aboutsummaryrefslogtreecommitdiff
path: root/crates/proc_macro_api/src/version.rs
blob: 28a4ac0862e8dacaa637964a60658d526be868c4 (plain)
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
129
130
131
132
133
//! Reading proc-macro rustc version information from binary data

use std::{
    fs::File,
    io::{self, Read},
    path::Path,
};

use memmap2::Mmap;
use object::read::{File as BinaryFile, Object, ObjectSection};
use snap::read::FrameDecoder as SnapDecoder;

#[derive(Debug)]
pub struct RustCInfo {
    pub version: (usize, usize, usize),
    pub channel: String,
    pub commit: String,
    pub date: String,
}

/// Read rustc dylib information
pub fn read_dylib_info(dylib_path: &Path) -> io::Result<RustCInfo> {
    macro_rules! err {
        ($e:literal) => {
            io::Error::new(io::ErrorKind::InvalidData, $e)
        };
    }

    let ver_str = read_version(dylib_path)?;
    let mut items = ver_str.split_whitespace();
    let tag = items.next().ok_or(err!("version format error"))?;
    if tag != "rustc" {
        return Err(err!("version format error (No rustc tag)"));
    }

    let version_part = items.next().ok_or(err!("no version string"))?;
    let mut version_parts = version_part.split('-');
    let version = version_parts.next().ok_or(err!("no version"))?;
    let channel = version_parts.next().unwrap_or_default().to_string();

    let commit = items.next().ok_or(err!("no commit info"))?;
    // remove (
    if commit.len() == 0 {
        return Err(err!("commit format error"));
    }
    let commit = commit[1..].to_string();
    let date = items.next().ok_or(err!("no date info"))?;
    // remove )
    if date.len() == 0 {
        return Err(err!("date format error"));
    }
    let date = date[0..date.len() - 2].to_string();

    let version_numbers = version
        .split('.')
        .map(|it| it.parse::<usize>())
        .collect::<Result<Vec<_>, _>>()
        .map_err(|_| err!("version number error"))?;

    if version_numbers.len() != 3 {
        return Err(err!("version number format error"));
    }
    let version = (version_numbers[0], version_numbers[1], version_numbers[2]);

    Ok(RustCInfo { version, channel, commit, date })
}

/// This is used inside read_version() to locate the ".rustc" section
/// from a proc macro crate's binary file.
fn read_section<'a>(dylib_binary: &'a [u8], section_name: &str) -> io::Result<&'a [u8]> {
    BinaryFile::parse(dylib_binary)
        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?
        .section_by_name(section_name)
        .ok_or_else(|| io::Error::new(io::ErrorKind::InvalidData, "section read error"))?
        .data()
        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
}

/// Check the version of rustc that was used to compile a proc macro crate's
///
/// binary file.
/// A proc macro crate binary's ".rustc" section has following byte layout:
/// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes
/// * ff060000 734e6150 is followed, it's the snappy format magic bytes,
///   means bytes from here(including this sequence) are compressed in
///   snappy compression format. Version info is inside here, so decompress
///   this.
/// The bytes you get after decompressing the snappy format portion has
/// following layout:
/// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes(again)
/// * [crate root bytes] next 4 bytes is to store crate root position,
///   according to rustc's source code comment
/// * [length byte] next 1 byte tells us how many bytes we should read next
///   for the version string's utf8 bytes
/// * [version string bytes encoded in utf8] <- GET THIS BOI
/// * [some more bytes that we don really care but still there] :-)
/// Check this issue for more about the bytes layout:
/// <https://github.com/rust-analyzer/rust-analyzer/issues/6174>
fn read_version(dylib_path: &Path) -> io::Result<String> {
    let dylib_file = File::open(dylib_path)?;
    let dylib_mmaped = unsafe { Mmap::map(&dylib_file) }?;

    let dot_rustc = read_section(&dylib_mmaped, ".rustc")?;

    let header = &dot_rustc[..8];
    const EXPECTED_HEADER: [u8; 8] = [b'r', b'u', b's', b't', 0, 0, 0, 5];
    // check if header is valid
    if header != EXPECTED_HEADER {
        return Err(io::Error::new(
            io::ErrorKind::InvalidData,
            format!("only metadata version 5 is supported, section header was: {:?}", header),
        ));
    }

    let snappy_portion = &dot_rustc[8..];

    let mut snappy_decoder = SnapDecoder::new(snappy_portion);

    // the bytes before version string bytes, so this basically is:
    // 8 bytes for [b'r',b'u',b's',b't',0,0,0,5]
    // 4 bytes for [crate root bytes]
    // 1 byte for length of version string
    // so 13 bytes in total, and we should check the 13th byte
    // to know the length
    let mut bytes_before_version = [0u8; 13];
    snappy_decoder.read_exact(&mut bytes_before_version)?;
    let length = bytes_before_version[12]; // what? can't use -1 indexing?

    let mut version_string_utf8 = vec![0u8; length as usize];
    snappy_decoder.read_exact(&mut version_string_utf8)?;
    let version_string = String::from_utf8(version_string_utf8);
    version_string.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
}