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monster.c
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monster.c
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/*
Copyright (c) the Selfie Project authors. All rights reserved.
Please see the AUTHORS file for details. Use of this source code is
governed by a BSD license that can be found in the LICENSE file.
Selfie is a project of the Computational Systems Group at the
Department of Computer Sciences of the University of Salzburg
in Austria. For further information and code please refer to:
selfie.cs.uni-salzburg.at
Monster is a hybrid symbolic execution and bounded model checking
engine that implements a sound and (up to a given bound) complete
translation of RISC-U code to SMT-LIB formulae. Monster serves as
research platform and facilitates teaching the absolute basics of
bit-precise reasoning on real code.
Given a RISC-U binary (or C* source code compiled to RISC-U, including
all of selfie and monster itself) and bounds on the number of machine
instructions (maximum execution depth) and the number of conditional
branch instructions (branching limit) to be executed on any code path,
monster generates an SMT-LIB file that models the bit-precise behavior
of the binary up to the maximum execution depth and branching limit on
a 64-bit machine with 4GB of memory. The SMT formulae of the model are
satisfiable if and only if there is input to the code such that the
code exits with non-zero exit codes or performs division by zero when
executing no more instructions than the maximum execution depth and no
more conditional branch instructions than the branching limit.
The first console argument is interpreted as maximum execution depth
where value zero means that the depth is unbounded. The following
optional console argument is interpreted as non-default branching
limit where value zero means that any conditional branch instruction
makes the engine backtrack. The following optional console argument
--merge-enabled instructs monster to generate a single SMT-LIB
formula for bounded model checking by merging all code paths (rather
than one SMT-LIB formula for each code path as in symbolic execution).
Any remaining console arguments are uninterpreted and passed on as
console arguments to the modeled RISC-U binary.
Monster is inspired by Professor Armin Biere from JKU Linz.
*/
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ------------------- I N T E R F A C E -------------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ----------------------- MIPSTER SYSCALLS ------------------------
// -----------------------------------------------------------------
void implement_symbolic_exit(uint64_t* context);
void implement_symbolic_read(uint64_t* context);
void implement_symbolic_write(uint64_t* context);
uint64_t down_load_concrete_string(uint64_t* context, uint64_t vstring, char* s);
void implement_symbolic_openat(uint64_t* context);
// -----------------------------------------------------------------
// ------------------------- MONSTER SWITCH ------------------------
// -----------------------------------------------------------------
uint64_t* mipster_symbolic_switch(uint64_t* to_context, uint64_t timeout);
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ----------------- A R C H I T E C T U R E -----------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ------------------------ SYMBOLIC MEMORY ------------------------
// -----------------------------------------------------------------
uint64_t* load_symbolic_memory(uint64_t vaddr);
void store_symbolic_memory(uint64_t vaddr, uint64_t val, char* sym, char* var, uint64_t bits);
uint64_t* find_word_in_unshared_symbolic_memory(uint64_t vaddr);
