r353990 - [HWASAN] Updated HWASAN design document to better portray the chance of missing a bug.

[Mitch Phillips via cfe-commits]

Author: hctim
Date: Wed Feb 13 15:14:54 2019
New Revision: 353990

URL: http://llvm.org/viewvc/llvm-project?rev=353990&view=rev
Log:
[HWASAN] Updated HWASAN design document to better portray the chance of missing a bug.

Summary: Provided rule of thumb percentage chances of miss for 4 and 8 bit tag sizes.

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58195

Modified:
    cfe/trunk/docs/HardwareAssistedAddressSanitizerDesign.rst

Modified: cfe/trunk/docs/HardwareAssistedAddressSanitizerDesign.rst
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/HardwareAssistedAddressSanitizerDesign.rst?rev=353990&r1=353989&r2=353990&view=diff
==============================================================================
--- cfe/trunk/docs/HardwareAssistedAddressSanitizerDesign.rst (original)
+++ cfe/trunk/docs/HardwareAssistedAddressSanitizerDesign.rst Wed Feb 13 15:14:54 2019
@@ -131,7 +131,8 @@ HWASAN:
     https://www.kernel.org/doc/Documentation/arm64/tagged-pointers.txt).
   * **Does not require redzones to detect buffer overflows**,
     but the buffer overflow detection is probabilistic, with roughly
-    `(2**TS-1)/(2**TS)` probability of catching a bug.
+    `1/(2**TS)` chance of missing a bug (6.25% or 0.39% with 4 and 8-bit TS
+    respectively).
   * **Does not require quarantine to detect heap-use-after-free,
     or stack-use-after-return**.
     The detection is similarly probabilistic.