disk: Make the sector size dynamic

Make the sector size dynamic in anticipation of disks with
non-512-byte logical sectors.

With this change, bsBytesPerSec *must* be correct; this still needs to
be added to the installers to enforce.  Furthermore, the number of
sectors in one extent can still only be < 64K.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/core/diskfs.inc b/core/diskfs.inc
index fc80a15..41391e7 100644 (file)
--- a/core/diskfs.inc
+++ b/core/diskfs.inc
@@ -30,8 +30,8 @@ LDLINUX_MAGIC equ 0x3eb202fe          ; A random number to identify ourselves with
 ; This indicates the general format of the last few bytes in the boot sector
 BS_MAGIC_VER   equ 0x1b << 9
 
-SECTOR_SHIFT   equ 9
-SECTOR_SIZE    equ (1 << SECTOR_SHIFT)
+MIN_SECTOR_SHIFT       equ 9
+MIN_SECTOR_SIZE                equ (1 << MIN_SECTOR_SHIFT)
 
 ;
 ; The following structure is used for "virtual kernels"; i.e. LILO-style

diff --git a/core/diskstart.inc b/core/diskstart.inc
index d2154d9..db4955f 100644 (file)
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -105,13 +105,15 @@ ldlinux_ent:
 ; Checksum data thus far
 ;
                mov si,ldlinux_sys
-               mov cx,SECTOR_SIZE >> 2
+               mov cx,[bsBytesPerSec]
+               shr cx,2
                mov edx,-LDLINUX_MAGIC
 .checksum:
                lodsd
                add edx,eax
                loop .checksum
                mov [CheckSum],edx              ; Save intermediate result
+               mov ebx,edi                     ; Start of the next sector
 
 ;
 ; Tell the user if we're using EBIOS or CBIOS
@@ -127,6 +129,7 @@ print_bios:
                call writestr_early
 
                section .earlybss
+               alignb 2
 %define        HAVE_BIOSNAME 1
 BIOSName       resw 1
 
@@ -135,8 +138,9 @@ BIOSName    resw 1
 ; Now we read the rest of LDLINUX.SYS.
 ;
 load_rest:
+               push bx                         ; LSW of load address
+
                lea esi,[SectorPtrs]
-               mov ebx,TEXT_START+2*SECTOR_SIZE ; Where we start loading
                mov cx,[DataSectors]
                dec cx                          ; Minus this sector
 
@@ -152,7 +156,7 @@ load_rest:
                xor bx,bx
                call getlinsec
                pop ebx
-               shl ebp,SECTOR_SHIFT
+               imul bp,[bsBytesPerSec]         ; Will be < 64K
                add ebx,ebp
                add si,10
                jmp .get_chunk
@@ -165,9 +169,11 @@ load_rest:
 ; by the time we get to the end it should all cancel out.
 ;
 verify_checksum:
-               mov si,ldlinux_sys + SECTOR_SIZE
-               mov ecx,[LDLDwords]
-               sub ecx,SECTOR_SIZE >> 2
+               pop si                          ; LSW of load address
+               movzx eax,word [bsBytesPerSec]
+               shr ax,2
+               mov ecx,[LDLDwords]             ; Total dwords
+               sub ecx,eax                     ; ... minus one sector
                mov eax,[CheckSum]
 .checksum:
                add eax,[si]
@@ -255,7 +261,7 @@ getlinsec_ebios:
                add eax,edi                     ; Advance sector pointer
                adc edx,0
                sub bp,di                       ; Sectors left
-                shl di,SECTOR_SHIFT            ; 512-byte sectors
+               imul di,[bsBytesPerSec]
                 add bx,di                      ; Advance buffer pointer
                 and bp,bp
                 jnz .loop
@@ -345,7 +351,7 @@ getlinsec_cbios:
                jc .error
 .resume:
                movzx ecx,al            ; ECX <- sectors transferred
-               shl ax,SECTOR_SHIFT     ; Convert sectors in AL to bytes in AX
+               imul ax,[bsBytesPerSec] ; Convert sectors in AL to bytes in AX
                pop bx
                add bx,ax
                pop bp
@@ -429,8 +435,8 @@ rl_checkpt_off      equ ($-$$)
 ;
                alignz 2
 MaxInitDataSize        equ 96 << 10
-MaxLMA         equ TEXT_START+SECTOR_SIZE+MaxInitDataSize
-SectorPtrs     zb 10*(MaxInitDataSize >> SECTOR_SHIFT)
+MaxLMA         equ LDLINUX_SYS+MaxInitDataSize
+SectorPtrs     zb 10*(MaxInitDataSize >> MIN_SECTOR_SHIFT)
 SectorPtrsEnd  equ $
 
 ; ----------------------------------------------------------------------------