[ELF] Produce DT_RISCV_VARIANT_CC

[MaskRay]

Summary

https://github.com/riscv/riscv-elf-psabi-doc/pull/190 introduced STO_RISCV_VARIANT_CC.
The linker should do:

• Copy the STO_RISCV_VARIANT_CC bit to .symtab/.dynsym: already fulfilled after 82ed93ea0552c8f82df05859ee93e70b71c4e65d
• Produce DT_RISCV_VARIANT_CC if at least one R_RISCV_JUMP_SLOT relocation references a symbol with the STO_RISCV_VARIANT_CC bit. Done by this patch.

[MaskRay]

rebase

[MaskRay]

simplify test

[kito-cheng]

LGTM, thanks for complete the lld part of STO_RISCV_VARIANT_CC !

lld/ELF/SyntheticSections.cpp

1459–1462

nit: Maybe llvm::any_of? although use llvm::_find_if can archive same purpose, but any_of might improve readable here?

[MaskRay]

use any_of

[MaskRay]

add release note

[MaskRay]

fix release note

[MaskRay]

lld/ELF/SyntheticSections.cpp

1459–1462

Thanks for the suggestion!

lld/ELF/SyntheticSections.cpp

case EM_SPARCV9:
       addInSec(DT_PLTGOT, in.plt);
       break;
     case EM_AARCH64:
       if (llvm::find_if(in.relaPlt->relocs, [](const DynamicReloc &r) {
            return r.type == target->pltRel &&
                   r.sym->stOther & STO_AARCH64_VARIANT_PCS;
           }) != in.relaPlt->relocs.end())
         addInt(DT_AARCH64_VARIANT_PCS, 0);
+      addInSec(DT_PLTGOT, in.gotPlt);
+      break;
+    case EM_RISCV:
+      if (llvm::find_if(in.relaPlt->relocs, [](const DynamicReloc &r) {
+            return r.type == target->pltRel &&
+                   (r.sym->stOther & STO_RISCV_VARIANT_CC);
+          }) != in.relaPlt->relocs.end())
+        addInt(DT_RISCV_VARIANT_CC, 0);
       LLVM_FALLTHROUGH;
     default:
       addInSec(DT_PLTGOT, in.gotPlt);
       break;
     }
     addInt(DT_PLTREL, config->isRela ? DT_RELA : DT_REL);
   }
 
for (SymbolTableEntry &ent : symbols) {
     // The 3 most significant bits of st_other are used by OpenPOWER ABI.
     // See getPPC64GlobalEntryToLocalEntryOffset() for more details.
     if (config->emachine == EM_PPC64)
       eSym->st_other |= sym->stOther & 0xe0;
     // The most significant bit of st_other is used by AArch64 ABI for the
     // variant PCS.
     else if (config->emachine == EM_AARCH64)
       eSym->st_other |= sym->stOther & STO_AARCH64_VARIANT_PCS;
+    else if (config->emachine == EM_RISCV)
+      eSym->st_other |= sym->stOther & STO_RISCV_VARIANT_CC;
 
     eSym->st_name = ent.strTabOffset;
     if (isDefinedHere)
       eSym->st_shndx = getSymSectionIndex(ent.sym);
     else
       eSym->st_shndx = 0;
 
