From 300fceac6eca99fd858678b03a47357e72856e10 Mon Sep 17 00:00:00 2001 From: LemonBoy Date: Tue, 10 Mar 2020 20:54:05 +0100 Subject: [PATCH] ir: Implement more safety checks for shl/shr The checks are now valid on types whose size is not a power of two. Closes #2096 --- src/all_types.hpp | 1 + src/codegen.cpp | 32 +++++++++++++++++++++++++++ src/ir.cpp | 48 ++++++++++++++++++++--------------------- test/compile_errors.zig | 35 ++++++++++++++++++++++++++++-- test/runtime_safety.zig | 31 ++++++++++++++++++++++++++ 5 files changed, 120 insertions(+), 27 deletions(-) diff --git a/src/all_types.hpp b/src/all_types.hpp index 14b99228ca..53aae9e236 100644 --- a/src/all_types.hpp +++ b/src/all_types.hpp @@ -1834,6 +1834,7 @@ enum PanicMsgId { PanicMsgIdBadNoAsyncCall, PanicMsgIdResumeNotSuspendedFn, PanicMsgIdBadSentinel, + PanicMsgIdShxTooBigRhs, PanicMsgIdCount, }; diff --git a/src/codegen.cpp b/src/codegen.cpp index 22cb975205..d659e27d86 100644 --- a/src/codegen.cpp +++ b/src/codegen.cpp @@ -974,6 +974,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) { return buf_create_from_str("resumed a non-suspended function"); case PanicMsgIdBadSentinel: return buf_create_from_str("sentinel mismatch"); + case PanicMsgIdShxTooBigRhs: + return buf_create_from_str("shift amount is greater than the type size"); } zig_unreachable(); } @@ -2841,6 +2843,26 @@ static LLVMValueRef gen_rem(CodeGen *g, bool want_runtime_safety, bool want_fast } +static void gen_shift_rhs_check(CodeGen *g, ZigType *lhs_type, ZigType *rhs_type, LLVMValueRef value) { + // We only check if the rhs value of the shift expression is greater or + // equal to the number of bits of the lhs if it's not a power of two, + // otherwise the check is useful as the allowed values are limited by the + // operand type itself + if (!is_power_of_2(lhs_type->data.integral.bit_count)) { + LLVMValueRef bit_count_value = LLVMConstInt(get_llvm_type(g, rhs_type), + lhs_type->data.integral.bit_count, false); + LLVMValueRef less_than_bit = LLVMBuildICmp(g->builder, LLVMIntULT, value, bit_count_value, ""); + LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckFail"); + LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckOk"); + LLVMBuildCondBr(g->builder, less_than_bit, ok_block, fail_block); + + LLVMPositionBuilderAtEnd(g->builder, fail_block); + gen_safety_crash(g, PanicMsgIdShxTooBigRhs); + + LLVMPositionBuilderAtEnd(g->builder, ok_block); + } +} + static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable, IrInstGenBinOp *bin_op_instruction) { @@ -2949,6 +2971,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable, { assert(scalar_type->id == ZigTypeIdInt); LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value); + + if (want_runtime_safety) { + gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value); + } + bool is_sloppy = (op_id == IrBinOpBitShiftLeftLossy); if (is_sloppy) { return LLVMBuildShl(g->builder, op1_value, op2_casted, ""); @@ -2965,6 +2992,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable, { assert(scalar_type->id == ZigTypeIdInt); LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value); + + if (want_runtime_safety) { + gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value); + } + bool is_sloppy = (op_id == IrBinOpBitShiftRightLossy); if (is_sloppy) { if (scalar_type->data.integral.is_signed) { diff --git a/src/ir.cpp b/src/ir.cpp index e5b28f84c2..b9b42141bc 100644 --- a/src/ir.cpp +++ b/src/ir.cpp @@ -16648,36 +16648,34 @@ static IrInstGen *ir_analyze_bit_shift(IrAnalyze *ira, IrInstSrcBinOp *bin_op_in return ira->codegen->invalid_inst_gen; } } else { + assert(op1->value->type->data.integral.bit_count > 0); ZigType *shift_amt_type = get_smallest_unsigned_int_type(ira->codegen, - op1->value->type->data.integral.bit_count - 1); - if (bin_op_instruction->op_id == IrBinOpBitShiftLeftLossy && - op2->value->type->id == ZigTypeIdComptimeInt) { - - ZigValue *op2_val = ir_resolve_const(ira, op2, UndefBad); - if (op2_val == nullptr) - return ira->codegen->invalid_inst_gen; - if (!bigint_fits_in_bits(&op2_val->data.x_bigint, - shift_amt_type->data.integral.bit_count, - op2_val->data.x_bigint.is_negative)) { - Buf *val_buf = buf_alloc(); - bigint_append_buf(val_buf, &op2_val->data.x_bigint, 10); - ErrorMsg* msg = ir_add_error(ira, - &bin_op_instruction->base.base, - buf_sprintf("RHS of shift is too large for LHS type")); - add_error_note( - ira->codegen, - msg, - op2->base.source_node, - buf_sprintf("value %s cannot fit into type %s", - buf_ptr(val_buf), - buf_ptr(&shift_amt_type->name))); - return ira->codegen->invalid_inst_gen; - } - } + op1->value->type->data.integral.bit_count - 1); casted_op2 = ir_implicit_cast(ira, op2, shift_amt_type); if (type_is_invalid(casted_op2->value->type)) return ira->codegen->invalid_inst_gen; + + if (instr_is_comptime(casted_op2)) { + ZigValue *op2_val = ir_resolve_const(ira, casted_op2, UndefBad); + if (op2_val == nullptr) + return ira->codegen->invalid_inst_gen; + + BigInt bit_count_value = {0}; + bigint_init_unsigned(&bit_count_value, op1->value->type->data.integral.bit_count); + + if (bigint_cmp(&op2_val->data.x_bigint, &bit_count_value) != CmpLT) { + ErrorMsg* msg = ir_add_error(ira, + &bin_op_instruction->base.base, + buf_sprintf("RHS of shift is too large for LHS type")); + add_error_note(ira->codegen, msg, op1->base.source_node, + buf_sprintf("type %s has only %u bits", + buf_ptr(&op1->value->type->name), + op1->value->type->data.integral.bit_count)); + + return ira->codegen->invalid_inst_gen; + } + } } if (instr_is_comptime(op1) && instr_is_comptime(casted_op2)) { diff --git a/test/compile_errors.zig b/test/compile_errors.zig index a2d4e8ac23..5078453332 100644 --- a/test/compile_errors.zig +++ b/test/compile_errors.zig @@ -2,6 +2,38 @@ const tests = @import("tests.zig"); const std = @import("std"); pub fn addCases(cases: *tests.CompileErrorContext) void { + cases.addTest("shift on type with non-power-of-two size", + \\export fn entry() void { + \\ const S = struct { + \\ fn a() void { + \\ var x: u24 = 42; + \\ _ = x >> 24; + \\ } + \\ fn b() void { + \\ var x: u24 = 42; + \\ _ = x << 24; + \\ } + \\ fn c() void { + \\ var x: u24 = 42; + \\ _ = @shlExact(x, 24); + \\ } + \\ fn d() void { + \\ var x: u24 = 42; + \\ _ = @shrExact(x, 24); + \\ } + \\ }; + \\ S.a(); + \\ S.b(); + \\ S.c(); + \\ S.d(); + \\} + , &[_][]const u8{ + "tmp.zig:5:19: error: RHS of shift is too large for LHS type", + "tmp.zig:9:19: error: RHS of shift is too large for LHS type", + "tmp.zig:13:17: error: RHS of shift is too large for LHS type", + "tmp.zig:17:17: error: RHS of shift is too large for LHS type", + }); + cases.addTest("combination of noasync and async", \\export fn entry() void { \\ noasync { @@ -4029,8 +4061,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void { \\} \\export fn entry() u16 { return f(); } , &[_][]const u8{ - "tmp.zig:3:14: error: RHS of shift is too large for LHS type", - "tmp.zig:3:17: note: value 8 cannot fit into type u3", + "tmp.zig:3:17: error: integer value 8 cannot be coerced to type 'u3'", }); cases.add("missing function call param", diff --git a/test/runtime_safety.zig b/test/runtime_safety.zig index e183c6979f..9855aae16b 100644 --- a/test/runtime_safety.zig +++ b/test/runtime_safety.zig @@ -1,6 +1,37 @@ const tests = @import("tests.zig"); pub fn addCases(cases: *tests.CompareOutputContext) void { + cases.addRuntimeSafety("shift left by huge amount", + \\const std = @import("std"); + \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn { + \\ std.debug.warn("{}\n", .{message}); + \\ if (std.mem.eql(u8, message, "shift amount is greater than the type size")) { + \\ std.process.exit(126); // good + \\ } + \\ std.process.exit(0); // test failed + \\} + \\pub fn main() void { + \\ var x: u24 = 42; + \\ var y: u5 = 24; + \\ var z = x >> y; + \\} + ); + + cases.addRuntimeSafety("shift right by huge amount", + \\const std = @import("std"); + \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn { + \\ if (std.mem.eql(u8, message, "shift amount is greater than the type size")) { + \\ std.process.exit(126); // good + \\ } + \\ std.process.exit(0); // test failed + \\} + \\pub fn main() void { + \\ var x: u24 = 42; + \\ var y: u5 = 24; + \\ var z = x << y; + \\} + ); + cases.addRuntimeSafety("slice sentinel mismatch - optional pointers", \\const std = @import("std"); \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {