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[AArch64][PAC][MC][ELF] Support PAuth ABI compatibility tag
Emit `GNU_PROPERTY_AARCH64_FEATURE_PAUTH` property in `.note.gnu.property` section depending on `aarch64-elf-pauthabi-platform` and `aarch64-elf-pauthabi-version` llvm module flags.
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6 files changed

+107
-14
lines changed

6 files changed

+107
-14
lines changed

‎llvm/include/llvm/BinaryFormat/ELF.h‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1673,6 +1673,7 @@ enum : unsigned {
16731673
GNU_PROPERTY_STACK_SIZE = 1,
16741674
GNU_PROPERTY_NO_COPY_ON_PROTECTED = 2,
16751675
GNU_PROPERTY_AARCH64_FEATURE_1_AND = 0xc0000000,
1676+
GNU_PROPERTY_AARCH64_FEATURE_PAUTH = 0xc0000001,
16761677
GNU_PROPERTY_X86_FEATURE_1_AND = 0xc0000002,
16771678

16781679
GNU_PROPERTY_X86_UINT32_OR_LO = 0xc0008000,

‎llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp‎

Lines changed: 16 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -265,6 +265,8 @@ void AArch64AsmPrinter::emitStartOfAsmFile(Module &M) {
265265
S, MCConstantExpr::create(Feat00Value, MMI->getContext()));
266266
}
267267

268+
// TODO: enhance naming to distinguish MachO ptrauth ABI version and ELF
269+
// pauthabi platform and version
268270
if (TM.getTargetTriple().isOSBinFormatMachO())
269271
EmitPtrAuthVersion(M);
270272

@@ -283,13 +285,24 @@ void AArch64AsmPrinter::emitStartOfAsmFile(Module &M) {
283285
if (Sign->getZExtValue())
284286
Flags |= ELF::GNU_PROPERTY_AARCH64_FEATURE_1_PAC;
285287

286-
if (Flags == 0)
287-
return;
288+
uint64_t PAuthABIPlatform = -1;
289+
if (const auto *PAP = mdconst::extract_or_null<ConstantInt>(
290+
M.getModuleFlag("aarch64-elf-pauthabi-platform")))
291+
PAuthABIPlatform = PAP->getZExtValue();
292+
uint64_t PAuthABIVersion = -1;
293+
if (const auto *PAV = mdconst::extract_or_null<ConstantInt>(
294+
M.getModuleFlag("aarch64-elf-pauthabi-version")))
295+
PAuthABIVersion = PAV->getZExtValue();
296+
297+
if ((PAuthABIPlatform == uint64_t(-1)) != (PAuthABIVersion == uint64_t(-1)))
298+
report_fatal_error(
299+
"either both or no 'aarch64-elf-pauthabi-platform' and "
300+
"'aarch64-elf-pauthabi-version' module flags must be present");
288301

289302
// Emit a .note.gnu.property section with the flags.
290303
auto *TS =
291304
static_cast<AArch64TargetStreamer *>(OutStreamer->getTargetStreamer());
292-
TS->emitNoteSection(Flags);
305+
TS->emitNoteSection(Flags, PAuthABIPlatform, PAuthABIVersion);
293306
}
294307

295308
void AArch64AsmPrinter::emitFunctionHeaderComment() {

‎llvm/lib/Target/AArch64/MCTargetDesc/AArch64TargetStreamer.cpp‎

Lines changed: 27 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -56,10 +56,20 @@ void AArch64TargetStreamer::emitConstantPools() {
5656
void AArch64TargetStreamer::finish() {
5757
if (MarkBTIProperty)
5858
emitNoteSection(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
59+
// TODO: do we need to handle GNU_PROPERTY_AARCH64_FEATURE_PAUTH here?
5960
}
6061

