SliTaz Repositories

     1.1 --- a/BootProg/stuff/boot32.asm	Tue Feb 22 16:15:28 2022 +0000
     1.2 +++ b/BootProg/stuff/boot32.asm	Wed Feb 23 11:49:52 2022 +0000
     1.3 @@ -11,7 +11,8 @@
     1.4  ;;                                                                          ;;
     1.5  ;;                                 Features:                                ;;
     1.6  ;;                                 ~~~~~~~~~                                ;;
     1.7 -;; - FAT32 supported using BIOS int 13h function 42h or 02h.                ;;
     1.8 +;; - FAT32 supported using BIOS int 13h function 42h (IOW, it will only     ;;
     1.9 +;;   work with modern BIOSes supporting HDDs bigger than 8 GB)              ;;
    1.10  ;;                                                                          ;;
    1.11  ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format       ;;
    1.12  ;;   from the root directory of a disk and transfers control to it          ;;
    1.13 @@ -262,30 +263,33 @@
    1.14  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.15  
    1.16          mov     ds, bp                  ; bp=ds=seg the file is loaded to
    1.17 +
    1.18          add     bp, [bx+08h]            ; bp = image base
    1.19          mov     ax, [bx+06h]            ; ax = reloc items
    1.20          mov     di, [bx+18h]            ; di = reloc table pointer
    1.21  
    1.22          cmp     word [bx], 5A4Dh        ; "MZ" signature?
    1.23 -
    1.24          je      RelocateEXE             ; yes, it's an EXE program
    1.25  
    1.26  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.27  ;; Setup and run a .COM program ;;
    1.28 -;; Set CS=DS=ES=SP SP=0 IP=100h ;;
    1.29 +;; Set CS=DS=ES=SS SP=0 IP=100h ;;
    1.30 +;; AX=0ffffh BX=0 CX=0 DX=drive ;;
    1.31  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.32  
    1.33 +        mov     ax, 0ffffh              ; both FCB in the PSP don't have a valid drive identifier
    1.34 +        mov     di, 100h                ; ip
    1.35          mov     bp, ImageLoadSeg-10h    ; "org 100h" stuff :)
    1.36          mov     ss, bp
    1.37          xor     sp, sp
    1.38          push    bp                      ; cs, ds and es
    1.39 -        mov     bh, 1                   ; ip
    1.40          jmp     short Run
    1.41  
    1.42  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.43  ;; Relocate, setup and run a .EXE program     ;;
    1.44  ;; Set CS:IP, SS:SP, DS, ES and AX according  ;;
    1.45  ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
    1.46 +;; AX=0ffffh BX=0 CX=0 DX=drive               ;;
    1.47  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.48  
    1.49  ReloCycle:
    1.50 @@ -308,11 +312,11 @@
    1.51          push    si                      ; containing the PSP structure
    1.52  
    1.53          add     bp, [bx+16h]            ; cs for EXE
    1.54 -        mov     bx, [bx+14h]            ; ip for EXE
    1.55 +        mov     di, [bx+14h]            ; ip for EXE
    1.56  Run:
    1.57          pop     ds
    1.58          push    bp
    1.59 -        push    bx
    1.60 +        push    di
    1.61          push    ds
    1.62          pop     es
    1.63  
    1.64 @@ -332,6 +336,7 @@
    1.65  ReadCluster:
    1.66          mov     bp, [bx(bpbBytesPerSector)]
    1.67          shr     bp, 4                           ; bp = paragraphs per sector
    1.68 +        add     eax, byte 1             ; adjust LBA for next sector
    1.69          inc     cx
    1.70          loop    ReadSectorLBA
    1.71  
    1.72 @@ -374,7 +379,6 @@
    1.73          add     eax, edx
    1.74          adc     word [bx(HiLBA)], bx
    1.75          add     eax, [bx(bpbHiddenSectors)]
    1.76 -        adc     word [bx(HiLBA)], bx
    1.77  
