[JITLink][RISC-V] Support R_RISCV_SET_ULEB128/R_RISCV_SUB_ULEB128 for…

[zengdage]

This patch is try to fix the issue #153775 . Now the LLVM JITLink don't support R_RISCV_SET_ULEB128 and R_RISCV_SUB_ULEB128 relocation type, so the bolt can't instrument the elf binary which has exception handling table.

[llvmbot]

@llvm/pr-subscribers-lld
@llvm/pr-subscribers-lld-elf
@llvm/pr-subscribers-llvm-support

@llvm/pr-subscribers-backend-risc-v

Author: Zhijin Zeng (zengdage)

Changes

This patch is try to fix the issue #153775 . Now the LLVM JITLink don't support R_RISCV_SET_ULEB128 and R_RISCV_SUB_ULEB128 relocation type, so the bolt can't instrument the elf binary which has exception handling table.

---

Full diff: https://github.com/llvm/llvm-project/pull/153778.diff

4 Files Affected:

• (modified) llvm/include/llvm/ExecutionEngine/JITLink/riscv.h (+12)
• (modified) llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp (+34-2)
• (modified) llvm/lib/ExecutionEngine/JITLink/riscv.cpp (+4)
• (added) llvm/test/ExecutionEngine/JITLink/RISCV/ELF_reloc_uleb128.s (+21)

diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/riscv.h b/llvm/include/llvm/ExecutionEngine/JITLink/riscv.h
index fcc99787c8e12..9786f5cde3615 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/riscv.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/riscv.h
@@ -221,6 +221,18 @@ enum EdgeKind_riscv : Edge::Kind {
   /// Fixup expression:
   ///   Fixup <- Fixup - Target + Addend
   NegDelta32,
+
+  /// Set ULEB128-encoded value
+  ///
+  /// Fixup expression:
+  ///   Fixup <- Target + Addend
+  R_RISCV_SET_ULEB128,
+
+  /// Subtract from ULEB128-encoded value
+  ///
+  /// Fixup expression:
+  ///   Fixup <- V - Target - Addend
+  R_RISCV_SUB_ULEB128,
 };
 
 /// Returns a string name for the given riscv edge. For debugging purposes
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
index 71a0f14368ac6..8830d023a7a77 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp
@@ -154,18 +154,22 @@ class ELFJITLinker_riscv : public JITLinker<ELFJITLinker_riscv> {
                      std::unique_ptr<LinkGraph> G, PassConfiguration PassConfig)
       : JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {
     JITLinkerBase::getPassConfig().PostAllocationPasses.push_back(
-        [this](LinkGraph &G) { return gatherRISCVPCRelHi20(G); });
+        [this](LinkGraph &G) { return gatherRISCVPair(G); });
   }
 
 private:
   DenseMap<std::pair<const Block *, orc::ExecutorAddrDiff>, const Edge *>
       RelHi20;
+  DenseMap<std::pair<const Block *, orc::ExecutorAddrDiff>, const Edge *>
+      SetULEB128;
 
-  Error gatherRISCVPCRelHi20(LinkGraph &G) {
+  Error gatherRISCVPair(LinkGraph &G) {
     for (Block *B : G.blocks())
       for (Edge &E : B->edges())
         if (E.getKind() == R_RISCV_PCREL_HI20)
           RelHi20[{B, E.getOffset()}] = &E;
+        else if (E.getKind() == R_RISCV_SET_ULEB128)
+          SetULEB128[{B, E.getOffset()}] = &E;
 
     return Error::success();
   }
@@ -189,6 +193,18 @@ class ELFJITLinker_riscv : public JITLinker<ELFJITLinker_riscv> {
                                     "for LO12 PCREL relocation type");
   }
 