61-
void AArch64TargetStreamer::emitNoteSection(unsigned Flags) {
62-
if (Flags == 0)
62+
void AArch64TargetStreamer::emitNoteSection(unsigned Flags,
63+
uint64_t PAuthABIPlatform,
64+
uint64_t PAuthABIVersion) {
65+
assert((PAuthABIPlatform == uint64_t(-1)) ==
66+
(PAuthABIVersion == uint64_t(-1)));
67+
uint64_t DescSz = 0;
68+
if (Flags != 0)
69+
DescSz += 4 * 4;
70+
if (PAuthABIPlatform != uint64_t(-1))
71+
DescSz += 4 + 4 + 8 * 2;
72+
if (DescSz == 0)
6373
return;
6474

6575
MCStreamer &OutStreamer = getStreamer();
@@ -80,15 +90,25 @@ void AArch64TargetStreamer::emitNoteSection(unsigned Flags) {
8090
// Emit the note header.
8191
OutStreamer.emitValueToAlignment(Align(8));
8292
OutStreamer.emitIntValue(4, 4); // data size for "GNU\0"
83-
OutStreamer.emitIntValue(4 * 4, 4); // Elf_Prop size
93+
OutStreamer.emitIntValue(DescSz, 4); // Elf_Prop array size
8494
OutStreamer.emitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4);
8595
OutStreamer.emitBytes(StringRef("GNU", 4)); // note name
8696

8797
// Emit the PAC/BTI properties.
88-
OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
89-
OutStreamer.emitIntValue(4, 4); // data size
90-
OutStreamer.emitIntValue(Flags, 4); // data
91-
OutStreamer.emitIntValue(0, 4); // pad
98+
if (Flags != 0) {
99+
OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
100+
OutStreamer.emitIntValue(4, 4); // data size
101+
OutStreamer.emitIntValue(Flags, 4); // data
102+
OutStreamer.emitIntValue(0, 4); // pad
103+
}
104+
105+
// Emit the PAuth ABI compatibility info
106+
if (PAuthABIPlatform != uint64_t(-1)) {
107+
OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_PAUTH, 4);
108+
OutStreamer.emitIntValue(8 * 2, 4); // data size
109+
OutStreamer.emitIntValue(PAuthABIPlatform, 8);
110+
OutStreamer.emitIntValue(PAuthABIVersion, 8);
111+
}
92112

93113
OutStreamer.endSection(Nt);
94114
OutStreamer.switchSection(Cur);

‎llvm/lib/Target/AArch64/MCTargetDesc/AArch64TargetStreamer.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -35,7 +35,8 @@ class AArch64TargetStreamer : public MCTargetStreamer {
3535
void emitCurrentConstantPool();
3636

3737
/// Callback used to implement the .note.gnu.property section.
38-
void emitNoteSection(unsigned Flags);
38+
void emitNoteSection(unsigned Flags, uint64_t PAuthABIPlatform = -1,
39+
uint64_t PAuthABIVersion = -1);
3940

4041
/// Callback used to implement the .inst directive.
4142
virtual void emitInst(uint32_t Inst);

