1 files changed, 423 insertions, 0 deletions
diff --git a/library/backtrace/src/symbolize/gimli/elf.rs b/library/backtrace/src/symbolize/gimli/elf.rs
new file mode 100644
index 000000000..bc71ee2c9
--- /dev/null
+++ b/library/backtrace/src/symbolize/gimli/elf.rs
@@ -0,0 +1,423 @@
+use super::mystd::ffi::{OsStr, OsString};
+use super::mystd::fs;
+use super::mystd::os::unix::ffi::{OsStrExt, OsStringExt};
+use super::mystd::path::{Path, PathBuf};
+use super::Either;
+use super::{Context, Mapping, Stash, Vec};
+use core::convert::{TryFrom, TryInto};
+use core::str;
+use object::elf::{ELFCOMPRESS_ZLIB, ELF_NOTE_GNU, NT_GNU_BUILD_ID, SHF_COMPRESSED};
+use object::read::elf::{CompressionHeader, FileHeader, SectionHeader, SectionTable, Sym};
+use object::read::StringTable;
+use object::{BigEndian, Bytes, NativeEndian};
+
+#[cfg(target_pointer_width = "32")]
+type Elf = object::elf::FileHeader32<NativeEndian>;
+#[cfg(target_pointer_width = "64")]
+type Elf = object::elf::FileHeader64<NativeEndian>;
+
+impl Mapping {
+    pub fn new(path: &Path) -> Option<Mapping> {
+        let map = super::mmap(path)?;
+        Mapping::mk_or_other(map, |map, stash| {
+            let object = Object::parse(&map)?;
+
+            // Try to locate an external debug file using the build ID.
+            if let Some(path_debug) = object.build_id().and_then(locate_build_id) {
+                if let Some(mapping) = Mapping::new_debug(path_debug, None) {
+                    return Some(Either::A(mapping));
+                }
+            }
+
+            // Try to locate an external debug file using the GNU debug link section.
+            if let Some((path_debug, crc)) = object.gnu_debuglink_path(path) {
+                if let Some(mapping) = Mapping::new_debug(path_debug, Some(crc)) {
+                    return Some(Either::A(mapping));
+                }
+            }
+
+            Context::new(stash, object, None).map(Either::B)
+        })
+    }
+
+    /// Load debuginfo from an external debug file.
+    fn new_debug(path: PathBuf, crc: Option<u32>) -> Option<Mapping> {
+        let map = super::mmap(&path)?;
+        Mapping::mk(map, |map, stash| {
+            let object = Object::parse(&map)?;
+
+            if let Some(_crc) = crc {
+                // TODO: check crc
+            }
+
+            // Try to locate a supplementary object file.
+            if let Some((path_sup, build_id_sup)) = object.gnu_debugaltlink_path(&path) {
+                if let Some(map_sup) = super::mmap(&path_sup) {
+                    let map_sup = stash.set_mmap_aux(map_sup);
+                    if let Some(sup) = Object::parse(map_sup) {
+                        if sup.build_id() == Some(build_id_sup) {
+                            return Context::new(stash, object, Some(sup));
+                        }
+                    }
+                }
+            }
+
+            Context::new(stash, object, None)
+        })
+    }
+}
+
+struct ParsedSym {
+    address: u64,
+    size: u64,
+    name: u32,
+}
+
+pub struct Object<'a> {
+    /// Zero-sized type representing the native endianness.
+    ///
+    /// We could use a literal instead, but this helps ensure correctness.
+    endian: NativeEndian,
+    /// The entire file data.
+    data: &'a [u8],
+    sections: SectionTable<'a, Elf>,
+    strings: StringTable<'a>,
+    /// List of pre-parsed and sorted symbols by base address.
