[stage2] Add GPT parsing code (tested on PC)

fusee/fusee-secondary/src/gpt.c

@@ -0,0 +1,91 @@
+#include <string.h>
+#include <errno.h>
+#include "gpt.h"
+
+int gpt_get_header(efi_header_t *out, FILE *disk) {
+    union {
+        uint8_t sector[512];
+        efi_header_t hdr;
+    } d;
+
+    if (disk == NULL || out == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    /* Read and check the protective MBR. */
+    if (fread(d.sector, 512, 1, disk) == 0) {
+        return -1;
+    }
+    if (d.sector[0x1FE] != 0x55 || d.sector[0x1FF] != 0xAA) {
+        errno = EILSEQ;
+        return -1;
+    }
+
+    /* We only allow for the GPT header to be at sector 1 (like nx-bootloader). */
+    if (fread(d.sector, 512, 1, disk) == 0) {
+        return -1;
+    }
+    /* Check for "EFI PART". */
+    if (memcmp(d.hdr.magic, "EFI PART", 8) != 0) {
+        errno = EILSEQ;
+        return -1;
+    }
+    /* Check whether we're really at sector 1, etc. (we won't check backup_lba). */
+    if (d.hdr.header_lba != 1 || d.hdr.entries_first_lba < 2 || d.hdr.partitions_last_lba < d.hdr.partitions_first_lba) {
+        errno = EILSEQ;
+        return -1;
+    }
+    if (d.hdr.header_size < sizeof(efi_header_t) || d.hdr.entry_size < sizeof(efi_entry_t)) {
+        errno = EILSEQ;
+        return -1;
+    }
+    /* Some more checks: */
+    if(d.hdr.header_size > 512 || d.hdr.revision != 0x10000) {
+        errno = ENOTSUP;
+        return -1;
+    }
+
+    memcpy(out, &d.hdr, sizeof(efi_header_t));
+
+    return 0;
+}
+
+int gpt_iterate_through_entries(FILE *disk, gpt_entry_iterator_t callback) {
+    efi_header_t hdr;
+    efi_entry_t entry;
+    size_t offset = 2 * 512; /* Sector #2. */
+    size_t delta;
+
+    /* Get the header. */
+    if (gpt_get_header(&hdr, disk) == -1) {
+        return -1;
+    }
+
+    /* Seek to the entry table. */
+    if (fseek(disk, 512 * hdr.entries_first_lba - offset, SEEK_CUR) != 0) {
+        return -1;
+    }
+
+    offset = 512 * hdr.entries_first_lba;
+    delta = hdr.entry_size - sizeof(efi_entry_t);
+
+    /* Iterate through the entries. */
+    for (uint32_t i = 0; i < hdr.entry_count; i++) {
+        if (fread(&entry, sizeof(efi_entry_t), 1, disk) == 0) {
+            return -1;
+        }
+
+        if (callback(&entry, offset, disk) != 0) {
+            return -1;
+        }
+
+        if (delta != 0 && fseek(disk, delta, SEEK_CUR) != 0) {
+            return -1;
+        }
+
+        offset += hdr.entry_size;
+    }
+
+    return 0;
+}