1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
|
//===- bolt/Rewrite/GNUPropertyRewriter.cpp -------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Read the .note.gnu.property section.
//
//===----------------------------------------------------------------------===//
#include "bolt/Rewrite/MetadataRewriter.h"
#include "bolt/Rewrite/MetadataRewriters.h"
#include "llvm/Support/Errc.h"
using namespace llvm;
using namespace bolt;
namespace {
class GNUPropertyRewriter final : public MetadataRewriter {
Expected<uint32_t> decodeGNUPropertyNote(StringRef Desc);
public:
GNUPropertyRewriter(StringRef Name, BinaryContext &BC)
: MetadataRewriter(Name, BC) {}
Error sectionInitializer() override;
};
Error GNUPropertyRewriter::sectionInitializer() {
ErrorOr<BinarySection &> Sec =
BC.getUniqueSectionByName(".note.gnu.property");
if (!Sec)
return Error::success();
// Accumulate feature bits
uint32_t FeaturesAcc = 0;
StringRef Buf = Sec->getContents();
DataExtractor DE(Buf, BC.AsmInfo->isLittleEndian(),
BC.AsmInfo->getCodePointerSize());
DataExtractor::Cursor Cursor(0);
while (Cursor && !DE.eof(Cursor)) {
const uint32_t NameSz = DE.getU32(Cursor);
const uint32_t DescSz = DE.getU32(Cursor);
const uint32_t Type = DE.getU32(Cursor);
StringRef Name =
NameSz ? Buf.slice(Cursor.tell(), Cursor.tell() + NameSz) : "<empty>";
Cursor.seek(alignTo(Cursor.tell() + NameSz, 4));
const uint64_t DescOffset = Cursor.tell();
StringRef Desc =
DescSz ? Buf.slice(DescOffset, DescOffset + DescSz) : "<empty>";
Cursor.seek(alignTo(DescOffset + DescSz, 4));
if (!Cursor)
return createStringError(
errc::executable_format_error,
"out of bounds while reading .note.gnu.property section: %s",
toString(Cursor.takeError()).c_str());
if (Type == ELF::NT_GNU_PROPERTY_TYPE_0 && Name.starts_with("GNU") &&
DescSz) {
auto Features = decodeGNUPropertyNote(Desc);
if (!Features)
return Features.takeError();
FeaturesAcc |= *Features;
}
}
if (BC.isAArch64()) {
BC.setUsesBTI(FeaturesAcc & llvm::ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
if (BC.usesBTI())
BC.outs() << "BOLT-WARNING: binary is using BTI. Optimized binary may be "
"corrupted\n";
}
return Error::success();
}
/// \p Desc contains an array of property descriptors. Each member has the
/// following structure:
/// typedef struct {
/// Elf_Word pr_type;
/// Elf_Word pr_datasz;
/// unsigned char pr_data[PR_DATASZ];
/// unsigned char pr_padding[PR_PADDING];
/// } Elf_Prop;
///
/// As there is no guarantee that the features are encoded in which element of
/// the array, we have to read all, and OR together the result.
Expected<uint32_t> GNUPropertyRewriter::decodeGNUPropertyNote(StringRef Desc) {
DataExtractor DE(Desc, BC.AsmInfo->isLittleEndian(),
BC.AsmInfo->getCodePointerSize());
DataExtractor::Cursor Cursor(0);
const uint32_t Align = DE.getAddressSize();
std::optional<uint32_t> Features = 0;
while (Cursor && !DE.eof(Cursor)) {
const uint32_t PrType = DE.getU32(Cursor);
const uint32_t PrDataSz = DE.getU32(Cursor);
const uint64_t PrDataStart = Cursor.tell();
const uint64_t PrDataEnd = PrDataStart + PrDataSz;
Cursor.seek(PrDataEnd);
if (!Cursor)
return createStringError(
errc::executable_format_error,
"out of bounds while reading .note.gnu.property section: %s",
toString(Cursor.takeError()).c_str());
if (PrType == llvm::ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND) {
if (PrDataSz != 4) {
return createStringError(
errc::executable_format_error,
"Property descriptor size has to be 4 bytes on AArch64\n");
}
DataExtractor::Cursor Tmp(PrDataStart);
// PrDataSz = 4 -> PrData is uint32_t
const uint32_t FeaturesItem = DE.getU32(Tmp);
if (!Tmp)
return createStringError(
errc::executable_format_error,
"failed to read property from .note.gnu.property section: %s",
toString(Tmp.takeError()).c_str());
Features = Features ? (*Features | FeaturesItem) : FeaturesItem;
}
Cursor.seek(alignTo(PrDataEnd, Align));
if (!Cursor)
return createStringError(errc::executable_format_error,
"out of bounds while reading property array in "
".note.gnu.property section: %s",
toString(Cursor.takeError()).c_str());
}
return Features.value_or(0u);
}
} // namespace
std::unique_ptr<MetadataRewriter>
llvm::bolt::createGNUPropertyRewriter(BinaryContext &BC) {
return std::make_unique<GNUPropertyRewriter>("gnu-property-rewriter", BC);
}
|
