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Differential D77647

[ELF][AArch64] Add R_AARCH64_PLT32 relocation type.
ClosedPublic

Authored by psmith on Apr 7 2020, 6:58 AM.

Details

Reviewers
leonardchan
mcgrathr
phosek
pcc
jakehehrlich
• espindola
jhenderson
psmith
MaskRay
Commits
rG02cd80e68ecf: [ELF][AArch64] Add R_AARCH64_PLT32 relocation type.
Summary

The R_AARCH64_PLT32 relocation type will be documented in the next release of ELF for the 64-bit Arm Architecture. It is being added in draft state for the benefit of the position independent vtable feature D72959

R_AARCH64_PLT32 is very similar to R_AARCH64_PREL32. The intention is to provide a signed 32-bit integer representing an offset from the place to a function.

  • It relocates 32-bit data
  • The expression is S + A - P
  • The overflow check for the expression is -2^31 <= X < 2^31
  • The relocation generates Thunks/Veneers/Stubs and PLT entries as per R_AARCH64_CALL26
  • If the symbol S is an undefined weak the ABI draft does not define its value.

The ABI defines a code for ilp32 for completeness, I have added the code but have only added to the existing reloc-types-elf-aarch64.text as there is no ilp32 equivalent test case.

Diff Detail

Event Timeline

psmith created this revision.Apr 7 2020, 6:58 AM
Herald added a reviewer: • espindola. · View Herald TranscriptApr 7 2020, 6:58 AM
Herald added a reviewer: jhenderson. · View Herald Transcript
Herald added subscribers: danielkiss, rupprecht, MaskRay and 2 others. · View Herald Transcript
mcgrathr accepted this revision.Apr 7 2020, 12:15 PM

Thanks!

This revision is now accepted and ready to land.Apr 7 2020, 12:15 PM
MaskRay added a reviewer: psmith.Apr 7 2020, 12:43 PM
MaskRay accepted this revision.EditedApr 7 2020, 1:16 PM

Ah, did not notice the author :/

A dedicated address insignificant relocation type will be useful. https://sourceware.org/pipermail/binutils/2020-April/000424.html

Closed by commit rG02cd80e68ecf: [ELF][AArch64] Add R_AARCH64_PLT32 relocation type. (authored by psmith). · Explain WhyApr 8 2020, 4:49 AM
This revision was automatically updated to reflect the committed changes.
Herald added a project: Restricted Project. · View Herald TranscriptApr 8 2020, 4:49 AM
leonardchan mentioned this in D81184: [lld][ELF][AArch64] Handle R_AARCH64_PLT32 relocation.Jun 4 2020, 11:54 AM
pcc added inline comments.Jun 5 2020, 3:08 PM
llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
135

I assume this isn't the final value of the relocation type? The range [0x400, ...] is reserved for dynamic relocations; I would have expected this to be added in the range [0x100, 0x200) together with the other non-TLS static relocations.

mcgrathr added inline comments.Jun 5 2020, 4:38 PM
llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
135

The draft shared by peter.smith@arm.com says:

+    | ELF64 Code | ELF32 Code | Name              | Operation | Comment                                                                   |
+    | 1033       | 189        | R\_<CLS>\_PLT32   | S + A - P | Check that -2\ :sup:`31` <= X < 2\ :sup:`31` see call and jump relocations|

I don't think it has been finalized yet so if different values make more sense, please follow up with him and/or arm.eabi@arm.com where these additions were discussed (and please CC: me and @leonardchan on any such discussion).

pcc added inline comments.Jun 5 2020, 6:36 PM
llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
135

Thanks, I followed up on the arm.eabi thread that everyone should already be cc'd on.

leonardchan mentioned this in rG723b5a178542: [lld][ELF][AArch64] Handle R_AARCH64_PLT32 relocation.Jun 23 2020, 4:12 PM

Revision Contents

PathSize
llvm/
include/
llvm/
BinaryFormat/
ELFRelocs/
2 lines
test/
tools/
llvm-readobj/
ELF/
2 lines

