docs/ELF_PACKAGE_METADATA: add detailed example

When the spec was initially written, we didn't add good documentation of how to
display the notes, also because there was no good way to display the data
except manually extracting the section to a file and running 'jq' on that. But
the tools have improved, so let's show the users how easy it is to use this
data.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2024-09-13 14:35:43 +02:00
parent dcc359010c
commit 9a2b54d9f7
2 changed files with 96 additions and 0 deletions

2
TODO
View File

@ -1518,6 +1518,8 @@ Features:
* systemd-analyze netif that explains predictable interface (or networkctl)
* systemd-analyze inspect-elf should show other notes too, at least build-id.
* Figure out naming of verbs in systemd-analyze: we have (singular) capability,
exit-status, but (plural) filesystems, architectures.

View File

@ -103,3 +103,97 @@ A set of well-known keys is defined here, and hopefully shared among all vendors
| architecture | The binary package architecture | arm32 |
| osCpe | A CPE name for the OS, typically corresponding to CPE_NAME in os-release | cpe:/o:fedoraproject:fedora:33 |
| debugInfoUrl | The debuginfod server url, if available | https://debuginfod.fedoraproject.org/ |
### Displaying package notes
The raw ELF section can be extracted using `objdump`:
```console
$ objdump -j .note.package -s /usr/bin/ls
/usr/bin/ls: file format elf64-x86-64
Contents of section .note.package:
03cc 04000000 7c000000 7e1afeca 46444f00 ....|...~...FDO.
03dc 7b227479 7065223a 2272706d 222c226e {"type":"rpm","n
03ec 616d6522 3a22636f 72657574 696c7322 ame":"coreutils"
03fc 2c227665 7273696f 6e223a22 392e342d ,"version":"9.4-
040c 372e6663 3430222c 22617263 68697465 7.fc40","archite
041c 63747572 65223a22 7838365f 3634222c cture":"x86_64",
042c 226f7343 7065223a 22637065 3a2f6f3a "osCpe":"cpe:/o:
043c 6665646f 72617072 6f6a6563 743a6665 fedoraproject:fe
044c 646f7261 3a343022 7d000000 dora:40"}...
```
It is more convenient to use a higher level tool:
```console
$ readelf --notes /usr/bin/ls
...
Displaying notes found in: .note.gnu.build-id
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 40e5a1570a9d97fc48f5c61cfb7690fec0f872b2
Displaying notes found in: .note.ABI-tag
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 3.2.0
Displaying notes found in: .note.package
Owner Data size Description
FDO 0x0000007c FDO_PACKAGING_METADATA
Packaging Metadata: {"type":"rpm","name":"coreutils","version":"9.4-7.fc40","architecture":"x86_64","osCpe":"cpe:/o:fedoraproject:fedora:40"}
...
$ systemd-analyze inspect-elf /usr/bin/ls
path: /usr/bin/ls
elfType: executable
elfArchitecture: AMD x86-64
type: rpm
name: coreutils
version: 9.4-7.fc40
architecture: x86_64
osCpe: cpe:/o:fedoraproject:fedora:40
buildId: 40e5a1570a9d97fc48f5c61cfb7690fec0f872b2
```
If the binary crashes, `systemd-coredump` will display the combined information
from the crashing binary and any shared libraries it links to:
```console
$ coredumpctl info
PID: 3987823 (ls)
Signal: 11 (SEGV)
Command Line: ls --color=tty -lR /
Executable: /usr/bin/ls
...
Storage: /var/lib/systemd/coredump/core.ls.1000.88dea1b9831c420dbb398f9d2ad9b41e.3987823.1726230641000000.zst (present)
Size on Disk: 194.4K
Package: coreutils/9.4-7.fc40
build-id: 40e5a1570a9d97fc48f5c61cfb7690fec0f872b2
Message: Process 3987823 (ls) of user 1000 dumped core.
Module /usr/bin/ls from rpm coreutils-9.4-7.fc40.x86_64
Module libz.so.1 from rpm zlib-ng-2.1.7-1.fc40.x86_64
Module libcrypto.so.3 from rpm openssl-3.2.2-3.fc40.x86_64
Module libmount.so.1 from rpm util-linux-2.40.1-1.fc40.x86_64
Module libcrypt.so.2 from rpm libxcrypt-4.4.36-5.fc40.x86_64
Module libblkid.so.1 from rpm util-linux-2.40.1-1.fc40.x86_64
Module libnss_sss.so.2 from rpm sssd-2.9.5-1.fc40.x86_64
Module libpcre2-8.so.0 from rpm pcre2-10.44-1.fc40.x86_64
Module libcap.so.2 from rpm libcap-2.69-8.fc40.x86_64
Module libselinux.so.1 from rpm libselinux-3.6-4.fc40.x86_64
Stack trace of thread 3987823:
#0 0x00007f19331c3f7e lgetxattr (libc.so.6 + 0x116f7e)
#1 0x00007f19332be4c0 lgetfilecon_raw (libselinux.so.1 + 0x134c0)
#2 0x00007f19332c3bd9 lgetfilecon (libselinux.so.1 + 0x18bd9)
#3 0x000056038273ad55 gobble_file.constprop.0 (/usr/bin/ls + 0x17d55)
#4 0x0000560382733c55 print_dir (/usr/bin/ls + 0x10c55)
#5 0x0000560382727c35 main (/usr/bin/ls + 0x4c35)
#6 0x00007f19330d7088 __libc_start_call_main (libc.so.6 + 0x2a088)
#7 0x00007f19330d714b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a14b)
#8 0x0000560382728f15 _start (/usr/bin/ls + 0x5f15)
ELF object binary architecture: AMD x86-64
```
(This is just a simulation. `ls` is not prone to crashing with a segmentation violation.)