simple tar initfs

disk/limine/limine.conf

@@ -1,6 +1,7 @@
 timeout: 0
-quiet: yes
+quiet:   yes
 
 /Calcite
-protocol: limine
-path: boot():/calcite/kernel.elf
+protocol:    limine
+path:        boot():/calcite/kernel.elf
+module_path: boot():/calcite/initfs.tar

kernel/include/initfs.h

@@ -0,0 +1,26 @@
+/* Calcite, kernel/include/initfs.h
+ * Copyright 2025 Benji Dial
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+void set_initfs(const uint8_t *start, uint64_t length);
+
+//if the file does not exist, *start_out is set to a null pointer.
+void look_up_initfs_file(
+  const char *path, const uint8_t **start_out, uint64_t *length_out);

kernel/src/entry.c

@@ -15,6 +15,7 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 
+#include <initfs.h>
 #include <limine.h>
 #include <paging.h>
 
@@ -44,6 +45,12 @@ static volatile struct limine_memmap_request memmap_request = {
   .response = 0
 };
 
+static volatile struct limine_module_request module_request = {
+  .id = LIMINE_MODULE_REQUEST,
+  .revision = 0,
+  .response = 0
+};
+
 [[noreturn]] static void die() {
   while (1)
     __asm__ ("hlt");
@@ -70,6 +77,9 @@ static int fb_width;
 static int fb_height;
 static int fb_pitch;
 
+static uint8_t *initfs_start;
+static uint64_t initfs_length;
+
 [[noreturn]] static void with_kernel_page_tables();
 
 [[noreturn]] void kernel_entry() {
@@ -78,7 +88,9 @@ static int fb_pitch;
 
   if (fb_request.response == 0 || hhdm_request.response == 0 ||
       ka_request.response == 0 || memmap_request.response == 0 ||
-      fb_request.response->framebuffer_count == 0)
+      module_request.response == 0 ||
+      fb_request.response->framebuffer_count == 0 ||
+      module_request.response->module_count == 0)
     die();
 
   struct limine_framebuffer *fb = fb_request.response->framebuffers[0];
@@ -88,6 +100,8 @@ static int fb_pitch;
       fb->blue_mask_shift != 0 || fb->blue_mask_size != 8)
     die();
 
+  struct limine_file *initfs = module_request.response->modules[0];
+
   //set up page tables. we will mark the regions with bootloader structures as
   //usable, so we need to be careful not to allocate any physical pages until
   //after we are done using bootloader structures. we map the kernel into our
@@ -131,6 +145,18 @@ static int fb_pitch;
   fb_height = fb->height;
   fb_pitch = fb->pitch;
 
+  //remap initfs module and store information.
+
+  uint64_t initfs_physical_start =
+    (uint64_t)initfs->address - hhdm_request.response->offset;
+
+  initfs_length = initfs->size;
+  uint64_t initfs_length_rounded = ((initfs_length - 1) / 4096 + 1) * 4096;
+
+  initfs_start = find_free_kernel_region(initfs_length_rounded);
+  map_kernel_region(
+    initfs_physical_start, initfs_start, initfs_length_rounded, 0, 0);
+
   //switch to kernel page tables!
 
   switch_to_kernel_page_tables(&with_kernel_page_tables);
@@ -139,7 +165,22 @@ static int fb_pitch;
 
 [[noreturn]] static void with_kernel_page_tables() {
 
-  //display our test pattern
+  //test initfs
+
+  set_initfs(initfs_start, initfs_length);
+
+  const uint8_t *hello_start;
+  uint64_t hello_length;
+  look_up_initfs_file("resx/hello.txt", &hello_start, &hello_length);
+
+  if (hello_length != 7)
+    die();
+
+  for (int i = 0; i < 7; ++i)
+    if (hello_start[i] != "Hello!\n"[i])
+      die();
+
+  //test framebuffer
 
