Dynamic symbols in shared library may have the same name, for example:
$ nm -D /lib/x86_64-linux-gnu/libc.so.6 | grep rwlock_wrlock
000000000009b1a0 T __pthread_rwlock_wrlock@GLIBC_2.2.5
000000000009b1a0 T pthread_rwlock_wrlock@@GLIBC_2.34
000000000009b1a0 T pthread_rwlock_wrlock@GLIBC_2.2.5
$ readelf -W --dyn-syms /lib/x86_64-linux-gnu/libc.so.6 | grep rwlock_wrlock
706: 000000000009b1a0 878 FUNC GLOBAL DEFAULT 15 __pthread_rwlock_wrlock@GLIBC_2.2.5
2568: 000000000009b1a0 878 FUNC GLOBAL DEFAULT 15 pthread_rwlock_wrlock@@GLIBC_2.34
2571: 000000000009b1a0 878 FUNC GLOBAL DEFAULT 15 pthread_rwlock_wrlock@GLIBC_2.2.5
There are two pthread_rwlock_wrlock symbols in .dynsym section of libc.
The one with @@ is the default version, the other is hidden.
Note that the version info is actually stored in .gnu.version and .gnu.version_d
sections of libc and the two symbols are at the same offset.
Currently, specify `pthread_rwlock_wrlock`, `pthread_rwlock_wrlock@@GLIBC_2.34`
or `pthread_rwlock_wrlock@GLIBC_2.2.5` in bpf_uprobe_opts::func_name won't work.
Because there are two `pthread_rwlock_wrlock` in .dynsym sections without the
version suffix and both are global bind.
This patchset adds symbol versioning ([0]) support for dynsym for uprobe,
so that we can handle the above case.
[0]: https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA.junk/symversion.html
Hengqi Chen (2):
libbpf: Resolve ambiguous matches at the same offset for uprobe
libbpf: Support symbol versioning for uprobe
tools/lib/bpf/elf.c | 103 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 94 insertions(+), 9 deletions(-)
--
2.39.3
