Debugging Information Manipulation Tools (pahole & friends)
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Description
dwarves is a set of tools that use the debugging information inserted in
ELF binaries by compilers such as GCC, used by well known debuggers such as
GDB, and more recent ones such as systemtap.
Utilities in the dwarves suite include pahole, that can be used to find
alignment holes in structs and classes in languages such as C, C++, but not
limited to these.
It also extracts other information such as CPU cacheline alignment, helping
pack those structures to achieve more cache hits.
These tools can also be used to encode and read the BTF type information format
used with the Linux kernel bpf syscall, using 'pahole -J' and 'pahole -F btf'.
A diff like tool, codiff can be used to compare the effects changes in source
code generate on the resulting binaries.
Another tool is pfunct, that can be used to find all sorts of information about
functions, inlines, decisions made by the compiler about inlining, etc.
One example of pfunct usage is in the fullcircle tool, a shell that drivers
pfunct to generate compileable code out of a .o file and then build it using
gcc, with the same compiler flags, and then use codiff to make sure the
original .o file and the new one generated from debug info produces the same
debug info.
Pahole also can be used to use all this type information to pretty print raw data
according to command line directions.
Headers can have its data format described from debugging info and offsets from
it can be used to further format a number of records.
The btfdiff utility compares the output of pahole from BTF and DWARF to make
sure they produce the same results.
* Fri Jun 20 2025 Gregory Bell <grbell@redhat.com> - 1.30-1
- New release: 1.30
- Better detection of abort during DWARF loader thread processing
- pahole now detects presence of libbpf APIs and BTF features using weak function
declarations when built using a shared library libbpf
- Type tags are emitted for BPF arena pointers with new BTF "attributes" feature
- New release: 1.29
- Multithreading is now in the DWARF loader using a jobs queue and a pool of worker threads.
- The BTF encoding now is always reproducible, and as fast/faster than before.
- The memory consumption is reduced.
- Support for multiple BTF_DECL_TAGs pointing to same tag.
- Verify that pfunct prints btf_decl_tags read from BTF.
- Don't print functions twice when using 'pfunct -f function_name'.
- New release: 1.28
- Various improvements to reduce the memory footprint of pahole, notably when doing BTF encoding.
- Show flexible arrays statistics
- Add '--padding N' and '--padding_ge N' to show structs with paddings
- Introduce --running_kernel_vmlinux to find a vmlinux that matches the build-id of the running kernel.
- Don't stop pfunct output at the first function that matches a filter, show all of them
- Allow encoding data about all global variables, not just per CPU ones
- Handle .BTF_ids section endianness, fully supporting cross builds
- Generate decl tags for bpf_fastcall for eligible kfuncs
- Add "distilled_base" BTF feature to split BTF generation.
- Use the ELF_C_READ_MMAP mode with libelf, reducing peak memory utilization
- Allow overriding /sys/kernel/btf/vmlinux via the PAHOLE_VMLINUX_BTF_FILENAME env var
- Allow setting the list of compile units via PAHOLE_LANG_EXCLUDE env var
- Serialize access to elfutils dwarf_getlocation().
- Honour --lang_exclude when merging LTO built CUs.
- Add the debuginfod client cache directory to the vmlinux search path.
- Print the CU's language when a tag isn't supported.
- Initial support for GNU_formal_parameter_pack, GNU_template_parameter_pack, template_value_param and template_type_param DWARF tags.
- Improve the parameter parsing by checking DW_OP_[GNU_]entry_value
- Introduce a tests/ directory with regression tests
* Mon Aug 12 2024 Davide Cavalca <dcavalca@centosproject.org> - 1.27-2
- Backport upstream bugfixes for clang builds
Resolves: RHEL-54022
* Thu Jun 20 2024 Viktor Malik <vmalik@redhat.com> - 1.27-1
- Resolves: RHEL-30780
- New release: v1.26
- When expanding types using 'pahole -E' do it for union and struct typedefs and for enums too.
- Print number of holes, bit holes and bit paddings in class member types.
- Introduce --contains_enumerator=ENUMERATOR_NAME:
- Fix pretty printing using DWARF, waiting for a CU with both class (-C) and a specified "type_enum".
- Add support for DW_TAG_constant in the DWARF loader, first seen in Go DWARF.
- Fix loading DW_TAG_subroutine_type generated by the Go compiler.
- Fix loading of 32-bit signed enums from BTF.
- Add 'pahole --btf_features' to allow consumers to specify an opt-in set of features they want to use in BTF encoding.
- Parallelize loading BTF and DWARF, speeding up a bit btfdiff.
- Do type expansion to cover "private" types and enumerations in btfdiff.
- New release: v1.27
- Reproducible parallel builds: multiple runs with different number of loading/encoding threads produce the same result.
- Inject kfunc decl tags into BTF from the BTF IDs ELF section in the Linux kernel vmlinux file.
- Sanitize unsupported DWARF int type with greater-than-16 byte, as BTF doesn't support it.
- Initial support for BTF_KIND_DECL_TAG in the BTF loader, adding support in pfunct output.
- Fix hole discovery with inheritance in C++.