    1.78  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.79  ;; Reads a sector using BIOS Int 13h fn 42h ;;
    1.80 @@ -386,6 +390,8 @@
    1.81  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    1.82  
    1.83  ReadSectorLBA:
    1.84 +        adc     word [bx(HiLBA)], bx
    1.85 +        mov     dx, [bx(bsDriveNumber)] ; restore BIOS boot drive number
    1.86          pusha
    1.87  
    1.88          push    bx
    1.89 @@ -395,43 +401,13 @@
    1.90          push    bx
    1.91          push    byte 1 ; sector count word = 1
    1.92          push    byte 16 ; packet size byte = 16, reserved byte = 0
    1.93 -        push    eax
    1.94 -        pop     cx                      ; low LBA
    1.95 -        pop     ax                      ; high LBA
    1.96 -        cwd                             ; clear dx (CHS disk <2TB)
    1.97 -        div     word [bx(bpbSectorsPerTrack)] ; up to 8GB CHS disks
    1.98 -
    1.99 -        xchg    ax, cx                  ; restore low LBA, save high LBA / SPT
   1.100 -        div     word [bx(bpbSectorsPerTrack)]
   1.101 -                                        ; ax = LBA / SPT
   1.102 -                                        ; dx = LBA % SPT         = sector - 1
   1.103 -        inc     dx
   1.104 -
   1.105 -        xchg    cx, dx                  ; restore high LBA / SPT, save sector no.
   1.106 -        div     word [bx(bpbHeadsPerCylinder)]
   1.107 -                                        ; ax = (LBA / SPT) / HPC = cylinder
   1.108 -                                        ; dx = (LBA / SPT) % HPC = head
   1.109 -        shl     ah, 6
   1.110 -        mov     ch, al
   1.111 -                                        ; ch = LSB 0...7 of cylinder no.
   1.112 -        or      cl, ah
   1.113 -                                        ; cl = MSB 8...9 of cylinder no. + sector no.
   1.114 -        mov     dh, dl
   1.115 -                                        ; dh = head no.
   1.116  
   1.117  ReadSectorLBARetry:
   1.118 -        mov     dl, [bx(bsDriveNumber)] ; restore BIOS boot drive number
   1.119          mov     si, sp
   1.120          mov     ah, 42h                 ; ah = 42h = extended read function no.
   1.121          int     13h                     ; extended read sectors (DL, DS:SI)
   1.122          jnc     ReadSuccess             ; CF = 0 if no error
   1.123  
   1.124 -ReadSectorCHSRetry:
   1.125 -        mov     ax, 201h                ; al = sector count = 1
   1.126 -                                        ; ah = 2 = read function no.
   1.127 -        int     13h                     ; read sectors (AL, CX, DX, ES:BX)
   1.128 -        jnc     ReadSuccess             ; CF = 0 if no error
   1.129 -
   1.130          cbw                             ; ah = 0 = reset function
   1.131          int     13h                     ; reset drive (DL)
   1.132  
   1.133 @@ -447,16 +423,12 @@
   1.134  
   1.135          popa
   1.136  
   1.137 -        add     eax, byte 1             ; adjust LBA for next sector
   1.138 -        adc     word [bx(HiLBA)], bx
   1.139 -
   1.140          stc
   1.141          loop    ReadSectorNext
   1.142  
   1.143          cmp     esi, 0FFFFFF8h          ; carry=0 if last cluster, and carry=1 otherwise
   1.144  
   1.145  ReadSectorNext:
   1.146 -        mov     dx, [bx(bsDriveNumber)] ; restore BIOS boot drive number
   1.147          ret
   1.148  
   1.149  ;;;;;;;;;;;;;;;;;;;;;;;;;;
   1.150 @@ -473,8 +445,8 @@
   1.151          cmp     al, '.'
   1.152          jne     puts
   1.153          cbw
   1.154 -;        int     16h                     ; wait for a key...
   1.155 -;        int     19h                     ; bootstrap
   1.156 +        int     16h                     ; wait for a key...
   1.157 +        int     19h                     ; bootstrap
   1.158  
   1.159  Stop:
   1.160          hlt