Cygwin: Adjust CWD magic to accommodate for the latest Windows previews #86
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Reportedly a very recent internal build of Windows 11 once again changed the current working directory logic a bit, and Cygwin's "magic" (or: "technologically sufficiently advanced") code needs to be adjusted accordingly. In particular, the following assembly code can be seen: ntdll!RtlpReferenceCurrentDirectory 598 00000001`800c6925 488d0db4cd0f00 lea rcx,[ntdll!FastPebLock (00000001`801c36e0)] 583 00000001`800c692c 4c897810 mov qword ptr [rax+10h],r15 588 00000001`800c6930 0f1140c8 movups xmmword ptr [rax-38h],xmm0 598 00000001`800c6934 e82774f4ff call ntdll!RtlEnterCriticalSection The change necessarily looks a bit different than 4840a56 (Cygwin: Adjust CWD magic to accommodate for the latest Windows previews, 2023-05-22): The needle `\x48\x8d\x0d` is already present, as the first version of the hack after Windows 8.1 was released. In that code, though, the `call` to `RtlEnterCriticalSection` followed the `lea` instruction immediately, but now there are two more instructions separating them. Note: In the long run, we may very well want to follow the insightful suggestion by a helpful Windows kernel engineer who pointed out that it may be less fragile to implement kind of a disassembler that has a better chance to adapt to the ever-changing code of `ntdll!RtlpReferenceCurrentDirectory` by skipping uninteresting instructions such as `mov %rsp,%rax`, `mov %rbx,0x20(%rax)`, `push %rsi` `sub $0x70,%rsp`, etc, and focuses on finding the `lea`, `call ntdll!RtlEnterCriticalSection` and `mov ..., rbx` instructions, much like it was prototyped out for ARM64 at https://gist.github.com/jeremyd2019/aa167df0a0ae422fa6ebaea5b60c80c9 Signed-off-by: Johannes Schindelin <[email protected]>
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/open pr The workflow run was started |
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I am upstreaming this to Cygwin via https://inbox.sourceware.org/cygwin-patches/6449d894879e33af3e8a4791896d2026f7c3f8bd.1740865389.git.johannes.schindelin@gmx.de/ |
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Reportedly a very recent internal build of Windows 11 once again changed the current working directory logic a bit, and Cygwin's "magic" (or: "technologically sufficiently advanced") code needs to be adjusted accordingly.
This fixes git-for-windows/git#5447.