Support zstd-compressed ELF sections.

.github/workflows/main.yml

@@ -22,6 +22,12 @@ jobs:
             rust: beta
           - os: ubuntu-20.04
             rust: nightly
+          - os: ubuntu-24.04
+            rust: stable
+          - os: ubuntu-24.04
+            rust: beta
+          - os: ubuntu-24.04
+            rust: nightly
           - os: macos-latest
             rust: stable
           - os: macos-latest
@@ -55,6 +61,12 @@ jobs:
         shell: bash
         if: contains(matrix.rust, 'i686')
 
+      # Starting with Ubuntu 22.04 libc6-dbg is needed.
+      - name: Install libc debug info
+        run: sudo apt-get install -y libc6-dbg
+        shell: bash
+        if: contains(matrix.os, 'ubuntu-24.04')
+
       - name: Enable collapse_debuginfo based on version
         run: echo RUSTFLAGS="--cfg dbginfo=\"collapsible\" $RUSTFLAGS" >> $GITHUB_ENV
         shell: bash
@@ -80,6 +92,11 @@ jobs:
         if: contains(matrix.os, 'ubuntu')
         env:
           RUSTFLAGS: "-C link-arg=-Wl,--compress-debug-sections=zlib"
+      - run: cargo test
+        if: contains(matrix.os, 'ubuntu-24.04') ||
+            (contains(matrix.os, 'ubuntu') && contains(matrix.rust, 'nightly'))
+        env:
+          RUSTFLAGS: "-C link-arg=-Wl,--compress-debug-sections=zstd"
 
       # Test that, on macOS, packed/unpacked debuginfo both work
       - run: cargo clean && cargo test
@@ -248,7 +265,7 @@ jobs:
         with:
           submodules: true
       - name: Install Rust
-        run: rustup update 1.65.0 --no-self-update && rustup default 1.65.0
+        run: rustup update 1.73.0 --no-self-update && rustup default 1.73.0
       - run: cargo build
 
   miri:

Cargo.toml

@@ -43,6 +43,7 @@ windows-targets = "0.52.6"
 
 [target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies]
 miniz_oxide = { version = "0.8", default-features = false }
+ruzstd = { version = "0.7.2", default-features = false }
 addr2line = { version = "0.24.0", default-features = false }
 libc = { version = "0.2.156", default-features = false }
 

crates/as-if-std/Cargo.toml

@@ -18,6 +18,7 @@ libc = { version = "0.2.156", default-features = false }
 
 [target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies]
 miniz_oxide = { version = "0.8", optional = true, default-features = false }
+ruzstd = { version = "0.7.2", optional = true, default-features = false }
 addr2line = { version = "0.24.0", optional = true, default-features = false }
 
 [target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies.object]
@@ -31,7 +32,7 @@ windows-targets = "0.52.6"
 
 [features]
 default = ['backtrace']
-backtrace = ['addr2line', 'miniz_oxide', 'object']
+backtrace = ['addr2line', 'miniz_oxide', 'object', 'ruzstd']
 std = []
 
 [lints.rust]

src/symbolize/gimli/elf.rs

@@ -9,7 +9,9 @@ use super::{gimli, Context, Endian, EndianSlice, Mapping, Stash, Vec};
 use alloc::sync::Arc;
 use core::convert::{TryFrom, TryInto};
 use core::str;
-use object::elf::{ELFCOMPRESS_ZLIB, ELF_NOTE_GNU, NT_GNU_BUILD_ID, SHF_COMPRESSED};
+use object::elf::{
+    ELFCOMPRESS_ZLIB, ELFCOMPRESS_ZSTD, 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};
@@ -213,22 +215,30 @@ impl<'a> Object<'a> {
             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.
+            // by ld's `--compress-debug-sections=zlib-gabi` and
+            // `--compress-debug-sections=zstd` flags.
             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;
+            match header.ch_type(self.endian) {
+                ELFCOMPRESS_ZLIB => {
+                    let size = usize::try_from(header.ch_size(self.endian)).ok()?;
+                    let buf = stash.allocate(size);
+                    decompress_zlib(data.0, buf)?;
+                    return Some(buf);
+                }
+                ELFCOMPRESS_ZSTD => {
+                    let size = usize::try_from(header.ch_size(self.endian)).ok()?;
+                    let buf = stash.allocate(size);
+                    decompress_zstd(data.0, buf)?;
+                    return Some(buf);
+                }
+                _ => return None, // Unknown compression type.
             }
-            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
@@ -347,6 +357,40 @@ fn decompress_zlib(input: &[u8], output: &mut [u8]) -> Option<()> {
     }
 }
 
+fn decompress_zstd(mut input: &[u8], mut output: &mut [u8]) -> Option<()> {
+    use ruzstd::frame::ReadFrameHeaderError;
+    use ruzstd::frame_decoder::FrameDecoderError;
+    use ruzstd::io::Read;
+
+    while !input.is_empty() {
+        let mut decoder = match ruzstd::StreamingDecoder::new(&mut input) {
+            Ok(decoder) => decoder,
+            Err(FrameDecoderError::ReadFrameHeaderError(ReadFrameHeaderError::SkipFrame {
+                length,
+                ..
+            })) => {
+                input = &input.get(length as usize..)?;
+                continue;
+            }
+            Err(_) => return None,
+        };
+        loop {
+            let bytes_written = decoder.read(output).ok()?;
+            if bytes_written == 0 {
+                break;
+            }
+            output = &mut output[bytes_written..];
+        }
+    }
+
+    if !output.is_empty() {
+        // Lengths didn't match, something is wrong.
+        return None;
+    }
+
+    Some(())
+}
+
 const DEBUG_PATH: &[u8] = b"/usr/lib/debug";
 
 fn debug_path_exists() -> bool {