kernel: initrd unpacking

2026-10-27 20:58:22 +00:00 · 2023-05-01 00:47:01 -03:00
parent d90f8d0950
commit ade8aa4e2b
3 changed files with 190 additions and 0 deletions
@@ -0,0 +1,182 @@
+#include <kernel/initrd.h>
+#include <limine.h>
+#include <string.h>
+#include <logging.h>
+#include <util.h>
+#include <kernel/vmm.h>
+#include <kernel/pmm.h>
+#include <kernel/abi.h>
+#include <time.h>
+#include <kernel/vfs.h>
+
+#define TAR_BLOCKSIZE 512
+#define TAR_FILE 0
+#define TAR_HARDLINK 1
+#define TAR_SYMLINK 2
+#define TAR_CHARDEV 3
+#define TAR_BLOCK 4
+#define TAR_DIR 5
+#define TAR_FIFO 6
+
+typedef struct {
+	char name[100];
+	char mode[8];
+	char uid[8];
+	char gid[8];
+	char size[12];
+	char modtime[12];
+	char checksum[8];
+	char type[1];
+	char link[100];
+	char indicator[6];
+	char version[2];
+	char uname[32];
+	char gname[32];
+	char devmajor[8];
+	char devminor[8];
+	char prefix[155];
+} tarheader_t;
+
+typedef struct {
+	char name[256];
+	mode_t mode;
+	gid_t gid;
+	uid_t uid;
+	size_t size;
+	timespec_t modtime;
+	short checksum;
+	short type;
+	char link[101];
+	char indicator[6];
+	char version[2];
+	short devminor;
+	short devmajor;
+} tarentry_t;
+
+static size_t convert(char *buff, size_t len) {
+	size_t result = 0;
+	while (len--) {
+		result *= 8;
+		result += *buff - '0';
+		buff++;
+	}
+	return result;
+}
+
+static void buildentry(tarentry_t *entry, void *addr) {
+	tarheader_t *header = addr;
+
+	char *namecpyptr = entry->name;
+	// name has a prefix
+	if (header->name[99]) {
+		size_t len = header->prefix[154] ? 155 : strlen(header->prefix);
+		memcpy(namecpyptr, header->prefix, len);
+		namecpyptr += len;
+	}
+	size_t namelen = header->name[99] ? 99 : strlen(header->name);
+	memcpy(namecpyptr, header->name, namelen);
+	entry->name[namelen] = '\0';
+
+	entry->mode = convert(header->mode, 7);
+	entry->uid = convert(header->uid, 7);
+	entry->gid = convert(header->gid, 7);
+	entry->size = convert(header->size, 11);
+	entry->modtime.s = convert(header->modtime, 11);
+	entry->modtime.ns = 0;
+	entry->checksum = convert(header->checksum, 7);
+	entry->type = convert(header->type, 1);
+	entry->devmajor = convert(header->devmajor, 7);
+	entry->devminor = convert(header->devminor, 7);
+
+	if (header->link[99]) {
+		memcpy(entry->link, header->link, 100);
+		entry->link[100] = '\0';
+	} else {
+		strcpy(entry->link, header->link);
+	}
+
+	memcpy(entry->indicator, header->indicator, 6);
+	memcpy(entry->version, header->version, 2);
+}
+
+static volatile struct limine_module_request modreq = {
+	.id = LIMINE_MODULE_REQUEST,
+	.revision = 0
+};
+
+void initrd_unpack() {
+	__assert(modreq.response);
+	
+	struct limine_file *initrd = NULL;
+	for (int i = 0; i < modreq.response->module_count; ++i) {
+		if (strcmp(modreq.response->modules[i]->path, "/initrd") == 0) {
+			initrd = modreq.response->modules[i];
+			break;
+		}
+	}
+	__assert(initrd);
+
+	printf("initrd at %p with size %lu (%lu pages)\n", initrd->address, initrd->size, ROUND_UP(initrd->size, PAGE_SIZE) / PAGE_SIZE);
+	__assert(((uintptr_t)initrd->address % PAGE_SIZE) == 0);
+
+	void *ptr = initrd->address;
+	tarentry_t entry;
+	void *cleanupptr = initrd->address;
+	size_t cleanupbytespassed = 0;
+	for (;;) {
+		if (cleanupbytespassed >= PAGE_SIZE) {
+			size_t pagec = cleanupbytespassed / PAGE_SIZE;
+			pmm_free(FROM_HHDM(cleanupptr), pagec);
+			cleanupptr = (void *)((uintptr_t)cleanupptr + ROUND_DOWN(cleanupbytespassed, PAGE_SIZE));
+			cleanupbytespassed %= PAGE_SIZE;
+		}
+
+		buildentry(&entry, ptr);
+
+		if (strncmp("ustar", entry.indicator, 5))
+			break;
+
+		vattr_t entryattr;
+		entryattr.gid = entry.gid;
+		entryattr.uid = entry.uid;
+		entryattr.mode = entry.mode;
+
+		void* datastart = (void *)((uintptr_t)ptr + TAR_BLOCKSIZE);
+		ptr = (void *)((uintptr_t)datastart + ROUND_UP(entry.size, TAR_BLOCKSIZE));
+		cleanupbytespassed += TAR_BLOCKSIZE;
+
+		int err = 0;
+		vnode_t *node;
+		size_t writecount;
+		switch (entry.type) {
+			case TAR_FILE:
+				cleanupbytespassed += ROUND_UP(entry.size, TAR_BLOCKSIZE);
+				err = vfs_create(vfsroot, entry.name, &entryattr, V_TYPE_REGULAR, &node);
+				if (err)
+					break;
+
+				err = vfs_write(node, datastart, entry.size, 0, &writecount, 0);
+				VOP_RELEASE(node);
+				break;
+			case TAR_DIR:
+				err = vfs_create(vfsroot, entry.name, &entryattr, V_TYPE_DIR, &node);
+				if (err)
+					break;
+
+				VOP_RELEASE(node);
+				break;
+			case TAR_SYMLINK:
+				err = vfs_link(NULL, entry.link, vfsroot, entry.name, V_TYPE_LINK, &entryattr);
+				break;
+			default:
+				__assert(!"Unsupported file type");
+				break;
+		}
+
+		if (err)
+			printf("initrd: failed to unpack %s: %lu\n", entry.name, err);
+	}
+
+	// free remaining pages to be freed
+	pmm_free(FROM_HHDM(cleanupptr), ROUND_UP(cleanupbytespassed, PAGE_SIZE) / PAGE_SIZE);
+}