void update_begin_of_shared_symbolic_memory(uint64_t* context, uint64_t* partner);
uint64_t is_symbolic_value(uint64_t* sword);
void print_symbolic_memory(uint64_t* sword);
// symbolic memory word struct:
// +---+-----------+
// | 0 | next word | pointer to next memory word
// | 1 | address | address of memory word
// | 2 | value | concrete value of memory word
// | 3 | symbolic | symbolic value of memory word
// | 4 | bits | number of bits in bit vector
// +---+-----------+
uint64_t* allocate_symbolic_memory_word() {
return smalloc(2 * sizeof(uint64_t*) + 3 * sizeof(uint64_t));
}
uint64_t* get_next_word(uint64_t* word) { return (uint64_t*) *word; }
uint64_t get_word_address(uint64_t* word) { return *(word + 1); }
uint64_t get_word_value(uint64_t* word) { return *(word + 2); }
char* get_word_symbolic(uint64_t* word) { return (char*) *(word + 3); }
uint64_t get_number_of_bits(uint64_t* word) { return *(word + 4); }
void set_next_word(uint64_t* word, uint64_t* next) { *word = (uint64_t) next; }
void set_word_address(uint64_t* word, uint64_t address) { *(word + 1) = address; }
void set_word_value(uint64_t* word, uint64_t value) { *(word + 2) = value; }
void set_word_symbolic(uint64_t* word, char* sym) { *(word + 3) = (uint64_t) sym; }
void set_number_of_bits(uint64_t* word, uint64_t bits) { *(word + 4) = bits; }
// -----------------------------------------------------------------
// ------------------------- INSTRUCTIONS --------------------------
// -----------------------------------------------------------------
void constrain_lui();
void constrain_addi();
void constrain_add_sub_mul_divu_remu_sltu(char* operator);
void zero_extend_sltu();
void constrain_load();
void constrain_store();
void constrain_beq();
void constrain_jalr();
// -----------------------------------------------------------------
// -------------------------- INTERPRETER --------------------------
// -----------------------------------------------------------------
void execute_symbolically();
void run_symbolically_until_exception();
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ---------------------- R U N T I M E ----------------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ---------------------------- CONTEXTS ---------------------------
// -----------------------------------------------------------------
uint64_t* new_symbolic_context();
uint64_t* copy_symbolic_context(uint64_t* original, uint64_t location, char* condition);
// symbolic context extension:
// +----+-----------------+
// | +0 | execution depth | number of executed instructions
// | +1 | path condition | pointer to path condition
// | +2 | symbolic memory | pointer to symbolic memory
// | +3 | symbolic regs | pointer to symbolic registers
// | +4 | beq counter | number of executed symbolic beq instructions
// | +5 | merge partner | pointer to the context from which this context was created
// | +6 | call stack | pointer to the corresponding node in the call stack tree
// +----+-----------------+
uint64_t* allocate_symbolic_context() {
return smalloc(CONTEXTENTRIES * sizeof(uint64_t) + 5 * sizeof(uint64_t*) + 2 * sizeof(uint64_t));
}
uint64_t get_execution_depth(uint64_t* context) { return *(context + CONTEXTENTRIES); }
char* get_path_condition(uint64_t* context) { return (char*) *(context + CONTEXTENTRIES + 1); }
uint64_t* get_symbolic_memory(uint64_t* context) { return (uint64_t*) *(context + CONTEXTENTRIES + 2); }
uint64_t* get_symbolic_regs(uint64_t* context) { return (uint64_t*) *(context + CONTEXTENTRIES + 3); }
uint64_t get_beq_counter(uint64_t* context) { return *(context + CONTEXTENTRIES + 4); }
uint64_t* get_merge_partner(uint64_t* context) { return (uint64_t*) *(context + CONTEXTENTRIES + 5); }
