci_bar_desc_read(uint16_t bdf, uint8_t barnum) {
 }
 
 void pci_bar_desc_print(const struct pci_bar_desc *desc) {
-    println("pci_bar_desc {");
+    printf("pci_bar_desc {\n");
+
     if (desc->type == PCI_BAR_TYPE_MEM) {
-        println("  type = MEM");
+        printf("  type = MEM\n");
         if (desc->locatable == PCI_BAR_LOCATABLE_32) {
-            println("  locatable = 32");
+            printf("  locatable = 32\n");
         } else if (desc->locatable == PCI_BAR_LOCATABLE_SMALL) {
-            println("  locatable = SMALL");
+            printf("  locatable = SMALL\n");
         } else {
-            println("  locatable = 64");
+            printf("  locatable = 64\n");
         }
-        puts("  prefetchable = ");
-        println(desc->prefetchable ? "true" : "false");
-        puts("  address = ");
-        print_u32x(desc->address);
-        println("");
-        puts("  length = ");
-        print_u32x(desc->length);
-        println("");
+        printf("  prefetchable = %s\n", desc->prefetchable ? "true" : "false");
+        printf("  address = %u\n", desc->address);
+        printf("  length = %u\n", desc->length);
     } else {
-        println("  type = IO");
-        puts("  address = ");
-        print_u32x(desc->address);
-        println("");
-        puts("  length = ");
-        print_u32x(desc->length);
-        println("");
+        printf("  type = IO\n");
+        printf("  address = %u\n", desc->address);
+        printf("  length = %u\n", desc->length);
     }
-    println("}");
+    printf("}\n");
 }
 
