USE_TRACE_PC unnecessary, set env AFL_LLVM_USE_TRACE_PC instead

docs/ChangeLog

@@ -21,9 +21,11 @@ Version ++2.60d (develop):
   - afl-fuzz:
      - now prints the real python version support compiled in
      - set stronger performance compile options and little tweaks
-  - afl-clang-fast now shows in the help output for which llvm version it
-    was compiled for
-  - added blacklisted function check in llvm_mode
+  - afl-clang-fast:
+     - show in the help output for which llvm version it was compiled for
+     - now does not need to be recompiled between trace-pc and pass
+       instrumentation. compile normally and set AFL_LLVM_USE_TRACE_PC :)
+  - added blacklisted function check in all modules of llvm_mode
   - added fix from Debian project to compile libdislocator and libtokencap
 
 

llvm_mode/README.md

@@ -198,24 +198,23 @@ PS. Because there are task switches still involved, the mode isn't as fast as
 faster than the normal fork() model, and compared to in-process fuzzing,
 should be a lot more robust.
 
-## 8) Bonus feature #3: new 'trace-pc-guard' mode
+## 8) Bonus feature #3: 'trace-pc-guard' mode
 
-Recent versions of LLVM are shipping with a built-in execution tracing feature
+LLVM is shipping with a built-in execution tracing feature
 that provides AFL with the necessary tracing data without the need to
 post-process the assembly or install any compiler plugins. See:
 
   http://clang.llvm.org/docs/SanitizerCoverage.html#tracing-pcs-with-guards
 
-If you have a sufficiently recent compiler and want to give it a try, build
-afl-clang-fast this way:
+If you have not an outdated compiler and want to give it a try, build
+targets this way:
 
 ```
-  AFL_TRACE_PC=1 make clean all
+ libtarget-1.0 $ AFL_LLVM_USE_TRACE_PC=1  make
 ```
 
-Note that this mode is currently about 20% slower than "vanilla" afl-clang-fast,
+Note that this mode is about 20% slower than "vanilla" afl-clang-fast,
 and about 5-10% slower than afl-clang. This is likely because the
-instrumentation is not inlined, and instead involves a function call. On systems
-that support it, compiling your target with -flto should help.
-
-
+instrumentation is not inlined, and instead involves a function call.
+On systems that support it, compiling your target with -flto can help
+a bit.

llvm_mode/afl-clang-fast.c

@@ -204,13 +204,24 @@ static void edit_params(u32 argc, char** argv) {
   // "-fsanitize-coverage=trace-cmp,trace-div,trace-gep";
   // cc_params[cc_par_cnt++] = "-sanitizer-coverage-block-threshold=0";
 #else
-  cc_params[cc_par_cnt++] = "-Xclang";
-  cc_params[cc_par_cnt++] = "-load";
-  cc_params[cc_par_cnt++] = "-Xclang";
-  if (getenv("AFL_LLVM_INSTRIM") != NULL || getenv("INSTRIM_LIB") != NULL)
-    cc_params[cc_par_cnt++] = alloc_printf("%s/libLLVMInsTrim.so", obj_path);
-  else
-    cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-pass.so", obj_path);
+  if (getenv("USE_TRACE_PC") || getenv("AFL_USE_TRACE_PC") ||
+      getenv("AFL_LLVM_USE_TRACE_PC") || getenv("AFL_TRACE_PC")) {
+
+    cc_params[cc_par_cnt++] =
+        "-fsanitize-coverage=trace-pc-guard";  // edge coverage by default
+
+  } else {
+
+    cc_params[cc_par_cnt++] = "-Xclang";
+    cc_params[cc_par_cnt++] = "-load";
+    cc_params[cc_par_cnt++] = "-Xclang";
+    if (getenv("AFL_LLVM_INSTRIM") != NULL || getenv("INSTRIM_LIB") != NULL)
+      cc_params[cc_par_cnt++] = alloc_printf("%s/libLLVMInsTrim.so", obj_path);
+    else
+      cc_params[cc_par_cnt++] = alloc_printf("%s/afl-llvm-pass.so", obj_path);
+
+  }
+
 #endif                                                     /* ^USE_TRACE_PC */
 
   cc_params[cc_par_cnt++] = "-Qunused-arguments";
@@ -282,8 +293,10 @@ static void edit_params(u32 argc, char** argv) {
 
 #ifdef USE_TRACE_PC
 
-  if (getenv("AFL_INST_RATIO"))
-    FATAL("AFL_INST_RATIO not available at compile time with 'trace-pc'.");
+  if (getenv("USE_TRACE_PC") || getenv("AFL_USE_TRACE_PC") ||
+      getenv("AFL_LLVM_USE_TRACE_PC") || getenv("AFL_TRACE_PC"))
+    if (getenv("AFL_INST_RATIO"))
+      FATAL("AFL_INST_RATIO not available at compile time with 'trace-pc'.");
 
 #endif                                                      /* USE_TRACE_PC */
 
@@ -455,6 +468,8 @@ int main(int argc, char** argv) {
 #ifdef USE_TRACE_PC
     SAYF(cCYA "afl-clang-fast" VERSION cRST
               " [tpcg] by <lszekeres@google.com>\n");
+#warning \
+    "You do not need to specifically compile with USE_TRACE_PC anymore, setting the environment variable AFL_LLVM_USE_TRACE_PC is enough."
 #else
     SAYF(cCYA "afl-clang-fast" VERSION cRST " by <lszekeres@google.com>\n");
 #endif                                                     /* ^USE_TRACE_PC */