Questions tagged [bios]

BIOS (basic input/output system) is a special program to get the computer system started after you turn it on.

Filter by
Sorted by
Tagged with
0 votes
0 answers
45 views

Windows boot sequence operation

I am targeting at creating software for the Windows pre-boot environment but I have hard time finding conclusive information about how it operates. For background: this software will communicate with ...
Claude's user avatar
  • 1
4 votes
0 answers
222 views

remove the computrace by flashing the bios

Is there a way to remove the computrace by flashing the bios or deleting/altering the contents of it? Someone gave me a laptop and I found out that it was not usable because it was equipped with ...
pao's user avatar
  • 81
4 votes
0 answers
252 views

BIOS serial number and UUID tampering

what happens if I tampered the serial number in the bios of a laptop? This laptop was issued to us by our company and what happened was we were laid out without any compensation for what happened so I ...
pao's user avatar
  • 81
2 votes
1 answer
104 views

IDA Pro 7, idc script to copy 8KB ROM to F000 Segment?

I updated an old .idc script so it will now copy 64kb of a 512kb BIOS file to the F000: Segment under IDA Pro (Free) 7 : #include <idc.idc> // The script relocates a copy of the highest 64 ...
TheStarman's user avatar
2 votes
0 answers
214 views

Fix screen resolutions to landscape in bios

I've got an x86 tablet (Dere D10). It works fine, except the screen reports portait resolutions (1200x1920, 768x1024, 600x800, etc.) which causes bootloaders (windows recovery menu, grub, ventoy, etc.)...
REmorin's user avatar
  • 21
4 votes
2 answers
1k views

Disassemble bios code

I have a Gigabyte G41MT-S2PT motherboard with Intel core 2 Pentium processor installed on it for test.I decided to disassemble its bios code.Its bios produced by Award Software International and its ...
Farshid's user avatar
  • 41
2 votes
1 answer
311 views

Where is the legacy BIOS stored on a UEFI system?

Where is the legacy BIOS (the 16 bit reset code that jumps to the POST entry point at F000:E05B and indeed POST itself and all the BIOS routines) originally stored on a UEFI system before it's ...
Lewis Kelsey's user avatar
2 votes
0 answers
499 views

How can i extract u-boot image from fgt90d.out firmware and install Openwrt image?

I have a lot of out of licensed Fortigate90D devices so i want to reuse and run Openwrt/pfsense on them. I have dumped and decoded the bios and got some useful datas, according to datas we can see u-...
alfa's user avatar
  • 21
0 votes
1 answer
530 views

How to get PI UEFI binary when mcrypt is used?

I am playing with a dump I made from a serial flash containing the BIOS of a ultra portable whose BIOS is protected by a password. I am trying to find the password or patch the routine which check the ...
rdpdo's user avatar
  • 43
1 vote
0 answers
479 views

Removing/bypassing a BIOS whitelist

I am trying to bypass or erase the BIOS whitelist on my Thinkpad T440p. So far I've used flashrom and a soic8 clip to dump the bios to a bios.img file made another dump and compared with diff bios....
BraveSentry's user avatar
5 votes
2 answers
483 views

BIOS first jump leads to empty memory

I'm trying to reverse a BIOS of an industrial PC in order to repair it. The device is based on an ETX-formfactor mobo, obscure Italian SECO M671, very similar to an old Kontron PM-15(C), but with a ...
kutukvpavel's user avatar
5 votes
1 answer
369 views

Undocumented Model-Specific Register on Broadwell Microarchitecture

I'm trying to reverse the BIOS of a machine to learn something. The bigger problem I'm facing is that during early initialization, the code is making heavy usage of MSRs, and most of the time, I found ...
Alessandro's user avatar
2 votes
0 answers
134 views

removing bios wireless white listing

I am trying to remove the white listing for wireless cards from my Thinkpad L540 running Debian Buster. I did the following steps: booted with kernel parameter iomem=relaxed used pawn to dump BIOS ...
Max's user avatar
  • 121
1 vote
1 answer
146 views

Flash ROM has lower max voltage than read device?