uint64_t* get_call_stack(uint64_t* context) { return (uint64_t*) *(context + CONTEXTENTRIES + 6); }
void set_execution_depth(uint64_t* context, uint64_t depth) { *(context + CONTEXTENTRIES) = depth; }
void set_path_condition(uint64_t* context, char* condition) { *(context + CONTEXTENTRIES + 1) = (uint64_t) condition; }
void set_symbolic_memory(uint64_t* context, uint64_t* memory) { *(context + CONTEXTENTRIES + 2) = (uint64_t) memory; }
void set_symbolic_regs(uint64_t* context, uint64_t* regs) { *(context + CONTEXTENTRIES + 3) = (uint64_t) regs; }
void set_beq_counter(uint64_t* context, uint64_t counter) { *(context + CONTEXTENTRIES + 4) = counter; }
void set_merge_partner(uint64_t* context, uint64_t* partner) { *(context + CONTEXTENTRIES + 5) = (uint64_t) partner; }
void set_call_stack(uint64_t* context, uint64_t* stack) { *(context + CONTEXTENTRIES + 6) = (uint64_t) stack; }
// -----------------------------------------------------------------
// -------------------------- MICROKERNEL --------------------------
// -----------------------------------------------------------------
uint64_t* create_symbolic_context(uint64_t* parent, uint64_t* vctxt);
// -----------------------------------------------------------------
// ---------------------------- KERNEL -----------------------------
// -----------------------------------------------------------------
uint64_t handle_symbolic_system_call(uint64_t* context);
uint64_t handle_symbolic_division_by_zero(uint64_t* context);
uint64_t handle_symbolic_timer(uint64_t* context);
uint64_t handle_symbolic_exception(uint64_t* context);
// ------------------------ GLOBAL CONSTANTS -----------------------
uint64_t EXITCODE_SYMBOLICEXECUTIONERROR = 1;
uint64_t SCHEDULE = 100; // extends DONOTEXIT and EXIT
// -----------------------------------------------------------------
// ------------------- SYMBOLIC EXECUTION ENGINE -------------------
// -----------------------------------------------------------------
char* bv_constant(uint64_t value);
char* bv_variable(uint64_t bits);
char* bv_zero_extension(uint64_t bits);
char* smt_value(uint64_t val, char* sym);
char* smt_variable(char* prefix, uint64_t bits);
char* smt_unary(char* opt, char* op);
char* smt_binary(char* opt, char* op1, char* op2);
char* smt_ternary(char* opt, char* op1, char* op2, char* op3);
void merge(uint64_t* active_context, uint64_t* mergeable_context, uint64_t location);
void merge_symbolic_memory_and_registers(uint64_t* active_context, uint64_t* mergeable_context);
void merge_symbolic_memory(uint64_t* active_context, uint64_t* mergeable_context);
void merge_registers(uint64_t* active_context, uint64_t* mergeable_context);
uint64_t* schedule_next_symbolic_context();
void check_if_mergeable_and_merge_if_possible(uint64_t* context);
void add_child(uint64_t* parent, uint64_t* child);
void step_into_call(uint64_t* context, uint64_t address);
void step_out_of_call(uint64_t* context);
void use_stdout();
void use_file();
void monster(uint64_t* to_context);
uint64_t selfie_run_symbolically();
// ------------------------ GLOBAL VARIABLES -----------------------
uint64_t w = 0; // number of written characters
uint64_t max_execution_depth = 1; // in number of instructions, unbounded with 0
uint64_t variable_version = 0; // generates unique SMT-LIB variable names
uint64_t* symbolic_contexts = (uint64_t*) 0;
char* path_condition = (char*) 0;
uint64_t* symbolic_memory = (uint64_t*) 0;
uint64_t* reg_sym = (uint64_t*) 0; // symbolic values in registers as strings in SMT-LIB format
char* smt_name = (char*) 0; // name of SMT-LIB file
uint64_t smt_fd = 0; // file descriptor of open SMT-LIB file
uint64_t merge_enabled = 0; // enable or disable the merging of paths
uint64_t debug_merge = 0; // enable or disable the debugging of merging in monster
uint64_t* call_stack_tree = (uint64_t*) 0; // tree representing the program structure (each node represents a procedure call)
// ------------------------ GLOBAL CONSTANTS -----------------------
uint64_t DELETED = -1; // indicates that a symbolic memory word has been deleted
uint64_t BEGIN_OF_SHARED_SYMBOLIC_MEMORY = -2; // indicates the beginning of the shared symbolic memory space
uint64_t beq_limit = 35; // limit of symbolic beq instructions on each path
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ------------------- I N T E R F A C E -------------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ----------------------- MIPSTER SYSCALLS ------------------------
// -----------------------------------------------------------------
void implement_symbolic_exit(uint64_t* context) {
// parameter;
uint64_t signed_int_exit_code;
signed_int_exit_code = *(get_regs(context) + REG_A0);
set_exit_code(context, sign_shrink(signed_int_exit_code, SYSCALL_BITWIDTH));
w = w
+ dprintf(output_fd, "\n(push 1)\n")
+ dprintf(output_fd, "(assert (and %s (not (= %s (_ bv0 64))))); exit in ",
path_condition,
smt_value(*(registers + REG_A0), (char*) *(reg_sym + REG_A0)))
+ print_code_context_for_instruction(pc);
if (debug_merge)
w = w + dprintf(output_fd, " -> exiting context: 0x%08lX", (uint64_t) context);
w = w + dprintf(output_fd, "\n(check-sat)\n(get-model)\n(pop 1)\n");
}
void implement_symbolic_read(uint64_t* context) {
// parameters
// fd not needed
uint64_t vbuffer;
uint64_t size;
// local variables
uint64_t read_total;
uint64_t bytes_to_read;
uint64_t failed;
vbuffer = *(get_regs(context) + REG_A1);
size = *(get_regs(context) + REG_A2);
read_total = 0;
bytes_to_read = WORDSIZE;
failed = 0;
while (size > 0) {
if (size < bytes_to_read)
bytes_to_read = size;
if (is_virtual_address_valid(vbuffer, WORDSIZE))
if (is_data_stack_heap_address(context, vbuffer))
if (is_virtual_address_mapped(get_pt(context), vbuffer)) {
store_symbolic_memory(vbuffer, 0, 0, smt_variable("i", bytes_to_read * 8), bytes_to_read * 8);
// save symbolic memory here since context switching has already happened
set_symbolic_memory(context, symbolic_memory);
read_total = read_total + bytes_to_read;
size = size - bytes_to_read;
if (size > 0)
vbuffer = vbuffer + WORDSIZE;
} else {
failed = 1;
size = 0;
use_stdout();
printf("%s: reading into virtual address 0x%08lX failed because the address is unmapped\n", selfie_name, vbuffer);
use_file();
}
else {
failed = 1;
size = 0;
use_stdout();
printf("%s: reading into virtual address 0x%08lX failed because the address is in an invalid segment\n", selfie_name, vbuffer);
use_file();
}
else {
failed = 1;
size = 0;
use_stdout();
printf("%s: reading into virtual address 0x%08lX failed because the address is invalid\n", selfie_name, vbuffer);
use_file();
}
}
if (failed)
*(get_regs(context) + REG_A0) = sign_shrink(-1, SYSCALL_BITWIDTH);
else
*(get_regs(context) + REG_A0) = read_total;
set_pc(context, get_pc(context) + INSTRUCTIONSIZE);
}
void implement_symbolic_write(uint64_t* context) {
// parameters
// fd not needed
uint64_t vbuffer;
uint64_t size;
// local variables
uint64_t written_total;
uint64_t bytes_to_write;
uint64_t failed;
vbuffer = *(get_regs(context) + REG_A1);
size = *(get_regs(context) + REG_A2);
written_total = 0;
bytes_to_write = WORDSIZE;
failed = 0;
while (size > 0) {
if (size < bytes_to_write)
bytes_to_write = size;
if (is_virtual_address_valid(vbuffer, WORDSIZE))
if (is_data_stack_heap_address(context, vbuffer))
if (is_virtual_address_mapped(get_pt(context), vbuffer)) {
// TODO: What should symbolically executed code actually output?
written_total = written_total + bytes_to_write;
size = size - bytes_to_write;
if (size > 0)
