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revolution 29 Mar 2008, 07:14
No, I suggested "jmp word $", you have used a 2-byte jump followed by a nop, that is not a 3-byte jump.
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29 Mar 2008, 07:14 |
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AlexP 29 Mar 2008, 07:32
Well, it's not making much of a difference... I made a partition table starting at offset 0x1BE, set the first byte to 0x80 (bootable partition), but it still gives me the "no bootable partiton in table) error when trying to boot. The rest of the partition table is NULLLL, and I don't know how many cyclinders a flash drive has, so I can't make much of a difference there
 . Here's the basic code so far:
Code: use16 org 0x7c00 jmp word $ ; --------------------------------------------------------------------------- ; ; partition tables ; --------------------------------------------------------------------------- rb 446-($-$$) ; partition 1 data table -> 0x1BE db 0x80 ; boot indicator = bootable partition rb 15 ; partition 2 data table -> 0x1CE rb 16 ; partition 3 data table -> 0x1DE rb 16 ; partition 4 data table -> 0x1EE rb 16 ; bootloader signature -> 0x1FE dw 0xaa55 |
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29 Mar 2008, 07:32 |
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Alphonso 29 Mar 2008, 07:44
AlexP wrote: I just got a BIOS error when trying to boot from my USB bootloader code, it said "No bootable partiton in table". Yes, it's spelled wrong.
The MBR points at the bootable sector. Mind you it's an oldish BIOS, maybe it works a bit differently from yours. |
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29 Mar 2008, 07:44 |
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AlexP 29 Mar 2008, 07:49
... so is there any way to get it my USB booting to work? That's what I'm trying to figure out now...
[edit]: So do I really need to make an entire MBR, tables and all just to get it to load the code into memory? [edit2]: I just re-formatted the drive for FAT, to dump the bootloader and see what it has. I can tell the jump, with offset 3c, then a nop, then quite a bit of sporatic strings for about 50 bytes or so including "MSDOS5.0" , "L.K.NO NAME" (I've seen that, drive label or something), and "FAT16". This must be the MBR or something, and following that is code, and then user strings until a couple of bytes from 0x55aa. Thought it would help, I can't make anything of it though. [edit3]: I am woeful to report that my BIOS gives the same error when I tried booting from a FAT16 flash drive. I think this should happen anyways, but I would really love to know if there is ANY way to boot an OS from a flash drive. |
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29 Mar 2008, 07:49 |
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revolution 29 Mar 2008, 09:12
If your BIOS is also looking for a valid table then just make a dummy table of any size drive (but not zero size) and see if it helps.
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29 Mar 2008, 09:12 |
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Alphonso 29 Mar 2008, 09:35
The BIOS I have just looks for the partition entry in the MBR on the usb flash. No MBR code is executed. Then it loads the boot sector indicated by the partition table. Might be an idea to check your disk geometry reported by the BIOS. The norm seems to be to have partitions start at start of new cylinder ie cylinder xx, head 0, sector 1. Place your boot sector here (as pointed to by the MBR partition table). Note that geometry reported by windows/BIOS may not be the same. For my 64MB flash, BIOS reports Cyl=11, HD=247 and SPT=47
Hope this helps. |
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29 Mar 2008, 09:35 |
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edfed 29 Mar 2008, 14:07
just imagine the future:
the bio$ only accepts a NTFS formated with VISTAHHHHHHHHHHHH. what an horror! _________________________________________________________________________ 64 MB flash??? but it's at least a 3 years old drive! now the minimal capacity is 1GB. be carefull, a flash drive can be writen only 100 000 times, after, the grids of the MOS-FET are dead. |
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29 Mar 2008, 14:07 |
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Dex4u 29 Mar 2008, 14:21
Here what i have found, first it no good you puting a marker as a bootable partion and then no info to where the partion is.