 int pci_search(uint16_t vendor_id, uint16_t device_id, uint16_t *found_out) {

src/std.c

@@ -0,0 +1,355 @@
+#include <stdarg.h>
+#include <stddef.h>
+
+#include "std.h"
+#include "x86_64/uart.h"
+
+#define BUFFER_SIZE 1024
+
+/* --- Memory Functions --- */
+void *memset(void *ptr, int value, size_t num) {
+    unsigned char *byte_ptr = (unsigned char *)ptr;
+    for (size_t i = 0; i < num; i++) {
+        byte_ptr[i] = (unsigned char)value;
+    }
+    return ptr;
+}
+
+void *memcpy(void *dest, const void *src, size_t n) {
+    unsigned char *d = (unsigned char *)dest;
+    const unsigned char *s = (const unsigned char *)src;
+    for (size_t i = 0; i < n; i++) {
+        d[i] = s[i];
+    }
+    return dest;
+}
+
+int memcmp(const void *ptr, const void *ptr2, size_t num) {
+    unsigned char *d = (unsigned char *)ptr;
+    unsigned char *b = (unsigned char *)ptr2;
+    for (size_t i = 0; i < num; i++) {
+        if (d[i] != b[i]) {
+            return (d[i] - b[i]);
+        }
+    }
+    return 0;
+}
+
+void *memmove(void *dest, const void *src, size_t num) {
+    unsigned char *d = (unsigned char *)dest;
+    const unsigned char *s = (const unsigned char *)src;
+    if (d < s || d >= (s + num)) {
+        for (size_t i = 0; i < num; i++) {
+            d[i] = s[i];
+        }
+    } else {
+        for (size_t i = num; i > 0; i--) {
+            d[i - 1] = s[i - 1];
+        }
+    }
+    return dest;
+}
+
+/* --- String functions --- */
+unsigned int strlen(const char *s) {
+    unsigned int len = 0;
+    while (*s != '\0') {
+        s++;
+        len++;
+    }
+    return len;
+}
+
+bool streq(const char *a, const char *b) {
+    while (*a != '\0' && *b != '\0') {
+        if (*a != *b) {
+            return false;
+        }
+        a++;
+        b++;
+    }
+    // must have same length
+    return *a == '\0' && *b == '\0';
+}
+
+bool strcontains(const char *s, char c) {
+    while (*s != '\0') {
+        if (*s++ == c) {
+            return true;
+        }
+    }
+    return false;
+}
+
+/* --- Line buffering --- */
+// DO NOT USE THESE FUNCTIONS ANYWHERE! USE THE PUBLIC API (EVEN IN THIS FILE)!
+static char linebuf[BUFFER_SIZE];
+static unsigned int current_buffer_position = 0;
+
+static void linebuf_flush(void) {
+    for (unsigned int i = 0; i < current_buffer_position; i++) {
+        uart_write_char(linebuf[i]);
+    }
+    current_buffer_position = 0;
+}
+
+static void linebuf_putc(char c) {
+    if (current_buffer_position == BUFFER_SIZE) {
+        linebuf_flush();
+    }
+    linebuf[current_buffer_position++] = c;
+}
+
+/* --- Low-level output functions --- */
+void putc(char c) {
+    if (c == '\n') {
+        linebuf_putc('\r');
+        linebuf_putc('\n');
+        linebuf_flush();
+    } else {
+        linebuf_putc(c);
+    }
+}
+
+void putln(void) {
+    putc('\n');
+}
+
+void puts(const char *s) {
+    while (*s != '\0') {
+        putc(*s++);
+    }
+}
+
+void putsln(const char *s) {
+    puts(s);
+    putln();
+}
+
+void put_charbuf(const char *buf, unsigned int len) {
+    for (unsigned int i = 0; i < len; i++) {
+        putc(buf[i]);
+    }
+}
+
+#define TO_HEX(n) ((n) < 10 ? (n) + '0' : (n) - 10 + 'a')
+#define PUTUXX(nd)                                                     \
+    do {                                                               \
+        putc('0');                                                     \
+        putc('x');                                                     \
+        for (int i = 0; i < nd; i++) {                                 \
+            uint8_t hexval = (value >> ((((nd) - 1) - i) << 2)) & 0xf; \
+            putc(TO_HEX(hexval));                                      \
+        }                                                              \
+    } while (0)
+
+void putu8x(uint8_t value) {
+    PUTUXX(2);
+}
+
+void putu16x(uint16_t value) {
+    PUTUXX(4);
+}
+
+void putu32x(uint32_t value) {
+    PUTUXX(8);
+}
+
+void putu64x(uint64_t value) {
+    PUTUXX(16);
+}
+
+/* --- Number Conversion Functions --- */
+
+// this does not include null byte
+#define TOA_MAX_BUF_SIZE 64
+
+/* Converts an int value to a string in a given base */
+void itoa(int value, unsigned int base, char *buffer) {
+    itoa_ll(value, base, buffer);
+}
+
+/* Converts an unsigned int value to a string in a given base */
+void utoa(unsigned int value, unsigned int base, char *buffer) {
+    utoa_ll(value, base, buffer);
+}
+
+/* Converts a long long value to a string in a given base */
+void itoa_ll(long long value, unsigned int base, char *buffer) {
+    bool is_negative = false;
+    unsigned long long uvalue;
+    if (base == 10 && value < 0) {
+        is_negative = true;
+        uvalue = -value;
+    } else {
+        uvalue = value;
+    }
+
+    if (is_negative) {
+        buffer[0] = '-';
+        utoa_ll(uvalue, base, buffer + 1);
+    } else {
+        utoa_ll(uvalue, base, buffer);
+    }
+}
+
+/* Converts an unsigned long long value to a string in a given base */
+void utoa_ll(unsigned long long value, unsigned int base, char *buffer) {