‎llvm/test/CodeGen/AArch64/note-gnu-property-elf-pauthabi.ll‎

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,48 @@
1+
; RUN: rm -rf %t && split-file %s %t && cd %t
2+
3+
;--- ok.ll
4+
5+
; RUN: llc -mtriple=aarch64-linux ok.ll -o - | \
6+
; RUN: FileCheck %s --check-prefix=ASM
7+
; RUN: llc -mtriple=aarch64-linux ok.ll -filetype=obj -o - | \
8+
; RUN: llvm-readelf --notes - | FileCheck %s --check-prefix=OBJ
9+
10+
!llvm.module.flags = !{!0, !1}
11+
12+
!0 = !{i32 1, !"aarch64-elf-pauthabi-platform", i32 2}
13+
!1 = !{i32 1, !"aarch64-elf-pauthabi-version", i32 31}
14+
15+
; ASM: .section .note.gnu.property,"a",@note
16+
; ASM-NEXT: .p2align 3, 0x0
17+
; ASM-NEXT: .word 4
18+
; ASM-NEXT: .word 24
19+
; ASM-NEXT: .word 5
20+
; ASM-NEXT: .asciz "GNU"
21+
; 3221225473 = 0xc0000001 = GNU_PROPERTY_AARCH64_FEATURE_PAUTH
22+
; ASM-NEXT: .word 3221225473
23+
; ASM-NEXT: .word 16
24+
; ASM-NEXT: .xword 2
25+
; ASM-NEXT: .xword 31
26+
27+
; TODO: llvm-readelf support
28+
; OBJ: <application-specific type 0xc0000001>
29+
30+
; ERR: either both or no 'aarch64-elf-pauthabi-platform' and 'aarch64-elf-pauthabi-version' module flags must be present
31+
32+
;--- err1.ll
33+
34+
; RUN: not --crash llc -mtriple=aarch64-linux err1.ll 2>&1 -o - | \
35+
; RUN: FileCheck %s --check-prefix=ERR
36+
37+
!llvm.module.flags = !{!0}
38+
39+
!0 = !{i32 1, !"aarch64-elf-pauthabi-platform", i32 2}
40+
41+
;--- err2.ll
42+
43+
; RUN: not --crash llc -mtriple=aarch64-linux err2.ll 2>&1 -o - | \
44+
; RUN: FileCheck %s --check-prefix=ERR
45+
46+
!llvm.module.flags = !{!0}
47+
48+
!0 = !{i32 1, !"aarch64-elf-pauthabi-version", i32 31}

‎llvm/test/tools/llvm-readobj/ELF/AArch64/aarch64-note-gnu-property.s‎

Lines changed: 13 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,23 +1,27 @@
1+
// TODO: support for GNU_PROPERTY_AARCH64_FEATURE_PAUTH
2+
13
// RUN: llvm-mc -filetype=obj -triple aarch64-linux-gnu %s -o %t
24
// RUN: llvm-readelf --notes %t | FileCheck %s --check-prefix=GNU
35
// RUN: llvm-readobj --notes %t | FileCheck %s --check-prefix=LLVM
46

57
// GNU: Displaying notes found in: .note.gnu.property
68
// GNU-NEXT: Owner Data size Description
7-
// GNU-NEXT: GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0 (property note)
9+
// GNU-NEXT: GNU 0x00000028 NT_GNU_PROPERTY_TYPE_0 (property note)
810
// GNU-NEXT: Properties: aarch64 feature: BTI, PAC
11+
// GNU-NEXT: <application-specific type 0xc0000001>
912

1013
// LLVM: Notes [
1114
// LLVM-NEXT: NoteSection {
1215
// LLVM-NEXT: Name: .note.gnu.property
1316
// LLVM-NEXT: Offset: 0x40
14-
// LLVM-NEXT: Size: 0x20
17+
// LLVM-NEXT: Size: 0x38
1518
// LLVM-NEXT: Note {
1619
// LLVM-NEXT: Owner: GNU
17-
// LLVM-NEXT: Data size: 0x10
20+
// LLVM-NEXT: Data size: 0x28
1821
// LLVM-NEXT: Type: NT_GNU_PROPERTY_TYPE_0 (property note)
1922
// LLVM-NEXT: Property [
2023
// LLVM-NEXT: aarch64 feature: BTI, PAC
24+
// LLVM-NEXT: <application-specific type 0xc0000001>
2125
// LLVM-NEXT: ]
2226
// LLVM-NEXT: }
2327
// LLVM-NEXT: }
@@ -35,4 +39,10 @@ begin:
3539
.long 4 /* Data size */
3640
.long 3 /* BTI and PAC */
3741
.p2align 3 /* Align to 8 byte for 64 bit */
42+
/* PAuth ABI property note */
43+
.long 0xc0000001 /* Type: GNU_PROPERTY_AARCH64_FEATURE_PAUTH */
44+
.long 16 /* Data size */
45+
.quad 2 /* PAuth ABI platform */
46+
.quad 31 /* PAuth ABI version */
47+
.p2align 3 /* Align to 8 byte for 64 bit */
3848
end:

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