diff options
| -rw-r--r-- | miasm/expression/simplifications.py | 2 | ||||
| -rw-r--r-- | miasm/expression/simplifications_common.py | 32 | ||||
| -rw-r--r-- | test/expression/simplifications.py | 5 |
3 files changed, 37 insertions, 2 deletions
diff --git a/miasm/expression/simplifications.py b/miasm/expression/simplifications.py index 585a9c6b..8f63ab91 100644 --- a/miasm/expression/simplifications.py +++ b/miasm/expression/simplifications.py @@ -58,7 +58,7 @@ class ExpressionSimplifier(object): simplifications_common.simp_test_signext_inf, simplifications_common.simp_test_zeroext_inf, simplifications_common.simp_cond_inf_eq_unsigned_zero, - + simplifications_common.simp_compose_and_mask, ], m2_expr.ExprSlice: [ diff --git a/miasm/expression/simplifications_common.py b/miasm/expression/simplifications_common.py index cda9c5e2..69d56997 100644 --- a/miasm/expression/simplifications_common.py +++ b/miasm/expression/simplifications_common.py @@ -607,7 +607,6 @@ def simp_compose(e_s, expr): return ExprCond(cond, arg1, arg2) return ExprCompose(*args) - def simp_cond(_, expr): """ Common simplifications on ExprCond. @@ -1554,3 +1553,34 @@ def simp_add_multiple(_, expr): if len(out) == 1: return out[0] return ExprOp('+', *out) + +def simp_compose_and_mask(_, expr): + """ + {X 0 8, Y 8 32} & 0xFF => zeroExt(X) + {X 0 8, Y 8 16, Z 16 32} & 0xFFFF => {X 0 8, Y 8 16, 0x0 16 32} + {X 0 8, 0x123456 8 32} & 0xFFFFFF => {X 0 8, 0x1234 8 24, 0x0 24 32} + """ + if not expr.is_op('&'): + return expr + # handle the case where arg2 = arg1.mask + if len(expr.args) != 2: + return expr + arg1, arg2 = expr.args + if not arg1.is_compose(): + return expr + if not arg2.is_int(): + return expr + int2 = int(arg2) + if (int2 + 1) & int2 != 0: + return expr + mask_size = int2.bit_length() + 7 // 8 + out = [] + for offset, arg in arg1.iter_args(): + if offset == mask_size: + return ExprCompose(*out).zeroExtend(expr.size) + elif mask_size > offset and mask_size < offset+arg.size and arg.is_int(): + out.append(ExprSlice(arg, 0, mask_size-offset)) + return ExprCompose(*out).zeroExtend(expr.size) + else: + out.append(arg) + return expr diff --git a/test/expression/simplifications.py b/test/expression/simplifications.py index 1a22c43d..e0b666da 100644 --- a/test/expression/simplifications.py +++ b/test/expression/simplifications.py @@ -192,6 +192,11 @@ to_test = [(ExprInt(1, 32) - ExprInt(1, 32), ExprInt(0, 32)), ExprOp('&', a, ExprInt(0x0FFFFFFF, 32))), (ExprOp('<<', ExprOp('>>', a, ExprInt(0x4, 32)), ExprInt(0x4, 32)), ExprOp('&', a, ExprInt(0xFFFFFFF0, 32))), + + (ExprCompose(ExprId("a", 8), ExprId("b", 24)) & ExprInt(0xFF, 32), ExprCompose(ExprId("a", 8), ExprInt(0x0, 24))), + (ExprCompose(ExprId("a", 8), ExprInt(0x12, 8), ExprId("b", 16)) & ExprInt(0xFFFF, 32), ExprCompose(ExprId("a", 8), ExprInt(0x12, 24))), + (ExprCompose(ExprId("a", 8), ExprInt(0x1234, 16), ExprId("b", 8)) & ExprInt(0xFFFF, 32), ExprCompose(ExprId("a", 8), ExprInt(0x34, 24))), + (a[:32], a), (a[:8][:8], a[:8]), (a[:16][:8], a[:8]), |