+  Expected<const Edge &> getRISCVSetULEB128(const Block &B, const Edge &E) const {
+    using namespace riscv;
+    assert(E.getKind() == R_RISCV_SUB_ULEB128 &&
+           "Can only have pair relocation for R_RISCV_SET_ULEB128 or");
+
+    auto It = SetULEB128.find({&B, E.getOffset()});
+    if (It != SetULEB128.end())
+      return *It->second;
+
+    return make_error<JITLinkError>("No RISCV_SET_ULEB128 relocation type be found");
+  }
+
   Error applyFixup(LinkGraph &G, Block &B, const Edge &E) const {
     using namespace riscv;
     using namespace llvm::support;
@@ -467,6 +483,18 @@ class ELFJITLinker_riscv : public JITLinker<ELFJITLinker_riscv> {
       *(little32_t *)FixupPtr = static_cast<uint32_t>(Value);
       break;
     }
+    case R_RISCV_SET_ULEB128:
+      break;
+    case R_RISCV_SUB_ULEB128: {
+      auto SetULEB128 = getRISCVSetULEB128(B, E);
+      if (!SetULEB128)
+        return SetULEB128.takeError();
+      uint64_t Value = SetULEB128->getTarget().getAddress() +
+                      SetULEB128->getAddend() - E.getTarget().getAddress() -
+                      E.getAddend();
+      encodeULEB128(Value, (reinterpret_cast<uint8_t *>(FixupPtr)));
+      break;
+    }
     }
     return Error::success();
   }
@@ -843,6 +871,10 @@ class ELFLinkGraphBuilder_riscv : public ELFLinkGraphBuilder<ELFT> {
       return EdgeKind_riscv::R_RISCV_32_PCREL;
     case ELF::R_RISCV_ALIGN:
       return EdgeKind_riscv::AlignRelaxable;
+    case ELF::R_RISCV_SET_ULEB128:
+      return EdgeKind_riscv::R_RISCV_SET_ULEB128;
+    case ELF::R_RISCV_SUB_ULEB128:
+      return EdgeKind_riscv::R_RISCV_SUB_ULEB128;
     }
 
     return make_error<JITLinkError>(
diff --git a/llvm/lib/ExecutionEngine/JITLink/riscv.cpp b/llvm/lib/ExecutionEngine/JITLink/riscv.cpp
index a4e4daef97fb5..9e9f4433a9fc2 100644
--- a/llvm/lib/ExecutionEngine/JITLink/riscv.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/riscv.cpp
@@ -84,6 +84,10 @@ const char *getEdgeKindName(Edge::Kind K) {
     return "AlignRelaxable";
   case NegDelta32:
     return "NegDelta32";
+  case R_RISCV_SET_ULEB128:
+    return "R_RISCV_SET_ULEB128";
+  case R_RISCV_SUB_ULEB128:
+    return "R_RISCV_SUB_ULEB128";
   }
   return getGenericEdgeKindName(K);
 }
diff --git a/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_reloc_uleb128.s b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_reloc_uleb128.s
new file mode 100644
index 0000000000000..2b9f6f7d6bb37
--- /dev/null
+++ b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_reloc_uleb128.s
@@ -0,0 +1,21 @@
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=riscv64 -filetype=obj -o %t/riscv64_reloc_uleb128.o %s
+# RUN: llvm-mc -triple=riscv32 -filetype=obj -o %t/riscv32_reloc_uleb128.o %s
+# RUN: llvm-jitlink -noexec -check %s %t/riscv64_reloc_uleb128.o
+# RUN: llvm-jitlink -noexec -check %s %t/riscv32_reloc_uleb128.o
+
+# jitlink-check: *{4}(foo+8) = 0x180
+
+.global main
+main:
+  lw a0, foo
+
+.section ".text","",@progbits
+.type foo,@function
+foo:
+  nop
+  nop
+  .reloc ., R_RISCV_SET_ULEB128, foo+129
+  .reloc ., R_RISCV_SUB_ULEB128, foo+1
+  .word 0
+  .size foo, 8

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[hahnjo]

Generally LGTM, but we may need a check that there actually was sufficient space

[hahnjo]

JITLink code LGTM

[zengdage]

ping

[zqb-all]

LGTM

[maksfb]

@zengdage Nice! Thanks for the fix.