[lld] Add infrastructure for handling RISCV vendor-specific relocations. (llvm#159987)

Author: resistor

lld/ELF/Arch/RISCV.cpp

@@ -8,6 +8,7 @@
 
 #include "InputFiles.h"
 #include "OutputSections.h"
+#include "RelocScan.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
 #include "Target.h"
@@ -38,6 +39,10 @@ class RISCV final : public TargetInfo {
   void writePltHeader(uint8_t *buf) const override;
   void writePlt(uint8_t *buf, const Symbol &sym,
                 uint64_t pltEntryAddr) const override;
+  template <class ELFT, class RelTy>
+  void scanSectionImpl(InputSectionBase &, Relocs<RelTy>);
+  template <class ELFT> void scanSection1(InputSectionBase &);
+  void scanSection(InputSectionBase &) override;
   RelType getDynRel(RelType type) const override;
   RelExpr getRelExpr(RelType type, const Symbol &s,
                      const uint8_t *loc) const override;
@@ -278,6 +283,7 @@ RelExpr RISCV::getRelExpr(const RelType type, const Symbol &s,
                           const uint8_t *loc) const {
   switch (type) {
   case R_RISCV_NONE:
+  case R_RISCV_VENDOR:
     return R_NONE;
   case R_RISCV_32:
   case R_RISCV_64:
@@ -1476,3 +1482,54 @@ void elf::mergeRISCVAttributesSections(Ctx &ctx) {
 }
 
 void elf::setRISCVTargetInfo(Ctx &ctx) { ctx.target.reset(new RISCV(ctx)); }
+
+template <class ELFT, class RelTy>
+void RISCV::scanSectionImpl(InputSectionBase &sec, Relocs<RelTy> rels) {
+  RelocScan rs(ctx, &sec);
+  // Many relocations end up in sec.relocations.
+  sec.relocations.reserve(rels.size());
+
+  StringRef rvVendor;
+  for (auto it = rels.begin(); it != rels.end(); ++it) {
+    RelType type = it->getType(false);
+    uint32_t symIndex = it->getSymbol(false);
+    Symbol &sym = sec.getFile<ELFT>()->getSymbol(symIndex);
+    const uint8_t *loc = sec.content().data() + it->r_offset;
+
+    if (type == R_RISCV_VENDOR) {
+      if (!rvVendor.empty())
+        Err(ctx) << getErrorLoc(ctx, loc)
+                 << "malformed consecutive R_RISCV_VENDOR relocations";
+      rvVendor = sym.getName();
+      continue;
+    } else if (!rvVendor.empty()) {
+      Err(ctx) << getErrorLoc(ctx, loc)
+               << "unknown vendor-specific relocation (" << type.v
+               << ") in namespace '" << rvVendor << "' against symbol '" << &sym
+               << "'";
+      rvVendor = "";
+      continue;
+    }
+
+    rs.scan<ELFT, RelTy>(it, type, rs.getAddend<ELFT>(*it, type));
+  }
+
+  // Sort relocations by offset for more efficient searching for
+  // R_RISCV_PCREL_HI20.
+  llvm::stable_sort(sec.relocs(),
+                    [](const Relocation &lhs, const Relocation &rhs) {
+                      return lhs.offset < rhs.offset;
+                    });
+}
+
+template <class ELFT> void RISCV::scanSection1(InputSectionBase &sec) {
+  const RelsOrRelas<ELFT> rels = sec.template relsOrRelas<ELFT>();
+  if (rels.areRelocsCrel())
+    scanSectionImpl<ELFT>(sec, rels.crels);
+  else
+    scanSectionImpl<ELFT>(sec, rels.relas);
+}
+
+void RISCV::scanSection(InputSectionBase &sec) {
+  invokeELFT(scanSection1, sec);
+}

lld/test/riscv-vendor-relocations.s

@@ -0,0 +1,18 @@
+# RUN: llvm-mc -triple riscv32 %s -filetype=obj -o %t.o
+# RUN: not ld.lld -pie %t.o -o /dev/null 2>&1 | FileCheck %s
+
+  .option exact
+
+  .global TARGET
+TARGET:
+  nop
+
+.global INVALID_VENDOR
+.reloc 1f, R_RISCV_VENDOR, INVALID_VENDOR+0
+.reloc 1f, R_RISCV_VENDOR, INVALID_VENDOR+0
+.reloc 1f, R_RISCV_CUSTOM255, TARGET
+1:
+  nop
+
+# CHECK: error: {{.*}}:(.text+0x4): malformed consecutive R_RISCV_VENDOR relocations
+# CHECK: error: {{.*}}:(.text+0x4): unknown vendor-specific relocation (255) in namespace 'INVALID_VENDOR' against symbol 'TARGET'