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- Opcode fingerprint (MEM) or edge RVA
(RET: callee->caller, ARG: caller->callee)
- 8-bit argument mask (ARG only)
---------------------------------------------------------------------------
SymDef IDs are computed as follows:
---------------------------------------------------------------------------
// MEM (load) definitions
uint64_t symdef_mem =
((uint64_t)pc_rva << 32)
| *reinterpret_cast<const uint32_t*>(instruction.getOpcode());
// RET (return) definitions
uint64_t symdef_ret =
((uint64_t)return_target_rva << 32)
| ret_instruction_rva;
// ARG (call) definitions
uint64_t base = ((uint64_t)called_function_rva << 32)
| call_site_rva;
uint64_t cleared = base & 0x00FFFFFFFFFFFFFFULL; // clear bits 56-63
uint64_t symdef_arg = ((uint64_t)sym_args_mask << 56) | cleared;
---------------------------------------------------------------------------
Invocation IDs then build on the SymDef ID by adding AST complexity:
---------------------------------------------------------------------------
uint64_t invocation = symdef /* _mem, _ret or _arg */
+ Ast->getLevel();
E0 stores both each SymDef ID and its corresponding invocation IDs
(SymDef ID + AST level) in its local SQLite database for de-duplication
and coverage tracking. In the future, we may incorporate a module-name
hash into the RVA to guard against any potential collisions, but to date
this simple 64-bit packing scheme has produced no ID conflicts.
--[ 8 - Data-Flow Coverage Metrics
Building on the selective symbolic instrumentation framework and the
symbolic definitions described in previous sections, E0 replaces
traditional, bitmap-based code-coverage metrics with a suite of high-
resolution data-flow coverage signals. Conventional coverage relies on a
bitmap, one bit per basic block or edge, to record whether a region has
been exercised, but this low-resolution mechanism ignores semantic
relevance. In practice, two inputs may mark the same basic blocks as
covered, yet one may carry no untrusted input into a critical function
argument while the other precisely steers untrusted bytes into a
vulnerable buffer. Data-Flow Coverage Guidance, by contrast, captures
exactly which instructions, and at which points in the def-use graph, are
influenced by symbolic ("guarded") inputs. Whenever a guarded memory load
produces a new symbolic operand, E0 invokes Triton to launch a targeted
emulation slice and logs a set of "Symbolic Definitions" (ARG, MEM, RET)
that record the precise ASTs showing how input bytes flow into registers
or memory.
Over the course of a single sample run, unlike code-coverage guidance
which typically instruments only one or few modules, our data-flow
approach fuses these definitions across all modules and threads to
construct a coherent, per-instruction map of data-flow. By tracking
symbolic dependencies at this level, E0 can distinguish execution paths
that visit identical basic blocks but differ in how untrusted bytes
influence computation. This finer granularity enables more efficient
sample mutation, reduces blind fuzzing on semantically irrelevant code
paths, and supplies downstream layers (SMT solver and LLM) with richer,
contextually precise information.
This fine-grained, instruction-level data-flow mapping supports multiple
quantitative metrics, ranging from higher-level, less precise signals to
lower-level, more precise signals, that E0 collects to guide data-flow
coverage:
---------------------------------------------------------------------------
1 | Symbolic Emulation Session Count per Run
---------------------------------------------------------------------------
Each time a guarded memory load produces a new symbolic operand, E0
invokes Triton to launch a targeted emulation slice. The total number of
such emulation slices/sessions per sample indicates how many distinct
data-dependent "frontiers" the input has exercised. A higher session count
implies deeper penetration into the def-use graph, reflecting multiple
layers of data propagation. By tracking this count over time, the system
deprioritizes further mutations of inputs that repeatedly trigger the same
sessions and instead focuses on samples that spawn novel emulation slices.
---------------------------------------------------------------------------
2 | Symbolic Definition Count per Run
---------------------------------------------------------------------------
Within each emulation session, E0 logs every new symbolic definition,
whether it arises from a guarded memory load (MEM), a function-call
argument boundary (ARG), or a return value (RET). Recording the total
number of definitions per sample run provides insight into (a) the depth
of def-use propagation (for example, whether untrusted bytes reached
multiple function boundaries) and (b) the exact points where input-derived
data influenced control flow or memory. By comparing this count against
previous runs, E0 identifies samples that expose new combinations of
data-flow events, even if they traverse identical basic blocks.
---------------------------------------------------------------------------
3 | Emulated Instructions Count per Run
---------------------------------------------------------------------------
Not all instructions in a targeted emulation slice involve symbolic
operands; nevertheless, E0 counts every instruction that Triton processes
under ONLY_ON_SYMBOLIZED mode from the moment a guarded load triggers
emulation until all live symbolic registers have been concretized. This