Unprivileged normalize API

[r1viollet]

Description

When using the current normalize API, we require elevated permissions. This is due to the usage of map_files.
Here is for instance the failing syscall from a strace:

4122778 openat(AT_FDCWD, "/proc/4122778/map_files/61bc0125c000-61bc0125e000", O_RDONLY|O_CLOEXEC) = -1 EPERM (Operation not permitted)

We could propose a normalization API that works from source.
The logic would be similar to what we propose here

This uses the mapping information (from proc/<PID>/maps) and the segment information from the file. Finding files associated to mappings can be a challenge. So perhaps it should be the responsibility of the user, to provide the matching elf file.

Motivation

This would allow us to use the API within a process (or a child process) to symbolize itself (or the parent).
Our use case is to annotate crashes or errors with associated symbols. From the associated stack trace, we could normalize and symbolize from source.

[r1viollet]

This is somewhat a different use case from the issues I previously submitted. Thanks again for being so fast in considering my issues.

[d-e-s-o]

Yeah, I can see it being useful to have a solution for cases where fewer permissions are available. We changed this behavior with 327f288 and effectively requiring root has certainly not been a great characteristic to have ever since.

We could propose a normalization API that works from source.

What are you referring to when you say "from source"?

We still keep what we call the symbolic path around, so we could introduce an option to use that instead of the maps_file. I can't think of a better API design off-hand.

[d-e-s-o]

@r1viollet I created #520, which I'd think should cater to your use case, if you set the map_files argument to false in the blaze_symbolize_src_process object. Feel free to give it a try and let us know if it works for you.

[d-e-s-o]

Closed via 8415b4e

[r1viollet]

Sorry for the late feedback. I was out for some days. This worked well for us! Thank you 🙇