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sentinel slicing improvements

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* add runtime safety for slicing pointers, arrays, and slices.
 * slicing without a sentinel value results in non-sentineled slice
 * improved `std.debug.panic` handling of panic-during-panic
This commit is contained in:
Andrew Kelley 2019-12-20 17:48:45 -05:00
parent 26f3c2d061
commit 8918cb06fc
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
6 changed files with 118 additions and 26 deletions
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34
lib/std/debug.zig
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@ -219,7 +219,7 @@ pub fn panic(comptime format: []const u8, args: var) noreturn {
}
/// TODO multithreaded awareness
var panicking: u8 = 0; // TODO make this a bool
var panicking: u8 = 0;
pub fn panicExtra(trace: ?*const builtin.StackTrace, first_trace_addr: ?usize, comptime format: []const u8, args: var) noreturn {
@setCold(true);
@ -230,21 +230,25 @@ pub fn panicExtra(trace: ?*const builtin.StackTrace, first_trace_addr: ?usize, c
resetSegfaultHandler();
}
if (@atomicRmw(u8, &panicking, builtin.AtomicRmwOp.Xchg, 1, builtin.AtomicOrder.SeqCst) == 1) {
// Panicked during a panic.
// TODO detect if a different thread caused the panic, because in that case
// we would want to return here instead of calling abort, so that the thread
// which first called panic can finish printing a stack trace.
os.abort();
switch (@atomicRmw(u8, &panicking, .Add, 1, .SeqCst)) {
0 => {
const stderr = getStderrStream();
stderr.print(format ++ "\n", args) catch os.abort();
if (trace) |t| {
dumpStackTrace(t.*);
}
dumpCurrentStackTrace(first_trace_addr);
},
1 => {
// TODO detect if a different thread caused the panic, because in that case
// we would want to return here instead of calling abort, so that the thread
// which first called panic can finish printing a stack trace.
warn("Panicked during a panic. Aborting.\n", .{});
},
else => {
// Panicked while printing "Panicked during a panic."
},
}
const stderr = getStderrStream();
stderr.print(format ++ "\n", args) catch os.abort();
if (trace) |t| {
dumpStackTrace(t.*);
}
dumpCurrentStackTrace(first_trace_addr);
os.abort();
}

4
lib/std/mem.zig
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@ -364,11 +364,11 @@ pub fn len(comptime T: type, ptr: [*:0]const T) usize {
}
pub fn toSliceConst(comptime T: type, ptr: [*:0]const T) [:0]const T {
return ptr[0..len(T, ptr)];
return ptr[0..len(T, ptr) :0];
}
pub fn toSlice(comptime T: type, ptr: [*:0]T) [:0]T {
return ptr[0..len(T, ptr)];
return ptr[0..len(T, ptr) :0];
}
/// Returns true if all elements in a slice are equal to the scalar value provided

1
src/all_types.hpp
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@ -1779,6 +1779,7 @@ enum PanicMsgId {
PanicMsgIdResumedFnPendingAwait,
PanicMsgIdBadNoAsyncCall,
PanicMsgIdResumeNotSuspendedFn,
PanicMsgIdBadSentinel,
PanicMsgIdCount,
};