I'm planning to read a MX25U1635E chip using the CH341a reader. The specs for that chip say it has a max voltage of 1.6-2.0 volts. The reader has an output of 3.3-5.0 volts. Most tutorials for the ...
gatzkerob's user avatar
  • 113
4 votes
1 answer
659 views

Undocumented MSR Machine Specific register

I'm reversing the BIOS of my laptop, for fun and for learning something new. Inside it, I just stepped into this piece of code: mov ecx, 13Ah rdmsr and eax, 1 jnz SkipCacheAsRAM Looking ...
Alessandro's user avatar
5 votes
1 answer
115 views

Passing a (string) argument via the return address?

I'm debugging an old PC BIOS and it has most of its constant strings interspersed directly with the code, like this: As the comment notes, the function putsc will take the string as its argument, ...
pesco's user avatar
  • 187
2 votes
1 answer
165 views

Why are these 0-byte jumps used as a delay?

I'm debugging an old PC BIOS and see a lot of what I assume are delay sequences, using 0-byte jump instructions (EB 00 = jmp short $+2). Why this particular instruction? I'm guessing it must have ...
pesco's user avatar
  • 187
2 votes
1 answer
3k views

Reverse Engineering BIOS (AMI A0.57)

Recently I got really interested in BIOS RE and I used chipsec to dump the content of SPI Flash ROM of my HP Omen Desktop PC to start my journey. But unlike older BIOSes, the binary file was pretty ...
LD2's user avatar
  • 21
1 vote
3 answers
2k views

Decompress and Analyse VMWARE EFI64 bios

I want to analyse this UEFI bios here. When I open it in IDA it looks compressed to me. Also IDA lists the processor type as ZLOG. Shouldn't this be the multi processor setting for IDA? Anyway, If I ...
LUser's user avatar
  • 793
3 votes
1 answer
210 views

Why BIOS is not asking for HDD password on reboot but only after power off?

I was reading about BIOS and I saw this: Next, BIOS will begin checking memory at 0000:0472h. This address contains a flag which will tell the BIOS if the system is booting from a cold boot or warm ...
J Johnson's user avatar
2 votes
1 answer
2k views

Find changes between two UEFI firmware versions?

I have saved a copy of the UEFI firmware currently running on my motherboard through the built-in flash utility. Now I want to compare the firmware dump with the newest firmware update from the ...
Ken Hansen's user avatar
0 votes
1 answer
159 views

BIOS code failed to check device and run into a infinite loop

I'm hacking a thinkpad BIOS to remove the card whitelist. I run the bios firmware in qemu and debug with IDApro. .\qemu-system-x86_64.exe -m 4096M -bios D:\W25Q32BV\old.bin -s -S But, the code run ...
sundw's user avatar
  • 1
15 votes
1 answer
8k views

How can BIOS routines be disassemblied?

There was once a disassembler on DOS named Sourcer that can disassembly BIOS routines. However, how do we access to BIOS ROM from software to do such a thing?
Amumu's user avatar
  • 253
4 votes
1 answer
2k views

How Can I Debug A Bios Better

I am trying to reverse engineer a firmkit in a bios, but in general I would like to know how can I debug a bios better. I found a way to attach IDA to a vmware instance usign a GDB session GDB ...
LUser's user avatar
  • 793
18 votes
2 answers
5k views

In which language is the BIOS written?

As I understand, the BIOS code/bitstream that held in the ROM should be generic (work alongside with multiple CPU types or ISAs). In addition, I saw mentions in the web that claim to have the ...
Reflection's user avatar
1 vote
3 answers
4k views

Reverse Engineering a Binary to reset a BIOS password

I have a laptop that I recently lost the BIOS Admin password for. I contacted the manufacturer and, after giving them some information about my BIOS (version, uuid), they sent me a file, smc.bin to ...
Jack's user avatar
  • 11