[Henglie]

Summary

ql_syscall_recv let BlockingIOError escape the syscall handler when a guest called recv on a non-blocking socket with no data pending. The guest emulation was then aborted instead of receiving -EAGAIN, which is what a real kernel returns.

This PR catches that condition in the syscall wrapper and returns -EAGAIN, and adds a regression test.

Fixes #1373.

Test

Added tests/test_socket.py::SocketTest::test_recv_on_nonblocking_socket_returns_eagain:

• creates a non-blocking socket pair
• registers one end as guest fd 3
• calls ql_syscall_recv with no data queued

Before the fix the test fails with the reported BlockingIOError. After the fix it passes with the return value -EAGAIN.

Local run (Windows 11, CPython 3.11.9, Unicorn 2.1.3):

python -m unittest -v test_socket test_shellcode
Ran 9 tests in 4.273s
OK

The test module is also imported from tests/test_posix.py, so it runs as part of the Linux test suite.

Not verified

• No full guest HTTP daemon or rootfs integration run; the regression test exercises the syscall handler directly.
• Only recv is covered here. recvfrom/recvmsg were not changed.

Related: open PR #1676 also touches errno handling in socket.py. This change is independent, but a trivial import rebase may be needed if #1676 merges first.

Checklist

Which kind of PR do you create?

• This PR only contains minor fixes.
• This PR contains major feature update.
• This PR introduces a new function/api for Qiling Framework.

Coding convention?

• The new code conforms to Qiling Framework naming convention.
• The imports are arranged properly.
• Essential comments are added. (No comment added: the three-line handler is self-explanatory.)
• The reference of the new code is pointed out.

Extra tests?

• No extra tests are needed for this PR.
• I have added enough tests for this PR.
• Tests will be added after some discussion and review.

Changelog?

• This PR doesn't need to update Changelog. (ChangeLog is organized by release.)
• Changelog will be updated after some proper review.
• Changelog has been updated in my PR.

Target branch?

• The target branch is dev branch.

One last thing

• I have read the contribution guide.