Here is a example of loading from a partion in DexOS Code: ;----------------------------------------------------; ; Test for FAT16/32. ; ;----------------------------------------------------; mov esi,MBRFat16n32 ; place in memory where MBR is add esi,450 mov al,byte[ds:esi] mov byte[SysID],al mov byte[FatID],16 cmp al,0x04 ; we check for Fat16 (offset 450) je SysIdOk cmp al,0x06 je SysIdOk cmp al,0x0E je SysIdOk mov byte[FatID],32 cmp al,0x0B ; Fat32 je SysIdOk cmp al,0x0C jne LoadMbrErrorIDSysIdOk: ;----------------------------------------------------; ; Find first partion. ; ;----------------------------------------------------; mov esi,MBRFat16n32 add esi,446 mov al,byte[ds:esi] cmp al,80h jne LoadMbrError mov dx,word[ds:esi] ; these are used for int 13h read mov cx,word[ds:esi+2] ;----------------------------------------------------; ; Store partition start cluster. ; ;----------------------------------------------------; push eax mov esi,MBRFat16n32 add esi,454 mov eax,dword[ds:esi] mov [partition_start_cluster],eax ;start of partion clust is here pop eax mov [countHdd],0int13hloop1: call FddRead ; call int 13h (also convert to LBA to cHs ) jc HddTryAgain1 So you need to add more info so it know Fat? and the address to load the boot sector from. I have also heard that it will not boot unless it has a certain OEM ID, i do not know if its true. See here: Quote:
See here for the full code: http://board.flatassembler.net/topic.php?p=51973#51973 I find the best and easist way is (under win98) format the usb as FAT and click add sys files, this makes it into a startup type disk, you can then add your OS to the autoexe.bat and it will boot it (if its a com or exe file). |
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29 Mar 2008, 14:21 |
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Alphonso 29 Mar 2008, 15:25
Alex, if it helps maybe it would be better to FAT format the usb then read sector 0 (MBR) dword offset 1C6 to get the boot sector number. Then you can overwrite it with your own code at the jump offset if you want to keep the FAT file system or just write over the whole boot sector with your own boot sector if you don't.
For instance FAT16 (FS=06) Partition 1 example Code: | Start | | End | |Act| HD |Cyl/Sec| FS | HD |Cyl/Sec| Sectors B4 | No. Sectors | 1BE |80 | 01 | 0001 | 06 | XX | XXXX | 3F 00 00 00 | XX XX XX XX | edfed wrote: just imagine the future: edfed wrote: 64 MB flash??? but it's at least a 3 years old drive! now the minimal capacity is 1GB. be carefull, a flash drive can be writen only 100 000 times, after, the grids of the MOS-FET are dead.  Trying to convince myself to buy a new T9300 / Blueray notebook but since I don't really push this PIII to it's limits it's a bit hard to justify other than having a chance to play with 64bit code. |
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29 Mar 2008, 15:25 |
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edfed 29 Mar 2008, 16:59
a good usb drive is the model from cibox (from 1G to 8G), it is supported by 98, then, it is the best choice
 i'm not payed by this company, it's not an add, just a suggestion
not expensive, the 1G model cost 7 € in a supermarket. then, one other way to have it working canbe to read the mbr, save the PT, overwrite the begining with a short boot loader, and a fun is thet you have at least 10 sectors after MBR that are not used by FAT, then, it can contain a little kernel. it's what i do with my USB KEY. the MBR is an *autentic* fat mbr. but as the sectors appears as empty, i wrie on them for testings. and it works, the drive is not in danger. it is both fat, and in hidden, it have a prototype file system. |
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29 Mar 2008, 16:59 |
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AlexP 29 Mar 2008, 17:47
I formatted in FAT32, and used
Quote: See here for the full code: Can I use an external floppy drive, aka one that connects via USB? I think that would be a heck of a lot easier than fooling around with file systems in a flash drive. |
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29 Mar 2008, 17:47 |
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Dex4u 29 Mar 2008, 18:56
That depends on your BIOS etc (it may need to emulate as floppy not sure ), i have had many coders, say that my OS works fine with a ext usb floppy drive, but i have not tryed it myself.
Your more than welcome to try my OS, if you have a usb floppy, but my OS has two floppy drivers one that goes to and from realmode and a pmode one, that why it work with USB. As it works with usb by using int 13h, so you will need to load the whole OS in unrealmode or go to and from realmode from pmode . http://www.dex4u.com/ |
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29 Mar 2008, 18:56 |
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AlexP 29 Mar 2008, 19:28
Yes, I've seen your OS. I will put the project to the side for now, it was scheduled for many weeks later anyway. I just wanted to get a simple boot going, and I'll re-try later. Thanks everyone!
