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
@@ -48,6 +54,12 @@ jobs:
     - run: echo RUSTFLAGS=-Dwarnings >> $GITHUB_ENV
       shell: bash
 
+    # 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')
+
     # full fidelity of backtraces on 32-bit msvc requires frame pointers, so
     # enable that for our tests
     - name: Force frame pointers
@@ -85,6 +97,10 @@ jobs:
       if: contains(matrix.os, 'ubuntu')
       env:
         RUSTFLAGS: "-C link-arg=-Wl,--compress-debug-sections=zlib-gnu"
+    - run: cargo test
+      if: contains(matrix.os, 'ubuntu-24.04')
+      env:
+        RUSTFLAGS: "-C link-arg=-Wl,--compress-debug-sections=zstd"
 
     # Test that, on macOS, packed/unpacked debuginfo both work
     - run: cargo clean && cargo test

Cargo.toml

@@ -39,12 +39,21 @@ cpp_demangle = { default-features = false, version = "0.4.0", optional = true, f
   "alloc",
 ] }
 
-[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies]
-miniz_oxide = { version = "0.7.0", default-features = false }
+# MSVC uses PDB, not DWARF. But UWP doesn't allow for APIs gimli (via addr2line) uses,
+# so skip that too.
+[target.'cfg(not(any(target_env = "msvc", target_vendor = "uwp")))'.dependencies]
 addr2line = { version = "0.22.0", default-features = false }
 libc = { version = "0.2.146", default-features = false }
 
-[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies.object]
+# Windows uses PE, not ELF, so libraries for ELF compression are unnecessary.
+[target.'cfg(not(windows))'.dependencies]
+miniz_oxide = { version = "0.7.0", default-features = false }
+
+# Also used for ELF compression, but doesn't build on illumos in CI.
+[target.'cfg(not(any(windows, target_os = "illumos")))'.dependencies]
+zstd = { version = "= 0.13.0", default-features = false }
+
+[target.'cfg(not(any(target_env = "msvc", target_vendor = "uwp")))'.dependencies.object]
 version = "0.35.0"
 default-features = false
 features = ['read_core', 'elf', 'macho', 'pe', 'xcoff', 'unaligned', 'archive']

ci/docker/arm-linux-androideabi/Dockerfile

@@ -15,4 +15,5 @@ ENV PATH=$PATH:/android-toolchain/ndk/toolchains/llvm/prebuilt/linux-x86_64/bin
 
 # TODO: run tests in an emulator eventually
 ENV CARGO_TARGET_ARM_LINUX_ANDROIDEABI_LINKER=armv7a-linux-androideabi19-clang \
+    CC=armv7a-linux-androideabi19-clang \
     CARGO_TARGET_ARM_LINUX_ANDROIDEABI_RUNNER=echo

ci/docker/armv7-linux-androideabi/Dockerfile

@@ -15,4 +15,5 @@ ENV PATH=$PATH:/android-toolchain/ndk/toolchains/llvm/prebuilt/linux-x86_64/bin
 
 # TODO: run tests in an emulator eventually
 ENV CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_LINKER=armv7a-linux-androideabi19-clang \
+    CC=armv7a-linux-androideabi19-clang \
     CARGO_TARGET_ARMV7_LINUX_ANDROIDEABI_RUNNER=echo

ci/docker/i686-linux-android/Dockerfile

@@ -15,4 +15,5 @@ ENV PATH=$PATH:/android-toolchain/ndk/toolchains/llvm/prebuilt/linux-x86_64/bin
 
 # TODO: run tests in an emulator eventually
 ENV CARGO_TARGET_I686_LINUX_ANDROID_LINKER=i686-linux-android19-clang \
+    CC=i686-linux-android19-clang \
     CARGO_TARGET_I686_LINUX_ANDROID_RUNNER=echo

crates/as-if-std/Cargo.toml

@@ -14,13 +14,18 @@ bench = false
 [dependencies]
 cfg-if = "1.0"
 rustc-demangle = "0.1.21"
+
+[target.'cfg(not(any(target_env = "msvc", target_vendor = "uwp")))'.dependencies]
 libc = { version = "0.2.146", default-features = false }
+addr2line = { version = "0.22.0", optional = true, default-features = false }
 
-[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies]
+[target.'cfg(not(windows))'.dependencies]
 miniz_oxide = { version = "0.7.0", optional = true, default-features = false }
-addr2line = { version = "0.22.0", optional = true, default-features = false }
 
-[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies.object]
+[target.'cfg(not(any(windows, target_os = "illumos")))'.dependencies]
+zstd = { version = "= 0.13.0", optional = true, default-features = false }
+
+[target.'cfg(not(any(target_env = "msvc", target_vendor = "uwp")))'.dependencies.object]
 version = "0.35.0"
 default-features = false
 optional = true
@@ -32,7 +37,7 @@ cc = "1.0.90"
 
 [features]
 default = ['backtrace']
-backtrace = ['addr2line', 'miniz_oxide', 'object']
+backtrace = ['addr2line', 'miniz_oxide', 'object', 'zstd']
 std = []
 
 [lints.rust]

src/symbolize/gimli/elf.rs

@@ -7,6 +7,8 @@ use super::{gimli, Context, Endian, EndianSlice, Mapping, Stash, Vec};
 use alloc::sync::Arc;
 use core::convert::{TryFrom, TryInto};
 use core::str;
+#[cfg(not(target_os = "illumos"))]
+use object::elf::ELFCOMPRESS_ZSTD;
 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;
@@ -170,22 +172,31 @@ 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);
+                }
+                #[cfg(not(target_os = "illumos"))]
+                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
@@ -304,6 +315,11 @@ fn decompress_zlib(input: &[u8], output: &mut [u8]) -> Option<()> {
     }
 }
 
+#[cfg(not(target_os = "illumos"))]
+fn decompress_zstd(input: &[u8], output: &mut [u8]) -> Option<()> {
+    zstd::stream::copy_decode(input, output).ok()
+}
+
 const DEBUG_PATH: &[u8] = b"/usr/lib/debug";
 
 fn debug_path_exists() -> bool {