From 7a9fab6984f7bce3fd52809ecf6e21b79f115be3 Mon Sep 17 00:00:00 2001 From: Luc Van Oostenryck Date: Fri, 9 Apr 2021 00:07:40 +0200 Subject: scheck: add a symbolic checker Some instruction simplifications can be quite tricky and thus easy to get wrong. Often, they also are hard to test (for example, you can test it with a few input values but of course not all combinations). I'm used to validate some of these with an independent tool (Alive cfr. [1], [2]) which is quite neat but has some issues: 1) This tool doesn't work with Sparse's IR or C source but it needs to have the tests written in its own language (very close to LLVM's IR). So it can be used to test if the logic of a simplification but not if implemented correctly. 2) This tool isn't maintained anymore (has some bugs too) and it's successor (Alive2 [3]) is not quite as handy to me (I miss the pre-conditions a lot). So, this patch implement the same idea but fully integrated with Sparse. This mean that you can write a test in C, let Sparse process and simplify it and then directly validate it and not only for a few values but symbolically, for all possible values. Note: Of course, this is not totally stand-alone and depends on an external library for the solver (Boolector, see [4], [5]). Note: Currently, it's just a proof of concept and, except the included tests, it's only very slightly tested (and untested with anything more complex than a few instructions). [1] https://blog.regehr.org/archives/1170 [2] https://www.cs.utah.edu/~regehr/papers/pldi15.pdf [3] https://blog.regehr.org/archives/1722 [4] https://boolector.github.io/ [5] https://boolector.github.io/papers/BrummayerBiere-TACAS09.pdf Signed-off-by: Luc Van Oostenryck --- .gitignore | 1 + Makefile | 7 ++ ident-list.h | 3 + scheck.c | 315 +++++++++++++++++++++++++++++++++++++++++++++++++ validation/scheck/ko.c | 10 ++ validation/scheck/ok.c | 14 +++ validation/test-suite | 6 + 7 files changed, 356 insertions(+) create mode 100644 scheck.c create mode 100644 validation/scheck/ko.c create mode 100644 validation/scheck/ok.c diff --git a/.gitignore b/.gitignore index 6a28fa50..b22f86b1 100644 --- a/.gitignore +++ b/.gitignore @@ -17,6 +17,7 @@ /example /graph /obfuscate +/scheck /semind /sparse /sparse-llvm diff --git a/Makefile b/Makefile index f9883da1..a0178a65 100644 --- a/Makefile +++ b/Makefile @@ -227,6 +227,13 @@ else $(warning Your system does not have llvm, disabling sparse-llvm) endif +ifeq ($(HAVE_BOOLECTOR),yes) +PROGRAMS += scheck +scheck-cflags := -I${BOOLECTORDIR}/include/boolector +scheck-ldflags := -L${BOOLECTORDIR}/lib +scheck-ldlibs := -lboolector -llgl -lbtor2parser +endif + ######################################################################## LIBS := libsparse.a OBJS := $(LIB_OBJS) $(EXTRA_OBJS) $(PROGRAMS:%=%.o) diff --git a/ident-list.h b/ident-list.h index 8049b694..918f54d7 100644 --- a/ident-list.h +++ b/ident-list.h @@ -78,6 +78,9 @@ IDENT(memset); IDENT(memcpy); IDENT(copy_to_user); IDENT(copy_from_user); IDENT(main); +/* used by the symbolic checker */ +IDENT(__assert); + #undef __IDENT #undef IDENT #undef IDENT_RESERVED diff --git a/scheck.c b/scheck.c new file mode 100644 index 00000000..63cbfa2d --- /dev/null +++ b/scheck.c @@ -0,0 +1,315 @@ +// SPDX-License-Identifier: MIT +// Copyright (C) 2021 Luc