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29 Mar 2008, 19:28 |
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Alphonso 29 Mar 2008, 21:18
Alex try this, it's a bit messy but hopefully your USB will boot with 'USB Boot' displayed.
Code: times 1beh db 0 db 80h ;Active db 1 ;Start head dw 1 ;Start Cyl 0, Sec 1 db 0BBh ;File System db 0fh ;End Head dw 3fh ;End Cyl 0, Sec 63 dd 3fh ;63 Sectors before dd 63*16-1 ;number of sectors ;Size is 500k times 510-($-$$) db 0 dw 0AA55h times 63*512-512 db 0 org 7c00h ;Boot Sector jmp near Start times $$-$+11 db 0 BPB: dw 512 ;Bytes/sect db 1 ;Sect/cluster dw 1 ;Reserved Sectors db 0 ;Fattys dw 0 ;Rootys dw 63*16-1 ;few sectors db 0f8h ;Media type dw 0 ;Sect/Fat dw 63 ;Sect/track dw 16 ;Heads dd 63 ;Sectors before dd 0 ;lots of sectors db 0 ;Drive No. Mess db 0dh,0ah,'USB Boot',0dh,0ah MessL=$-Mess Start: mov ax,cs mov ds,ax mov es,ax mov cx,MessL mov si,Mess @@: mov ah,0eh lodsb int 10h dec cx jnz @b mov ah,0 int 16h int 19h times 510-($-$$) db 0 dw 0AA55h |
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29 Mar 2008, 21:18 |
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AlexP 29 Mar 2008, 22:05
Okay, I'll try it
[edit] I tried it in all three USB modes offered by my BIOS, none worked. Same error. BIOS = Some Pheonix, I'll find specifics next time Modes of booting allowed: 1) USB Flash 2) USB Optical Drive 3) USB Hard DIsk Drive 4) INternal Hard Drive 5) Internal Optical Drive 6) Floppy Disk Drive (I have none) 7) Network PS: Someone told me that 0x1BE actually refers to 0x1BD, because of the 0 offset. THe utiilty "hex workshop" doesn't let me copy & paste the file, I tried burning using DD before but I don't know if it worked..,. |
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29 Mar 2008, 22:05 |
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Alphonso 30 Mar 2008, 06:34
1) USB Flash should be OK.
0x1BE is an absolute offset and refers to 0x1BE. If you count bytes from offset 0 it would be the 0x1BF byte. If you mean in the statement 'times 1beh db 0' then yes, that would write upto and including offset 0x1BD. I have not used "hex workshop" or even Vista, so it's hard for me to guess what is going wrong on your system. Windows used to come with it's own crude disk editor in the support tools called dskprobe.exe, don't know if Vista supports this. If you can use it, be very careful not to write to the wrong disk as you could lose some/all of your data. Hopefully you do regular backups.  Another utility you may be interested in is PTEDIT32 which will show you if the partition table looks correct and if you set the file system to FAT on the MBR, the boot sector BPB as well.