vbuffer = vbuffer + WORDSIZE;
} else {
failed = 1;
size = 0;
use_stdout();
printf("%s: writing from virtual address 0x%08lX failed because the address is unmapped\n", selfie_name, vbuffer);
use_file();
}
else {
failed = 1;
size = 0;
use_stdout();
printf("%s: writing from virtual address 0x%08lX failed because the address is in an invalid segment\n", selfie_name, vbuffer);
use_file();
}
else {
failed = 1;
size = 0;
use_stdout();
printf("%s: writing from virtual address 0x%08lX failed because the address is invalid\n", selfie_name, vbuffer);
use_file();
}
}
if (failed)
*(get_regs(context) + REG_A0) = sign_shrink(-1, SYSCALL_BITWIDTH);
else
*(get_regs(context) + REG_A0) = written_total;
set_pc(context, get_pc(context) + INSTRUCTIONSIZE);
}
uint64_t down_load_concrete_string(uint64_t* context, uint64_t vaddr, char* s) {
uint64_t i;
uint64_t* sword;
uint64_t j;
i = 0;
while (i < MAX_FILENAME_LENGTH) {
if (is_virtual_address_valid(vaddr, WORDSIZE))
if (is_data_stack_heap_address(context, vaddr)) {
if (is_virtual_address_mapped(get_pt(context), vaddr)) {
sword = load_symbolic_memory(vaddr);
if (sword) {
if (is_symbolic_value(sword)) {
use_stdout();
printf("%s: detected symbolic value ", selfie_name);
print_symbolic_memory(sword);
printf(" in filename of open call\n");
exit(EXITCODE_SYMBOLICEXECUTIONERROR);
} else
// CAUTION: at boot levels higher than zero, s is only accessible
// in C* at machine word granularity, not individual characters
store_word((uint64_t*) s, i, 1, get_word_value(sword));
} else
// assert: vaddr is mapped
store_word((uint64_t*) s, i, 1, load_virtual_memory(get_pt(context), vaddr));
} else {
use_stdout();
printf("%s: opening file failed because the file name address 0x%08lX is unmapped\n", selfie_name, vaddr);
use_file();
return 0;
}
// WORDSIZE may be less than sizeof(uint64_t)
j = i % sizeof(uint64_t);
// check if string ends in the current word
while (j - i % sizeof(uint64_t) < WORDSIZE) {
if (load_character((char*) ((uint64_t*) s + i / sizeof(uint64_t)), j) == 0)
return 1;
j = j + 1;
}
// advance to the next word in virtual memory
vaddr = vaddr + WORDSIZE;
// advance to the corresponding word in our memory
i = i + WORDSIZE;
} else {
use_stdout();
printf("%s: opening file failed because the file name address 0x%08lX is in an invalid segment\n", selfie_name, vaddr);
use_file();
return 0;
}
else {
use_stdout();
printf("%s: opening file failed because the file name address 0x%08lX is invalid\n", selfie_name, vaddr);
use_file();
return 0;
}
}
use_stdout();
printf("%s: opening file failed because the file name is too long at address 0x%08lX\n", selfie_name, vaddr);
use_file();
return 0;
}
void implement_symbolic_openat(uint64_t* context) {
// parameters
uint64_t vfilename;
// flags not needed
// mode not needed
vfilename = *(get_regs(context) + REG_A1);
if (down_load_concrete_string(context, vfilename, filename_buffer))
// TODO: check if opening vfilename has been attempted before
*(get_regs(context) + REG_A0) = 0; // file descriptor 0
else
*(get_regs(context) + REG_A0) = sign_shrink(-1, SYSCALL_BITWIDTH);
set_pc(context, get_pc(context) + INSTRUCTIONSIZE);
}
// -----------------------------------------------------------------
// ------------------------- MONSTER SWITCH ------------------------
// -----------------------------------------------------------------
uint64_t* mipster_symbolic_switch(uint64_t* to_context, uint64_t timeout) {
uint64_t execution_depth;
path_condition = get_path_condition(to_context);
reg_sym = get_symbolic_regs(to_context);
symbolic_memory = get_symbolic_memory(to_context);
restore_context(to_context);
do_switch(to_context, timeout);
execution_depth = get_total_number_of_instructions();
run_symbolically_until_exception();