   for (int y = 0; y < fb_height; ++y)
     for (int x = 0; x < fb_width; ++x) {

kernel/src/initfs.c

@@ -0,0 +1,74 @@
+/* Calcite, kernel/src/initfs.c
+ * Copyright 2025 Benji Dial
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <initfs.h>
+
+static const uint8_t *initfs_start;
+static uint64_t initfs_length;
+
+void set_initfs(const uint8_t *start, uint64_t length) {
+  initfs_start = start;
+  initfs_length = length;
+}
+
+static uint64_t decode_octal(const char *from) {
+  uint64_t value = 0;
+  while (*from != '\0') {
+    value = value * 8 + *from - '0';
+    ++from;
+  }
+  return value;
+}
+
+void look_up_initfs_file(
+  const char *path, const uint8_t **start_out, uint64_t *length_out) {
+
+  int path_len = 0;
+  while (path[path_len] != '\0')
+    ++path_len;
+
+  uint64_t offset = 0;
+
+  while (1) {
+
+    if (offset + 512 > initfs_length) {
+      *start_out = 0;
+      return;
+    }
+
+    uint64_t length =
+      decode_octal((const char *)(initfs_start + offset + 0x7c));
+
+    int found_it = 1;
+
+    for (int i = 0; i < path_len; ++i)
+      if (initfs_start[offset + i] != path[i]) {
+        found_it = 0;
+        break;
+      }
+
+    if (found_it) {
+      *start_out = initfs_start + offset + 512;
+      *length_out = length;
+      return;
+    }
+
+    offset += 512 + ((length - 1) / 512 + 1) * 512;
+
+  }
+
+}

makefile

@@ -1,5 +1,6 @@
-CC_EXTRA_FLAGS = -O3 -Wall -Wextra
-CC_FLAGS = -std=c23 -mno-sse -ffreestanding ${CC_EXTRA_FLAGS}
+COMMON_CC_EXTRA_FLAGS = -O3 -Wall -Wextra
+COMMON_CC_FLAGS = -std=c23 ${CC_EXTRA_FLAGS}
+KERNEL_CC_FLAGS = -mno-sse -ffreestanding ${COMMON_CC_FLAGS}
 
 .PHONY: default
 default: build/disk.iso
@@ -14,7 +15,7 @@ clean:
 
 # kernel
 
-KERNEL_SOURCES = entry.c paging.asm paging.c
+KERNEL_SOURCES = entry.c initfs.c paging.asm paging.c
 
 build/kernel/%.asm.o: kernel/src/%.asm
 	@mkdir -p ${@D}
@@ -22,14 +23,22 @@ build/kernel/%.asm.o: kernel/src/%.asm
 
 build/kernel/%.c.o: kernel/src/%.c
 	@mkdir -p ${@D}
-	cc -c ${CC_FLAGS} -I dependencies/limine -I kernel/include $^ -o $@
+	cc -c ${KERNEL_CC_FLAGS} -I dependencies/limine -I kernel/include $^ -o $@
 
 build/kernel/kernel.elf: ${KERNEL_SOURCES:%=build/kernel/%.o}
 	ld -T kernel/link.ld $^ -o $@
 
+# initfs
+
+build/initfs.tar:
+	rm -rf build/initfs
+	mkdir -p build/initfs/resx
+	echo Hello! > build/initfs/resx/hello.txt
+	cd build/initfs; tar cf ../initfs.tar *
+
 # disk
 
-build/disk.iso: build/kernel/kernel.elf
+build/disk.iso: build/kernel/kernel.elf build/initfs.tar
 	rm -rf build/disk
 	cp -r disk build/disk
 	cp dependencies/limine/limine-uefi-cd.bin build/disk/limine/
@@ -39,6 +48,7 @@ build/disk.iso: build/kernel/kernel.elf
 	cp dependencies/limine/BOOTX64.EFI build/disk/EFI/BOOT/
 	mkdir build/disk/calcite
 	cp build/kernel/kernel.elf build/disk/calcite/
+	cp build/initfs.tar build/disk/calcite/
 	xorriso \
 	  -as mkisofs -R -r -J -b limine/limine-bios-cd.bin -no-emul-boot \
 	  -boot-load-size 4 -boot-info-table -hfsplus -apm-block-size 2048 \