lib/lock: put the syndrome bits back

Took them out because the old way of doing things broke the
tools build. This way works just as well, is simpler and easier
to understand.

Signed-off-by: Marcelo Vanzin <mvanzin@vmware.com>

diff --git a/open-vm-tools/lib/lock/ul.c b/open-vm-tools/lib/lock/ul.c
index 0ef4e813ddbc3ea2f50e636be5d96e01b7233cd7..59d68a48800bbec9f8c9ab467c4a75efecc8482f 100644 (file)
--- a/open-vm-tools/lib/lock/ul.c
+++ b/open-vm-tools/lib/lock/ul.c
@@ -23,7 +23,6 @@
 #include "ulInt.h"
 #include "ulIntShared.h"
 #include "hashTable.h"
-#include "random.h"
 #include "hostinfo.h"
 
 
@@ -123,26 +122,32 @@ MXUserSyndrome(void)
    syndrome = Atomic_Read(&syndromeMem);
 
    if (syndrome == 0) {
+       void *token;
+
        /*
-        * Use the cryto quality source of bytes. This comes from the
-        * host system. Should take somehow fail use the host's uptime
+        * It is extremely rare for malloc/calloc to be diverted into multiple
+        * heaps or to fail in our environment - one heap per program; addresses
+        * must be unique. Attempt a small allocation and use its address for
+        * the syndrome bits.
+        *
+        * This is an intentional "leak" albeit only once per program (or
+        * copy of MXUser).
         */
 
-       do {
-          if (!Random_Crypto(sizeof(syndrome), &syndrome)) {
-//             syndrome = Hostinfo_SystemUpTime() & 0xFFFFFFFF;
-             syndrome = 1;  // work around tools build
-          }
-       } while (syndrome == 0);  // syndrome bits must be non-zero
+       token = malloc(4);
 
-       /*
-        * Attempt to update the syndrome value with the computed value using
-        * a blind conditional write. One thread or another will have updated
-        * the value.
-        */
+       syndrome = ((uintptr_t) token) & 0xFFFFFFFF;
+
+       if (UNLIKELY(syndrome == 0)) {
+          syndrome++;  // live with the exceedingly rare outcome
+       }
+
+       if (Atomic_ReadIfEqualWrite(&syndromeMem, 0, syndrome)) {
+          free(token);
+       }
 
-       Atomic_ReadIfEqualWrite(&syndromeMem, 0, syndrome);
        syndrome = Atomic_Read(&syndromeMem);
+       ASSERT(syndrome);
    }
 
    return syndrome;