bpf-developer-tutorial/BLAZESYM_BUILD_WORKAROUND.md

Blazesym Build Workaround for ARM64 Platforms

This document provides workarounds for the blazesym build issue reported in issue #148.

Issue Description

When building blazesym with the cheader feature on ARM64 (aarch64) platforms, you may encounter the following error:

/usr/bin/ld: discarded output section: `.got.plt'
collect2: error: ld returned 1 exit status

This error occurs because the linker script used for generating test files is too aggressive in discarding sections, including the .got.plt section which is essential on ARM64 platforms.

Solution

The tutorial repository already includes a workaround for this issue. The examples that use blazesym (like src/12-profile and src/16-memleak) are configured to use the dont-generate-test-files feature flag when building blazesym.

You can see this in their Makefiles:

$(LIBBLAZESYM_SRC)/target/release/libblazesym.a::
	$(Q)cd $(LIBBLAZESYM_SRC) && $(CARGO) build --features=cheader,dont-generate-test-files --release

If You Encounter This Issue

For Tutorial Examples

Simply use the provided Makefiles:

cd src/12-profile  # or src/16-memleak
make

For Manual Blazesym Building

If you need to build blazesym manually, use the dont-generate-test-files feature:

cd src/third_party/blazesym
cargo build --features=cheader,dont-generate-test-files

Alternative Workarounds

1. Skip C Header Generation (if you don't need C headers):

   cd src/third_party/blazesym
   cargo build
   

2. Install LLVM Tools (if you want full test support):

   # On Ubuntu/Debian:
   sudo apt install llvm
   
   # Then build normally:
   cargo build --features=cheader
   

Technical Details

The issue is caused by the linker script in data/test-gsym.ld being too aggressive in discarding sections. On ARM64 platforms, the .got.plt section is essential and cannot be discarded.

The dont-generate-test-files feature flag bypasses the generation of test files that require this problematic linker script, allowing blazesym to build successfully while maintaining all core functionality.

Impact

• Core blazesym functionality: ✅ Not affected
• C header generation: ✅ Works with the workaround
• Test file generation: ⚠️ Skipped on problematic platforms
• Symbol resolution: ✅ Works normally

References

• Issue #148
• Blazesym Repository
• ARM64 GOT/PLT Documentation