uhyve 0.9.1

A specialized hypervisor for Hermit
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use std::{
	ffi::CString,
	os::{fd::RawFd, unix::ffi::OsStrExt},
};

use uhyve_interface::{GuestPhysAddr, v2::parameters::*};

use crate::{
	hypercall::{decode_guest_path, translate_last_errno},
	isolation::{
		fd::{FdData, GuestFd},
		filemap::{NodeStatRef, UhyveFileMap},
	},
	mem::MmapMemory,
};

fn virtual_file_attr(data: &[u8]) -> FileAttr {
	FileAttr {
		st_mode: (libc::S_IFREG | 0o444).into(),
		st_nlink: 1,
		st_size: data.len().try_into().unwrap_or(i64::MAX),
		st_blksize: 4096,
		st_blocks: (data.len() as i64).saturating_add(511) / 512,
		..Default::default()
	}
}

fn mapped_directory_attr() -> FileAttr {
	FileAttr {
		st_mode: (libc::S_IFDIR | 0o755).into(),
		st_nlink: 2,
		st_blksize: 4096,
		..Default::default()
	}
}

fn host_stat_path(path: &std::path::Path, kind: StatKind) -> Result<FileAttr, i32> {
	let path = CString::new(path.as_os_str().as_bytes()).map_err(|_| EINVAL)?;
	let path = path.as_c_str().as_ptr();
	let mut st = unsafe { core::mem::zeroed() };
	let ret = unsafe {
		match kind {
			StatKind::Stat => libc::stat(path, &mut st),
			StatKind::LStat => libc::lstat(path, &mut st),
		}
	};
	if ret < 0 {
		return Err(translate_last_errno().unwrap_or(EIO));
	}
	Ok(crate::os::fs::host_stat_to_file_attr(st))
}

fn host_fstat(fd: RawFd) -> Result<FileAttr, i32> {
	let mut st = unsafe { core::mem::zeroed() };
	let ret = unsafe { libc::fstat(fd, &mut st) };
	if ret < 0 {
		return Err(translate_last_errno().unwrap_or(EIO));
	}
	Ok(crate::os::fs::host_stat_to_file_attr(st))
}

fn fstat_attr_for_fd_data(fdata: &FdData) -> Result<FileAttr, i32> {
	match fdata {
		FdData::Raw(fd) => host_fstat(*fd),
		FdData::Virtual { data, .. } => Ok(virtual_file_attr(data)),
		FdData::MappedDirectory { .. } => Ok(mapped_directory_attr()),
	}
}

fn write_stat_attr(mem: &MmapMemory, attr_addr: GuestPhysAddr, attr: FileAttr) -> StatResult {
	match unsafe { mem.get_ref_mut(attr_addr) } {
		Ok(guest_attr) => {
			*guest_attr = attr;
			StatResult::Success
		}
		Err(_) => {
			warn!("Unable to get host address for stat buffer");
			StatResult::Error(EFAULT)
		}
	}
}

/// Handles a stat/lstat hypercall.
pub(crate) fn stat(mem: &MmapMemory, sysstat: &mut StatParams, file_map: &UhyveFileMap) {
	sysstat.ret = unsafe { decode_guest_path(mem, sysstat.name) }
		.ok_or_else(|| {
			error!("The kernel requested stat() on a non-UTF8 path: Rejecting...");
			EINVAL
		})
		.and_then(|guest_path| {
			file_map
				.get_host_stat_node(guest_path, matches!(sysstat.kind, StatKind::Stat))
				.ok_or_else(|| {
					debug!("stat {guest_path:?}: path not found in file map");
					ENOENT
				})
		})
		.and_then(|node| match node {
			NodeStatRef::VirtualDirectory(_) => Ok(mapped_directory_attr()),
			NodeStatRef::VirtualFile(v) => Ok(virtual_file_attr(v)),
			NodeStatRef::OnHost(host_path) => host_stat_path(&host_path, sysstat.kind),
		})
		.map_or_else(StatResult::Error, |attr| {
			write_stat_attr(mem, sysstat.attr, attr)
		});
}

/// Handles an fstat hypercall.
pub(crate) fn fstat(mem: &MmapMemory, sysfstat: &mut FstatParams, file_map: &UhyveFileMap) {
	let gfd = GuestFd(sysfstat.fd);
	// Stdio fds are not guest-managed; fstat would leak host metadata (st_dev, st_rdev, …).
	if sysfstat.fd < 0 || gfd.is_standard() {
		sysfstat.ret = StatResult::Error(EBADF);
		return;
	}

	sysfstat.ret = file_map
		.fdmap
		.get(gfd)
		.ok_or_else(|| {
			debug!("fstat on invalid fd {gfd}");
			EBADF
		})
		.and_then(fstat_attr_for_fd_data)
		.map_or_else(StatResult::Error, |attr| {
			write_stat_attr(mem, sysfstat.attr, attr)
		});
}