+    syms: Vec<ParsedSym>,
+}
+
+impl<'a> Object<'a> {
+    fn parse(data: &'a [u8]) -> Option<Object<'a>> {
+        let elf = Elf::parse(data).ok()?;
+        let endian = elf.endian().ok()?;
+        let sections = elf.sections(endian, data).ok()?;
+        let mut syms = sections
+            .symbols(endian, data, object::elf::SHT_SYMTAB)
+            .ok()?;
+        if syms.is_empty() {
+            syms = sections
+                .symbols(endian, data, object::elf::SHT_DYNSYM)
+                .ok()?;
+        }
+        let strings = syms.strings();
+
+        let mut syms = syms
+            .iter()
+            // Only look at function/object symbols. This mirrors what
+            // libbacktrace does and in general we're only symbolicating
+            // function addresses in theory. Object symbols correspond
+            // to data, and maybe someone's crazy enough to have a
+            // function go into static data?
+            .filter(|sym| {
+                let st_type = sym.st_type();
+                st_type == object::elf::STT_FUNC || st_type == object::elf::STT_OBJECT
+            })
+            // skip anything that's in an undefined section header,
+            // since it means it's an imported function and we're only
+            // symbolicating with locally defined functions.
+            .filter(|sym| sym.st_shndx(endian) != object::elf::SHN_UNDEF)
+            .map(|sym| {
+                let address = sym.st_value(endian).into();
+                let size = sym.st_size(endian).into();
+                let name = sym.st_name(endian);
+                ParsedSym {
+                    address,
+                    size,
+                    name,
+                }
+            })
+            .collect::<Vec<_>>();
+        syms.sort_unstable_by_key(|s| s.address);
+        Some(Object {
+            endian,
+            data,
+            sections,
+            strings,
+            syms,
+        })
+    }
+
+    pub fn section(&self, stash: &'a Stash, name: &str) -> Option<&'a [u8]> {
+        if let Some(section) = self.section_header(name) {
+            let mut data = Bytes(section.data(self.endian, self.data).ok()?);
+
+            // Check for DWARF-standard (gABI) compression, i.e., as generated
+            // by ld's `--compress-debug-sections=zlib-gabi` flag.
+            let flags: u64 = section.sh_flags(self.endian).into();
+            if (flags & u64::from(SHF_COMPRESSED)) == 0 {
+                // Not compressed.
+                return Some(data.0);
+            }
+
+            let header = data.read::<<Elf as FileHeader>::CompressionHeader>().ok()?;
+            if header.ch_type(self.endian) != ELFCOMPRESS_ZLIB {
+                // Zlib compression is the only known type.
+                return None;
+            }
+            let size = usize::try_from(header.ch_size(self.endian)).ok()?;
+            let buf = stash.allocate(size);
+            decompress_zlib(data.0, buf)?;
+            return Some(buf);
+        }
+
+        // Check for the nonstandard GNU compression format, i.e., as generated
+        // by ld's `--compress-debug-sections=zlib-gnu` flag. This means that if
+        // we're actually asking for `.debug_info` then we need to look up a
+        // section named `.zdebug_info`.
+        if !name.starts_with(".debug_") {
+            return None;
+        }
+        let debug_name = name[7..].as_bytes();
+        let compressed_section = self
+            .sections
+            .iter()
+            .filter_map(|header| {
+                let name = self.sections.section_name(self.endian, header).ok()?;
+                if name.starts_with(b".zdebug_") && &name[8..] == debug_name {
+                    Some(header)
+                } else {
+                    None
+                }
+            })
+            .next()?;
+        let mut data = Bytes(compressed_section.data(self.endian, self.data).ok()?);
+        if data.read_bytes(8).ok()?.0 != b"ZLIB\0\0\0\0" {
+            return None;
+        }
+        let size = usize::try_from(data.read::<object::U32Bytes<_>>().ok()?.get(BigEndian)).ok()?;
+        let buf = stash.allocate(size);
