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boot: allow instsect to match the filesystem ID string 

Reference: https://hg.ulukai.org/ecm/instsect/file/33218c729b43/instsect.asm#l1257

lDOS's instsect recently started to default to checking
the filesystem ID string in order to validate that the
boot sector loader to write matches the detected FS.
Using the /S=filename option or building instsect to
include the FreeDOS kernel's loaders would require use
of the /SN switch without this commit.

In addition, boot.asm and oemboot.asm are made to check
that exactly one of the ISFAT12 and ISFAT16 defs is
defined so as to select the FS. Prior to this commit
using both or neither def would silently result in a
broken loader.
This commit is contained in:
C. Masloch 2020-11-28 14:17:59 +01:00 committed by Kenneth J Davis
parent 6e42bb6d7c
commit 92ae538f1d
4 changed files with 40 additions and 5 deletions
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15
boot/boot.asm
View File

@ -100,7 +100,20 @@ Entry: jmp short real_start
;-----------------------------------------------------------------------
times 0x3E-$+$$ db 0
times 36h - ($ - $$) db 0
; The filesystem ID is used by lDOS's instsect (by ecm)
; by default to validate that the filesystem matches.
%ifdef ISFAT12
db "FAT12"
%ifdef ISFAT16
%error Must select one FS
%endif
%elifdef ISFAT16
db "FAT16"
%else
%error Must select one FS
%endif
times 3Eh - ($ - $$) db 32
; using bp-Entry+loadseg_xxx generates smaller code than using just
; loadseg_xxx, where bp is initialized to Entry, so bp-Entry equals 0

9
boot/boot32.asm
View File

@ -57,11 +57,16 @@ Entry: jmp short real_start
%define xrootClst bp+0x2c ; Starting cluster of root directory
%define drive bp+0x40 ; Drive number
times 0x5a-$+$$ db 0
times 52h - ($ - $$) db 0
; The filesystem ID is used by lDOS's instsect (by ecm)
; by default to validate that the filesystem matches.
db "FAT32"
times 5Ah - ($ - $$) db 32
%define LOADSEG 0x0060
%define FATSEG 0x2000
%define FATSEG 0x2000
%define fat_sector bp+0x48 ; last accessed sector of the FAT

6
boot/boot32lb.asm
View File

@ -96,7 +96,11 @@ Entry: jmp short real_start
%define data_start bp+0x4c ; first data sector (dd)
; (overwriting unused bytes)
times 0x5a-$+$$ db 0
times 52h - ($ - $$) db 0
; The filesystem ID is used by lDOS's instsect (by ecm)
; by default to validate that the filesystem matches.
db "FAT32"
times 5Ah - ($ - $$) db 32
; not used: [0x42] = byte 0x29 (ext boot param flag)
; [0x43] = dword serial
; [0x47] = label (padded with 00, 11 bytes)

15
boot/oemboot.asm
View File

@ -223,7 +223,20 @@ Entry: jmp short real_start
db 0x29 ; extended boot record id
dd 0x12345678 ; volume serial number
db 'NO NAME '; volume label
db 'FAT12 ' ; filesystem id
times 36h - ($ - $$) db 0
; The filesystem ID is used by lDOS's instsect (by ecm)
; by default to validate that the filesystem matches.
%ifdef ISFAT12
db "FAT12" ; filesystem id
%ifdef ISFAT16
%error Must select one FS
%endif
%elifdef ISFAT16
db "FAT16"
%else
%error Must select one FS
%endif
times 3Eh - ($ - $$) db 32
;-----------------------------------------------------------------------
; ENTRY