[PATCH][lld] ELF/AArch64: Add support for checking for ABS32 overflow

[Rui Ueyama]

LGTM

On Wed, Jan 21, 2015 at 10:03 AM, Will Newton <will.newton at linaro.org>
wrote:

> Add support for checking overflow when applying a R_AARCH64_ABS32
> relocation and add a test to ensure it behaves correctly.
> ---
>  .../ELF/AArch64/AArch64RelocationHandler.cpp       | 20 ++++++--
>  test/elf/AArch64/rel-abs32-overflow.test           | 53
> ++++++++++++++++++++++
>  2 files changed, 68 insertions(+), 5 deletions(-)
>  create mode 100644 test/elf/AArch64/rel-abs32-overflow.test
>
> diff --git a/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
> b/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
> index 924836d..85a3038 100644
> --- a/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
> +++ b/lib/ReaderWriter/ELF/AArch64/AArch64RelocationHandler.cpp
> @@ -16,6 +16,13 @@ using namespace elf;
>
>  #define PAGE(X) ((X) & ~0x0FFFL)
>
> +/// \brief Check X is in the interval (-2^(bits-1), 2^bits]
> +bool withinSignedUnsignedRange(int64_t X, int bits) {
> +  if (X < -(1L << (bits - 1)) || X >= (1L << bits))
> +    return false;
> +  return true;
> +}
> +
>  /// \brief R_AARCH64_ABS64 - word64: S + A
>  static void relocR_AARCH64_ABS64(uint8_t *location, uint64_t P, uint64_t
> S,
>                                   int64_t A) {
> @@ -41,9 +48,11 @@ static void relocR_AARCH64_PREL32(uint8_t *location,
> uint64_t P, uint64_t S,
>  }
>
>  /// \brief R_AARCH64_ABS32 - word32:  S + A
> -static void relocR_AARCH64_ABS32(uint8_t *location, uint64_t P, uint64_t
> S,
> -                                 int64_t A) {
> -  int32_t result = (int32_t)(S + A);
> +static std::error_code relocR_AARCH64_ABS32(uint8_t *location, uint64_t P,
> +                                            uint64_t S, int64_t A) {
> +  int64_t result = S + A;
> +  if (!withinSignedUnsignedRange(result, 32))
>

Because you only pass 32 as an argument, I'd probably write (result !=
(int32_t)result), because it's easy to understand.


> +    return make_out_of_range_reloc_error();
>    DEBUG_WITH_TYPE(
>        "AArch64", llvm::dbgs() << "\t\tHandle " << LLVM_FUNCTION_NAME << "
> -";
>        llvm::dbgs() << " S: 0x" << Twine::utohexstr(S);
> @@ -53,6 +62,7 @@ static void relocR_AARCH64_ABS32(uint8_t *location,
> uint64_t P, uint64_t S,
>    *reinterpret_cast<llvm::support::ulittle32_t *>(location) =
>        result |
>        (int32_t) * reinterpret_cast<llvm::support::little32_t *>(location);
> +  return std::error_code();
>  }
>
>  /// \brief R_AARCH64_ADR_PREL_PG_HI21 - Page(S+A) - Page(P)
> @@ -385,8 +395,8 @@ std::error_code
> AArch64TargetRelocationHandler::applyRelocation(
>                            ref.addend());
>      break;
>    case R_AARCH64_ABS32:
> -    relocR_AARCH64_ABS32(location, relocVAddress, targetVAddress,
> ref.addend());
> -    break;
> +    return relocR_AARCH64_ABS32(location, relocVAddress, targetVAddress,
> +                                ref.addend());
>    // Runtime only relocations. Ignore here.
>    case R_AARCH64_RELATIVE:
>    case R_AARCH64_IRELATIVE:
> diff --git a/test/elf/AArch64/rel-abs32-overflow.test
> b/test/elf/AArch64/rel-abs32-overflow.test
> new file mode 100644
> index 0000000..be65ebc
> --- /dev/null
> +++ b/test/elf/AArch64/rel-abs32-overflow.test
> @@ -0,0 +1,53 @@
> +# Check handling of R_AARCH64_ABS32 relocation overflow.
> +# RUN: yaml2obj -format=elf %s > %t-obj
> +# RUN: not lld -flavor gnu -target arm64 -o %t-exe %t-obj 2>&1 |
> FileCheck %s
> +
> +# CHECK: Relocation out of range in file {{.*}}: reference from data1+0
> to data2+34359738369 of type 258 (R_AARCH64_ABS32)
> +# CHECK: Relocation out of range in file {{.*}}: reference from data2+0
> to data1+34359738369 of type 258 (R_AARCH64_ABS32)
> +
> +!ELF
> +FileHeader: !FileHeader
> +  Class: ELFCLASS64
> +  Data: ELFDATA2LSB
> +  Type: ET_REL
> +  Machine: EM_AARCH64
> +
> +Sections:
> +- Name: .text
> +  Type: SHT_PROGBITS
> +  Content: "00000000"
> +  AddressAlign: 16
> +  Flags: [SHF_ALLOC, SHF_EXECINSTR]
> +- Name: .data
> +  Type: SHT_PROGBITS
> +  Content: "0000000000000000"
> +  AddressAlign: 16
> +  Flags: [SHF_ALLOC, SHF_WRITE]
> +
> +- Name: .rela.data
> +  Type: SHT_RELA
> +  Info: .data
> +  AddressAlign: 8
> +  Relocations:
> +    - Offset: 0x0
> +      Symbol: data2
> +      Type: R_AARCH64_ABS32
> +      Addend: 0x800000001
> +    - Offset: 0x4
> +      Symbol: data1
> +      Type: R_AARCH64_ABS32
> +      Addend: 0x800000001
> +
> +Symbols:
> +  Global:
> +    - Name: _start
> +      Section: .text
> +      Value: 0x0
> +      Size: 4
> +    - Name: data1
> +      Section: .data
> +      Size: 4
> +    - Name: data2
> +      Section: .data
> +      Value: 0x4
> +      Size: 4
> --
> 2.1.0
>
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