+    char temp[TOA_MAX_BUF_SIZE];
+    int index = 0;
+    if (value == 0) {
+        temp[index++] = '0';
+    } else {
+        while (value > 0) {
+            unsigned int digit = value % base;
+            temp[index++] = "0123456789ABCDEF"[digit];
+            value /= base;
+        }
+    }
+    int out_index = 0;
+    for (int i = index - 1; i >= 0; i--) {
+        buffer[out_index++] = temp[i];
+    }
+    buffer[out_index] = '\0';
+}
+
+/* --- Helper Functions --- */
+unsigned int toa_buf_size(unsigned int bits, unsigned int base) {
+    unsigned int sz;
+    if (base == 2) {
+        sz = bits; // Binary: 1 symbol per bit
+    } else if (base == 8) {
+        sz = (bits + 2) / 3; // Octal: 3 bits per digit
+    } else if (base == 16) {
+        sz = (bits + 3) / 4; // Hex: 4 bits per digit
+    } else if (base == 10) {
+        sz = (bits * 30103) / 100000 + 1; // Approximate log10(2) ≈ 0.30103
+    } else {
+        UNREACHABLE();
+    }
+    return sz + 1; // null byte inclusive
+}
+
+/* --- Custom printf Implementation --- */
+#define IS_PRINTABLE(c) ((c) >= ' ' && (c) <= '~')
+
+void printf(const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+
+    while (*format) {
+        if (*format == '%') {
+            format++;
+            bool do_number = false;
+            int number_size_bits = 32;
+            char number_buffer[TOA_MAX_BUF_SIZE + 1];
+            char base;
+            bool sign;
+            // Check for length modifiers:
+            switch (*format) {
+                case 'h':
+                    do_number = true;
+                    number_size_bits = 16; // 16-bit (promoted to int in varargs)
+                    format++;
+                    break;
+                case 'l':
+                    do_number = true;
+                    number_size_bits = 64; // 64-bit
+                    format++;
+                    break;
+                default:
+                    break;
+            }
+            if (do_number && !strcontains("duxob", *format)) {
+                PANIC("printf: expected number format specifier after %h or %l");
+            }
+
+            switch (*format) {
+                case 'd':
+                    do_number = true;
+                    base = 10;
+                    sign = true;
+                    break;
+                case 'u':
+                    do_number = true;
+                    base = 10;
+                    sign = false;
+                    break;
+                case 'x':
+                    do_number = true;
+                    base = 16;
+                    sign = false;
+                    break;
+                case 'o':
+                    do_number = true;
+                    base = 8;
+                    sign = false;
+                case 'b':
+                    do_number = true;
+                    base = 2;
+                    sign = false;
+                    break;
+                case 'c': {
+                    char ch = (char)va_arg(args, int);
+                    putc(ch);
+                    break;
+                }
+                case 's': {
+                    char *str = va_arg(args, char *);
+                    puts(str);
+                    break;
+                }
+                case 'p': {
+                    void *ptr = va_arg(args, void *);
+                    putu64x((uint64_t)(intptr_t)ptr);
+                    break;
+                }
+                case '%': {
+                    putc('%');
+                    break;
+                }
+                default: {
+                    PANIC("printf: unsupported format specifier");
+                    break;
+                }
+            }
+            if (do_number) {
+                if (number_size_bits == 64) {
+                    long long value = va_arg(args, long long);
+                    if (sign) {
+                        itoa_ll(value, base, number_buffer);
+                    } else {
+                        utoa_ll((unsigned long long)value, base, number_buffer);
+                    }
+                } else {
+                    int value = va_arg(args, int);
+                    if (sign) {
+                        itoa(value, base, number_buffer);
+                    } else {
+                        utoa((unsigned int)value, base, number_buffer);
+                    }
+                }
+                puts(number_buffer);
+            }
+            format++;
+        } else if (IS_PRINTABLE(*format) || *format == '\n') {
+            putc(*format);
+            format++;
+        } else {
+            // we disallow everything else for now (including \r, \t)
+            putc('[');
+            putu8x(*format);
+            putc(']');
+            format++;
+        }
+    }
+    va_end(args);
+}
+
+/* --- Debug helpers --- */
+__attribute__((noreturn)) void panic(const char *file, unsigned int line, const char *msg) {
+    printf("PANIC@%s:%d: %s\n", file, line, msg);
+    while (1) {
+        // loop forever
+    }
+}

