:: commit 4a9b8fe90bcd26f82986234e9151ea885fd3c427
host/limine: Perform automatic conversion of GPT to MBR for ISOHYBRIDs if possible
diff --git a/host/limine.c b/host/limine.c
index 62c930c4..b554fb1f 100644
--- a/host/limine.c
+++ b/host/limine.c
@@ -13,6 +13,7 @@
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
+#include <time.h>
#ifndef LIMINE_NO_BIOS
#include "limine-bios-hdd.h"
@@ -72,6 +73,7 @@ static int set_pos(FILE *stream, uint64_t pos) {
return 0;
}
+#define SIZEOF_ARRAY(array) (sizeof(array) / sizeof(array[0]))
#define DIV_ROUNDUP(a, b) (((a) + ((b) - 1)) / (b))
struct gpt_table_header {
@@ -158,6 +160,31 @@ static const uint32_t crc32_table[] = {
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};
+struct gpt2mbr_type_conv {
+ uint64_t gpt_type1;
+ uint64_t gpt_type2;
+ uint8_t mbr_type;
+};
+
+// This table is very incomplete, but it should be enough for covering
+// all that matters for ISOHYBRIDs.
+// Of course, though, expansion is welcome.
+static struct gpt2mbr_type_conv gpt2mbr_type_conv_table[] = {
+ { 0x11d2f81fc12a7328, 0x3bc93ec9a0004bba, 0xef }, // EFI system partition
+ { 0x4433b9e5ebd0a0a2, 0xc79926b7b668c087, 0x07 }, // Microsoft basic data
+ { 0x11aa000048465300, 0xacec4365300011aa, 0xaf }, // HFS/HFS+
+};
+
+static int gpt2mbr_type(uint64_t gpt_type1, uint64_t gpt_type2) {
+ for (size_t i = 0; i < SIZEOF_ARRAY(gpt2mbr_type_conv_table); i++) {
+ if (gpt2mbr_type_conv_table[i].gpt_type1 == gpt_type1
+ && gpt2mbr_type_conv_table[i].gpt_type2 == gpt_type2) {
+ return gpt2mbr_type_conv_table[i].mbr_type;
+ }
+ }
+ return -1;
+}
+
static uint32_t crc32(void *_stream, size_t len) {
uint8_t *stream = _stream;
uint32_t ret = 0xffffffff;
@@ -572,6 +599,11 @@ static void bios_install_usage(void) {
printf(" Set the input (for --uninstall) or output file\n");
printf(" name of the file which contains uninstall data\n");
printf("\n");
+ printf(" --no-gpt-to-mbr-isohybrid-conversion\n");
+ printf(" Do not automatically convert a GPT partition table found on\n");
+ printf(" an ISOHYBRID image into an MBR partition table (which is\n");
+ printf(" done for better hardware compatibility)\n");
+ printf("\n");
printf(" --quiet Do not print verbose diagnostic messages\n");
printf("\n");
printf(" --help | -h Display this help message\n");
@@ -581,6 +613,7 @@ static void bios_install_usage(void) {
static int bios_install(int argc, char *argv[]) {
int ok = EXIT_FAILURE;
int force_mbr = 0;
+ bool gpt2mbr_allowed = true;
bool uninstall_mode = false;
const uint8_t *bootloader_img = binary_limine_hdd_bin_data;
size_t bootloader_file_size = sizeof(binary_limine_hdd_bin_data);
@@ -612,6 +645,8 @@ static int bios_install(int argc, char *argv[]) {
fprintf(stderr, "%s: warning: --force-mbr already set.\n", program_name);
}
force_mbr = 1;
+ } else if (strcmp(argv[i], "--no-gpt-to-mbr-isohybrid-conversion") == 0) {
+ gpt2mbr_allowed = false;
} else if (strcmp(argv[i], "--uninstall") == 0) {
if (uninstall_mode && !quiet) {
fprintf(stderr, "%s: warning: --uninstall already set.\n", program_name);
@@ -705,6 +740,124 @@ static int bios_install(int argc, char *argv[]) {
}
}
+ // Check if this is an ISO w/ a GPT, in which case try converting it
+ // to MBR for improved compatibility with a whole range of hardware that
+ // does not like booting off of GPT in BIOS or CSM mode, and other
+ // broken hardware.
+ if (gpt && gpt2mbr_allowed == true) {
+ char iso_signature[5];
+ device_read(iso_signature, 32769, 5);
+
+ if (strncmp(iso_signature, "CD001", 5) != 0) {
+ goto no_mbr_conv;
+ }
+
+ if (!quiet) {
+ fprintf(stderr, "Detected ISOHYBRID with a GPT partition table.\n");
+ fprintf(stderr, "Converting to MBR for improved compatibility...\n");
+ }
+
+ // Gather the (up to 4) GPT partition to convert.
+ struct {
+ uint64_t lba_start;
+ uint64_t lba_end;
+ uint8_t type;
+ } part_to_conv[4];
+ size_t part_to_conv_i = 0;
+
+ for (int64_t i = 0; i < (int64_t)ENDSWAP(gpt_header.number_of_partition_entries); i++) {
+ struct gpt_entry gpt_entry;
+ device_read(&gpt_entry,
+ (ENDSWAP(gpt_header.partition_entry_lba) * lb_size)
+ + (i * ENDSWAP(gpt_header.size_of_partition_entry)),
+ sizeof(struct gpt_entry));
+
+ if (gpt_entry.unique_partition_guid[0] == 0 &&
+ gpt_entry.unique_partition_guid[1] == 0) {
+ continue;
+ }
+
+ if (ENDSWAP(gpt_entry.starting_lba) > UINT32_MAX) {
+ if (!quiet) {
+ fprintf(stderr, "Starting LBA of partition %zu is greater than UINT32_MAX, will not convert GPT.\n", i + 1);
+ }
+ goto no_mbr_conv;
+ }
+ part_to_conv[part_to_conv_i].lba_start = ENDSWAP(gpt_entry.starting_lba);
+ if (ENDSWAP(gpt_entry.ending_lba) > UINT32_MAX) {
+ if (!quiet) {
+ fprintf(stderr, "Ending LBA of partition %zu is greater than UINT32_MAX, will not convert GPT.\n", i + 1);
+ }
+ goto no_mbr_conv;
+ }
+ part_to_conv[part_to_conv_i].lba_end = ENDSWAP(gpt_entry.ending_lba);
+
+ int type = gpt2mbr_type(ENDSWAP(gpt_entry.partition_type_guid[0]),
+ ENDSWAP(gpt_entry.partition_type_guid[1]));
+ if (type == -1) {
+ if (!quiet) {
+ fprintf(stderr, "Cannot convert partition type for partition %zu, will not convert GPT.\n", i + 1);
+ }
+ goto no_mbr_conv;
+ }
+
+ if (part_to_conv_i == 4) {
+ if (!quiet) {
+ fprintf(stderr, "GPT contains more than 4 partitions, will not convert.\n");
+ }
+ goto no_mbr_conv;
+ }
+
+ part_to_conv[part_to_conv_i].type = type;
+
+ part_to_conv_i++;
+ }
+
+ // Nuke the GPTs.
+ void *empty_lba = calloc(1, lb_size);
+ if (empty_lba == NULL) {
+ perror_wrap("error: bios_install(): malloc()");
+ goto cleanup;
+ }
+
+ // ... nuke primary GPT + protective MBR.
+ for (size_t i = 0; i < 34; i++) {
+ device_write(empty_lba, i * lb_size, lb_size);
+ }
+
+ // ... nuke secondary GPT.
+ for (size_t i = 0; i < 33; i++) {
+ device_write(empty_lba, ((ENDSWAP(gpt_header.alternate_lba) - 32) + i) * lb_size, lb_size);
+ }
+
+ free(empty_lba);
+
+ // We're no longer GPT.
+ gpt = 0;
+
+ // Generate pseudorandom MBR disk ID.
+ srand(time(NULL));
+ for (size_t i = 0; i < 4; i++) {
+ uint8_t r = rand();
+ device_write(&r, 0x1b8 + i, 1);
+ }
+
+ // Write out the partition entries.
+ for (size_t i = 0; i < part_to_conv_i; i++) {
+ device_write(&part_to_conv[i].type, 0x1be + i * 16 + 0x04, 1);
+ uint32_t lba_start = ENDSWAP(part_to_conv[i].lba_start);
+ device_write(&lba_start, 0x1be + i * 16 + 0x08, 4);
+ uint32_t sect_count = ENDSWAP((part_to_conv[i].lba_end - part_to_conv[i].lba_start) + 1);
+ device_write(§_count, 0x1be + i * 16 + 0x0c, 4);
+ }
+
+ if (!quiet) {
+ fprintf(stderr, "Conversion successful.\n");
+ }
+ }
+
+no_mbr_conv:;
+
int mbr = 0;
if (gpt == 0) {
// Do all sanity checks on MBR
