Skip to content

blockdev: find esp based on MBR or GPT #1773

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Nov 19, 2025
Merged

blockdev: find esp based on MBR or GPT #1773

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
32 changes: 30 additions & 2 deletions crates/blockdev/src/blockdev.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,13 @@ use serde::Deserialize;

use bootc_utils::CommandRunExt;

/// EFI System Partition (ESP) on MBR
/// Refer to <https://en.wikipedia.org/wiki/Partition_type>
pub const ESP_ID_MBR: &[u8] = &[0x06, 0xEF];

/// EFI System Partition (ESP) for UEFI boot on GPT
pub const ESP: &str = "c12a7328-f81f-11d2-ba4b-00a0c93ec93b";

#[derive(Debug, Deserialize)]
struct DevicesOutput {
blockdevices: Vec<Device>,
Expand Down Expand Up @@ -175,6 +182,19 @@ impl PartitionTable {
pub fn find_partition_of_bootable(&self) -> Option<&Partition> {
self.partitions.iter().find(|p| p.is_bootable())
}

/// Find the esp partition.
pub fn find_partition_of_esp(&self) -> Result<Option<&Partition>> {
match &self.label {
PartitionType::Dos => Ok(self.partitions.iter().find(|b| {
u8::from_str_radix(&b.parttype, 16)
.map(|pt| ESP_ID_MBR.contains(&pt))
.unwrap_or(false)
})),
PartitionType::Gpt => Ok(self.find_partition_of_type(ESP)),
_ => Err(anyhow::anyhow!("Unsupported partition table type")),
}
}
}

impl Partition {
Expand Down Expand Up @@ -612,10 +632,14 @@ mod test {
.find_partition_of_type("00000000-0000-0000-0000-000000000000");
assert!(nonexistent.is_none());

// Find esp partition on GPT
let esp = table.partitiontable.find_partition_of_esp()?.unwrap();
assert_eq!(esp.node, "/dev/loop0p1");

Ok(())
}
#[test]
fn test_find_partition_of_bootable() -> Result<()> {
fn test_find_partition_of_type_mbr() -> Result<()> {
let fixture = indoc::indoc! { r#"
{
"partitiontable": {
Expand All @@ -640,7 +664,7 @@ mod test {
"node": "/dev/mmcblk0p3",
"start": 3125248,
"size": 121610240,
"type": "83"
"type": "ef"
}
]
}
Expand All @@ -655,6 +679,10 @@ mod test {
.find_partition_of_bootable()
.expect("bootable partition not found");
assert_eq!(esp.node, "/dev/mmcblk0p1");

// Find esp partition on MBR
let esp1 = table.partitiontable.find_partition_of_esp()?.unwrap();
assert_eq!(esp1.node, "/dev/mmcblk0p1");
Ok(())
}
}