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Support zstd-compressed ELF sections. #625

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Support zstd-compressed ELF sections. #625

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78167bb
Support zstd-compressed ELF sections.
khuey May 24, 2024
eda500c
Clean up cfgs for crate includes.
khuey May 25, 2024
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16 changes: 16 additions & 0 deletions .github/workflows/main.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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
Expand Down Expand Up @@ -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
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49 changes: 49 additions & 0 deletions Cargo.lock
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3 changes: 3 additions & 0 deletions Cargo.toml
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Expand Up @@ -44,6 +44,9 @@ miniz_oxide = { version = "0.7.0", default-features = false }
addr2line = { version = "0.22.0", default-features = false }
libc = { version = "0.2.146", default-features = false }

[target.'cfg(not(any(all(windows, target_env = "msvc", not(target_vendor = "uwp")), target_os = "illumos")))'.dependencies]
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Why is this dependency added for uwp?

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It's not. Unless I screwed something up that part of the condition is copied from the section above. What's new here is that illumos is excluded as well.

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The conditional evaluates as follows on x86_64-uwp-windows-msvc:

  • not(any(all(windows, target_env = "msvc", not(target_vendor = "uwp")), target_os = "illumos"))
    • any(all(windows, target_env = "msvc", not(target_vendor = "uwp")), target_os = "illumos")
      • all(windows, target_env = "msvc", not(target_vendor = "uwp"))
        • windows
        • target_env = "msvc"
        • not(target_vendor = "uwp")
          • target_vendor = "uwp"
      • target_os = "illumos"

So it will include zstd on x86_64-uwp-windows-msvc.

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Why is Windows included at all? Surely even gnu does not use elf sections due to the binary format being different on Windows?

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Sorry, you're right. This is what I get for commenting at 6:30 AM.

The uwp part was copied from the above section with miniz_oxide, addr2line, and libc. That exclusion was added in #543 without explanation.

The correct handling here would be for addr2line/libc to be gated on not using msvc (because mingw produces DWARF, not PDBs) and for miniz_oxide/zstd to be gated on not windows (because no Windows target uses ELF and these are for ELF compression).

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Ok I pushed a commit that cleans this up. Even if backtrace doesn't end up taking this PR it'll probably want something like that commit.

zstd = { version = "= 0.13.0", default-features = false }
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@bjorn3 bjorn3 May 24, 2024 •
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Using the C implementation of zstd makes cross-compilation harder, especially for miri which currently is able to test for any supported target without installing any toolchain for the target.

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Yes, I discussed that in the commit message. I could disable this for miri too.


[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies.object]
version = "0.35.0"
default-features = false
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1 change: 1 addition & 0 deletions ci/docker/arm-linux-androideabi/Dockerfile
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Expand Up @@ -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
1 change: 1 addition & 0 deletions ci/docker/armv7-linux-androideabi/Dockerfile
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Expand Up @@ -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
1 change: 1 addition & 0 deletions ci/docker/i686-linux-android/Dockerfile
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Expand Up @@ -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
5 changes: 4 additions & 1 deletion crates/as-if-std/Cargo.toml
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Expand Up @@ -20,6 +20,9 @@ libc = { version = "0.2.146", default-features = false }
miniz_oxide = { version = "0.7.0", optional = true, default-features = false }
addr2line = { version = "0.22.0", optional = true, default-features = false }

[target.'cfg(not(any(all(windows, target_env = "msvc", not(target_vendor = "uwp")), target_os = "illumos")))'.dependencies]
zstd = { version = "= 0.13.0", optional = true, default-features = false }

[target.'cfg(not(all(windows, target_env = "msvc", not(target_vendor = "uwp"))))'.dependencies.object]
version = "0.35.0"
default-features = false
Expand All @@ -32,7 +35,7 @@ cc = "1.0.90"

[features]
default = ['backtrace']
backtrace = ['addr2line', 'miniz_oxide', 'object']
backtrace = ['addr2line', 'miniz_oxide', 'object', 'zstd']
std = []

[lints.rust]
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32 changes: 24 additions & 8 deletions src/symbolize/gimli/elf.rs
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Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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 {
Expand Down
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