[lld] [lld][AArch64][ELF][PAC] Support AUTH relocations and AUTH ELF marking (PR #72714)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,66 @@
+// REQUIRES: aarch64
+
+// RUN: llvm-mc -filetype=obj -triple=aarch64 %p/Inputs/shared2.s -o %t.so.o
+// RUN: ld.lld -shared %t.so.o -soname=so -o %t.so
+// RUN: llvm-mc -filetype=obj -triple=aarch64 %s -o %t.o
+// RUN: ld.lld -pie -z nopack-relative-relocs %t.o %t.so -o %t2
+// RUN: llvm-readobj -r %t2 | FileCheck --check-prefix=UNPACKED %s
+
+// UNPACKED:          Section ({{.+}}) .rela.dyn {
+// UNPACKED-NEXT:       0x303C8 R_AARCH64_AUTH_RELATIVE - 0x1
+// UNPACKED-NEXT:       0x303E1 R_AARCH64_AUTH_RELATIVE - 0x2
+// UNPACKED-NEXT:       0x303D0 R_AARCH64_AUTH_ABS64 zed2 0x0
+// UNPACKED-NEXT:       0x303D8 R_AARCH64_AUTH_ABS64 bar2 0x0
+// UNPACKED-NEXT:     }
+
+// RUN: ld.lld -pie -z pack-relative-relocs %t.o %t.so -o %t2
+// RUN: llvm-readobj -S --dynamic-table %t2 | FileCheck --check-prefix=RELR-HEADERS %s
+// RUN: llvm-readobj -r --raw-relr %t2 | FileCheck --check-prefix=RAW-RELR %s
+// RUN: llvm-readobj -r %t2 | FileCheck --check-prefix=RELR %s
+
+// RELR-HEADERS:       Index: 1
+// RELR-HEADERS-NEXT:  Name: .dynsym
+
+// RELR-HEADERS:       Name: .relr.auth.dyn
+// RELR-HEADERS-NEXT:  Type: SHT_AARCH64_AUTH_RELR
+// RELR-HEADERS-NEXT:  Flags [ (0x2)
+// RELR-HEADERS-NEXT:    SHF_ALLOC (0x2)
+// RELR-HEADERS-NEXT:  ]
+// RELR-HEADERS-NEXT:  Address: [[ADDR:.*]]
+// RELR-HEADERS-NEXT:  Offset: [[ADDR]]
+// RELR-HEADERS-NEXT:  Size: 8
+// RELR-HEADERS-NEXT:  Link: 0
+// RELR-HEADERS-NEXT:  Info: 0
+// RELR-HEADERS-NEXT:  AddressAlignment: 8
+// RELR-HEADERS-NEXT:  EntrySize: 8
+
+// RELR-HEADERS:       0x0000000070000012 AARCH64_AUTH_RELR    [[ADDR]]
+// RELR-HEADERS:       0x0000000070000011 AARCH64_AUTH_RELRSZ  8 (bytes)
+// RELR-HEADERS:       0x0000000070000013 AARCH64_AUTH_RELRENT 8 (bytes)
+
+/// SHT_RELR section contains address/bitmap entries
+/// encoding the offsets for relative relocation.
+// RAW-RELR:           Section ({{.+}}) .relr.auth.dyn {
+// RAW-RELR-NEXT:      0x303E8
+// RAW-RELR-NEXT:      }
+
+/// Decoded SHT_RELR section is same as UNPACKED,
+/// but contains only the relative relocations.
+/// Any relative relocations with odd offset stay in SHT_RELA.
+
+// RELR:      Section ({{.+}}) .rela.dyn {
+// RELR-NEXT:   0x30401 R_AARCH64_AUTH_RELATIVE - 0x2
+// RELR-NEXT:   0x303F0 R_AARCH64_AUTH_ABS64 zed2 0x0
+// RELR-NEXT:   0x303F8 R_AARCH64_AUTH_ABS64 bar2 0x0
+// RELR-NEXT: }
+// RELR-NEXT: Section ({{.+}}) .relr.auth.dyn {
+// RELR-NEXT:   0x303E8 R_AARCH64_RELATIVE -
+// RELR-NEXT: }
+
+.section .test, "aw"
+.p2align 3
+.quad (__ehdr_start + 1)@AUTH(da,42)
----------------
MaskRay wrote:

There is only one RELR entry, which means that feature isn't properly tested.

Perhaps
```
.quad (__ehdr_start + 1)@AUTH(da,42)
.quad (__ehdr_start + 2)@AUTH(ia,43)
.quad (__ehdr_start + 3)@AUTH(da,44)
.quad (__ehdr_start + 0x100000000)@AUTH(ia,45)
...

.byte 0 # switch to odd offset
.quad (__ehdr_start + 1)@AUTH(da,42)
.byte 0 # switch to even offset
.quad (__ehdr_start + 1)@AUTH(da,42)
```

We also need to check section content using `llvm-readelf -x .test`

https://github.com/llvm/llvm-project/pull/72714