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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ELF_DLOPEN_METADATA.md | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/docs/ELF_DLOPEN_METADATA.md b/docs/ELF_DLOPEN_METADATA.md index 5c3bf1eae2..cb196d1ac7 100644 --- a/docs/ELF_DLOPEN_METADATA.md +++ b/docs/ELF_DLOPEN_METADATA.md @@ -87,3 +87,90 @@ of the libraries they specify in order to be enabled. | required | Core functionality needs the dependency, the binary will not work if it cannot be found | | recommended | Important functionality needs the dependency, the binary will work but in most cases the dependency should be provided | | suggested | Secondary functionality needs the dependency, the binary will work and the dependency is only needed for full-featured installations | + +### Displaying `dlopen()` notes + +The raw ELF section can be extracted using `objdump`: +```console +$ objdump -j .note.dlopen -s /usr/lib64/systemd/libsystemd-shared-257.so + +/usr/lib64/systemd/libsystemd-shared-257.so: file format elf64-x86-64 + +Contents of section .note.dlopen: + 0334 04000000 8e000000 0a0c7c40 46444f00 ..........|@FDO. + 0344 5b7b2266 65617475 7265223a 22627066 [{"feature":"bpf + 0354 222c2264 65736372 69707469 6f6e223a ","description": + 0364 22537570 706f7274 20666972 6577616c "Support firewal + 0374 6c696e67 20616e64 2073616e 64626f78 ling and sandbox + 0384 696e6720 77697468 20425046 222c2270 ing with BPF","p + 0394 72696f72 69747922 3a227375 67676573 riority":"sugges + 03a4 74656422 2c22736f 6e616d65 223a5b22 ted","soname":[" + 03b4 6c696262 70662e73 6f2e3122 2c226c69 libbpf.so.1","li + 03c4 62627066 2e736f2e 30225d7d 5d000000 bbpf.so.0"]}]... + 03d4 04000000 9e000000 0a0c7c40 46444f00 ..........|@FDO. +... +``` + +It is more convenient to use a higher level tool: +```console +$ dlopen-notes /usr/lib64/systemd/libsystemd-shared-257.so +# /usr/lib64/systemd/libsystemd-shared-257.so +[ + { + "feature": "archive", + "description": "Support for decompressing archive files", + "priority": "suggested", + "soname": [ + "libarchive.so.13" + ] + }, + { + "feature": "bpf", + "description": "Support firewalling and sandboxing with BPF", + "priority": "suggested", + "soname": [ + "libbpf.so.1", + "libbpf.so.0" + ] + }, +... +``` + +`dlopen-notes` can display the notes grouped in a few different ways. +One option is to filter the libraries by "feature". This answers the +question "what libraries are needed to provide specified features": + +```console +$ dlopen-notes.py -f archive,bpf /usr/lib64/systemd/libsystemd-shared-257.so +# grouped by feature +{ + "bpf": { + "description": "Support firewalling and sandboxing with BPF", + "sonames": { + "libbpf.so.1": "suggested", + "libbpf.so.0": "suggested" + } + }, + "archive": { + "description": "Support for decompressing archive files", + "sonames": { + "libarchive.so.13": "suggested" + } + } +} + +The format that is used when building `deb` packages: +```console +$ dlopen-notes -s /usr/lib64/systemd/libsystemd-shared-257.so +libarchive.so.13 suggested +libbpf.so.0 suggested +libbpf.so.1 suggested +... +``` + +The format that can be useful when building `rpm` packages: +```console +$ dlopen-notes --rpm-requires archive --rpm-recommends bpf /usr/lib64/systemd/libsystemd-shared-257.so +Requires: libarchive.so.13()(64bit) +Recommends: libbpf.so.1()(64bit) +``` |