Setup. s code comment

1!
2! Setup. S (c) 1991 Linus Torvalds
3!
4! Setup. S is responsible for getting the system data from the bios,
5! And putting them into the appropriate places in system memory.
6! Both setup. s and system has been loaded by the bootblock.
7!
8! This code asks the BIOS for memory/Disk/other parameters, and
9! Puts them in a "safe" Place: 0x90000-0x901ff, ie where
10! Boot-block used to be. It is then up to the Protected Mode
11! System to read them from there before the area is overwritten
12! For buffer-blocks.
!
! Setup. S is responsible for Retrieving System data from the bios and placing the data in a proper place in the system memory.
! At this time, setup. s and system have been loaded into the memory by the bootsect boot block.
!
! This code asks the BIOS about memory/Disk/other parameters, and puts these parameters into one
! "Safe": 0x90000-0x901ff, that is, the original bootsect code block was
! And then read by the protection mode system before it is overwritten by the buffer block.
13!
14
15! Note! These had better be the same as in bootsect. s!

! The following parameters are recommended to be the same as those in bootsect. s!
16
17 initseg = 0x9000! We move boot here-Out of the way! The original bootsect segment.
18 sysseg = 0x1000! System loaded at 0x10000 (65536 ).! System is at 0x10000 (64 K.
19 setupseg = 0x9020! This is the current segment! The segment address of the program.
20
21. globl begtext, begdata, begbss, endtext, enddata, endbss
22. Text
23 begtext:
24. Data
25 begdata:
26. BSS
27 begbss:
28. Text
29
30 Entry start
31 start:
32
33! OK, the read went well so we get current cursor position and save it
34! Posterity.
! OK. The entire disk reading process is normal. Now, save the cursor position for future use.
35
36 mov ax, # initseg! This is done in bootsect already,...
! Set ds to # initseg (0x9000 ). This is already in the bootsect Program
! But now it's a setup program. Linus thinks it needs to be set again.
! Set it.
37 mov ds, ax
38 mov ah, #0x03! Read cursor POS
! BiOS interrupt 0x10 read cursor function number AH = 0x03
! Input: bH = page number
! Return: CH = scanning start line, CL = scanning slave line,
! DH = row number (0x00 is the top), DL = column number (0x00 is the left ).
39 xor bh, BH
40 int 0x10! Save it in known place, con_init fetches
41 mov [0], dx! From 0x90000.
! The last two sentences are used to store the cursor position information at 0x90000. The Console
! It will be retrieved during initialization.
42
43! Get memory size (Extended MEM, KB )! In the following three sentences, the size of the extended memory is measured in KB ).
! Yes, the call is interrupted 0x15, and the function number AH = 0x88
! Returns the extended memory size (Kb) starting from 0x100000 (1 MB ).
! If an error occurs, CF is set to a bit, and AX = the error code.
44
45 mov ah, #0x88
46 int 0x15
47 mov [2], ax! The extended memory value is 0x90002 (1 word ).
48
49! Get video-card data :! The following section is used to obtain the current display mode of the display card.
! 0x10 for BIOS interruption, function ID Ah = 0x0f
! Return Value: Ah = number of columns, Al = display mode, BH = current display page.
! 0x90004 (1 Word) stores the current page, 0x90006 display mode, 0x90007 character columns.
50
51 mov ah, # 0x0f

52 int 0x10
53 mov [4], BX! BH = display page
54 mov [6], ax! Al = video mode, Ah = window width
55
56! Check for parameters/VGA and some config parameters! Check the display mode (Measures/VGA) and take the parameters.
! Call the BIOS to interrupt 0x10. Select the "Retrieve Method" option for the additional function.
! Function No.: Ah = 0x12, BL = 0x10
! Return: bH = display status
! (0x00-color mode, I/O port = 0x3dx)
! (0x01-monochrome mode, I/O port = 0x3bx)
! BL = installed Display memory
! (0x00-64 K, 0x01-128 K, 0x02-192 K, 0x03 = 256 K)
! Cx = display card feature parameters (see the description after the program ).
57
58 mov ah, #0x12
59 mov BL, #0x10
60 int 0x10
61 mov [8], ax! 0x90008 = ??
62 mov [10], BX! 0x9000a = memory for installation, 0x9000b = display status (color/monochrome)
63 mov [12], CX! 0x9000c = display card feature parameters.
64
65! Get hd0 data! Take the information of the first hard disk (copy the hard disk parameter table ).
! The first address of the 1st hard disk parameter table is the Vector Value of the interrupt vector 0x41! And 2nd Hard Disks
! The parameter table is followed by 1st tables, and the Vector Value of the interrupt vector 0x46 also points to the 2nd hard disks.
! The first address of the parameter table. The table length is 16 bytes (0x10 ).
! The following two procedures copy the BIOS parameter table for two hard disks, and store 90080 data disks at 0 x 1st.
! Hard Disk table, where 90090 hard disks are stored at 0 x 2nd.
66
67 mov ax, #0x0000.
68 mov ds, ax
69 lDs Si, [4*0x41]! Take the value of the interrupt vector 0x41, that is, the address of the hd0 parameter table.