Diff 255962

llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def

Show First 20 Lines • Show All 126 Lines • ▼ Show 20 Lines
// 0x404 and 0x405 are now R_AARCH64_TLS_IMPDEF1 and R_AARCH64_TLS_IMPDEF2 // 0x404 and 0x405 are now R_AARCH64_TLS_IMPDEF1 and R_AARCH64_TLS_IMPDEF2
// We follow GNU and define TLS_IMPDEF1 as TLS_DTPMOD64 and TLS_IMPDEF2 as // We follow GNU and define TLS_IMPDEF1 as TLS_DTPMOD64 and TLS_IMPDEF2 as
// TLS_DTPREL64 // TLS_DTPREL64
ELF_RELOC(R_AARCH64_TLS_DTPMOD64, 0x404) ELF_RELOC(R_AARCH64_TLS_DTPMOD64, 0x404)
ELF_RELOC(R_AARCH64_TLS_DTPREL64, 0x405) ELF_RELOC(R_AARCH64_TLS_DTPREL64, 0x405)
ELF_RELOC(R_AARCH64_TLS_TPREL64, 0x406) ELF_RELOC(R_AARCH64_TLS_TPREL64, 0x406)
ELF_RELOC(R_AARCH64_TLSDESC, 0x407) ELF_RELOC(R_AARCH64_TLSDESC, 0x407)
ELF_RELOC(R_AARCH64_IRELATIVE, 0x408) ELF_RELOC(R_AARCH64_IRELATIVE, 0x408)
ELF_RELOC(R_AARCH64_PLT32, 0x409)
pccUnsubmitted
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I assume this isn't the final value of the relocation type? The range [0x400, ...] is reserved for dynamic relocations; I would have expected this to be added in the range [0x100, 0x200) together with the other non-TLS static relocations.

pcc: I assume this isn't the final value of the relocation type? The range `[0x400, ...]` is…
mcgrathrUnsubmitted
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The draft shared by peter.smith@arm.com says:

+    | ELF64 Code | ELF32 Code | Name              | Operation | Comment                                                                   |
+    | 1033       | 189        | R\_<CLS>\_PLT32   | S + A - P | Check that -2\ :sup:`31` <= X < 2\ :sup:`31` see call and jump relocations|

I don't think it has been finalized yet so if different values make more sense, please follow up with him and/or arm.eabi@arm.com where these additions were discussed (and please CC: me and @leonardchan on any such discussion).

mcgrathr: The draft shared by peter.smith@arm.com says: ``` + | ELF64 Code | ELF32 Code | Name…
pccUnsubmitted
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Thanks, I followed up on the arm.eabi thread that everyone should already be cc'd on.

pcc: Thanks, I followed up on the arm.eabi thread that everyone should already be cc'd on.
// ELF_RELOC(R_AARCH64_P32_NONE, 0) // ELF_RELOC(R_AARCH64_P32_NONE, 0)
ELF_RELOC(R_AARCH64_P32_ABS32, 0x001) ELF_RELOC(R_AARCH64_P32_ABS32, 0x001)
ELF_RELOC(R_AARCH64_P32_ABS16, 0x002) ELF_RELOC(R_AARCH64_P32_ABS16, 0x002)
ELF_RELOC(R_AARCH64_P32_PREL32, 0x003) ELF_RELOC(R_AARCH64_P32_PREL32, 0x003)
ELF_RELOC(R_AARCH64_P32_PREL16, 0x004) ELF_RELOC(R_AARCH64_P32_PREL16, 0x004)
ELF_RELOC(R_AARCH64_P32_MOVW_UABS_G0, 0x005) ELF_RELOC(R_AARCH64_P32_MOVW_UABS_G0, 0x005)
ELF_RELOC(R_AARCH64_P32_MOVW_UABS_G0_NC, 0x006) ELF_RELOC(R_AARCH64_P32_MOVW_UABS_G0_NC, 0x006)
▲ Show 20 Lines • Show All 71 Lines • ▼ Show 20 Lines
ELF_RELOC(R_AARCH64_P32_GLOB_DAT, 0x0b5) ELF_RELOC(R_AARCH64_P32_GLOB_DAT, 0x0b5)
ELF_RELOC(R_AARCH64_P32_JUMP_SLOT, 0x0b6) ELF_RELOC(R_AARCH64_P32_JUMP_SLOT, 0x0b6)
ELF_RELOC(R_AARCH64_P32_RELATIVE, 0x0b7) ELF_RELOC(R_AARCH64_P32_RELATIVE, 0x0b7)
ELF_RELOC(R_AARCH64_P32_TLS_DTPREL, 0x0b8) ELF_RELOC(R_AARCH64_P32_TLS_DTPREL, 0x0b8)
ELF_RELOC(R_AARCH64_P32_TLS_DTPMOD, 0x0b9) ELF_RELOC(R_AARCH64_P32_TLS_DTPMOD, 0x0b9)
ELF_RELOC(R_AARCH64_P32_TLS_TPREL, 0x0ba) ELF_RELOC(R_AARCH64_P32_TLS_TPREL, 0x0ba)
ELF_RELOC(R_AARCH64_P32_TLSDESC, 0x0bb) ELF_RELOC(R_AARCH64_P32_TLSDESC, 0x0bb)
ELF_RELOC(R_AARCH64_P32_IRELATIVE, 0x0bc) ELF_RELOC(R_AARCH64_P32_IRELATIVE, 0x0bc)
ELF_RELOC(R_AARCH64_P32_PLT32, 0x0bd)