execution_depth = get_total_number_of_instructions() - execution_depth;
save_context(current_context);
set_execution_depth(current_context, get_execution_depth(current_context) + execution_depth);
set_path_condition(current_context, path_condition);
set_symbolic_memory(current_context, symbolic_memory);
return current_context;
}
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ----------------- A R C H I T E C T U R E -----------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ------------------------ SYMBOLIC MEMORY ------------------------
// -----------------------------------------------------------------
uint64_t* load_symbolic_memory(uint64_t vaddr) {
uint64_t* sword;
sword = symbolic_memory;
while (sword != (uint64_t*) 0) {
if (get_word_address(sword) == vaddr)
return sword;
sword = get_next_word(sword);
}
return (uint64_t*) 0;
}
void store_symbolic_memory(uint64_t vaddr, uint64_t val, char* sym, char* var, uint64_t bits) {
uint64_t* sword;
// we overwrite values, if they already exist in the unshared symbolic memory space, so that there are no duplicates in any unshared symbolic memory space
sword = find_word_in_unshared_symbolic_memory(vaddr);
// new value in this unshared symbolic memory space
if (sword == (uint64_t*) 0) {
sword = allocate_symbolic_memory_word();
set_next_word(sword, symbolic_memory);
symbolic_memory = sword;
}
set_word_address(sword, vaddr);
set_word_value(sword, val);
if (var)
set_word_symbolic(sword, var);
else if (sym) {
set_word_symbolic(sword, smt_variable("m", WORDSIZEINBITS));
w = w
+ dprintf(output_fd, "(assert (= %s %s)); store in ", get_word_symbolic(sword), sym)
+ print_code_context_for_instruction(pc)
+ dprintf(output_fd, "\n");
} else
set_word_symbolic(sword, 0);
set_number_of_bits(sword, bits);
}
uint64_t* find_word_in_unshared_symbolic_memory(uint64_t vaddr) {
uint64_t* sword;
sword = get_symbolic_memory(current_context);
while (sword) {
if (get_word_address(sword) == BEGIN_OF_SHARED_SYMBOLIC_MEMORY)
return (uint64_t*) 0;
if (get_word_address(sword) == vaddr)
return sword;
sword = get_next_word(sword);
}
return (uint64_t*) 0;
}
void update_begin_of_shared_symbolic_memory(uint64_t* context, uint64_t* partner) {
uint64_t* sword_of_shared_store;
uint64_t* sword;
if (context == (uint64_t*) 0)
return;
sword_of_shared_store = (uint64_t*) 0;
sword = get_symbolic_memory(partner);
while (sword) {
if (get_word_address(sword) == BEGIN_OF_SHARED_SYMBOLIC_MEMORY) {
// remember beginning of shared symbolic memory portion in partner context
sword_of_shared_store = get_next_word(sword);
sword = (uint64_t*) 0;
} else
sword = get_next_word(sword);
}
sword = get_symbolic_memory(context);
while (sword) {
if (get_word_address(sword) == BEGIN_OF_SHARED_SYMBOLIC_MEMORY) {
// only unshare symbolic memory if both contexts point to the same shared portion
if (get_next_word(sword) == sword_of_shared_store)
set_word_address(sword, DELETED);
else if (debug_merge)
w = w + dprintf(output_fd, "; unbalanced shared symbolic memory detected, skip unsharing\n");
return;
}
sword = get_next_word(sword);
}
}
uint64_t is_symbolic_value(uint64_t* sword) {
return get_word_symbolic(sword) != (char*) 0;
}
void print_symbolic_memory(uint64_t* sword) {
if (is_symbolic_value(sword))
w = w + dprintf(output_fd, "%s", get_word_symbolic(sword));
w = w + dprintf(output_fd, "[0x%lX]@0x%lX\n", get_word_value(sword), get_word_address(sword));
}
// -----------------------------------------------------------------
// ------------------------- INSTRUCTIONS --------------------------
// -----------------------------------------------------------------
void constrain_lui() {
if (rd != REG_ZR)
*(reg_sym + rd) = 0;
}
void constrain_addi() {
if (rd != REG_ZR) {
if (*(reg_sym + rs1))
