gh-127076: Ignore memory mmap in FileIO testing

[cmaloney]

mmap, munmap, and mprotect are used by CPython for memory management which may occur in the middle of the FileIO tests. The system calls can also be used with files, so strace includes them in its %file and %desc filters.

Filter out the mmap system calls related to memory allocation for the file tests. Currently FileIO doesn't do mmap at all, so didn't add code to track from mmap through munmap since it wouldn't be used. For now if an mmap on a fd happens, the call will be included (which may cause tests to fail), and at that time support for tracking the address through munmap could be added.

cc: @mgorny this should fix the glibc and musl Gentoo general failures outside sandbox
cc: @brandtbucher This re-enables for PYTHON_JIT, and filters out the mmap calls used for memory management

• Issue: FileIO Strace test fails on Gentoo (test_fileio test_syscalls_read)  #127076

[mgorny]

Suggested change

	if call.syscall == 'mmap' and call.args[0] == 'NULL':
	if call.syscall == 'mmap' and call.args[4] == '-1':

I think the key here is that they pass -1 as fd.

[cmaloney]

Unfortunately for glibc man pages at least -1 isn't required... Going to see if I can look for MAP_ANONYMOUS easily. (Fortunately this code is linux only, MacOS did MAP_ANON....)

---

       MAP_ANONYMOUS
              The mapping is not backed by any file; its contents are initialized to zero.  The fd argument is ignored; however, some implementations require fd to be -1 if MAP_ANONYMOUS (or MAP_ANON) is specified, and portable applications should ensure this.  The  off‐
              set argument should be zero.  Support for MAP_ANONYMOUS in conjunction with MAP_SHARED was added in Linux 2.4.

https://man7.org/linux/man-pages/man2/mmap.2.html

[cmaloney]

Validated by modifying test_fileio test_syscalls_read to include a big string which results in an allocation:

        # "open, read, close" file using different common patterns.
        check_readall(
            "open builtin with default options",
            f"""
            f = open('{TESTFN}')
            a = "123" * 100000
            f.read()
            f.close()
            """
        )