46
src/codegen.cpp
View File

@ -941,6 +941,8 @@ static Buf *panic_msg_buf(PanicMsgId msg_id) {
return buf_create_from_str("async function called with noasync suspended");
case PanicMsgIdResumeNotSuspendedFn:
return buf_create_from_str("resumed a non-suspended function");
case PanicMsgIdBadSentinel:
return buf_create_from_str("sentinel mismatch");
}
zig_unreachable();
}
@ -1419,6 +1421,22 @@ static void add_bounds_check(CodeGen *g, LLVMValueRef target_val,
LLVMPositionBuilderAtEnd(g->builder, ok_block);
}
static void add_sentinel_check(CodeGen *g, LLVMValueRef sentinel_elem_ptr, ZigValue *sentinel) {
LLVMValueRef expected_sentinel = gen_const_val(g, sentinel, "");
LLVMValueRef actual_sentinel = gen_load_untyped(g, sentinel_elem_ptr, 0, false, "");
LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntEQ, actual_sentinel, expected_sentinel, "");
LLVMBasicBlockRef fail_block = LLVMAppendBasicBlock(g->cur_fn_val, "SentinelFail");
LLVMBasicBlockRef ok_block = LLVMAppendBasicBlock(g->cur_fn_val, "SentinelOk");
LLVMBuildCondBr(g->builder, ok_bit, ok_block, fail_block);
LLVMPositionBuilderAtEnd(g->builder, fail_block);
gen_safety_crash(g, PanicMsgIdBadSentinel);
LLVMPositionBuilderAtEnd(g->builder, ok_block);
}
static LLVMValueRef gen_assert_zero(CodeGen *g, LLVMValueRef expr_val, ZigType *int_type) {
LLVMValueRef zero = LLVMConstNull(get_llvm_type(g, int_type));
LLVMValueRef ok_bit = LLVMBuildICmp(g->builder, LLVMIntEQ, expr_val, zero, "");
@ -5244,6 +5262,9 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
bool want_runtime_safety = instruction->safety_check_on && ir_want_runtime_safety(g, &instruction->base);
ZigType *res_slice_ptr_type = instruction->base.value->type->data.structure.fields[slice_ptr_index]->type_entry;
ZigValue *sentinel = res_slice_ptr_type->data.pointer.sentinel;
if (array_type->id == ZigTypeIdArray ||
(array_type->id == ZigTypeIdPointer && array_type->data.pointer.ptr_len == PtrLenSingle))
{
@ -5265,6 +5286,15 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
LLVMValueRef array_end = LLVMConstInt(g->builtin_types.entry_usize->llvm_type,
array_type->data.array.len, false);
add_bounds_check(g, end_val, LLVMIntEQ, nullptr, LLVMIntULE, array_end);
if (sentinel != nullptr) {
LLVMValueRef indices[] = {
LLVMConstNull(g->builtin_types.entry_usize->llvm_type),
end_val,
};
LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, array_ptr, indices, 2, "");
add_sentinel_check(g, sentinel_elem_ptr, sentinel);
}
}
}
if (!type_has_bits(array_type)) {
@ -5297,6 +5327,10 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
if (want_runtime_safety) {
add_bounds_check(g, start_val, LLVMIntEQ, nullptr, LLVMIntULE, end_val);
if (sentinel != nullptr) {
LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, array_ptr, &end_val, 1, "");
add_sentinel_check(g, sentinel_elem_ptr, sentinel);
}
}
if (type_has_bits(array_type)) {
@ -5337,18 +5371,24 @@ static LLVMValueRef ir_render_slice(CodeGen *g, IrExecutable *executable, IrInst
end_val = prev_end;
}
LLVMValueRef src_ptr_ptr = LLVMBuildStructGEP(g->builder, array_ptr, (unsigned)ptr_index, "");
LLVMValueRef src_ptr = gen_load_untyped(g, src_ptr_ptr, 0, false, "");
if (want_runtime_safety) {
assert(prev_end);
add_bounds_check(g, start_val, LLVMIntEQ, nullptr, LLVMIntULE, end_val);
if (instruction->end) {
add_bounds_check(g, end_val, LLVMIntEQ, nullptr, LLVMIntULE, prev_end);
if (sentinel != nullptr) {
LLVMValueRef sentinel_elem_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &end_val, 1, "");
add_sentinel_check(g, sentinel_elem_ptr, sentinel);
}
}
}
LLVMValueRef src_ptr_ptr = LLVMBuildStructGEP(g->builder, array_ptr, (unsigned)ptr_index, "");
LLVMValueRef src_ptr = gen_load_untyped(g, src_ptr_ptr, 0, false, "");
LLVMValueRef ptr_field_ptr = LLVMBuildStructGEP(g->builder, tmp_struct_ptr, (unsigned)ptr_index, "");
LLVMValueRef slice_start_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &start_val, (unsigned)len_index, "");
LLVMValueRef slice_start_ptr = LLVMBuildInBoundsGEP(g->builder, src_ptr, &start_val, 1, "");
gen_store_untyped(g, slice_start_ptr, ptr_field_ptr, 0, false);
LLVMValueRef len_field_ptr = LLVMBuildStructGEP(g->builder, tmp_struct_ptr, (unsigned)len_index, "");

