On Fri, 4 Feb 2022, Andrii Nakryiko wrote:

On Mon, Jan 31, 2022 at 8:13 AM Alan Maguire [off-list ref] wrote:

quoted

Now that u[ret]probes can use name-based specification, it makes
sense to add support for auto-attach based on SEC() definition.
The format proposed is

        SEC("u[ret]probe//path/to/prog:[raw_offset|[function_name[+offset]]")

For example, to trace malloc() in libc:

        SEC("uprobe//usr/lib64/libc.so.6:malloc")

I assume that path to library can be relative path as well, right?

Also, should be look at trying to locate library in the system if it's
specified as "libc"? Or if the binary is "bash", for example. Just
bringing this up, because I think it came up before in the context of
one of libbpf-tools.

This is a great suggestion for usability, but I'm trying to puzzle
out how to carry out the location search for cases where the path 
specified is not a relative or absolute path.

A few things we can can do - use search paths from PATH and
LD_LIBRARY_PATH, with an appended set of standard locations
such as /usr/bin, /usr/sbin for cases where those environment
variables are missing or incomplete.

However, when it comes to libraries, do we search in /usr/lib64 or 
/usr/lib? We could use whether the version of libbpf is 64-bit or not I 
suppose, but it's at least conceivable that the user might want to 
instrument a 32-bit library from a 64-bit libbpf.  Do you think that
approach is sufficient, or are there other things we should do? Thanks!

Alan