src/tar.c

@@ -1,7 +1,6 @@
 #include "std.h"
 #include "tar.h"
 #include "bootboot.h"
-#include "output.h"
 
 extern BOOTBOOT bootboot; // see bootboot.h
 
@@ -36,11 +35,8 @@ int tar_get_file(const char *name, struct tar_header *hd_out) {
     struct tar_header hd;
 
 find_begin:
-    if (hard_follow_count > 1) {
-        panic("tar error: hardlink points to hardlink?");
-    } else if (sym_follow_count == SYM_FOLLOW_CAP) {
-        panic("tar error: symlink chain too long");
-    }
+    ASSERT(hard_follow_count <= 1);
+    ASSERT(sym_follow_count < SYM_FOLLOW_CAP);
 
     uint64_t p = bootboot.initrd_ptr;
     while (p < end) {

src/x86_64/asm.c

@@ -1,31 +1,31 @@
 #include "x86_64/asm.h"
 
 uint8_t in8(int port) {
-	unsigned char value;
-	__asm__ ("inb %%dx" : "=a"(value) : "d"(port));
-	return value;
+    unsigned char value;
+    __asm__("inb %%dx" : "=a"(value) : "d"(port));
+    return value;
 }
 
 uint16_t in16(int port) {
-	uint16_t value;
-	__asm__ ("inw %%dx" : "=a"(value) : "d"(port));
-	return value;
+    uint16_t value;
+    __asm__("inw %%dx" : "=a"(value) : "d"(port));
+    return value;
 }
 
 uint32_t in32(int port) {
     uint32_t value;
-    __asm__ ("inl %%dx" : "=a"(value) : "d"(port));
+    __asm__("inl %%dx" : "=a"(value) : "d"(port));
     return value;
 }
 
 void out8(int port, uint8_t value) {
-	__asm__ ("outb %%dx" :: "d"(port), "a"(value));
+    __asm__("outb %%dx" ::"d"(port), "a"(value));
 }
 
 void out16(int port, uint16_t value) {
-	__asm__ ("outw %%dx" :: "d"(port), "a"(value));
+    __asm__("outw %%dx" ::"d"(port), "a"(value));
 }
 
 void out32(int port, uint32_t value) {
-	__asm__ ("outl %%dx" :: "d"(port), "a"(value));
+    __asm__("outl %%dx" ::"d"(port), "a"(value));
 }

src/x86_64/mem.c

@@ -1,35 +1,30 @@
 #include <stdint.h>
-#include "output.h" // remove later, this is only for interrupt handler
+#include "std.h" // remove later, this is only for interrupt handler
 
 uint64_t gdt[3];
 
 void write_segment_descriptor(uint64_t *entry, uint8_t dpl, uint8_t executable) {
-    uint8_t access_byte =
-        (1 << 7) // present bit
-        | (dpl << 5)
-        | (1 << 4) // S
-        | (executable << 3)
-        | (0 << 2) // DC
+    uint8_t access_byte = (1 << 7) // present bit
+        | (dpl << 5) | (1 << 4) // S
+        | (executable << 3) | (0 << 2) // DC
         | (1 << 1) // RW
         | (0 << 0) // A
-    ;
+        ;
 
-    uint8_t flags = 
-        (1 << 3) // G
+    uint8_t flags = (1 << 3) // G
         | (0 << 2) // DB
         | (1 << 1) // L
         | (0 << 0) // reserved
-    ;
-        
-    *entry = 
-        0xffff // limit
+        ;
+
+    *entry = 0xffff // limit
         | ((uint64_t)0x0000 << 16) // base
         | ((uint64_t)0x00 << 32) // base
         | ((uint64_t)access_byte << 40) // access byte
         | ((uint64_t)0xf << 48) // limit
         | ((uint64_t)flags << 52) // flags
         | ((uint64_t)0x00 << 56) // base
-    ;
+        ;
 }
 
 #define CODE_SEGMENT 1
@@ -42,13 +37,13 @@ void init_gdt() {
 
     uint8_t gdtr[10];
 
-    *(uint16_t*)gdtr = sizeof(gdt) - 1;
-    *(uint64_t**)(gdtr + 2) = (uint64_t*)gdt;
+    *(uint16_t *)gdtr = sizeof(gdt) - 1;
+    *(uint64_t **)(gdtr + 2) = (uint64_t *)gdt;
 
-	__asm__ ("lgdt (%0)" :: "r"(gdtr));
+    __asm__("lgdt (%0)" ::"r"(gdtr));
 
-	__asm__ ("mov %0, %%ds" :: "r"(DATA_SEGMENT << 3));
-	// TODO set code segment -> iret?
+    __asm__("mov %0, %%ds" ::"r"(DATA_SEGMENT << 3));
+ // TODO set code segment -> iret?
 }
 
 __attribute__ ((packed))
@@ -88,7 +83,7 @@ void write_int_desc_entry(struct int_desc_entry *e, uint64_t offset) {
 }
 
 void basic_interrupt_handler(void) {
-    panic("Hello Interrupt!\n");
+    PANIC("Hello Interrupt!");
 }
 
 #define NUM_INTERRUPTS 256

src/x86_64/uart.c

@@ -2,13 +2,13 @@
 
 #define COM1_BASE_PORT 0x3F8
 
-void
-uart_write_char(char c)
-{
-	while (1) {
-		int line_status = in8(COM1_BASE_PORT + 5);
-		if (line_status & 0x20) break;
-	}
+void uart_write_char(char c) {
+    while (1) {
+        int line_status = in8(COM1_BASE_PORT + 5);
+        if (line_status & 0x20) {
+            break;
+        }
+    }
 
-	out8(COM1_BASE_PORT, c);
+    out8(COM1_BASE_PORT, c);
 }