about summary refs log tree commit diff
path: root/docs
diff options
context:
space:
mode:
Diffstat (limited to 'docs')
-rw-r--r--docs/ChangeLog2
-rw-r--r--docs/env_variables.txt8
2 files changed, 10 insertions, 0 deletions
diff --git a/docs/ChangeLog b/docs/ChangeLog
index b758b211..b8d0d7ac 100644
--- a/docs/ChangeLog
+++ b/docs/ChangeLog
@@ -17,6 +17,8 @@ sending a mail to <afl-users+subscribe@googlegroups.com>.
 Version ++2.52d (tbd):
 -----------------------------
 
+  - added never zero counters for afl-gcc and optional (because of an
+    optimization issue in llvm < 9) for llvm_mode (AFL_LLVM_NEVER_ZERO=1)
   - more cpu power for afl-system-config
   - added forkserver patch to afl-tmin, makes it much faster (originally from
     github.com/nccgroup/TriforceAFL)
diff --git a/docs/env_variables.txt b/docs/env_variables.txt
index 2a824766..d854ea8d 100644
--- a/docs/env_variables.txt
+++ b/docs/env_variables.txt
@@ -106,6 +106,14 @@ Then there are a few specific features that are only available in llvm_mode:
 
     See llvm_mode/README.whitelist for more information.
 
+  OTHER
+  =====
+    - Setting export AFL_LLVM_NOT_ZERO=1 during compilation will use counters
+      that skip zero on overflow. This is the default for llvm >= 9,
+      however for llvm versions below that this will increase an unnecessary
+      slowdown due a performance issue that is only fixed in llvm 9+.
+      This feature increases path discovery by a little bit.
+
 Note that AFL_INST_RATIO will behave a bit differently than for afl-gcc,
 because functions are *not* instrumented unconditionally - so low values
 will have a more striking effect. For this tool, 0 is not a valid choice.