BPF: fix relocation types in lib/Object/RelocationResolver.cpp

[yonghong-song]

Summary

Commit 6a2ea84600ba ("BPF: Add more relocation kinds")
added new relocations R_BPF_64_ABS64 and R_BPF_64_ABS32
for normal 64-bit and 32-bit data relocations.
This is to replace some of functionalities with
R_BPF_64_64 and R_BPF_64_32 so that new R_BPF_64_64
and R_BPF_64_32 semantics are for ld_imm64 and
call instructions only.

The BPF support in lib/Object/RelocationResolver.cpp
is used to perform normal data relocations for
the case like DWARFObjInMemory with an object file
(search function getRelocationResolver() in file
DebugInfo/DWARF/DWARFContext.cpp) or llvm-readobj
to dump ".stack_sizes" section data.
In all these casees, normal 64-bit and 32-bit relocations
are performed and such resolution resolution
is exactly what implemented in RelocationResolver.cpp.

But Commit 6a2ea84600ba missed to change
R_BPF_64_64/R_BPF_64_32 to R_BPF_64_ABS64/R_BPF_64_ABS32.
This patch fixed the issue and added a test for it
with llvm-readobj dumping ".stack_sizes" section.

llvm/lib/Object/RelocationResolver.cpp

case ELF::R_AARCH64_PREL64:
     return S + Addend - Offset;
   default:
     llvm_unreachable("Invalid relocation type");
   }
 }
 
 static bool supportsBPF(uint64_t Type) {
   switch (Type) {
-  case ELF::R_BPF_64_32:
-  case ELF::R_BPF_64_64:
+  case ELF::R_BPF_64_ABS32:
+  case ELF::R_BPF_64_ABS64:
     return true;
   default:
     return false;
   }
 }
 
 static uint64_t resolveBPF(uint64_t Type, uint64_t Offset, uint64_t S,
                            uint64_t LocData, int64_t /*Addend*/) {
   switch (Type) {
-  case ELF::R_BPF_64_32:
+  case ELF::R_BPF_64_ABS32:
     return (S + LocData) & 0xFFFFFFFF;
-  case ELF::R_BPF_64_64:
+  case ELF::R_BPF_64_ABS64:
     return S + LocData;
   default:
     llvm_unreachable("Invalid relocation type");
   }
 }
 
 static bool supportsMips64(uint64_t Type) {
   switch (Type) {

llvm/test/Object/BPF/lit.local.cfg

+if not 'BPF' in config.root.targets:
+    config.unsupported = True

llvm/test/Object/BPF/yaml2obj-elf-bpf-rel.yaml

+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj -r --stack-sizes %t | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT:   Section (3) .rel.text {
+# CHECK-NEXT:     0x0 R_BPF_64_64 g
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section (5) .rel.stack_sizes {
+# CHECK-NEXT:     0x0 R_BPF_64_ABS64 .text
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+# CHECK:      StackSizes [
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Function: test
+# CHECK-NEXT:     Size: 0x0
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_BPF
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x8
+    Content:         '1801000000000000000000000000000061100000000000009500000000000000'
+  - Name:            .stack_sizes
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_LINK_ORDER ]
+    Link:            .text
+    AddressAlign:    0x1
+    Entries:
+      - Size:            0x0
+  - Name:            .bss
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x4
+    Size:            0x4
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    AddressAlign:    0x8
+    Info:            .text
+    Relocations:
+      - Symbol:          g
+        Type:            R_BPF_64_64
+  - Name:            .rel.stack_sizes
+    Type:            SHT_REL
+    Link:            .symtab
+    AddressAlign:    0x8
+    Info:            .stack_sizes
+    Relocations:
+      - Symbol:          .text
+        Type:            R_BPF_64_ABS64
+  - Type:            SectionHeaderTable
+    Sections:
+      - Name:            .strtab
+      - Name:            .text
+      - Name:            .rel.text
+      - Name:            .stack_sizes
+      - Name:            .rel.stack_sizes
+      - Name:            .bss
+      - Name:            .symtab
+      - Name:            .shstrtab
+Symbols:
+  - Name:            t.c
+    Type:            STT_FILE
+    Index:           SHN_ABS
+  - Name:            .text
+    Type:            STT_SECTION
+    Section:         .text
+  - Name:            test
+    Type:            STT_FUNC
+    Section:         .text
+    Binding:         STB_GLOBAL
+    Size:            0x20
+  - Name:            g
+    Type:            STT_OBJECT
+    Section:         .bss
+    Binding:         STB_GLOBAL
+    Size:            0x4
+...