* path.cc (find_fast_cwd_pointer): Fix for W8 CP 32 bit.

2 files changed, 58 insertions, 21 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 1300321..c8186e4 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,7 @@
+2012-04-27  Corinna Vinschen  <corinna@vinschen.de>
+
+	* path.cc (find_fast_cwd_pointer): Fix for W8 CP 32 bit.
+
 2012-04-25  Thomas Wolff  <towo@towo.net>
 
 	* fhandler.h (class dev_console): Add member ext_mouse_mode5.
diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index 3524c0c..59e6de3 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -3699,31 +3699,64 @@ find_fast_cwd_pointer ()
   /* ...which should be followed by "mov edi, crit-sect-addr" then
      "push edi", or by just a single "push crit-sect-addr". */
   const uint8_t *movedi = pushedi + 1;
-  if (movedi[0] == 0xbf && movedi[5] == 0x57)
-    rcall = movedi + 6;
-  else if (movedi[0] == 0x68)
-    rcall = movedi + 5;
+  const uint8_t *mov_pfast_cwd;
+  if (movedi[0] == 0x8b && movedi[1] == 0xff)	/* mov edi,edi -> W8 */
+    {
+      /* Windows 8 CP 32 bit (after a Windows Update?) does not call
+         RtlEnterCriticalSection.  For some reason the function manipulates
+	 the FastPebLock manually, kind of like RtlEnterCriticalSection has
+	 been converted to an inline function.
+
+	 Next we search for a `mov eax, some address'.  This address points
+	 to the LockCount member of the FastPebLock structure, so the address
+	 is equal to FastPebLock + 4. */
+      const uint8_t *moveax = (const uint8_t *) memchr (movedi, 0xb8, 16);
+      if (!moveax)
+	return NULL;
+      offset = (ptrdiff_t) peek32 (moveax + 1) - 4;
+      /* Compare the address with the known PEB lock as stored in the PEB. */
+      if ((PRTL_CRITICAL_SECTION) offset != NtCurrentTeb ()->Peb->FastPebLock)
+	return NULL;
+      /* Now search for the mov instruction fetching the address of the global
+	 PFAST_CWD *. */
+      mov_pfast_cwd = moveax;
+      do
+	{
+	  mov_pfast_cwd = (const uint8_t *) memchr (++mov_pfast_cwd, 0x8b, 48);
+	}
+      while (mov_pfast_cwd && mov_pfast_cwd[1] != 0x1d
+	     && (mov_pfast_cwd - moveax) < 48);
+      if (!mov_pfast_cwd || mov_pfast_cwd[1] != 0x1d)
+	return NULL;
+    }
   else
-    return NULL;
-  /* Compare the address used for the critical section with the known
-     PEB lock as stored in the PEB. */
-  if ((PRTL_CRITICAL_SECTION) peek32 (movedi + 1)
-      != NtCurrentTeb ()->Peb->FastPebLock)
-    return NULL;
-  /* To check we are seeing the right code, we check our expectation that
-     the next instruction is a relative call into RtlEnterCriticalSection. */
-  if (rcall[0] != 0xe8)
-    return NULL;
-  /* Check that this is a relative call to RtlEnterCriticalSection. */
-  offset = (ptrdiff_t) peek32 (rcall + 1);
-  if (rcall + 5 + offset != ent_crit)
-    return NULL;
+    {
+      if (movedi[0] == 0xbf && movedi[5] == 0x57)
+	rcall = movedi + 6;
+      else if (movedi[0] == 0x68)
+	rcall = movedi + 5;
+      else
+	return NULL;
+      /* Compare the address used for the critical section with the known
+	 PEB lock as stored in the PEB. */
+      if ((PRTL_CRITICAL_SECTION) peek32 (movedi + 1)
+	  != NtCurrentTeb ()->Peb->FastPebLock)
+	return NULL;
+      /* To check we are seeing the right code, we check our expectation that
+	 the next instruction is a relative call into RtlEnterCriticalSection. */
+      if (rcall[0] != 0xe8)
+	return NULL;
+      /* Check that this is a relative call to RtlEnterCriticalSection. */
+      offset = (ptrdiff_t) peek32 (rcall + 1);
+      if (rcall + 5 + offset != ent_crit)
+	return NULL;
+      mov_pfast_cwd = rcall + 5;
+    }
   /* After locking the critical section, the code should read the global
      PFAST_CWD * pointer that is guarded by that critical section. */
-  const uint8_t *movesi = rcall + 5;
-  if (movesi[0] != 0x8b)
+  if (mov_pfast_cwd[0] != 0x8b)
     return NULL;
-  return (fcwd_access_t **) peek32 (movesi + 2);
+  return (fcwd_access_t **) peek32 (mov_pfast_cwd + 2);
 }
 
 static fcwd_access_t **