Van Oostenryck + +/// +// Symbolic checker for Sparse's IR +// -------------------------------- +// +// This is an example client program with a dual purpose: +// # It shows how to translate Sparse's IR into the language +// of SMT solvers (only the part concerning integers, +// floating-point and memory is ignored). +// # It's used as a simple symbolic checker for the IR. +// The idea is to create a mini-language that allows to +// express some assertions with some pre-conditions. + +#include +#include +#include +#include +#include +#include +#include + +#include +#include "lib.h" +#include "expression.h" +#include "linearize.h" +#include "symbol.h" +#include "builtin.h" + + +#define dyntype incomplete_ctype +static const struct builtin_fn builtins_scheck[] = { + { "__assert", &void_ctype, 0, { &bool_ctype }, .op = &generic_int_op }, + {} +}; + + +static BoolectorSort get_sort(Btor *btor, struct symbol *type, struct position pos) +{ + if (!is_int_type(type)) { + sparse_error(pos, "invalid type"); + return NULL; + } + return boolector_bitvec_sort(btor, type->bit_size); +} + +static BoolectorNode *mkvar(Btor *btor, BoolectorSort s, pseudo_t pseudo) +{ + static char buff[33]; + BoolectorNode *n; + + if (pseudo->priv) + return pseudo->priv; + + switch (pseudo->type) { + case PSEUDO_VAL: + sprintf(buff, "%llx", pseudo->value); + return boolector_consth(btor, s, buff); + case PSEUDO_ARG: + case PSEUDO_REG: + n = boolector_var(btor, s, show_pseudo(pseudo)); + break; + default: + fprintf(stderr, "invalid pseudo: %s\n", show_pseudo(pseudo)); + return NULL; + } + return pseudo->priv = n; +} + +static BoolectorNode *get_arg(Btor *btor, struct instruction *insn, int idx) +{ + pseudo_t arg = ptr_list_nth(insn->arguments, idx); + struct symbol *type = ptr_list_nth(insn->fntypes, idx + 1); + BoolectorSort s = get_sort(btor, type, insn->pos); + + return mkvar(btor, s, arg); +} + +static BoolectorNode *zext(Btor *btor, struct instruction *insn, BoolectorNode *s) +{ + int old = boolector_get_width(btor, s); + int new = insn->type->bit_size; + return boolector_uext(btor, s, new - old); +} + +static BoolectorNode *sext(Btor *btor, struct instruction *insn, BoolectorNode *s) +{ + int old = boolector_get_width(btor, s); + int new = insn->type->bit_size; + return boolector_sext(btor, s, new - old); +} + +static BoolectorNode *slice(Btor *btor, struct instruction *insn, BoolectorNode *s) +{ + int old = boolector_get_width(btor, s); + int new = insn->type->bit_size; + return boolector_slice(btor, s, old - new - 1, 0); +} + +static void binary(Btor *btor, BoolectorSort s, struct instruction *insn) +{ + BoolectorNode *t, *a, *b; + + a = mkvar(btor, s, insn->src1); + b = mkvar(btor, s, insn->src2); + if (!a || !b) + return; + switch (insn->opcode) { + case OP_ADD: t = boolector_add(btor, a, b); break; + case OP_SUB: t = boolector_sub(btor, a, b); break; + case OP_MUL: t = boolector_mul(btor, a, b); break; + case OP_AND: t = boolector_and(btor, a, b); break; + case OP_OR: t = boolector_or (btor, a, b); break; + case OP_XOR: t = boolector_xor(btor, a, b); break; + case OP_SHL: t = boolector_sll(btor, a, b); break; + case OP_LSR: t = boolector_srl(btor, a, b); break; + case OP_ASR: t = boolector_sra(btor, a, b); break; + case OP_DIVS: t = boolector_sdiv(btor, a, b); break; + case