diff options
Diffstat (limited to 'DuetPkg/BootSector/bootsect.S')
| -rw-r--r-- | DuetPkg/BootSector/bootsect.S | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/DuetPkg/BootSector/bootsect.S b/DuetPkg/BootSector/bootsect.S index 62f50aca49..91a1966c9b 100644 --- a/DuetPkg/BootSector/bootsect.S +++ b/DuetPkg/BootSector/bootsect.S @@ -9,13 +9,25 @@ #* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
#* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
#*
-#* bootsect.asm
+#* bootsect.S
#*
-#* Abstract:
+#* bootsect.S is built as 16-bit binary file in 512 bytes and patched to disk/partition's
+#* first section - boot sector.
+#*
+#* The startup sequence for DUET disk boot sector is:
+#*
+#* 1, LegacyBios check 0xAA55 signature at boot sectore offset 0x1FE to judget
+#* whether disk/partition is bootable.
+#* 2, LegacyBios will load boot sector to 0x7c00 in real mode, pass BPB data and
+#* hand off control to 0x7c00 code.
+#* 3, boot sector code simply parse FAT format in boot disk and find EfiLdr binary file
+#* and EfiVar.bin if exists. For first boot, EfiVar.bin does not exist.
+#* 4, boot sector load the first sector of EfiLdr binary which is start.com to
+#* 0x2000:0x0000 address.
+#* 5, boot sector handoff control to 0x2000:0x0000 for start.com binary.
#*
#------------------------------------------------------------------------------
- #.MODEL small
.stack:
.486p:
.code16
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