ELFRelocs/AArch64: update canonical reference URL (NFC)

[artagnon]

Update the URL of the reference to be used for AArch64.def, and add some comments. The canonical aaelf64 document can be found at:

https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst

[llvmbot]

@llvm/pr-subscribers-llvm-binary-utilities

Author: Ramkumar Ramachandra (artagnon)

Changes

As per the released specification of aaelf64, there is no longer any R_AARCH64_AUTH_RELATIVE. Stripping it from the def file has no consequences, as it is unused in the code, so this change is non-functional.

---

Full diff: https://github.com/llvm/llvm-project/pull/86955.diff

1 Files Affected:

• (modified) llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def (+12-7)

diff --git a/llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def b/llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
index 5fb3fa4aeb7beb..f01470d49bca35 100644
--- a/llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
+++ b/llvm/include/llvm/BinaryFormat/ELFRelocs/AArch64.def
@@ -1,18 +1,19 @@
-
 #ifndef ELF_RELOC
 #error "ELF_RELOC must be defined"
 #endif
 
-// Based on ABI release 1.1-beta, dated 6 November 2013. NB: The cover page of
-// this document, IHI0056C_beta_aaelf64.pdf, on infocenter.arm.com, still
-// labels this as release 1.0.
+// Based on released ABI: https://github.com/ARM-software/abi-aa, aaelf64.
+// ELF64
+// Null relocation: also 0x100 for ELF64
 ELF_RELOC(R_AARCH64_NONE,                                0)
+// Data relocations
 ELF_RELOC(R_AARCH64_ABS64,                           0x101)
 ELF_RELOC(R_AARCH64_ABS32,                           0x102)
 ELF_RELOC(R_AARCH64_ABS16,                           0x103)
 ELF_RELOC(R_AARCH64_PREL64,                          0x104)
 ELF_RELOC(R_AARCH64_PREL32,                          0x105)
 ELF_RELOC(R_AARCH64_PREL16,                          0x106)
+// Static relocations
 ELF_RELOC(R_AARCH64_MOVW_UABS_G0,                    0x107)
 ELF_RELOC(R_AARCH64_MOVW_UABS_G0_NC,                 0x108)
 ELF_RELOC(R_AARCH64_MOVW_UABS_G1,                    0x109)
@@ -60,11 +61,13 @@ ELF_RELOC(R_AARCH64_LD64_GOT_LO12_NC,                0x138)
 ELF_RELOC(R_AARCH64_LD64_GOTPAGE_LO15,               0x139)
 ELF_RELOC(R_AARCH64_PLT32,                           0x13a)
 ELF_RELOC(R_AARCH64_GOTPCREL32,                      0x13b)
+// General dynamic TLS relocations
 ELF_RELOC(R_AARCH64_TLSGD_ADR_PREL21,                0x200)
 ELF_RELOC(R_AARCH64_TLSGD_ADR_PAGE21,                0x201)
 ELF_RELOC(R_AARCH64_TLSGD_ADD_LO12_NC,               0x202)
 ELF_RELOC(R_AARCH64_TLSGD_MOVW_G1,                   0x203)
 ELF_RELOC(R_AARCH64_TLSGD_MOVW_G0_NC,                0x204)
+// Local dynamic TLS relocations
 ELF_RELOC(R_AARCH64_TLSLD_ADR_PREL21,                0x205)
 ELF_RELOC(R_AARCH64_TLSLD_ADR_PAGE21,                0x206)
 ELF_RELOC(R_AARCH64_TLSLD_ADD_LO12_NC,               0x207)
@@ -92,6 +95,7 @@ ELF_RELOC(R_AARCH64_TLSIE_MOVW_GOTTPREL_G0_NC,       0x21c)
 ELF_RELOC(R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21,       0x21d)
 ELF_RELOC(R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC,     0x21e)
 ELF_RELOC(R_AARCH64_TLSIE_LD_GOTTPREL_PREL19,        0x21f)
+// Local exec TLS relocations
 ELF_RELOC(R_AARCH64_TLSLE_MOVW_TPREL_G2,             0x220)
 ELF_RELOC(R_AARCH64_TLSLE_MOVW_TPREL_G1,             0x221)
 ELF_RELOC(R_AARCH64_TLSLE_MOVW_TPREL_G1_NC,          0x222)
@@ -108,6 +112,7 @@ ELF_RELOC(R_AARCH64_TLSLE_LDST32_TPREL_LO12,         0x22c)
 ELF_RELOC(R_AARCH64_TLSLE_LDST32_TPREL_LO12_NC,      0x22d)
 ELF_RELOC(R_AARCH64_TLSLE_LDST64_TPREL_LO12,         0x22e)
 ELF_RELOC(R_AARCH64_TLSLE_LDST64_TPREL_LO12_NC,      0x22f)
+// TLS descriptor relocations
 ELF_RELOC(R_AARCH64_TLSDESC_LD_PREL19,               0x230)
 ELF_RELOC(R_AARCH64_TLSDESC_ADR_PREL21,              0x231)
 ELF_RELOC(R_AARCH64_TLSDESC_ADR_PAGE21,              0x232)
@@ -123,7 +128,7 @@ ELF_RELOC(R_AARCH64_TLSLE_LDST128_TPREL_LO12_NC,     0x23b)
 ELF_RELOC(R_AARCH64_TLSLD_LDST128_DTPREL_LO12,       0x23c)
 ELF_RELOC(R_AARCH64_TLSLD_LDST128_DTPREL_LO12_NC,    0x23d)
 ELF_RELOC(R_AARCH64_AUTH_ABS64,                      0x244)
-// Dynamic relocations start
+// Dynamic relocations
 ELF_RELOC(R_AARCH64_COPY,                            0x400)
 ELF_RELOC(R_AARCH64_GLOB_DAT,                        0x401)
 ELF_RELOC(R_AARCH64_JUMP_SLOT,                       0x402)
@@ -136,8 +141,8 @@ ELF_RELOC(R_AARCH64_TLS_DTPREL64,                    0x405)
 ELF_RELOC(R_AARCH64_TLS_TPREL64,                     0x406)
 ELF_RELOC(R_AARCH64_TLSDESC,                         0x407)
 ELF_RELOC(R_AARCH64_IRELATIVE,                       0x408)
-ELF_RELOC(R_AARCH64_AUTH_RELATIVE,                   0x411)
 
