[lld] r249254 - [ELF2/AArch64] Add support for AARCH64_ABS{16, 32, 64} relocations.

[Rui Ueyama via llvm-commits]

On Sat, Oct 3, 2015 at 5:59 PM, Davide Italiano via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: davide
> Date: Sat Oct  3 19:59:16 2015
> New Revision: 249254
>
> URL: http://llvm.org/viewvc/llvm-project?rev=249254&view=rev
> Log:
> [ELF2/AArch64] Add support for AARCH64_ABS{16,32,64} relocations.
>
> I saw these in the wild while trying to link shared libraries.
>
> Added:
>     lld/trunk/test/elf2/aarch64-data-relocs.s
> Modified:
>     lld/trunk/ELF/Target.cpp
>
> Modified: lld/trunk/ELF/Target.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Target.cpp?rev=249254&r1=249253&r2=249254&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Target.cpp (original)
> +++ lld/trunk/ELF/Target.cpp Sat Oct  3 19:59:16 2015
> @@ -267,6 +267,26 @@ static uint64_t AArch64GetPage(uint64_t
>    return Expr & (~static_cast<uint64_t>(0xFFF));
>  }
>
> +static void handle_ABS16(uint8_t *Location, uint64_t S, int64_t A) {
> +  uint64_t X = S + A;
> +  if (!isInt<16>(X)) // -2^15 <= X < 2^16
> +    error("Relocation R_AARCH64_ABS16 out of range");
> +  write16le(Location, read32le(Location) | X);
> +}
>

This reads 32 bits and writes back 16 bits.


> +
> +static void handle_ABS32(uint8_t *Location, uint64_t S, int64_t A) {
> +  uint64_t X = S + A;
> +  if (!isInt<32>(X)) // -2^31 <= X < 2^32
> +    error("Relocation R_AARCH64_ABS32 out of range");
> +  write32le(Location, read32le(Location) | X);
> +}
> +
> +static void handle_ABS64(uint8_t *Location, uint64_t S, int64_t A) {
> +  uint64_t X = S + A;
> +  // No overflow check.
> +  write64le(Location, read32le(Location) | X);
> +}
>

And this is 32 bits and 64 bits. Are these correct?


> +
>  static void handle_ADD_ABS_LO12_NC(uint8_t *Location, uint64_t S, int64_t
> A) {
>    // No overflow check.
>    uint64_t X = ((S + A) & 0xFFF) << 10;
> @@ -300,6 +320,15 @@ void AArch64TargetInfo::relocateOne(uint
>    int64_t A = Rel.r_addend;
>    uint64_t P = BaseAddr + Rel.r_offset;
>    switch (Type) {
> +  case R_AARCH64_ABS16:
> +    handle_ABS16(Location, S, A);
> +    break;
> +  case R_AARCH64_ABS32:
> +    handle_ABS32(Location, S, A);
> +    break;
> +  case R_AARCH64_ABS64:
> +    handle_ABS64(Location, S, A);
> +    break;
>    case R_AARCH64_ADD_ABS_LO12_NC:
>      handle_ADD_ABS_LO12_NC(Location, S, A);
>      break;
>
> Added: lld/trunk/test/elf2/aarch64-data-relocs.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/aarch64-data-relocs.s?rev=249254&view=auto
>
> ==============================================================================
> --- lld/trunk/test/elf2/aarch64-data-relocs.s (added)
> +++ lld/trunk/test/elf2/aarch64-data-relocs.s Sat Oct  3 19:59:16 2015
> @@ -0,0 +1,29 @@
> +// RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t
> +// RUN: lld -flavor gnu2 -shared %t -o %t2
> +// RUN: llvm-objdump -d %t2 | FileCheck %s
> +// REQUIRES: aarch64
> +
> +.section .R_AARCH64_ABS16, "ax", at progbits
> +  .hword sym+12
> +
> +.section .R_AARCH64_ABS32, "ax", at progbits
> +  .word sym+24
> +
> +.section .R_AARCH64_ABS64, "ax", at progbits
> +  .xword sym+36
> +
> +// CHECK: Disassembly of section .R_AARCH64_ABS16:
> +// CHECK-NEXT: $d.0:
> +// CHECK-NEXT:     2000:       0c 00   .short
> +//                             ^-- A = 0xc
> +
> +// CHECK-NEXT: Disassembly of section .R_AARCH64_ABS32:
> +// CHECK-NEXT: $d.1:
> +// CHECK-NEXT:     2002:       18 00 00 00     .word
> +//                             ^-- A = 0x18
> +
> +// CHECK-NEXT: Disassembly of section .R_AARCH64_ABS64:
> +// CHECK-NEXT: $d.2:
> +// CHECK-NEXT:     2006:       24 00 00 00     .word
> +//                             ^-- A = 0x24
> +// CHECK-NEXT:     200a:       00 00 00 00     .word
>
>
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