+        decompress_zlib(data.0, buf)?;
+        Some(buf)
+    }
+
+    fn section_header(&self, name: &str) -> Option<&<Elf as FileHeader>::SectionHeader> {
+        self.sections
+            .section_by_name(self.endian, name.as_bytes())
+            .map(|(_index, section)| section)
+    }
+
+    pub fn search_symtab<'b>(&'b self, addr: u64) -> Option<&'b [u8]> {
+        // Same sort of binary search as Windows above
+        let i = match self.syms.binary_search_by_key(&addr, |sym| sym.address) {
+            Ok(i) => i,
+            Err(i) => i.checked_sub(1)?,
+        };
+        let sym = self.syms.get(i)?;
+        if sym.address <= addr && addr <= sym.address + sym.size {
+            self.strings.get(sym.name).ok()
+        } else {
+            None
+        }
+    }
+
+    pub(super) fn search_object_map(&self, _addr: u64) -> Option<(&Context<'_>, u64)> {
+        None
+    }
+
+    fn build_id(&self) -> Option<&'a [u8]> {
+        for section in self.sections.iter() {
+            if let Ok(Some(mut notes)) = section.notes(self.endian, self.data) {
+                while let Ok(Some(note)) = notes.next() {
+                    if note.name() == ELF_NOTE_GNU && note.n_type(self.endian) == NT_GNU_BUILD_ID {
+                        return Some(note.desc());
+                    }
+                }
+            }
+        }
+        None
+    }
+
+    // The contents of the ".gnu_debuglink" section is documented at:
+    // https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+    fn gnu_debuglink_path(&self, path: &Path) -> Option<(PathBuf, u32)> {
+        let section = self.section_header(".gnu_debuglink")?;
+        let data = section.data(self.endian, self.data).ok()?;
+        let len = data.iter().position(|x| *x == 0)?;
+        let filename = &data[..len];
+        let offset = (len + 1 + 3) & !3;
+        let crc_bytes = data
+            .get(offset..offset + 4)
+            .and_then(|bytes| bytes.try_into().ok())?;
+        let crc = u32::from_ne_bytes(crc_bytes);
+        let path_debug = locate_debuglink(path, filename)?;
+        Some((path_debug, crc))
+    }
+
+    // The format of the ".gnu_debugaltlink" section is based on gdb.
+    fn gnu_debugaltlink_path(&self, path: &Path) -> Option<(PathBuf, &'a [u8])> {
+        let section = self.section_header(".gnu_debugaltlink")?;
+        let data = section.data(self.endian, self.data).ok()?;
+        let len = data.iter().position(|x| *x == 0)?;
+        let filename = &data[..len];
+        let build_id = &data[len + 1..];
+        let path_sup = locate_debugaltlink(path, filename, build_id)?;
+        Some((path_sup, build_id))
+    }
+}
+
+fn decompress_zlib(input: &[u8], output: &mut [u8]) -> Option<()> {
+    use miniz_oxide::inflate::core::inflate_flags::{
+        TINFL_FLAG_PARSE_ZLIB_HEADER, TINFL_FLAG_USING_NON_WRAPPING_OUTPUT_BUF,
+    };
+    use miniz_oxide::inflate::core::{decompress, DecompressorOxide};
+    use miniz_oxide::inflate::TINFLStatus;
+
+    let (status, in_read, out_read) = decompress(
+        &mut DecompressorOxide::new(),
+        input,
+        output,
+        0,
+        TINFL_FLAG_USING_NON_WRAPPING_OUTPUT_BUF | TINFL_FLAG_PARSE_ZLIB_HEADER,
+    );
+    if status == TINFLStatus::Done && in_read == input.len() && out_read == output.len() {
+        Some(())
+    } else {
+        None
+    }
+}
+
+const DEBUG_PATH: &[u8] = b"/usr/lib/debug";
+
+fn debug_path_exists() -> bool {
+    cfg_if::cfg_if! {
+        if #[cfg(any(target_os = "freebsd", target_os = "linux"))] {
+            use core::sync::atomic::{AtomicU8, Ordering};
+            static DEBUG_PATH_EXISTS: AtomicU8 = AtomicU8::new(0);
+
+            let mut exists = DEBUG_PATH_EXISTS.load(Ordering::Relaxed);
+            if exists == 0 {
+                exists = if Path::new(OsStr::from_bytes(DEBUG_PATH)).is_dir() {
+                    1
+                } else {
+                    2
+                };
+                DEBUG_PATH_EXISTS.store(exists, Ordering::Relaxed);
+            }
+            exists == 1
+        } else {
+            false
+        }
+    }
+}
+
+/// Locate a debug file based on its build ID.
