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 4840a56325 (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 <johannes.schinde...@gmx.de> --- Published-As: https://github.com/dscho/msys2-runtime/releases/tag/adjust-fast-cwd-pointer-logic-once-again-cygwin-v1 Fetch-It-Via: git fetch https://github.com/dscho/msys2-runtime adjust-fast-cwd-pointer-logic-once-again-cygwin-v1 winsup/cygwin/path.cc | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc index 599809f941..49740ac465 100644 --- a/winsup/cygwin/path.cc +++ b/winsup/cygwin/path.cc @@ -4539,6 +4539,18 @@ find_fast_cwd_pointer () %rcx for the subsequent RtlEnterCriticalSection call. */ lock = (const uint8_t *) memmem ((const char *) use_cwd, 80, "\x48\x8d\x0d", 3); + if (lock) + { + /* A recent Windows 11 Preview calls `lea rel(rip),%rcx' then + a `mov` and a `movups` instruction, and only then + `callq RtlEnterCriticalSection'. + */ + if (memmem (lock + 7, 8, "\x4c\x89\x78\x10\x0f\x11\x40\xc8", 8)) + { + call_rtl_offset = 15; + } + } + if (!lock) { /* Windows 8.1 Preview calls `lea rel(rip),%r12' then some unrelated base-commit: 08e65dd685bec34d4d74f45c06129d271b210bc7 -- 2.48.1.windows.1