The dump you sent earlier of the boot sector was 192 bytes out of sync so that the first part was missing. If it was actually like that, and not a slip of the cut and paste, then it would not have worked. Another utility you might try just to get that USB to the boot stage is PeToUSB. ftp://ftp.symantec.com/public/english_us_canada/tools/pq/utilities/PTEDIT32.zip http://gocoding.com/projects/petousb/8F0P5/PeToUSB_3.0.0.7.zip |
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30 Mar 2008, 06:34 |
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edfed 30 Mar 2008, 06:46
just for clarification of a normative usage:
the fact that the first element is zero is the "zero based" convention. there are many others conventions, as the "one based", "three based", "what you want based". etc. for example, the boot sector is one based in chs, zero based in lba and 07c00h based in the RAM. then, many dumbs errors are made in assembly because of this (don't depend on the level of the coder, just it's not a natural convention). then, take a good care about the base convention, as well in asm and electronics. it is really one of the main causes of errors. |
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30 Mar 2008, 06:46 |
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AlexP 30 Mar 2008, 14:21
I had met someone in an IRC called #osdev, and they told me that the offsets were wrong because of the zero-base, I didn't think so though... Apparently the dump is off, I will try the utilities alphonso mentioned, and it looks like the dump is a little off. I used the 'dd' software,
http://www.chrysocome.net/dd Which writes to a disk starting at the base. Alphonso: How is it 192 bytes off? I wrote the 512 bytes directly to the base address, and the 'partition table' is supposed to be near the end of that. Well, I'll definitely try some of those utilities. Thanks [edit]: The first program I tried had an error, "#5 PowerQuest" or something, and the second one cannot find my USB drive! I formatted the USB to Fat (16 kb) with Windows, then restarted the program, and it still could not find it. Windows XP/2003 is required for another utility that website offers, a DOS booter, and it appears they used the same code for both to find the drive. I have Vista so I believe that is the problem. [anotheredit]: Okay, I poured over MSDN docs, online stuff, and I wrote this to test: Code: ; --------------------------------------------------------------------------- ; ; AdvEnSta-OS Flash Drive (USB External) Bootloader ; ; Current features: ; ; - basic boot, string printing ; ; Future add-ons: ; ; - string writing ; - 32-bit protected mode conversion ; - kernel files loading into memory ; ; --------------------------------------------------------------------------- use16 ; Apparently the MBR goes here? *partition tables db 80h ;Active db 1 ;Start head dw 1 ;Start Cyl 0, Sec 1 db 0BBh ;File System db 0fh ;End Head dw 3fh ;End Cyl 0, Sec 63 dd 3fh ;63 Sectors before dd 63*16-1 ;number of sectors ;Size is 500k times 510-($-$$) db 0 dw 0xaa55 ; And here is the partition that the MBR references to load times 63*512-512 db 0 org 0x7c00 ; is this right for partition load? I don't think so... ; three-byte jump to start of code jmp word start ; OEM ID db 'MSWIN6.0' ; I don't know... ; BPB (BIOS Parameter Block) dw 512 ; Bytes Per Sector db 8 ; Sector Per Cluster (test value) dw 1 ; Reserved Sectors db 2 ; FATs (test value, normally 2) dw 512 ; Root Entries dw 0 ; Small Sectors db 0xF0 ; Media Descriptor (3.5-inch, 2-sided, 18-sector) dw 1 ; Sectors Per FAT (test value) dw 63 ; Sectors Per Track (test value) dw 16 ; Heads dd 63 ; Hidden Sectors dd 63 ; Large Sectors ; start bootloader code section in sector 63 start: mov ax, 0 mov ds, ax mov si, boot_str @@: mov ah, 0x0e lodsb or al, al jz @f int 0x10 jmp @b @@: jmp $ boot_str: db 'Boot',0 ; first FAT goes here I believe. The first part is from Alphonso, , but I threw in some random values for other parts. I will give you the BIOS name in a second, along with whether it worked. The compiled code was written directly to the base of the drive, double-checked with two utilities for the sector 63 code.
[edit] The code posted above does not work. I selected "USB Flash" in the BIOS, but it reported the same error message. I did, however, get the BIOS name and version: Name: Phoenix TrustedCore Version: R0130J9 |
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30 Mar 2008, 14:21 |
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Alphonso 30 Mar 2008, 17:48
AlexP wrote: Alphonso: How is it 192 bytes off? I wrote the 512 bytes directly to the base address, and the 'partition table' is supposed to be near the end of that. I don't know why those programs didn't work for you, according to what I read they should work with root/admin privilege under Vista, sorry about that. Okay Alex, I tried DD with the 32k bin file from the source code posted earlier, and it worked Okay for this system. Hardisk1 was my 64MB flash drive. Code: dd if=d:\code.bin of=\\?\Device\Harddisk1\Partition0 bs=32k count=1 AFAIK FAT16 file system is the mostly accepted file system for a USB bootable drive although others will work with certain systems. I really would have thought you would have got to a ntldr missing or other message with just formating the USB with FAT. Not familiar with your BIOS, but there seems to be an "External Drive Boot" Enable/Disable option, is there also a USB legacy enable? Another thing you can do is try the BOOT MENU function key (at start of bootup), maybe F11 or F8/F12/ESC? etc. You should then see your USB flash if it's recognised by the machine. You've probably done all those things anyway, just thought I'd mention it. |
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30 Mar 2008, 17:48 |
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