From a22c46c10262c7999c8ed4161608963fb100377a Mon Sep 17 00:00:00 2001
From: Alexander Evgin <aleasims@gmail.com>
Date: Wed, 15 Jan 2025 19:30:30 +0400
Subject: [PATCH] Remove included EXTLINUX MBR file

Read bootcode file from EXTLINUX locations instead,
or use --mbr-file option.
---
 .../linux_vm/data/extlinux/mbr.bin            | Bin 440 -> 0 bytes
 src/builders_v2/linux_vm/extlinux.rs          |  51 ++++++++++++++----
 2 files changed, 41 insertions(+), 10 deletions(-)
 delete mode 100644 src/builders_v2/linux_vm/data/extlinux/mbr.bin

diff --git a/src/builders_v2/linux_vm/data/extlinux/mbr.bin b/src/builders_v2/linux_vm/data/extlinux/mbr.bin
deleted file mode 100644
index 646a6848dc54986513bb0731e84d30b3db684ab5..0000000000000000000000000000000000000000
GIT binary patch
literal 0
HcmV?d00001

literal 440
zcmXp$@T>1e--SI4HJ#7c!ut;V{<EKfZ6^cc=cTXY*%%mtg0?vBUKMJ1(%{?Av%*Ef
zjlV-zmGWMES<IPsoUNB_i_>e-s4X04g_|GR2l8(_=J5StP(YgDfwY+~(imQtGWuo~
z7iZ?BE94iX7A2N|SjCmaC8@c3yj*DsX@-|}Gt{I7r3J7BXEA08bUsV_ZuX`6z!SEP
zhaE>JeKY$}-EoZLq2mrlrY^Bx)n|o!Qv}iy55G9_f8V~^{rlK=DlmLrdN?hi^XYCN
zhlRoLKyctU_J$H>ht7M=hXo#e_9%(2w2X}Ia%ZvOFJV)uw_z<+O6zv#Nb3$0Nn^Z_
zrg*88Ij!^1i#7j?m|txBpVsXr^J2k&kk&IGd&(GmOLIyx3vyBw5|c|Z%Tg5z5{pVQ
zOEUBGia{RecHu~4c9Ti#bm4em@V`hst<jF5Cc-V)sgyIV`2focng77>vinyXx{AN`
z)4x5xs-xoBfBk>*LXN>7EjSc%@)J`OQj3c6i+~2lt=YoYWtYUVnf<JQ4Oi*Mvl3rk
I|7Ab}067@FKL7v#

diff --git a/src/builders_v2/linux_vm/extlinux.rs b/src/builders_v2/linux_vm/extlinux.rs
index eaebddc..d6805b1 100644
--- a/src/builders_v2/linux_vm/extlinux.rs
+++ b/src/builders_v2/linux_vm/extlinux.rs
@@ -1,8 +1,8 @@
-use anyhow::{anyhow, Context, Result};
+use anyhow::{anyhow, bail, Context, Result};
 use log::{debug, info};
 use std::ffi::OsStr;
 use std::fs;
-use std::io::Write;
+use std::io::{Read, Write};
 use std::path::{self, Path, PathBuf};
 
 use crate::builders::Step;
@@ -13,12 +13,6 @@ use super::{InitSystemOpts, LinuxVMBuildContext};
 
 const DEFAULT_EXTLINUX_DIR: &str = "/boot/extlinux";
 
-/// This boot code is copied from extlinux 6.04.
-const BOOTCODE: &[u8; 440] = include_bytes!(concat!(
-    env!("CARGO_MANIFEST_DIR"),
-    "/src/builders_v2/linux_vm/data/extlinux/mbr.bin"
-));
-
 /// EXTLINUX wrapper.
 #[derive(Clone, Debug)]
 pub struct Extlinux {
@@ -46,6 +40,30 @@ impl Extlinux {
             .context("failed to stip prefix from extlinux target directory")
     }
 
+    /// Get path to `mbr.bin` file of EXTLINUX, e.g. `/usr/share/syslinux/mbr.bin`.
+    ///
+    /// This function will try a number of paths and return `None`, if none of them succeeds.
+    pub fn mbr_bin_path() -> Option<PathBuf> {
+        const CANDIDATES: &[&str] = &[
+            "/usr/share/extlinux/mbr.bin",
+            "/usr/share/syslinux/mbr.bin",
+            "/usr/lib/extlinux/mbr/mbr.bin",
+            "/usr/lib/syslinux/mbr/mbr.bin",
+            "/usr/lib/extlinux/bios/mbr.bin",
+            "/usr/lib/syslinux/bios/mbr.bin",
+        ];
+        CANDIDATES
+            .into_iter()
+            .map(PathBuf::from)
+            .find_map(|candidate| {
+                if candidate.exists() {
+                    return Some(candidate);
+                } else {
+                    return None;
+                }
+            })
+    }
+
     /// Install EXTLINUX.
     pub fn install<P: AsRef<Path>>(directory: P, mountpoint: &Path) -> Result<Self> {
         let extlinux = Extlinux {
@@ -96,12 +114,25 @@ impl Step<LinuxVMBuildContext> for InstallExtlinux {
         let extlinux = Extlinux::install(DEFAULT_EXTLINUX_DIR, &mountpoint)
             .context("failed to install EXTLINUX")?;
 
+        let mbr_path = if let Some(mbr_path) = &ctx.opts().mbr_file {
+            mbr_path.clone()
+        } else if let Some(mbr_path) = Extlinux::mbr_bin_path() {
+            mbr_path
+        } else {
+            bail!("cannot install EXTLINUX: MBR bootcode file not found");
+        };
+        let mut bootcode = [0u8; Mbr::BOOTCODE_SIZE];
+        fs::File::open(&mbr_path)
+            .context("failed to open MBR bootcode file")?
+            .read_exact(&mut bootcode)
+            .context("failed to read MBR bootcode file")?;
+
         let mbr = ctx
             .get_mut::<Mbr>("mbr")
             .ok_or(anyhow!("cannot install EXTLINUX: MBR not found"))?;
 
-        debug!("writing MBR bootcode");
-        mbr.write_bootcode(BOOTCODE.clone())
+        debug!("writing MBR bootcode from {}", mbr_path.display());
+        mbr.write_bootcode(bootcode)
             .context("failed to write MBR bootcode")?;
 
         ctx.set("extlinux", Box::new(extlinux));