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[AArch64][MachO] Encode @AUTH to ARM64_RELOC_AUTHENTICATED_POINTER.

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This adds MachO support for emission of authenticated pointer
relocations.

We already support AArch64AuthMCExpr, to represent assembly expressions
such as:
  .quad <symbol>@AUTH(<key>, <discriminator> [, addr])
For example:
  .quad _g3@AUTH(ib, 1234, addr)

These @AUTH expressions lower to a new kind of MachO relocation:
  ARM64_RELOC_AUTHENTICATED_POINTER (11)

The relocation points to the referenced symbol.
The other data, describing the signing scheme and original addend
(only 32 bits instead of 64), is encoded into the addend (in the
relocated location):

  |63|62|61-51|50-49|  48  |47     -     32|31  -  0|
  | 1| 0|  0  | key | addr | discriminator | addend |
This commit is contained in:
Ahmed Bougacha
2024-08-16 11:58:59 -07:00
parent e6b9f12b0a
commit 464fa3b3b0
4 changed files with 174 additions and 1 deletions
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13
llvm/docs/PointerAuth.md
View File

@@ -374,6 +374,19 @@ For example:
.quad _sym@AUTH(ia,12,addr)
```
#### MachO Object File Representation
At the object file level, authenticated relocations are represented using the
``ARM64_RELOC_AUTHENTICATED_POINTER`` relocation kind (with value ``11``).
The pointer authentication information is encoded into the addend as follows:
```
| 63 | 62 | 61-51 | 50-49 | 48 | 47 - 32 | 31 - 0 |
| -- | -- | ----- | ----- | ------ | --------------- | -------- |
| 1 | 0 | 0 | key | addr | discriminator | addend |
```
#### ELF Object File Representation
At the object file level, authenticated relocations are represented

2
llvm/lib/Object/MachOObjectFile.cpp
View File

@@ -2341,7 +2341,7 @@ void MachOObjectFile::getRelocationTypeName(
"ARM64_RELOC_PAGEOFF12", "ARM64_RELOC_GOT_LOAD_PAGE21",
"ARM64_RELOC_GOT_LOAD_PAGEOFF12", "ARM64_RELOC_POINTER_TO_GOT",
"ARM64_RELOC_TLVP_LOAD_PAGE21", "ARM64_RELOC_TLVP_LOAD_PAGEOFF12",
"ARM64_RELOC_ADDEND"
"ARM64_RELOC_ADDEND", "ARM64_RELOC_AUTHENTICATED_POINTER"
};
if (RType >= std::size(Table))

41
llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
View File

@@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/AArch64FixupKinds.h"
#include "MCTargetDesc/AArch64MCExpr.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/MachO.h"
@@ -394,6 +395,46 @@ void AArch64MachObjectWriter::recordRelocation(
Value = 0;
}
if (Target.getRefKind() == AArch64MCExpr::VK_AUTH ||
Target.getRefKind() == AArch64MCExpr::VK_AUTHADDR) {
auto *Expr = cast<AArch64AuthMCExpr>(Fixup.getValue());
assert(Type == MachO::ARM64_RELOC_UNSIGNED);
if (IsPCRel) {
Asm.getContext().reportError(Fixup.getLoc(),
"invalid PC relative auth relocation");
return;
}
if (Log2Size != 3) {
Asm.getContext().reportError(
Fixup.getLoc(), "invalid auth relocation size, must be 8 bytes");
return;
}
if (Target.getSymB()) {
Asm.getContext().reportError(
Fixup.getLoc(),
"invalid auth relocation, can't reference two symbols");
return;
}
uint16_t Discriminator = Expr->getDiscriminator();
AArch64PACKey::ID Key = Expr->getKey();
if (!isInt<32>(Value)) {
Asm.getContext().reportError(Fixup.getLoc(),
"addend too big for relocation");
return;
}
Type = MachO::ARM64_RELOC_AUTHENTICATED_POINTER;
Value = (uint32_t(Value)) | (uint64_t(Discriminator) << 32) |
(uint64_t(Expr->hasAddressDiversity()) << 48) |
(uint64_t(Key) << 49) | (1ULL << 63);
}
// If there's any addend left to handle, encode it in the instruction.
FixedValue = Value;

119
llvm/test/MC/AArch64/arm64e-authenticated-pointer-reloc.s Normal file
View File

@@ -0,0 +1,119 @@
// RUN: llvm-mc -triple=arm64-apple-darwin < %s | \
// RUN: FileCheck %s --check-prefix=ASM
// RUN: llvm-mc -triple=arm64-apple-darwin -filetype=obj < %s | \
// RUN: llvm-readobj --expand-relocs --sections \
// RUN: --section-relocations --section-data - | \
// RUN: FileCheck %s --check-prefix=RELOC
// RELOC: Sections [
// RELOC-LABEL: Section {
// RELOC-LABEL: Section {
// RELOC-NEXT: Index: 1
// RELOC-NEXT: Name: __const (5F 5F 63 6F 6E 73 74 00 00 00 00 00 00 00 00 00)
// RELOC-NEXT: Segment: __DATA (5F 5F 44 41 54 41 00 00 00 00 00 00 00 00 00 00)
.section __DATA,__const
.p2align 3
// RELOC-LABEL: Relocations [
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x70
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g 7
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x60
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g 6
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x50
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g5
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x40
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g4
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x30
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g3
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x20
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g2
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x10
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g1
// RELOC-NEXT: }
// RELOC-NEXT: Relocation {
// RELOC-NEXT: Offset: 0x0
// RELOC-NEXT: PCRel: 0
// RELOC-NEXT: Length: 3
// RELOC-NEXT: Type: ARM64_RELOC_AUTHENTICATED_POINTER (11)
// RELOC-NEXT: Symbol: _g0
// RELOC-NEXT: }
// RELOC-NEXT: ]
// RELOC-NEXT: SectionData (
// RELOC-NEXT: 0000: 00000000 2A000080
// ASM: .quad _g0@AUTH(ia,42)
.quad _g0@AUTH(ia,42)
.quad 0
// RELOC-NEXT: 0010: 00000000 00000280
// ASM: .quad _g1@AUTH(ib,0)
.quad _g1@AUTH(ib,0)
.quad 0
// RELOC-NEXT: 0020: 00000000 05000580
// ASM: .quad _g2@AUTH(da,5,addr)
.quad _g2@AUTH(da,5,addr)
.quad 0
// RELOC-NEXT: 0030: 00000000 FFFF0780
// ASM: .quad _g3@AUTH(db,65535,addr)
.quad _g3@AUTH(db,0xffff,addr)
.quad 0
// RELOC-NEXT: 0040: 07000000 00000080
// ASM: .quad (_g4+7)@AUTH(ia,0)
.quad (_g4 + 7)@AUTH(ia,0)
.quad 0
// RELOC-NEXT: 0050: FDFFFFFF 00DE0280
// ASM: .quad (_g5-3)@AUTH(ib,56832)
.quad (_g5 - 3)@AUTH(ib,0xde00)
.quad 0
// RELOC-NEXT: 0060: 00000000 FF000780
// ASM: .quad "_g 6"@AUTH(db,255,addr)
.quad "_g 6"@AUTH(db,0xff,addr)
.quad 0
// RELOC-NEXT: 0070: 07000000 10000080
// ASM: .quad ("_g 7"+7)@AUTH(ia,16)
.quad ("_g 7" + 7)@AUTH(ia,16)
.quad 0