*(reg_sym + rd) = (uint64_t) smt_binary("bvadd", (char*) *(reg_sym + rs1), bv_constant(imm));
else
*(reg_sym + rd) = 0;
}
}
void constrain_add_sub_mul_divu_remu_sltu(char* operator) {
char* op1;
char* op2;
if (rd != REG_ZR) {
op1 = (char*) *(reg_sym + rs1);
op2 = (char*) *(reg_sym + rs2);
if (op1 == (char*) 0) {
if (op2 == (char*) 0) {
*(reg_sym + rd) = 0;
return;
} else
op1 = bv_constant(*(registers + rs1));
} else if (op2 == (char*) 0)
op2 = bv_constant(*(registers + rs2));
*(reg_sym + rd) = (uint64_t) smt_binary(operator, op1, op2);
// checking for division by zero
if (string_compare(operator, "bvudiv"))
w = w
+ dprintf(output_fd, "(push 1)\n")
+ dprintf(output_fd, "(assert (and %s %s)); check if a division by zero is possible", path_condition, smt_binary("=", op2, bv_constant(0)))
+ dprintf(output_fd, "\n(check-sat)\n(get-model)\n(pop 1)\n");
}
}
void zero_extend_sltu() {
if (rd != REG_ZR)
if (*(reg_sym + rd))
*(reg_sym + rd) = (uint64_t) smt_unary(bv_zero_extension(1), (char*) *(reg_sym + rd));
}
void constrain_load() {
uint64_t vaddr;
uint64_t* sword;
uint64_t a;
// load double word
if (*(reg_sym + rs1)) {
use_stdout();
// symbolic memory addresses not yet supported
printf("%s: symbolic memory address in load instruction at 0x%lX", selfie_name, pc);
print_code_line_number_for_instruction(pc, code_start);
printf("\n");
exit(EXITCODE_SYMBOLICEXECUTIONERROR);
}
read_register(rs1);
vaddr = *(registers + rs1) + imm;
if (is_virtual_address_valid(vaddr, WORDSIZE)) {
if (is_valid_segment_read(vaddr)) {
if (is_virtual_address_mapped(pt, vaddr)) {
// semantics of load double word
if (rd != REG_ZR) {
sword = load_symbolic_memory(vaddr);
if (sword) {
*(registers + rd) = get_word_value(sword);
if (get_number_of_bits(sword) < WORDSIZEINBITS)
*(reg_sym + rd) = (uint64_t) smt_unary(bv_zero_extension(get_number_of_bits(sword)), get_word_symbolic(sword));
else
*(reg_sym + rd) = (uint64_t) get_word_symbolic(sword);
} else {
*(registers + rd) = load_virtual_memory(pt, vaddr);
*(reg_sym + rd) = 0;
}
}
write_register(rd);
// keep track of instruction address for profiling loads
a = (pc - code_start) / INSTRUCTIONSIZE;
pc = pc + INSTRUCTIONSIZE;
// keep track of number of loads in total
ic_load = ic_load + 1;
// and individually
*(loads_per_instruction + a) = *(loads_per_instruction + a) + 1;
} else
throw_exception(EXCEPTION_PAGEFAULT, page_of_virtual_address(vaddr));
} else
throw_exception(EXCEPTION_SEGMENTATIONFAULT, vaddr);
} else
// invalid concrete memory address
throw_exception(EXCEPTION_INVALIDADDRESS, vaddr);
}
void constrain_store() {
uint64_t vaddr;
uint64_t a;
// store double word
if (*(reg_sym + rs1)) {
use_stdout();
// symbolic memory addresses not yet supported
printf("%s: symbolic memory address in sd instruction at 0x%lX", selfie_name, pc);
print_code_line_number_for_instruction(pc, code_start);
printf("\n");
exit(EXITCODE_SYMBOLICEXECUTIONERROR);
}
read_register(rs1);
vaddr = *(registers + rs1) + imm;
if (is_virtual_address_valid(vaddr, WORDSIZE)) {
if (is_valid_segment_write(vaddr)) {
if (is_virtual_address_mapped(pt, vaddr)) {
// semantics of store double word
store_symbolic_memory(vaddr,
*(registers + rs2),
(char*) *(reg_sym + rs2),
0,
WORDSIZEINBITS);
// keep track of instruction address for profiling stores
a = (pc - code_start) / INSTRUCTIONSIZE;
pc = pc + INSTRUCTIONSIZE;
// keep track of number of stores in total
ic_store = ic_store + 1;
// and individually
*(stores_per_instruction + a) = *(stores_per_instruction + a) + 1;
} else
throw_exception(EXCEPTION_PAGEFAULT, page_of_virtual_address(vaddr));
} else
throw_exception(EXCEPTION_SEGMENTATIONFAULT, vaddr);
} else
// invalid concrete memory address
throw_exception(EXCEPTION_INVALIDADDRESS, vaddr);
}
void constrain_beq() {
char* op1;