6
src/ir.cpp
View File

@ -25122,14 +25122,16 @@ static IrInstruction *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstruction
if (array_type->data.pointer.ptr_len == PtrLenC) {
array_type = adjust_ptr_len(ira->codegen, array_type, PtrLenUnknown);
}
non_sentinel_slice_ptr_type = array_type;
ZigType *maybe_sentineled_slice_ptr_type = array_type;
non_sentinel_slice_ptr_type = adjust_ptr_sentinel(ira->codegen, maybe_sentineled_slice_ptr_type, nullptr);
if (!end) {
ir_add_error(ira, &instruction->base, buf_sprintf("slice of pointer must include end value"));
return ira->codegen->invalid_instruction;
}
}
} else if (is_slice(array_type)) {
non_sentinel_slice_ptr_type = array_type->data.structure.fields[slice_ptr_index]->type_entry;
ZigType *maybe_sentineled_slice_ptr_type = array_type->data.structure.fields[slice_ptr_index]->type_entry;
non_sentinel_slice_ptr_type = adjust_ptr_sentinel(ira->codegen, maybe_sentineled_slice_ptr_type, nullptr);
elem_type = non_sentinel_slice_ptr_type->data.pointer.child_type;
} else {
ir_add_error(ira, &instruction->base,

53
test/runtime_safety.zig
View File

@ -1,12 +1,57 @@
const tests = @import("tests.zig");
pub fn addCases(cases: *tests.CompareOutputContext) void {
cases.addRuntimeSafety("intToPtr with misaligned address",
cases.addRuntimeSafety("pointer slice sentinel mismatch",
\\const std = @import("std");
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ if (@import("std").mem.eql(u8, message, "incorrect alignment")) {
\\ @import("std").os.exit(126); // good
\\ if (std.mem.eql(u8, message, "sentinel mismatch")) {
\\ std.process.exit(126); // good
\\ }
\\ @import("std").os.exit(0); // test failed
\\ std.process.exit(0); // test failed
\\}
\\pub fn main() void {
\\ var buf: [4]u8 = undefined;
\\ const ptr = buf[0..].ptr;
\\ const slice = ptr[0..3 :0];
\\}
);
cases.addRuntimeSafety("slice slice sentinel mismatch",
\\const std = @import("std");
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ if (std.mem.eql(u8, message, "sentinel mismatch")) {
\\ std.process.exit(126); // good
\\ }
\\ std.process.exit(0); // test failed
\\}
\\pub fn main() void {
\\ var buf: [4]u8 = undefined;
\\ const slice = buf[0..];
\\ const slice2 = slice[0..3 :0];
\\}
);
cases.addRuntimeSafety("array slice sentinel mismatch",
\\const std = @import("std");
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ if (std.mem.eql(u8, message, "sentinel mismatch")) {
\\ std.process.exit(126); // good
\\ }
\\ std.process.exit(0); // test failed
\\}
\\pub fn main() void {
\\ var buf: [4]u8 = undefined;
\\ const slice = buf[0..3 :0];
\\}
);
cases.addRuntimeSafety("intToPtr with misaligned address",
\\const std = @import("std");
\\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
\\ if (std.mem.eql(u8, message, "incorrect alignment")) {
\\ std.os.exit(126); // good
\\ }
\\ std.os.exit(0); // test failed
\\}
\\pub fn main() void {
\\ var x: usize = 5;