Complete the pidfd API

[milantracy]

Description

Implement pidfd API for gVisor.

See https://lwn.net/Articles/794707/ for details

Is this feature related to a specific bug?

N/A

Do you have a specific solution in mind?

[milantracy]

some use cases are listed at oven-sh/bun#5803 (comment)

I will start work on it

[EtiennePerot]

This API has lots of surface area with various associated system calls. It would be good to enumerate them and to sort them by whether or not bun uses them.

Might also be good to add a tests for the bun runtime, similar to our node runtime tests.

[milantracy]

Syscalls that are expected to be done are listed in the order of priorities:

• pidfd_open is the only one that bun expects (while there is workaround for them)
• pidfd_getfd
• pidfd_send_signal
  let me know if i miss anything

[EtiennePerot]

It seems hard to believe that pidfd_open is the only one bun expects. Why use pidfd_open at all if the program is not going to use the functionality that pidfd offers?

[ayushr2]

You can poll(2) on FD returned by pidfd_open() to get a notification when the process represented by that pidfd exits. So maybe that's how bun uses it?

[milantracy]

is the only one bun expects. Why use pidfd_open at all if the program is not going to use the functionality that pidfd offers?

I didn't read into very details of their code base, as they said google-auth-library is the one who introduces the issue, the program crashed when it sees the pidfd_open. I will add pidfd_open to see if there is anything I shall follow with.

You can poll(2) on FD returned by pidfd_open() to get a notification when the process represented by that pidfd exits. So maybe that's how bun uses it?

from oven-sh/bun#6724 , they are working around the issue in a very similar way

[EtiennePerot]

Another bun user hitting this issue: oven-sh/bun#16063