authorgravatar for thatlemon@gmail.comLemonBoy <thatlemon@gmail.com> 2020-03-10 20:54:05+01:00
committergravatar for thatlemon@gmail.comLemonBoy <thatlemon@gmail.com> 2020-03-10 20:54:05+01:00
log300fceac6eca99fd858678b03a47357e72856e10
treee0a165d8ce2bdb1b394acf16e8b1a465ab84f9a8
parent9c4dc7b1bb79b2e1cf5a88d99b9e187640426769

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

5 files changed, 115 insertions(+), 22 deletions(-)

src/all_types.hpp+1
...@@ -1834,6 +1834,7 @@ enum PanicMsgId {...@@ -1834,6 +1834,7 @@ enum PanicMsgId {
1834 PanicMsgIdBadNoAsyncCall,1834 PanicMsgIdBadNoAsyncCall,
1835 PanicMsgIdResumeNotSuspendedFn,1835 PanicMsgIdResumeNotSuspendedFn,
1836 PanicMsgIdBadSentinel,1836 PanicMsgIdBadSentinel,
1837 PanicMsgIdShxTooBigRhs,
18371838
1838 PanicMsgIdCount,1839 PanicMsgIdCount,
1839};1840};
src/codegen.cpp+32
...@@ -974,6 +974,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {...@@ -974,6 +974,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
974 return buf_create_from_str("resumed a non-suspended function");974 return buf_create_from_str("resumed a non-suspended function");
975 case PanicMsgIdBadSentinel:975 case PanicMsgIdBadSentinel:
976 return buf_create_from_str("sentinel mismatch");976 return buf_create_from_str("sentinel mismatch");
977 case PanicMsgIdShxTooBigRhs:
978 return buf_create_from_str("shift amount is greater than the type size");
977 }979 }
978 zig_unreachable();980 zig_unreachable();
979}981}
...@@ -2841,6 +2843,26 @@ static LLVMValueRef gen_rem(CodeGen *g, bool want_runtime_safety, bool want_fast...@@ -2841,6 +2843,26 @@ static LLVMValueRef gen_rem(CodeGen *g, bool want_runtime_safety, bool want_fast
28412843
2842}2844}
28432845
2846static void gen_shift_rhs_check(CodeGen *g, ZigType *lhs_type, ZigType *rhs_type, LLVMValueRef value) {
2847 // We only check if the rhs value of the shift expression is greater or
2848 // equal to the number of bits of the lhs if it's not a power of two,
2849 // otherwise the check is useful as the allowed values are limited by the
2850 // operand type itself
2851 if (!is_power_of_2(lhs_type->data.integral.bit_count)) {
2852 LLVMValueRef bit_count_value = LLVMConstInt(get_llvm_type(g, rhs_type),
2853 lhs_type->data.integral.bit_count, false);
2854 LLVMValueRef less_than_bit = LLVMBuildICmp(g->builder, LLVMIntULT, value, bit_count_value, "");
2855 LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckFail");
2856 LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "CheckOk");
2857 LLVMBuildCondBr(g->builder, less_than_bit, ok_block, fail_block);
2858
2859 LLVMPositionBuilderAtEnd(g->builder, fail_block);
2860 gen_safety_crash(g, PanicMsgIdShxTooBigRhs);
2861
2862 LLVMPositionBuilderAtEnd(g->builder, ok_block);
2863 }
2864}
2865
2844static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,2866static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
2845 IrInstGenBinOp *bin_op_instruction)2867 IrInstGenBinOp *bin_op_instruction)
2846{2868{
...@@ -2949,6 +2971,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,...@@ -2949,6 +2971,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
2949 {2971 {
2950 assert(scalar_type->id == ZigTypeIdInt);2972 assert(scalar_type->id == ZigTypeIdInt);
2951 LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);2973 LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);
2974
2975 if (want_runtime_safety) {
2976 gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value);
2977 }
2978
2952 bool is_sloppy = (op_id == IrBinOpBitShiftLeftLossy);2979 bool is_sloppy = (op_id == IrBinOpBitShiftLeftLossy);
2953 if (is_sloppy) {2980 if (is_sloppy) {
