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ptgen fixes and improvements #58

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f890bd4
ptgen: fix bug caused by not completely correct reverts
mkshevetskiy Jan 5, 2026
da0f783
ptgen: allow to specify index of gpt entries to be used
mkshevetskiy Jan 5, 2026
d79a966
ptgen: add an option to disable stub partition creation
mkshevetskiy Jan 5, 2026
702db15
ptgen: add long option support
mkshevetskiy Jan 5, 2026
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121 changes: 105 additions & 16 deletions src/ptgen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
#include <inttypes.h>
#include <fcntl.h>
#include <stdint.h>
#include <getopt.h>
#include "cyg_crc.h"

#if __BYTE_ORDER == __BIG_ENDIAN
Expand Down Expand Up @@ -131,6 +132,7 @@ struct partinfo {
bool has_guid;
guid_t guid;
uint64_t gattr; /* GPT partition attributes */
unsigned part_index; /* index of GPT entry to be used */
};

/* GPT Partition table header */
Expand Down Expand Up @@ -169,7 +171,9 @@ int sectors = -1;
int kb_align = 0;
bool ignore_null_sized_partition = false;
bool use_guid_partition_table = false;
bool allow_stub_partition = true;
struct partinfo parts[GPT_ENTRY_MAX];
bool entry_used[GPT_ENTRY_MAX] = { false };
char *filename = NULL;

int gpt_split_image = false;
Expand Down Expand Up @@ -422,7 +426,7 @@ static int gen_gptable(uint32_t signature, guid_t guid, unsigned nr)
uint64_t start, end;
uint64_t sect = GPT_SIZE + gpt_first_entry_sector;
int fd, ret = -1;
unsigned i, pmbr = 1;
unsigned i, index, pmbr = 1;
char img_name[strlen(filename) + 20];

memset(pte, 0, sizeof(struct pte) * MBR_ENTRY_MAX);
Expand Down Expand Up @@ -452,13 +456,15 @@ static int gen_gptable(uint32_t signature, guid_t guid, unsigned nr)
return ret;
}
parts[i].actual_start = start;
gpte[i].start = cpu_to_le64(start);

index = parts[i].part_index;
gpte[index].start = cpu_to_le64(start);

sect = start + parts[i].size * 2;
gpte[i].end = cpu_to_le64(sect -1);
gpte[i].guid = guid;
gpte[i].guid.b[sizeof(guid_t) -1] += i + 1;
gpte[i].type = parts[i].guid;
gpte[index].end = cpu_to_le64(sect -1);
gpte[index].guid = guid;
gpte[index].guid.b[sizeof(guid_t) -1] += i + 1;
gpte[index].type = parts[i].guid;

if (parts[i].hybrid && pmbr < MBR_ENTRY_MAX) {
pte[pmbr].active = ((i + 1) == active) ? 0x80 : 0;
Expand All @@ -469,16 +475,16 @@ static int gen_gptable(uint32_t signature, guid_t guid, unsigned nr)
to_chs(sect - 1, pte[1].chs_end);
pmbr++;
}
gpte[i].attr = parts[i].gattr;
gpte[index].attr = parts[i].gattr;

if (parts[i].name)
init_utf16(parts[i].name, (uint16_t *)gpte[i].name, GPT_ENTRY_NAME_SIZE / sizeof(uint16_t));
init_utf16(parts[i].name, (uint16_t *)gpte[index].name, GPT_ENTRY_NAME_SIZE / sizeof(uint16_t));

if ((i + 1) == (unsigned)active)
gpte[i].attr |= GPT_ATTR_LEGACY_BOOT;
gpte[index].attr |= GPT_ATTR_LEGACY_BOOT;

if (parts[i].required)
gpte[i].attr |= GPT_ATTR_PLAT_REQUIRED;
gpte[index].attr |= GPT_ATTR_PLAT_REQUIRED;

if (verbose)
fprintf(stderr, "Partition %d: start=%" PRIu64 ", end=%" PRIu64 ", size=%" PRIu64 "\n",
Expand All @@ -489,7 +495,8 @@ static int gen_gptable(uint32_t signature, guid_t guid, unsigned nr)
printf("%" PRIu64 "\n", (sect - start) * DISK_SECTOR_SIZE);
}

if (parts[0].actual_start > GPT_FIRST_ENTRY_SECTOR + GPT_SIZE) {
if (parts[0].actual_start > gpt_first_entry_sector + GPT_SIZE &&
allow_stub_partition && !entry_used[GPT_ENTRY_MAX - 1]) {
gpte[GPT_ENTRY_MAX - 1].start = cpu_to_le64(gpt_first_entry_sector + GPT_SIZE);
gpte[GPT_ENTRY_MAX - 1].end = cpu_to_le64(parts[0].actual_start - 1);
gpte[GPT_ENTRY_MAX - 1].type = GUID_PARTITION_BIOS_BOOT;
Expand Down Expand Up @@ -618,10 +625,35 @@ static int gen_gptable(uint32_t signature, guid_t guid, unsigned nr)

static void usage(char *prog)
{
fprintf(stderr, "Usage: %s [-v] [-n] [-b] [-g] -h <heads> -s <sectors> -o <outputfile>\n"
" [-a <part number>] [-l <align kB>] [-G <guid>]\n"
" [-e <gpt_entry_offset>] [-d <gpt_disk_size>]\n"
" [[-t <type> | -T <GPT part type>] [-r] [-N <name>] -p <size>[@<start>]...] \n", prog);
fprintf(stderr, "Usage: %s [OPTION]...\n"
"Generate hard drive image with predefined partitions\n"
"\n"
"Mandatory arguments to long options are mandatory for short options too.\n"
" -?, --help display this help and exit\n"
" -v, --verbose enable vervose output\n"
" -l, --alignment=SIZE align partition boundaries to SIZE Kbytes\n"
" -n, --ignore-null-sized-parts do not create null sized partitions\n"
" -D, --disable-gpt-stub-part do not fill a gap before 1-st GPT partition\n"
" -o, --output=FILENAME write an image to a file FILENAME\n"
" -h, --heads=COUNT use CHS scheme, defines heads number\n"
" -s, --sectors=COUNT use CHS scheme, defines sectors count\n"
" -S, --mbr-disk-signature=VALUE defines MBR disk signature [default: 0x5452574F ('OWRT')]\n"
" -a, --active-part=PART_NUMBER defines active (boot) partition\n"
" -g, --gpt use GPT instead of MBR\n"
" -G, --gpt-guid=GUID defines custom GPT GUID\n"
" -e, --gpt-entry-offset=OFFSET defines custom placement of GPT Entry table (default: 1K)\n"
" -d, --gpt-disk-size=SIZE defines total size of disk image (used for ALT GPT headers)\n"
" -b, --gpt-split-images generate 2 or 3 images (depends on entry table placement):\n"
" GPT header + GPT Entry Table, Alt Entry Table + ALT Header\n"
" GPT header, GPT Entry Table, Alt Entry Table + ALT Header\n"
" -p, --part=SIZE[@START] defines partition of size SIZE, started at offset START\n"
" -t, --mbr-part-type=TYPE defines partition type by MBR partition type\n"
" -T, --gpt-part-type=TYPE_NAME defines partinion type by GPT type name\n"
" -N, --gpt-part-name=NAME defines GPT partition name\n"
" -r, --gpt-part-attr-required mark partition with GPT required attribute\n"
" -H, --gpt-part-hybrid put GPT partition to the MBR as well\n"
" -i, --gpt-part-index=INDEX use custom INDEX for the partition in the GPT Entry Table\n",
prog);