     // Copy symbol size if it is a defined symbol. st_size is not significant

lld/test/ELF/riscv-variant-cc.s

+# REQUIRES: riscv
+# RUN: split-file %s %t
+
+# RUN: llvm-mc -filetype=obj -triple=riscv32 %t/test1 -o %t.o
+# RUN: ld.lld %t.o --shared -o %t.so
+# RUN: llvm-readelf --dynamic-table %t.so | FileCheck --check-prefix T1-CCDYN %s
+# RUN: llvm-readelf --symbols %t.so | FileCheck --check-prefix T1-CCSYM %s
+
+# T1-CCDYN-NOT:  (RISCV_VARIANT_CC)
+# T1-CCSYM:      Symbol table '.dynsym'
+# T1-CCSYM:      0 NOTYPE GLOBAL DEFAULT [VARIANT_CC] [[#]] func_global_def
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 %t/test2 -o %t.o
+# RUN: ld.lld %t.o --shared -o %t.so
+# RUN: llvm-readelf --dynamic-table %t.so | FileCheck --check-prefix T2-CCDYN %s
+# RUN: llvm-readelf --symbols %t.so | FileCheck --check-prefix T2-CCSYM %s
+
+# T2-CCDYN:      0x0000000070000001 (RISCV_VARIANT_CC) 0
+# T2-CCSYM:      Symbol table '.dynsym'
+# T2-CCSYM:      0 NOTYPE GLOBAL DEFAULT [VARIANT_CC] [[#]] func_global_def
+
+# RUN: llvm-mc -filetype=obj -triple=riscv32 %t/test3 -o %t.o
+# RUN: ld.lld %t.o --shared -o %t.so
+# RUN: llvm-readelf --dynamic-table %t.so | FileCheck --check-prefix T3-CCDYN %s
+# RUN: llvm-readelf --symbols %t.so | FileCheck --check-prefix T3-CCSYM %s
+
+# T3-CCDYN:      0x70000001 (RISCV_VARIANT_CC) 0
+# T3-CCSYM:      Symbol table '.dynsym'
+# T3-CCSYM:      0 IFUNC  GLOBAL DEFAULT [VARIANT_CC] UND   ifunc_global_def
+# T3-CCSYM:      0 NOTYPE GLOBAL DEFAULT               [[#]] func_global_def
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 %t/test4 -o %t.o
+# RUN: ld.lld %t.o --shared -o %t.so
+# RUN: llvm-readelf --dynamic-table %t.so | FileCheck --check-prefix T4-CCDYN %s
+# RUN: llvm-readelf --symbols %t.so | FileCheck --check-prefix T4-CCSYM %s
+
+# T4-CCDYN-NOT:  0x0000000070000001 (RISCV_VARIANT_CC) 0
+# T4-CCSYM:      Symbol table '.dynsym'
+# T4-CCSYM:      0 IFUNC GLOBAL DEFAULT [VARIANT_CC]  [[#]] ifunc_global_def
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 %t/test5 -o %t.o
+# RUN: ld.lld %t.o --shared -o %t.so
+# RUN: llvm-readelf --symbols %t.so | FileCheck --check-prefix T5-CCSYM %s
+
+# T5-CCSYM:      Symbol table '.dynsym'
+# T5-CCSYM:      0 NOTYPE  GLOBAL DEFAULT [VARIANT_CC] UND   func_global_undef
+# T5-CCSYM-NEXT: 0 NOTYPE  GLOBAL DEFAULT [VARIANT_CC] [[#]] func_global_def
+# T5-CCSYM-NEXT: 0 IFUNC   GLOBAL DEFAULT [VARIANT_CC] [[#]] ifunc_global_def
+# T5-CCSYM:      Symbol table '.symtab' contains 10 entries:
+# T5-CCSYM:      0 NOTYPE  LOCAL  DEFAULT [VARIANT_CC] [[#]] func_local
+# T5-CCSYM-NEXT: 0 IFUNC   LOCAL  DEFAULT [VARIANT_CC] [[#]] ifunc_local
+# T5-CCSYM:      0 NOTYPE  LOCAL  HIDDEN  [VARIANT_CC] [[#]] func_global_hidden
+# T5-CCSYM-NEXT: 0 IFUNC   LOCAL  HIDDEN  [VARIANT_CC] [[#]] ifunc_global_hidden
+# T5-CCSYM:      0 NOTYPE  GLOBAL DEFAULT [VARIANT_CC] [[#]] func_global_def
+# T5-CCSYM-NEXT: 0 NOTYPE  GLOBAL DEFAULT [VARIANT_CC] UND   func_global_undef
+# T5-CCSYM-NEXT: 0 IFUNC   GLOBAL DEFAULT [VARIANT_CC] [[#]] ifunc_global_def
+
+
+#--- test1
+## An object with a variant_pcs symbol but without a R_RISCV_JMP_SLOT
+## should not generate a DT_RISCV_VARIANT_CC.
+.text
+.global func_global_def
+.variant_cc func_global_def
+
+func_global_def:
+  ret
+
+#--- test2
+## An object with a variant_cc symbol and with a R_RISCV_JMP_SLOT
+## should generate a DT_RISCV_VARIANT_CC.
+.text
+.global func_global_def
+.variant_cc func_global_def
+
+func_global_def:
+  bl func_global_def
+
+#--- test3
+## Same as before, but targeting a GNU IFUNC.
+.text
+.global ifunc_global_def
+.global func_global_def
+.variant_cc ifunc_global_def
+.type ifunc_global_def, %gnu_indirect_function
+
+func_global_def:
+  bl ifunc_global_def
+
+#--- test4
+## An object with a variant_cc symbol and with a R_RISCV_IRELATIVE
+## should not generate a DT_RISCV_VARIANT_CC.
+.text
+.global ifunc_global_def
+.global func_global_def
+.variant_cc ifunc_global_def
+.type ifunc_global_def, %gnu_indirect_function
+
+ifunc_global_def:
+  bl func_global_def
+
+#--- test5
+## Check if STO_RISCV_VARIANT_CC is kept on symbol st_other for both undef,
+## local, and hidden visibility.
+.text
+.global func_global_def, func_global_undef, func_global_hidden
+.global ifunc_global_def, ifunc_global_hidden
+.local func_local
+
+.hidden func_global_hidden, ifunc_global_hidden
+
+.type ifunc_global_def, %gnu_indirect_function
+.type ifunc_global_hidden, %gnu_indirect_function
+.type ifunc_local, %gnu_indirect_function
+
+.variant_cc func_global_def
+.variant_cc func_global_undef
+.variant_cc func_global_hidden
+.variant_cc func_local
+.variant_cc ifunc_global_def
+.variant_cc ifunc_global_hidden
+.variant_cc ifunc_local
+
+func_global_def:
+func_global_hidden:
+func_local:
+ifunc_global_def:
+ifunc_global_hidden:
+ifunc_local:
+  ret