+// ELF32
 // ELF_RELOC(R_AARCH64_P32_NONE,                         0)
 ELF_RELOC(R_AARCH64_P32_ABS32,                       0x001)
 ELF_RELOC(R_AARCH64_P32_ABS16,                       0x002)
@@ -216,7 +221,7 @@ ELF_RELOC(R_AARCH64_P32_TLSDESC_ADR_PAGE21,          0x07c)
 ELF_RELOC(R_AARCH64_P32_TLSDESC_LD32_LO12,           0x07d)
 ELF_RELOC(R_AARCH64_P32_TLSDESC_ADD_LO12,            0x07e)
 ELF_RELOC(R_AARCH64_P32_TLSDESC_CALL,                0x07f)
-// Dynamic relocations start
+// Dynamic relocations
 ELF_RELOC(R_AARCH64_P32_COPY,                        0x0b4)
 ELF_RELOC(R_AARCH64_P32_GLOB_DAT,                    0x0b5)
 ELF_RELOC(R_AARCH64_P32_JUMP_SLOT,                   0x0b6)

[kovdan01]

The relocation is defined in https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst. The relocation is present in the spec (just not in the aaelf64 where you've tried to find it in but in pauthabielf64), we already use it in downstream and are submitting related patches to upstream - see, for example, #72714. Please don't delete it.

I suppose that @smithp35 can add something in terms of how Arm spec is organized, but basically I'm absolutely sure that the relocation is definitely needed. I see that there are other minor changes like changing comments in AArch64.def and adding a link to the aaelf64 spec - this might be useful, and, for example, a comment with a link to pauthabielf64 could be added.

Also tagging @asl

[artagnon]

Hi @kovdan01. Thanks for the review: now updated (with new commit message).

[kovdan01]

Looks reasonable as for me, but I want to see other opinions on this. AFAIK, @smithp35 will be available next week.

Also, please do not override old history via force-pushes. While the PR is pretty trivial, it's still nice to see history of the changes.

[MaskRay]

Looks reasonable as for me, but I want to see other opinions on this. AFAIK, @smithp35 will be available next week.

Also, please do not override old history via force-pushes. While the PR is pretty trivial, it's still nice to see history of the changes.

The update looks good me, but the official sign-off should probably be from an ABI maintainer like @smithp35

[smithp35]

One small correction to use Static AArch64 relocations to match https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#static-aarch64-relocations otherwise LGTM.

It is true that the full definition of the AUTH relocations are in the PAuthABI. They should be mentioned in aaelf64 too as I recently merged that change. Currently checking aaelf64 it looks like there's a couple of mistakes that I've created ARM-software/abi-aa#254 to fix.

Given that PAuthABI is needed to understand the relocations I think it is fine to have this as the canonical reference.

[smithp35]

LGTM thanks for the update