invoxiplaygames.uk
UEFI utility to spoof the brand string of modern AMD processors via Machine State Registers. (Mirrored from https://github.com/InvoxiPlayGames/amd-brand-string-edit )
initial commit
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Cargo.lock
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Cargo.lock
···
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# It is not intended for manual editing.
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Cargo.toml
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Cargo.toml
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README.md
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README.md
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# amd-brand-string-edit
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UEFI utility to edit the brand string of AMD processors (Family 10h through
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Family 19h) via the `Core::X86::Msr::ProcNameString` Machine State Registers.
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This is temporary and doesn't modify the CPU in any way, and the change is
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purely aesthetic. This does not work on Intel, TransMeta, WinChip, or VIA CPUs.
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## Usage
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Replace the brand string in `src/main.rs` with your desired brand string, then
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run `cargo build --release --target x86_64-unknown-uefi`. Run the output .efi
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file (`target/x86_64-unknown-uefi/amd-brand-string-edit.efi`) on the computer
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via either an EFI shell or with the boot picker and the file located at
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`EFI/Boot/bootx64.efi` on removable storage.
media/uefi_output.png
media/uefi_output.png
This is a binary file and will not be displayed.
media/windows_display.png
media/windows_display.png
This is a binary file and will not be displayed.
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src/main.rs
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src/main.rs
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#![no_main]
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#![no_std]
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// CHANGE ME!
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// new brand string must be EXACTLY 48 characters (pad with spaces)
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static NEW_BRAND_STRING: &'static str = "Lappy 486 ";
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// 48 character reference: ------------------------------------------------
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use uefi::print;
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use uefi::prelude::*;
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use x86::cpuid::CpuId;
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use core::arch::asm;
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use core::convert::TryInto;
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unsafe fn wrmsr_amd(msr: u32, value: u64) {
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let low = value as u32;
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let high = (value >> 32) as u32;
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// wrmsr with the AMD "secret" key - not necessary for these MSRs
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let secret = 0x9c5a203a as u32;
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unsafe {
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asm!("wrmsr", in("ecx") msr, in("eax") low, in("edx") high, in("edi") secret);
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}
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}
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pub fn brand_string_to_int64(brand_str: &str) -> Option<[u64; 6]> {
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// make sure we have exactly 48 characters for the brand string
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if brand_str.len() != 48 {
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return None
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}
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let str_bytes = brand_str.as_bytes();
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let mut out = [0u64; 6];
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// convert it to an array of 6 LE integers
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// does rust seriously not support for loops
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let mut i = 0;
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while i < 6 {
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let start = i * 8;
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let chunk: [u8; 8] = str_bytes[start..start + 8].try_into().unwrap();
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out[i] = u64::from_le_bytes(chunk);
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i += 1;
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}
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Some(out)
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}
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#[entry]
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fn main() -> Status {
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uefi::helpers::init().unwrap();
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// get the vendor (we only work on AMD)
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let cpu_id = CpuId::new();
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let vendor_name = cpu_id.get_vendor_info().unwrap();
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print!("CPU vendor: {}\n", vendor_name.as_str());
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if vendor_name.as_str() == "AuthenticAMD" {
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// get the current CPU brand string
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let old_brand_string = cpu_id.get_processor_brand_string().unwrap();
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print!("Current brand: \"{}\"\n", old_brand_string.as_str());
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// convert to integers to set in the MSRs
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match brand_string_to_int64(NEW_BRAND_STRING) {
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None => print!("Invalid format for brand string\n\"{}\".\n", NEW_BRAND_STRING),
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Some(ints) => {
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// set the Core::X86::Msr::ProcNameString registers to our new string
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let mut i = 0;
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while i < 6 {
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unsafe {
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wrmsr_amd(0xC0010030 + i, ints[i as usize]);
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}
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i += 1;
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}
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// verify that the string has actually changed
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let verify_brand_string = cpu_id.get_processor_brand_string().unwrap();
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print!("New brand: \"{}\"\n", verify_brand_string.as_str());
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}
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}
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} else {
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print!("This program only supports AuthenticAMD.\n");
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}
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// stall for 7 seconds to let you read the console output
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boot::stall(7_000_000);
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Status::SUCCESS
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}