chain: Implement GPT hand-over protocol as documented

When a partition was yielded by a GPT partition iterator,
we follow the protocol documented in syslinux/doc/gpt.txt.

Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>

diff --git a/NEWS b/NEWS
index fdf33cf..93b64a6 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,7 @@ to all derivatives.
 Changes in 4.00:
        * chain.c32: support booting GPT partitions by index
        * chain.c32: support booting the Syslinux partition with "fs"
+       * chain.c32: implement gpt.txt hand-over protocol
 Changes in 3.86:
        * chain.c32: fix chainloading the MBR of a hard disk (broken
          in 3.85).

diff --git a/com32/modules/chain.c b/com32/modules/chain.c
index 2652de8..6f3729f 100644 (file)
--- a/com32/modules/chain.c
+++ b/com32/modules/chain.c
@@ -1419,6 +1419,53 @@ int main(int argc, char *argv[])
        ndata++;
     }
 
+    /* Do GPT hand-over, if applicable (as per syslinux/doc/gpt.txt) */
+    if (cur_part && (cur_part->next == next_gpt_part)) {
+       struct part_entry *record;
+       /* Look at the GPT partition */
+       const struct gpt_part *gp = (const struct gpt_part *)
+           (cur_part->block +
+            (cur_part->private.gpt.size * cur_part->private.gpt.index));
+       /* Note the partition length */
+       uint64_t lba_count = gp->lba_last - gp->lba_first + 1;
+       /* The length of the hand-over */
+       int synth_size =
+           sizeof(struct part_entry) + sizeof(uint32_t) +
+           cur_part->private.gpt.size;
+       /* Will point to the partition record length in the hand-over */
+       uint32_t *plen;
+
+       /* Allocate the hand-over record */
+       record = malloc(synth_size);
+       if (!record) {
+           error("Could not build GPT hand-over record!\n");
+           goto bail;
+       }
+       /* Synthesize the record */
+       memset(record, 0, synth_size);
+       record->active_flag = 0x80;
+       record->ostype = 0xED;
+       /* All bits set by default */
+       record->start_lba = ~(uint32_t) 0;
+       record->length = ~(uint32_t) 0;
+       /* If these fit the precision, pass them on */
+       if (cur_part->lba_data < record->start_lba)
+           record->start_lba = cur_part->lba_data;
+       if (lba_count < record->length)
+           record->length = lba_count;
+       /* Next comes the GPT partition record length */
+       plen = (uint32_t *) (record + 1);
+       plen[0] = cur_part->private.gpt.size;
+       /* Next comes the GPT partition record copy */
+       memcpy(plen + 1, gp, plen[0]);
+       cur_part->record = record;
+       regs.eax.l = 0x54504721;        /* '!GPT' */
+#if DEBUG
+       mbr_part_dump(record);
+       gpt_part_dump((struct gpt_part *)(plen + 1));
+#endif
+    }
+
     if (cur_part && cur_part->record) {
        /* 0x7BE is the canonical place for the first partition entry. */
        data[ndata].data = (void *)cur_part->record;
@@ -1431,8 +1478,10 @@ int main(int argc, char *argv[])
     do_boot(data, ndata, &regs);
 
 bail:
-    if (cur_part)
+    if (cur_part) {
        free(cur_part->block);
+       free((void *)cur_part->record);
+    }
     free(cur_part);
     free(mbr);
     return 255;