char* op2;
char* bvar;
char* pvar;
op1 = (char*) *(reg_sym + rs1);
op2 = (char*) *(reg_sym + rs2);
if (op1 == (char*) 0) {
if (op2 == (char*) 0) {
do_beq();
return;
} else
op1 = bv_constant(*(registers + rs1));
} else if (op2 == (char*) 0)
op2 = bv_constant(*(registers + rs2));
bvar = smt_variable("b", 1);
w = w
+ dprintf(output_fd, "(assert (= %s %s)); beq in ", bvar, smt_binary("bvcomp", op1, op2))
+ print_code_context_for_instruction(pc)
+ dprintf(output_fd, "\n");
pvar = smt_variable("p", 1);
w = w
+ dprintf(output_fd, "(assert (= %s %s)); path condition in ", pvar, path_condition)
+ print_code_context_for_instruction(pc)
+ dprintf(output_fd, "\n");
// increase the number of executed symbolic beq instructions
set_beq_counter(current_context, get_beq_counter(current_context) + 1);
if (get_beq_counter(current_context) < beq_limit) {
// save symbolic memory so that it is copied correctly afterwards
set_symbolic_memory(current_context, symbolic_memory);
// the copied context is executed later and takes the other path
copy_symbolic_context(current_context, pc + imm, smt_binary("and", pvar, bvar));
path_condition = smt_binary("and", pvar, smt_unary("not", bvar));
pc = pc + INSTRUCTIONSIZE;
}
}
void constrain_jalr() {
if (*(reg_sym + rs1)) {
use_stdout();
// symbolic memory addresses not yet supported
printf("%s: symbolic memory address in jalr instruction at 0x%lX", selfie_name, pc);
print_code_line_number_for_instruction(pc, code_start);
printf("\n");
exit(EXITCODE_SYMBOLICEXECUTIONERROR);
}
}
// -----------------------------------------------------------------
// -------------------------- INTERPRETER --------------------------
// -----------------------------------------------------------------
void execute_symbolically() {
// assert: 1 <= is <= number of RISC-U instructions
if (is == ADDI) {
constrain_addi();
do_addi();
} else if (is == LOAD)
constrain_load();
else if (is == STORE)
constrain_store();
else if (is == ADD) {
constrain_add_sub_mul_divu_remu_sltu("bvadd");
do_add();
} else if (is == SUB) {
constrain_add_sub_mul_divu_remu_sltu("bvsub");
do_sub();
} else if (is == MUL) {
constrain_add_sub_mul_divu_remu_sltu("bvmul");
do_mul();
} else if (is == DIVU) {
constrain_add_sub_mul_divu_remu_sltu("bvudiv");
do_divu();
} else if (is == REMU) {
constrain_add_sub_mul_divu_remu_sltu("bvurem");
do_remu();
} else if (is == SLTU) {
constrain_add_sub_mul_divu_remu_sltu("bvult");
zero_extend_sltu();
do_sltu();
} else if (is == BEQ)
constrain_beq();
else if (is == JAL) {
// the JAL instruction is a procedure call, if rd is REG_RA
if (rd == REG_RA)
// push the procedure at pc + imm onto the callstack of the current context
step_into_call(current_context, pc + imm);
do_jal();
} else if (is == JALR) {
// pop off call stack, when we return from a procedure
if (rd == REG_ZR)
if (rs1 == REG_RA)
if (imm == 0)
step_out_of_call(current_context);
constrain_jalr();
do_jalr();
} else if (is == LUI) {
constrain_lui();
do_lui();
} else if (is == ECALL)
do_ecall();
}
void run_symbolically_until_exception() {
trap = 0;
while (trap == 0) {
fetch();
decode();
execute_symbolically();
interrupt();
}
trap = 0;
}
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ---------------------- R U N T I M E ----------------------
// -----------------------------------------------------------------
// *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~ *~*~
// -----------------------------------------------------------------
// ---------------------------- CONTEXTS ---------------------------
// -----------------------------------------------------------------
uint64_t* new_symbolic_context() {
// insert new symbolic context at top of free-list of contexts
free_context(allocate_symbolic_context());