mprotect ineffective after fork

[korli]

I took a few tests from libhugetlbfs, combined them in fork-mprotect-cow to check the page protection after fork. this actually succeeds on Linux and fails on Haiku.

Test output on Linux

Starting testcase "./fork-mprotect-cow", pid 15944
Mapping synchronization area..done
Mapping hugepage area...mapped at 0x7f59034f2000
Parent writes pre-fork...1234abcd
mprotect()ing to prot=0
Parent reading..SIGSEGV at 0x7f59034f2000 (sig_expected=0x7f59034f2000)
-1
Child starts..
Child reading..SIGSEGV at 0x7f59034f2000 (sig_expected=0x7f59034f2000)
-1
Child exits...
PASS

Test output on Haiku

Starting testcase "./fork-mprotect-cow", pid 585
Mapping synchronization area..done
Mapping hugepage area...mapped at 0x6e1872f000
Parent writes pre-fork...1234abcd
mprotect()ing to prot=0
Parent reading..Read back 305441741
0
Child starts..
Child reading..SIGSEGV at 0x6e1872f000 (sig_expected=0x6e1872f000)
-1
Child exits...
FAIL	Parent read succeeded on mmap(prot=0)

[korli]

​https://review.haiku-os.org/c/haiku/+/5601

[waddlesplash]

Fix merged in hrev56392. Should we add this testcase to the tree, perhaps?

[korli]

Thanks, the testcase licensing is LGPL, I wasn't sure it can be added to the tree.

[waddlesplash]

I think it's fine for testcases to be LGPL, we mostly care about things actually distributed to not be GPL.