On Tue, Sep 05, 2023 at 03:12:55PM +0000, Hengqi Chen wrote:
> 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@xxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
jirka
> ---
> tools/lib/bpf/elf.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> index 9d0296c1726a..5c9e588b17da 100644
> --- a/tools/lib/bpf/elf.c
> +++ b/tools/lib/bpf/elf.c
> @@ -214,7 +214,10 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
>
> if (ret > 0) {
> /* handle multiple matches */
> - if (last_bind != STB_WEAK && cur_bind != STB_WEAK) {
> + if (elf_sym_offset(sym) == ret) {
> + /* same offset, no problem */
> + continue;
> + } else if (last_bind != STB_WEAK && cur_bind != STB_WEAK) {
> /* Only accept one non-weak bind. */
> pr_warn("elf: ambiguous match for '%s', '%s' in '%s'\n",
> sym->name, name, binary_path);
> --
> 2.34.1
