On Wed, Apr 26, 2023 at 02:47:27PM -0700, Yonghong Song wrote: > > > On 4/23/23 11:55 AM, Espen Grindhaug wrote: > > This change fixes the handling of versions in elf_find_func_offset. > > In the previous implementation, we incorrectly assumed that the > > Could you give more explanation/example in the commit message > what does 'incorrectly' mean here? In which situations the > current libbpf implementation will not be correct? > How about something like this? libbpf: Improve version handling when attaching uprobe This change fixes the handling of versions in elf_find_func_offset. For example, let's assume we are trying to attach an uprobe to pthread_create in glibc. Prior to this commit, it would fail with an error message saying 'elf: ambiguous match [...]', this is because there are two entries in the symbol table with that name. $ nm -D /lib/x86_64-linux-gnu/libc.so.6 | grep pthread_create 0000000000094cc0 T pthread_create@GLIBC_2.2.5 0000000000094cc0 T pthread_create@@GLIBC_2.34 So we go ahead and modify our code to attach to 'pthread_create@@GLIBC_2.34', and this also fails, but this time with the error 'elf: failed to find symbol [...]'. This fails because we incorrectly assumed that the version information would be present in the string found in the string table, but there is only the string 'pthread_create'. This patch reworks how we compare the symbol name provided by the user if it is qualified with a version (using @ or @@). We now look up the correct version string in the version symbol table before constructing the full name, as also done above by nm, before comparing. > > version information would be present in the string found in the > > string table. > > > > We now look up the correct version string in the version symbol > > table before constructing the full name and then comparing. > > > > This patch adds support for both name@version and name@@version to > > match output of the various elf parsers. > > > > Signed-off-by: Espen Grindhaug <espen.grindhaug@xxxxxxxxx> > > [...]
