[ELF] Always write non-immediate bits for AArch64 branch instruction.
To support errata patching on AArch64 we need to be able to overwrite an arbitrary instruction with a branch. For AArch64 it is sufficient to always write all the bits of the branch instruction and not just the immediate field. This is safe as the non-immediate bits of the branch instruction are always the same. Differential Revision: https://reviews.llvm.org/D36745 llvm-svn: 312727
This commit is contained in:
parent
9927431d81
commit
20489ec563
|
@ -232,8 +232,17 @@ void AArch64::relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
|
|||
checkInt<21>(Loc, Val, Type);
|
||||
write32AArch64Addr(Loc, Val);
|
||||
break;
|
||||
case R_AARCH64_CALL26:
|
||||
case R_AARCH64_JUMP26:
|
||||
// Normally we would just write the bits of the immediate field, however
|
||||
// when patching instructions for the cpu errata fix -fix-cortex-a53-843419
|
||||
// we want to replace a non-branch instruction with a branch immediate
|
||||
// instruction. By writing all the bits of the instruction including the
|
||||
// opcode and the immediate (0 001 | 01 imm26) we can do this
|
||||
// transformation by placing a R_AARCH64_JUMP26 relocation at the offset of
|
||||
// the instruction we want to patch.
|
||||
write32le(Loc, 0x14000000);
|
||||
LLVM_FALLTHROUGH;
|
||||
case R_AARCH64_CALL26:
|
||||
checkInt<28>(Loc, Val, Type);
|
||||
or32le(Loc, (Val & 0x0FFFFFFC) >> 2);
|
||||
break;
|
||||
|
|
|
@ -0,0 +1,48 @@
|
|||
# REQUIRES: aarch64
|
||||
|
||||
# RUN: yaml2obj %s -o %t.o
|
||||
# RUN: ld.lld %t.o -o %t.out
|
||||
# RUN: llvm-objdump -d -triple=aarch64-none-linux %t.out | FileCheck %s
|
||||
|
||||
# Check that the R_AARCH64_JUMP26 writes the branch opcode as well as the
|
||||
# immediate. We use this property to overwrite instructions with a branch.
|
||||
|
||||
# CHECK: Disassembly of section .text:
|
||||
# CHECK-NEXT: foo:
|
||||
# CHECK-NEXT: 20000: 01 00 00 14 b #4
|
||||
# CHECK: bar:
|
||||
# CHECK-NEXT: 20004: ff ff ff 17 b #-4
|
||||
|
||||
!ELF
|
||||
FileHeader:
|
||||
Class: ELFCLASS64
|
||||
Data: ELFDATA2LSB
|
||||
Type: ET_REL
|
||||
Machine: EM_AARCH64
|
||||
Sections:
|
||||
- Type: SHT_PROGBITS
|
||||
Name: .text
|
||||
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
|
||||
Content: "0000000000000000"
|
||||
- Type: SHT_RELA
|
||||
Name: .rela.text
|
||||
Link: .symtab
|
||||
Info: .text
|
||||
Relocations:
|
||||
- Offset: 0
|
||||
Symbol: bar
|
||||
Type: R_AARCH64_JUMP26
|
||||
- Offset: 4
|
||||
Symbol: foo
|
||||
Type: R_AARCH64_JUMP26
|
||||
|
||||
Symbols:
|
||||
Local:
|
||||
- Type: STT_FUNC
|
||||
Section: .text
|
||||
Name: foo
|
||||
Value: 0
|
||||
- Type: STT_FUNC
|
||||
Section: .text
|
||||
Name: bar
|
||||
Value: 4
|
Loading…
Reference in New Issue