2954 return LLVMBuildShl(g->builder, op1_value, op2_casted, "");2981 return LLVMBuildShl(g->builder, op1_value, op2_casted, "");
...@@ -2965,6 +2992,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,...@@ -2965,6 +2992,11 @@ static LLVMValueRef ir_render_bin_op(CodeGen *g, IrExecutableGen *executable,
2965 {2992 {
2966 assert(scalar_type->id == ZigTypeIdInt);2993 assert(scalar_type->id == ZigTypeIdInt);
2967 LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);2994 LLVMValueRef op2_casted = gen_widen_or_shorten(g, false, op2->value->type, scalar_type, op2_value);
2995
2996 if (want_runtime_safety) {
2997 gen_shift_rhs_check(g, scalar_type, op2->value->type, op2_value);
2998 }
2999
2968 bool is_sloppy = (op_id == IrBinOpBitShiftRightLossy);3000 bool is_sloppy = (op_id == IrBinOpBitShiftRightLossy);
2969 if (is_sloppy) {3001 if (is_sloppy) {
2970 if (scalar_type->data.integral.is_signed) {3002 if (scalar_type->data.integral.is_signed) {
src/ir.cpp+18-20
...@@ -16648,36 +16648,34 @@ static IrInstGen *ir_analyze_bit_shift(IrAnalyze *ira, IrInstSrcBinOp *bin_op_in...@@ -16648,36 +16648,34 @@ static IrInstGen *ir_analyze_bit_shift(IrAnalyze *ira, IrInstSrcBinOp *bin_op_in
16648 return ira->codegen->invalid_inst_gen;16648 return ira->codegen->invalid_inst_gen;
16649 }16649 }
16650 } else {16650 } else {
16651 assert(op1->value->type->data.integral.bit_count > 0);
16651 ZigType *shift_amt_type = get_smallest_unsigned_int_type(ira->codegen,16652 ZigType *shift_amt_type = get_smallest_unsigned_int_type(ira->codegen,
16652 op1->value->type->data.integral.bit_count - 1);16653 op1->value->type->data.integral.bit_count - 1);
16653 if (bin_op_instruction->op_id == IrBinOpBitShiftLeftLossy &&
16654 op2->value->type->id == ZigTypeIdComptimeInt) {
1665516654
16656 ZigValue *op2_val = ir_resolve_const(ira, op2, UndefBad);16655 casted_op2 = ir_implicit_cast(ira, op2, shift_amt_type);
16656 if (type_is_invalid(casted_op2->value->type))
16657 return ira->codegen->invalid_inst_gen;
16658
16659 if (instr_is_comptime(casted_op2)) {
16660 ZigValue *op2_val = ir_resolve_const(ira, casted_op2, UndefBad);
16657 if (op2_val == nullptr)16661 if (op2_val == nullptr)
16658 return ira->codegen->invalid_inst_gen;16662 return ira->codegen->invalid_inst_gen;
16659 if (!bigint_fits_in_bits(&op2_val->data.x_bigint,16663
16660 shift_amt_type->data.integral.bit_count,16664 BigInt bit_count_value = {0};
16661 op2_val->data.x_bigint.is_negative)) {16665 bigint_init_unsigned(&bit_count_value, op1->value->type->data.integral.bit_count);
16662 Buf *val_buf = buf_alloc();16666
16663 bigint_append_buf(val_buf, &op2_val->data.x_bigint, 10);16667 if (bigint_cmp(&op2_val->data.x_bigint, &bit_count_value) != CmpLT) {
16664 ErrorMsg* msg = ir_add_error(ira,16668 ErrorMsg* msg = ir_add_error(ira,
16665 &bin_op_instruction->base.base,16669 &bin_op_instruction->base.base,
16666 buf_sprintf("RHS of shift is too large for LHS type"));16670 buf_sprintf("RHS of shift is too large for LHS type"));
16667 add_error_note(16671 add_error_note(ira->codegen, msg, op1->base.source_node,
16668 ira->codegen,16672 buf_sprintf("type %s has only %u bits",
16669 msg,16673 buf_ptr(&op1->value->type->name),
16670 op2->base.source_node,16674 op1->value->type->data.integral.bit_count));
16671 buf_sprintf("value %s cannot fit into type %s",16675
16672 buf_ptr(val_buf),
16673 buf_ptr(&shift_amt_type->name)));
16674 return ira->codegen->invalid_inst_gen;16676 return ira->codegen->invalid_inst_gen;
16675 }16677 }
16676 }16678 }
16677
16678 casted_op2 = ir_implicit_cast(ira, op2, shift_amt_type);