llvm/test/tools/llvm-readobj/ELF/reloc-types-elf-aarch64.test

Show First 20 Lines • Show All 121 Lines • ▼ Show 20 Lines
# CHECK: Type: R_AARCH64_GLOB_DAT (1025) # CHECK: Type: R_AARCH64_GLOB_DAT (1025)
# CHECK: Type: R_AARCH64_JUMP_SLOT (1026) # CHECK: Type: R_AARCH64_JUMP_SLOT (1026)
# CHECK: Type: R_AARCH64_RELATIVE (1027) # CHECK: Type: R_AARCH64_RELATIVE (1027)
# CHECK: Type: R_AARCH64_TLS_DTPMOD64 (1028) # CHECK: Type: R_AARCH64_TLS_DTPMOD64 (1028)
# CHECK: Type: R_AARCH64_TLS_DTPREL64 (1029) # CHECK: Type: R_AARCH64_TLS_DTPREL64 (1029)
# CHECK: Type: R_AARCH64_TLS_TPREL64 (1030) # CHECK: Type: R_AARCH64_TLS_TPREL64 (1030)
# CHECK: Type: R_AARCH64_TLSDESC (1031) # CHECK: Type: R_AARCH64_TLSDESC (1031)
# CHECK: Type: R_AARCH64_IRELATIVE (1032) # CHECK: Type: R_AARCH64_IRELATIVE (1032)
# CHECK: Type: R_AARCH64_PLT32 (1033)
--- !ELF --- !ELF
FileHeader: FileHeader:
Class: ELFCLASS64 Class: ELFCLASS64
Data: ELFDATA2LSB Data: ELFDATA2LSB
Type: ET_REL Type: ET_REL
Machine: EM_AARCH64 Machine: EM_AARCH64
Sections: Sections:
▲ Show 20 Lines • Show All 124 Lines • ▼ Show 20 Lines Relocations:
- Type: R_AARCH64_GLOB_DAT - Type: R_AARCH64_GLOB_DAT
- Type: R_AARCH64_JUMP_SLOT - Type: R_AARCH64_JUMP_SLOT
- Type: R_AARCH64_RELATIVE - Type: R_AARCH64_RELATIVE
- Type: R_AARCH64_TLS_DTPMOD64 - Type: R_AARCH64_TLS_DTPMOD64
- Type: R_AARCH64_TLS_DTPREL64 - Type: R_AARCH64_TLS_DTPREL64
- Type: R_AARCH64_TLS_TPREL64 - Type: R_AARCH64_TLS_TPREL64
- Type: R_AARCH64_TLSDESC - Type: R_AARCH64_TLSDESC
- Type: R_AARCH64_IRELATIVE - Type: R_AARCH64_IRELATIVE
- Type: R_AARCH64_PLT32