+///
+/// The format of build id paths is documented at:
+/// https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+fn locate_build_id(build_id: &[u8]) -> Option<PathBuf> {
+    const BUILD_ID_PATH: &[u8] = b"/usr/lib/debug/.build-id/";
+    const BUILD_ID_SUFFIX: &[u8] = b".debug";
+
+    if build_id.len() < 2 {
+        return None;
+    }
+
+    if !debug_path_exists() {
+        return None;
+    }
+
+    let mut path =
+        Vec::with_capacity(BUILD_ID_PATH.len() + BUILD_ID_SUFFIX.len() + build_id.len() * 2 + 1);
+    path.extend(BUILD_ID_PATH);
+    path.push(hex(build_id[0] >> 4));
+    path.push(hex(build_id[0] & 0xf));
+    path.push(b'/');
+    for byte in &build_id[1..] {
+        path.push(hex(byte >> 4));
+        path.push(hex(byte & 0xf));
+    }
+    path.extend(BUILD_ID_SUFFIX);
+    Some(PathBuf::from(OsString::from_vec(path)))
+}
+
+fn hex(byte: u8) -> u8 {
+    if byte < 10 {
+        b'0' + byte
+    } else {
+        b'a' + byte - 10
+    }
+}
+
+/// Locate a file specified in a `.gnu_debuglink` section.
+///
+/// `path` is the file containing the section.
+/// `filename` is from the contents of the section.
+///
+/// Search order is based on gdb, documented at:
+/// https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
+///
+/// gdb also allows the user to customize the debug search path, but we don't.
+///
+/// gdb also supports debuginfod, but we don't yet.
+fn locate_debuglink(path: &Path, filename: &[u8]) -> Option<PathBuf> {
+    let path = fs::canonicalize(path).ok()?;
+    let parent = path.parent()?;
+    let mut f = PathBuf::from(OsString::with_capacity(
+        DEBUG_PATH.len() + parent.as_os_str().len() + filename.len() + 2,
+    ));
+    let filename = Path::new(OsStr::from_bytes(filename));
+
+    // Try "/parent/filename" if it differs from "path"
+    f.push(parent);
+    f.push(filename);
+    if f != path && f.is_file() {
+        return Some(f);
+    }
+
+    // Try "/parent/.debug/filename"
+    let mut s = OsString::from(f);
+    s.clear();
+    f = PathBuf::from(s);
+    f.push(parent);
+    f.push(".debug");
+    f.push(filename);
+    if f.is_file() {
+        return Some(f);
+    }
+
+    if debug_path_exists() {
+        // Try "/usr/lib/debug/parent/filename"
+        let mut s = OsString::from(f);
+        s.clear();
+        f = PathBuf::from(s);
+        f.push(OsStr::from_bytes(DEBUG_PATH));
+        f.push(parent.strip_prefix("/").unwrap());
+        f.push(filename);
+        if f.is_file() {
+            return Some(f);
+        }
+    }
+
+    None
+}
+
+/// Locate a file specified in a `.gnu_debugaltlink` section.
+///
+/// `path` is the file containing the section.
+/// `filename` and `build_id` are the contents of the section.
+///
+/// Search order is based on gdb:
+/// - filename, which is either absolute or relative to `path`
+/// - the build ID path under `BUILD_ID_PATH`
+///
+/// gdb also allows the user to customize the debug search path, but we don't.
+///
+/// gdb also supports debuginfod, but we don't yet.
+fn locate_debugaltlink(path: &Path, filename: &[u8], build_id: &[u8]) -> Option<PathBuf> {
+    let filename = Path::new(OsStr::from_bytes(filename));
+    if filename.is_absolute() {
+        if filename.is_file() {
+            return Some(filename.into());
+        }
+    } else {
+        let path = fs::canonicalize(path).ok()?;
+        let parent = path.parent()?;
+        let mut f = PathBuf::from(parent);
+        f.push(filename);
+        if f.is_file() {
+            return Some(f);
+        }
+    }
+
+    locate_build_id(build_id)
+}