[newlib-cygwin] Cygwin: Adjust CWD magic to accommodate for the latest Windows previews

[Jon Turney]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=4840a5632520c1a3c1598f73f9d1cdd37df371ba

commit 4840a5632520c1a3c1598f73f9d1cdd37df371ba
Author: Johannes Schindelin <johannes.schindelin@gmx.de>
Date:   Mon May 22 13:36:27 2023 +0200

    Cygwin: Adjust CWD magic to accommodate for the latest Windows previews
    
    Reportedly Windows 11 build 25*** from Insider changed the current
    working directory logic a bit, and Cygwin's "magic" (or:
    "technologically sufficiently advanced") code needs to be adjusted
    accordingly.
    
    This fixes https://github.com/git-for-windows/git/issues/4429
    
    Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Diff:
---
 winsup/cygwin/path.cc | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index 582238d15..37e46c08b 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -4511,13 +4511,27 @@ find_fast_cwd_pointer ()
       if (!lock)
 	{
 	  /* Windows 8.1 Preview calls `lea rel(rip),%r12' then some unrelated
-	     or, then `mov %r12,%rcx', then `callq RtlEnterCriticalSection'. */
+	     ops, then `mov %r12,%rcx', then `callq RtlEnterCriticalSection'. */
 	  lock = (const uint8_t *) memmem ((const char *) use_cwd, 80,
 					   "\x4c\x8d\x25", 3);
-	  if (!lock)
-	    return NULL;
 	  call_rtl_offset = 14;
 	}
+
+      if (!lock)
+	{
+	  /* A recent Windows 11 Preview calls `lea rel(rip),%r13' then
+	     some unrelated instructions, then `callq RtlEnterCriticalSection'.
+	     */
+	  lock = (const uint8_t *) memmem ((const char *) use_cwd, 80,
+					   "\x4c\x8d\x2d", 3);
+	  call_rtl_offset = 24;
+	}
+
+      if (!lock)
+	{
+	  return NULL;
+	}
+
       PRTL_CRITICAL_SECTION lockaddr =
         (PRTL_CRITICAL_SECTION) (lock + 7 + peek32 (lock + 3));
       /* Test if lock address is FastPebLock. */