The changelog ended up in a different file. Added it below now.
On Tue, Feb 21, 2023 at 11:44:57PM +0000, Daniel Müller wrote:
> On Android, APKs (android packages; zip packages with somewhat
> prescriptive contents) are first class citizens in the system: the
> shared objects contained in them don't exist in unpacked form on the
> file system. Rather, they are mmaped directly from within the archive
> and the archive is also what the kernel is aware of.
>
> For users that complicates the process of attaching a uprobe to a
> function contained in a shared object in one such APK: they'd have to
> find the byte offset of said function from the beginning of the archive.
> That is cumbersome to do manually and can be fragile, because various
> changes could invalidate said offset.
>
> That is why for uprobes inside ELF files (not inside an APK), commit
> d112c9ce249b ("libbpf: Support function name-based attach uprobes") added
> support for attaching to symbols by name. On Android, that mechanism
> currently does not work, because this logic is not APK aware.
>
> This patch set introduces first class support for attaching uprobes to
> functions inside ELF objects contained in APKs via function names. We
> add support for recognizing the following syntax for a binary path:
> <archive>!/<binary-in-archive>
>
> (e.g., /system/app/test-app.apk!/lib/arm64-v8a/libc++.so)
>
> This syntax is common in the Android eco system and used by tools such
> as simpleperf. It is also what is being proposed for bcc [0].
>
> If the user provides such a binary path, we find <binary-in-archive>
> (lib/arm64-v8a/libc++.so in the example) inside of <archive>
> (/system/app/test-app.apk). We perform the regular ELF offset search
> inside the binary and add that to the offset within the archive itself,
> to retrieve the offset at which to attach the uprobe.
>
> [0] https://github.com/iovisor/bcc/pull/4440
Changelog
---------
v1->v2:
- removed unaligned_* types
- switched to using __u32 and __u16
- switched to using errno constants instead of hard-coded negative values
- added another pr_debug() message
- shortened central_directory_* to cd_*
- inlined cd_file_header_at_offset() function
- bunch of syntactical changes
> Daniel Müller (3):
> libbpf: Implement basic zip archive parsing support
> libbpf: Introduce elf_find_func_offset_from_file() function
> libbpf: Add support for attaching uprobes to shared objects in APKs
>
> tools/lib/bpf/Build | 2 +-
> tools/lib/bpf/libbpf.c | 142 ++++++++++++++----
> tools/lib/bpf/zip.c | 326 +++++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/zip.h | 47 ++++++
> 4 files changed, 489 insertions(+), 28 deletions(-)
> create mode 100644 tools/lib/bpf/zip.c
> create mode 100644 tools/lib/bpf/zip.h
>
> --
> 2.30.2
>
