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
Currently, users can't attach a uprobe to pthread_rwlock_wrlock because
there are two symbols named pthread_rwlock_wrlock and both are global
bind. And libbpf considers it as a conflict.
Since both of them are at the same offset we could accept one of them
harmlessly. Note that we already does this in elf_resolve_syms_offsets.
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20230918024813.237475-2-hengqi.chen@gmail.com
Adding elf_resolve_pattern_offsets function that looks up
offsets for symbols specified by pattern argument.
The 'pattern' argument allows wildcards (*?' supported).
Offsets are returned in allocated array together with its
size and needs to be released by the caller.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-13-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Adding elf symbol iterator object (and some functions) that follow
open-coded iterator pattern and some functions to ease up iterating
elf object symbols.
The idea is to iterate single symbol section with:
struct elf_sym_iter iter;
struct elf_sym *sym;
if (elf_sym_iter_new(&iter, elf, binary_path, SHT_DYNSYM))
goto error;
while ((sym = elf_sym_iter_next(&iter))) {
...
}
I considered opening the elf inside the iterator and iterate all symbol
sections, but then it gets more complicated wrt user checks for when
the next section is processed.
Plus side is the we don't need 'exit' function, because caller/user is
in charge of that.
The returned iterated symbol object from elf_sym_iter_next function
is placed inside the struct elf_sym_iter, so no extra allocation or
argument is needed.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-11-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