OP_DIVU: t = boolector_udiv(btor, a, b); break; + case OP_MODS: t = boolector_srem(btor, a, b); break; + case OP_MODU: t = boolector_urem(btor, a, b); break; + case OP_SET_EQ: t = zext(btor, insn, boolector_eq(btor, a, b)); break; + case OP_SET_NE: t = zext(btor, insn, boolector_ne(btor, a, b)); break; + case OP_SET_LT: t = zext(btor, insn, boolector_slt(btor, a, b)); break; + case OP_SET_LE: t = zext(btor, insn, boolector_slte(btor, a, b)); break; + case OP_SET_GE: t = zext(btor, insn, boolector_sgte(btor, a, b)); break; + case OP_SET_GT: t = zext(btor, insn, boolector_sgt(btor, a, b)); break; + case OP_SET_B: t = zext(btor, insn, boolector_ult(btor, a, b)); break; + case OP_SET_BE: t = zext(btor, insn, boolector_ulte(btor, a, b)); break; + case OP_SET_AE: t = zext(btor, insn, boolector_ugte(btor, a, b)); break; + case OP_SET_A: t = zext(btor, insn, boolector_ugt(btor, a, b)); break; + default: + fprintf(stderr, "unsupported insn\n"); + return; + } + insn->target->priv = t; +} + +static void binop(Btor *btor, struct instruction *insn) +{ + BoolectorSort s = get_sort(btor, insn->type, insn->pos); + binary(btor, s, insn); +} + +static void icmp(Btor *btor, struct instruction *insn) +{ + BoolectorSort s = get_sort(btor, insn->itype, insn->pos); + binary(btor, s, insn); +} + +static void unop(Btor *btor, struct instruction *insn) +{ + BoolectorSort s = get_sort(btor, insn->type, insn->pos); + BoolectorNode *t, *a; + + a = mkvar(btor, s, insn->src1); + if (!a) + return; + switch (insn->opcode) { + case OP_NEG: t = boolector_neg(btor, a); break; + case OP_NOT: t = boolector_not(btor, a); break; + case OP_SEXT: t = sext(btor, insn, a); break; + case OP_ZEXT: t = zext(btor, insn, a); break; + case OP_TRUNC: t = slice(btor, insn, a); break; + default: + fprintf(stderr, "unsupported insn\n"); + return; + } + insn->target->priv = t; +} + +static void ternop(Btor *btor, struct instruction *insn) +{ + BoolectorSort s = get_sort(btor, insn->type, insn->pos); + BoolectorNode *t, *a, *b, *c, *z, *d; + + a = mkvar(btor, s, insn->src1); + b = mkvar(btor, s, insn->src2); + c = mkvar(btor, s, insn->src3); + if (!a || !b || !c) + return; + switch (insn->opcode) { + case OP_SEL: + z = boolector_zero(btor, s); + d = boolector_ne(btor, a, z); + t = boolector_cond(btor, d, b, c); + break; + default: + fprintf(stderr, "unsupported insn\n"); + return; + } + insn->target->priv = t; +} + +static bool check_btor(Btor *btor, BoolectorNode *n, struct instruction *insn) +{ + char model_format[] = "btor"; + int res; + + boolector_assert(btor, boolector_not(btor, n)); + res = boolector_sat(btor); + switch (res) { + case BOOLECTOR_UNSAT: + return 1; + case BOOLECTOR_SAT: + sparse_error(insn->pos, "assertion failed"); + show_entry(insn->bb->ep); + boolector_dump_btor(btor, stdout); + boolector_print_model(btor, model_format, stdout); + break; + default: + sparse_error(insn->pos, "SMT failure"); + break; + } + return 0; +} + +static bool check_assert(Btor *btor, struct instruction *insn) +{ + BoolectorNode *a = get_arg(btor, insn, 0); + BoolectorNode *z = boolector_zero(btor, boolector_get_sort(btor, a)); + BoolectorNode *n = boolector_ne(btor, a, z); + return check_btor(btor, n, insn); +} + +static bool check_call(Btor *btor, struct instruction *insn) +{ + pseudo_t func = insn->func; + struct ident *ident = func->ident; + + if (ident == &__assert_ident) + return check_assert(btor, insn); + return 0; +} + +static bool check_function(struct entrypoint *ep) +{ + Btor *btor = boolector_new(); + struct basic_block *bb; + int rc = 0; + + boolector_set_opt(btor, BTOR_OPT_MODEL_GEN, 1); + + FOR_EACH_PTR(ep->bbs, bb) { + struct instruction *insn; + FOR_EACH_PTR(bb->insns, insn) { + if (!insn->bb) + continue; + switch (insn->opcode) { + case OP_ENTRY: + continue; + case OP_BINARY ... OP_BINARY_END: + binop(btor, insn); + break; + case OP_BINCMP ... OP_BINCMP_END: + icmp(btor, insn); + break; + case OP_UNOP ... OP_UNOP_END: + unop(btor, insn); + break; + case OP_SEL: + ternop(btor, insn); + break; + case OP_CALL: + rc = check_call(btor, insn); + goto out; + case OP_RET: + goto out; + default: + fprintf(stderr, "unsupported insn\n"); + goto out; + } + } END_FOR_EACH_PTR(insn); + } END_FOR_EACH_PTR(bb); + fprintf(stderr, "unterminated function\n"); + +out: + boolector_release_all(btor); + boolector_delete(btor); + return rc; +} + +static void check_functions(struct symbol_list *list) +{ + struct symbol *sym; + + FOR_EACH_PTR(list, sym) { + struct entrypoint *ep; + + expand_symbol(sym); + ep = linearize_symbol(sym); + if (!ep || !ep->entry) + continue; + check_function(ep); + } END_FOR_EACH_PTR(sym); +} + +int main(int argc, char **argv) +{ + struct string_list *filelist = NULL; + char *file; + + Wdecl = 0; + + sparse_initialize(argc, argv, &filelist); + + declare_builtins(0, builtins_scheck); + + // Expand, linearize and check. + FOR_EACH_PTR(filelist, file) { + check_functions(sparse(file)); + } END_FOR_EACH_PTR(file); + return 0; +} diff --git a/validation/scheck/ko.c b/validation/scheck/ko.c new file mode 100644 index 00000000..dbd861ea --- /dev/null +++ b/validation/scheck/ko.c @@ -0,0 +1,10 @@ +static void ko(int x) +{ + __assert((~x) == (~0 + x)); +} + +/* + * check-name: scheck-ko + * check-command: scheck $file + * check-known-to-fail + */ diff --git a/validation/scheck/ok.c b/validation/scheck/ok.c new file mode 100644 index 00000000..113912e0 --- /dev/null +++ b/validation/scheck/ok.c @@ -0,0 +1,14 @@ +static void ok(int x) +{ + __assert((~x) == (~0 - x)); // true but not simplified yet +} + +static void always(int x) +{ + __assert((x - x) == 0); // true and simplified +} + +/* + * check-name: scheck-ok + * check-command: scheck $file + */ diff --git a/validation/test-suite b/validation/test-suite index 1b05c75e..2f7950ef 100755 --- a/validation/test-suite +++ b/validation/test-suite @@ -13,6 +13,9 @@ prog_name=`basename $0` if [ ! -x "$default_path/sparse-llvm" ]; then disabled_cmds="sparsec sparsei sparse-llvm sparse-llvm-dis" fi +if [ ! -x "$default_path/scheck" ]; then + disabled_cmds="$disabled_cmds scheck" +fi # flags: # - some tests gave an unexpected result @@ -513,6 +516,7 @@ echo " -a append the created test to the input file" echo " -f write a test known to fail" echo " -l write a test for linearized code" echo " -p write a test for pre-processing" +echo " -s write a test for symbolic checking" echo echo "argument(s):" echo " file file containing the test case(s)" @@ -540,6 +544,8 @@ do_format() linear=1 ;; -p) def_cmd='sparse -E $file' ;; + -s) + def_cmd='scheck $file' ;; help|-*) do_format_help -- cgit 1.2.3-korg