1//= OSLog.h - Analysis of calls to os_log builtins --*- C++ -*-===============//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines APIs for determining the layout of the data buffer for
10// os_log() and os_trace().
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_OSLOG_H
15#define LLVM_CLANG_ANALYSIS_ANALYSES_OSLOG_H
16
17#include "clang/AST/ASTContext.h"
18#include "clang/AST/Expr.h"
19
20namespace clang {
21namespace analyze_os_log {
22
23/// An OSLogBufferItem represents a single item in the data written by a call
24/// to os_log() or os_trace().
25class OSLogBufferItem {
26public:
27  enum Kind {
28    // The item is a scalar (int, float, raw pointer, etc.). No further copying
29    // is required. This is the only kind allowed by os_trace().
30    ScalarKind = 0,
31
32    // The item is a count, which describes the length of the following item to
33    // be copied. A count may only be followed by an item of kind StringKind,
34    // WideStringKind, or PointerKind.
35    CountKind,
36
37    // The item is a pointer to a C string. If preceded by a count 'n',
38    // os_log() will copy at most 'n' bytes from the pointer.
39    StringKind,
40
41    // The item is a pointer to a block of raw data. This item must be preceded
42    // by a count 'n'. os_log() will copy exactly 'n' bytes from the pointer.
43    PointerKind,
44
45    // The item is a pointer to an Objective-C object. os_log() may retain the
46    // object for later processing.
47    ObjCObjKind,
48
49    // The item is a pointer to wide-char string.
50    WideStringKind,
51
52    // The item is corresponding to the '%m' format specifier, no value is
53    // populated in the buffer and the runtime is loading the errno value.
54    ErrnoKind,
55
56    // The item is a mask type.
57    MaskKind
58  };
59
60  enum {
61    // The item is marked "private" in the format string.
62    IsPrivate = 0x1,
63
64    // The item is marked "public" in the format string.
65    IsPublic = 0x2,
66
67    // The item is marked "sensitive" in the format string.
68    IsSensitive = 0x4 | IsPrivate
69  };
70
71private:
72  Kind TheKind = ScalarKind;
73  const Expr *TheExpr = nullptr;
74  CharUnits ConstValue;
75  CharUnits Size; // size of the data, not including the header bytes
76  unsigned Flags = 0;
77  StringRef MaskType;
78
79public:
80  OSLogBufferItem(Kind kind, const Expr *expr, CharUnits size, unsigned flags,
81                  StringRef maskType = StringRef())
82      : TheKind(kind), TheExpr(expr), Size(size), Flags(flags),
83        MaskType(maskType) {
84    assert(((Flags == 0) || (Flags == IsPrivate) || (Flags == IsPublic) ||
85            (Flags == IsSensitive)) &&
86           "unexpected privacy flag");
87  }
88
89  OSLogBufferItem(ASTContext &Ctx, CharUnits value, unsigned flags)
90      : TheKind(CountKind), ConstValue(value),
91        Size(Ctx.getTypeSizeInChars(Ctx.IntTy)), Flags(flags) {}
92
93  unsigned char getDescriptorByte() const {
94    unsigned char result = Flags;
95    result |= ((unsigned)getKind()) << 4;
96    return result;
97  }
98
99  unsigned char getSizeByte() const { return size().getQuantity(); }
100
101  Kind getKind() const { return TheKind; }
102  bool getIsPrivate() const { return (Flags & IsPrivate) != 0; }
103
104  const Expr *getExpr() const { return TheExpr; }
105  CharUnits getConstValue() const { return ConstValue; }
106  CharUnits size() const { return Size; }
107
108  StringRef getMaskType() const { return MaskType; }
109};
110
111class OSLogBufferLayout {
112public:
113  SmallVector<OSLogBufferItem, 4> Items;
114
115  enum Flags { HasPrivateItems = 1, HasNonScalarItems = 1 << 1 };
116
117  CharUnits size() const {
118    CharUnits result;
119    result += CharUnits::fromQuantity(2); // summary byte, num-args byte
120    for (auto &item : Items) {
121      // descriptor byte, size byte
122      result += item.size() + CharUnits::fromQuantity(2);
123    }
124    return result;
125  }
126
127  bool hasPrivateItems() const {
128    return llvm::any_of(
129        Items, [](const OSLogBufferItem &Item) { return Item.getIsPrivate(); });
130  }
131
132  bool hasNonScalarOrMask() const {
133    return llvm::any_of(Items, [](const OSLogBufferItem &Item) {
134      return Item.getKind() != OSLogBufferItem::ScalarKind ||
135             !Item.getMaskType().empty();
136    });
137  }
138
139  unsigned char getSummaryByte() const {
140    unsigned char result = 0;
141    if (hasPrivateItems())
142      result |= HasPrivateItems;
143    if (hasNonScalarOrMask())
144      result |= HasNonScalarItems;
145    return result;
146  }
147
148  unsigned char getNumArgsByte() const { return Items.size(); }
149};
150
151// Given a call 'E' to one of the builtins __builtin_os_log_format() or
152// __builtin_os_log_format_buffer_size(), compute the layout of the buffer that
153// the call will write into and store it in 'layout'. Returns 'false' if there
154// was some error encountered while computing the layout, and 'true' otherwise.
155bool computeOSLogBufferLayout(clang::ASTContext &Ctx, const clang::CallExpr *E,
156                              OSLogBufferLayout &layout);
157
158} // namespace analyze_os_log
159} // namespace clang
160#endif
161