16679 if (type_is_invalid(casted_op2->value->type))
16680 return ira->codegen->invalid_inst_gen;
16681 }16679 }
1668216680
16683 if (instr_is_comptime(op1) && instr_is_comptime(casted_op2)) {16681 if (instr_is_comptime(op1) && instr_is_comptime(casted_op2)) {
test/compile_errors.zig+33-2
...@@ -2,6 +2,38 @@ const tests = @import("tests.zig");...@@ -2,6 +2,38 @@ const tests = @import("tests.zig");
2const std = @import("std");2const std = @import("std");
33
4pub fn addCases(cases: *tests.CompileErrorContext) void {4pub fn addCases(cases: *tests.CompileErrorContext) void {
5 cases.addTest("shift on type with non-power-of-two size",
6 \\export fn entry() void {
7 \\ const S = struct {
8 \\ fn a() void {
9 \\ var x: u24 = 42;
10 \\ _ = x >> 24;
11 \\ }
12 \\ fn b() void {
13 \\ var x: u24 = 42;
14 \\ _ = x << 24;
15 \\ }
16 \\ fn c() void {
17 \\ var x: u24 = 42;
18 \\ _ = @shlExact(x, 24);
19 \\ }
20 \\ fn d() void {
21 \\ var x: u24 = 42;
22 \\ _ = @shrExact(x, 24);
23 \\ }
24 \\ };
25 \\ S.a();
26 \\ S.b();
27 \\ S.c();
28 \\ S.d();
29 \\}
30 , &[_][]const u8{
31 "tmp.zig:5:19: error: RHS of shift is too large for LHS type",
32 "tmp.zig:9:19: error: RHS of shift is too large for LHS type",
33 "tmp.zig:13:17: error: RHS of shift is too large for LHS type",
34 "tmp.zig:17:17: error: RHS of shift is too large for LHS type",
35 });
36
5 cases.addTest("combination of noasync and async",37 cases.addTest("combination of noasync and async",
6 \\export fn entry() void {38 \\export fn entry() void {
7 \\ noasync {39 \\ noasync {
...@@ -4029,8 +4061,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {...@@ -4029,8 +4061,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
4029 \\}4061 \\}
4030 \\export fn entry() u16 { return f(); }4062 \\export fn entry() u16 { return f(); }
4031 , &[_][]const u8{4063 , &[_][]const u8{
4032 "tmp.zig:3:14: error: RHS of shift is too large for LHS type",4064 "tmp.zig:3:17: error: integer value 8 cannot be coerced to type 'u3'",
4033 "tmp.zig:3:17: note: value 8 cannot fit into type u3",
4034 });4065 });
40354066
4036 cases.add("missing function call param",4067 cases.add("missing function call param",
test/runtime_safety.zig+31
...@@ -1,6 +1,37 @@...@@ -1,6 +1,37 @@
1const tests = @import("tests.zig");1const tests = @import("tests.zig");
22
3pub fn addCases(cases: *tests.CompareOutputContext) void {3pub fn addCases(cases: *tests.CompareOutputContext) void {
4 cases.addRuntimeSafety("shift left by huge amount",
5 \\const std = @import("std");
6 \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
7 \\ std.debug.warn("{}\n", .{message});
8 \\ if (std.mem.eql(u8, message, "shift amount is greater than the type size")) {
9 \\ std.process.exit(126); // good
10 \\ }
11 \\ std.process.exit(0); // test failed
12 \\}
13 \\pub fn main() void {
14 \\ var x: u24 = 42;
15 \\ var y: u5 = 24;
16 \\ var z = x >> y;
17 \\}
18 );
19
20 cases.addRuntimeSafety("shift right by huge amount",
21 \\const std = @import("std");
22 \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
23 \\ if (std.mem.eql(u8, message, "shift amount is greater than the type size")) {
24 \\ std.process.exit(126); // good
25 \\ }
26 \\ std.process.exit(0); // test failed
27 \\}
28 \\pub fn main() void {
29 \\ var x: u24 = 42;
30 \\ var y: u5 = 24;
31 \\ var z = x << y;
32 \\}
33 );
34
4 cases.addRuntimeSafety("slice sentinel mismatch - optional pointers",35 cases.addRuntimeSafety("slice sentinel mismatch - optional pointers",
5 \\const std = @import("std");36 \\const std = @import("std");
6 \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {37 \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {