llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_suppressions.h

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//===-- sanitizer_suppressions.h --------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Suppression parsing/matching code.
//
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_SUPPRESSIONS_H
#define SANITIZER_SUPPRESSIONS_H
#include "sanitizer_common.h"
#include "sanitizer_atomic.h"
#include "sanitizer_internal_defs.h"
namespace __sanitizer {
struct Suppression {
Suppression() { internal_memset(this, 0, sizeof(*this)); }
const char *type;
char *templ;
atomic_uint32_t hit_count;
uptr weight;
};
class SuppressionContext {
public:
// Create new SuppressionContext capable of parsing given suppression types.
SuppressionContext(const char *supprression_types[],
int suppression_types_num);
void ParseFromFile(const char *filename);
void Parse(const char *str);
bool Match(const char *str, const char *type, Suppression **s);
uptr SuppressionCount() const;
bool HasSuppressionType(const char *type) const;
const Suppression *SuppressionAt(uptr i) const;
void GetMatched(InternalMmapVector<Suppression *> *matched);
private:
[UBSan][clang][compiler-rt] Applying non-zero offset to nullptr is undefined behaviour Summary: Quote from http://eel.is/c++draft/expr.add#4: ``` 4 When an expression J that has integral type is added to or subtracted from an expression P of pointer type, the result has the type of P. (4.1) If P evaluates to a null pointer value and J evaluates to 0, the result is a null pointer value. (4.2) Otherwise, if P points to an array element i of an array object x with n elements ([dcl.array]), the expressions P + J and J + P (where J has the value j) point to the (possibly-hypothetical) array element i+j of x if 0≤i+j≤n and the expression P - J points to the (possibly-hypothetical) array element i−j of x if 0≤i−j≤n. (4.3) Otherwise, the behavior is undefined. ``` Therefore, as per the standard, applying non-zero offset to `nullptr` (or making non-`nullptr` a `nullptr`, by subtracting pointer's integral value from the pointer itself) is undefined behavior. (*if* `nullptr` is not defined, i.e. e.g. `-fno-delete-null-pointer-checks` was *not* specified.) To make things more fun, in C (6.5.6p8), applying *any* offset to null pointer is undefined, although Clang front-end pessimizes the code by not lowering that info, so this UB is "harmless". Since rL369789 (D66608 `[InstCombine] icmp eq/ne (gep inbounds P, Idx..), null -> icmp eq/ne P, null`) LLVM middle-end uses those guarantees for transformations. If the source contains such UB's, said code may now be miscompiled. Such miscompilations were already observed: * https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190826/687838.html * https://github.com/google/filament/pull/1566 Surprisingly, UBSan does not catch those issues ... until now. This diff teaches UBSan about these UB's. `getelementpointer inbounds` is a pretty frequent instruction, so this does have a measurable impact on performance; I've addressed most of the obvious missing folds (and thus decreased the performance impact by ~5%), and then re-performed some performance measurements using my [[ https://github.com/darktable-org/rawspeed | RawSpeed ]] benchmark: (all measurements done with LLVM ToT, the sanitizer never fired.) * no sanitization vs. existing check: average `+21.62%` slowdown * existing check vs. check after this patch: average `22.04%` slowdown * no sanitization vs. this patch: average `48.42%` slowdown Reviewers: vsk, filcab, rsmith, aaron.ballman, vitalybuka, rjmccall, #sanitizers Reviewed By: rsmith Subscribers: kristof.beyls, nickdesaulniers, nikic, ychen, dtzWill, xbolva00, dberris, arphaman, rupprecht, reames, regehr, llvm-commits, cfe-commits Tags: #clang, #sanitizers, #llvm Differential Revision: https://reviews.llvm.org/D67122 llvm-svn: 374293
2019-10-10 17:25:02 +08:00
static const int kMaxSuppressionTypes = 64;
const char **const suppression_types_;
const int suppression_types_num_;
InternalMmapVector<Suppression> suppressions_;
bool has_suppression_type_[kMaxSuppressionTypes];
bool can_parse_;
};
} // namespace __sanitizer
#endif // SANITIZER_SUPPRESSIONS_H