exit(EXIT_FAILURE);
}
Expand Down Expand Up @@ -653,21 +685,57 @@ int main (int argc, char **argv)
char *p;
int ch;
int part = 0;
unsigned part_index = 0;
char *name = NULL;
unsigned short int hybrid = 0, required = 0;
uint64_t total_sectors;
uint32_t signature = 0x5452574F; /* 'OWRT' */
guid_t guid = GUID_INIT( signature, 0x2211, 0x4433, \
0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0x00);

while ((ch = getopt(argc, argv, "h:s:p:a:t:T:o:vnbHN:gl:rS:G:e:d:")) != -1) {
while (1) {
int option_index = 0;
static struct option long_options[] = {
{"help", no_argument, 0, '?'},
{"verbose", no_argument, 0, 'v'},
{"kb_alignment", required_argument, 0, 'l'},
{"ignore-null-sized-parts", no_argument, 0, 'n'},
{"disable-gpt-stub-part", no_argument, 0, 'D'},
{"output", required_argument, 0, 'o'},
{"heads", required_argument, 0, 'h'},
{"sectors", required_argument, 0, 's'},
{"mbr-disk-signature", required_argument, 0, 'S'},
{"active-part", required_argument, 0, 'a'},
{"gpt", no_argument, 0, 'g'},
{"gpt-guid", required_argument, 0, 'G'},
{"gpt-entry-offset", required_argument, 0, 'e'},
{"gpt-disk-size", required_argument, 0, 'd'},
{"gpt-split-images", no_argument, 0, 'b'},
{"part", required_argument, 0, 'p'},
{"mbr-part-type", required_argument, 0, 't'},
{"gpt-part-type", required_argument, 0, 'T'},
{"gpt-part-name", required_argument, 0, 'N'},
{"gpt-part-attr-required", no_argument, 0, 'r'},
{"gpt-part-hybrid", no_argument, 0, 'H'},
{"gpt-part-index", required_argument, 0, 'i'},
{NULL, 0, 0, 0 },
};

ch = getopt_long(argc, argv, "?h:s:p:a:t:T:o:DvnbHN:gl:rS:G:e:d:i:",
long_options, &option_index);
if (ch == -1)
break;

switch (ch) {
case 'o':
filename = optarg;
break;
case 'v':
verbose++;
break;
case 'D':
allow_stub_partition = false;
break;
case 'n':
ignore_null_sized_partition = true;
break;
Expand Down Expand Up @@ -719,6 +787,11 @@ int main (int argc, char **argv)
fputs("Too many partitions\n", stderr);
exit(EXIT_FAILURE);
}
if (entry_used[part_index]) {
fprintf(stderr, "Partition entry with index %d already defined\n", part_index);
exit(EXIT_FAILURE);
}

p = strchr(optarg, '@');
if (p) {
*(p++) = 0;
Expand All @@ -731,6 +804,7 @@ int main (int argc, char **argv)
parts[part].required = required;
parts[part].name = name;
parts[part].hybrid = hybrid;
parts[part].part_index = part_index;
fprintf(stderr, "part %lld %lld\n", parts[part].start, parts[part].size);
parts[part++].type = type;
/*
Expand All @@ -740,13 +814,28 @@ int main (int argc, char **argv)
name = NULL;
required = 0;
hybrid = 0;

/* mark index as used, switch to next index */
entry_used[part_index++] = true;
if (part_index > GPT_ENTRY_MAX - 1 ||
(!use_guid_partition_table && part_index > 3))
part_index = 0;

break;
case 'N':
name = optarg;
break;
case 'r':
required = 1;
break;
case 'i':
part_index = (int)strtoul(optarg, NULL, 0);
if (part_index > GPT_ENTRY_MAX - 1 ||
(!use_guid_partition_table && part_index > 3)) {
fprintf(stderr, "Too big GPT/MBR entry index %d\n", part_index);
exit(EXIT_FAILURE);
}
break;
case 't':
type = (char)strtoul(optarg, NULL, 16);
break;
Expand Down