[PATCH] D33500: [LLD][ELF] .ARM.exidx sentinel section writeTo() should use InputSectionDescriptions.

[Peter Smith via Phabricator via llvm-commits]

peter.smith updated this revision to Diff 100385.
peter.smith added a comment.

The inputSectionRanges() was previously defined in https://reviews.llvm.org/D33496, I've removed it from that review to use Script->getCmd() instead. Sorry for the confusion.

I've now put it back here using an OutputSection* and getCmd() instead of StringRef, I've also started the search for the InputSection that precedes the Sentinel from the end as the sections are sorted in ascending order.


https://reviews.llvm.org/D33500

Files:
  ELF/LinkerScript.cpp
  ELF/LinkerScript.h
  ELF/SyntheticSections.cpp


Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -2181,13 +2181,29 @@
 // This section will have been sorted last in the .ARM.exidx table.
 // This table entry will have the form:
 // | PREL31 upper bound of code that has exception tables | EXIDX_CANTUNWIND |
+// The sentinel must have the PREL31 value of an address higher than any
+// address described by any other table entry.
 void ARMExidxSentinelSection::writeTo(uint8_t *Buf) {
-  // Get the InputSection before us, we are by definition last
-  auto RI = this->OutSec->Sections.rbegin();
-  InputSection *LE = *(++RI);
-  InputSection *LC = cast<InputSection>(LE->getLinkOrderDep());
-  uint64_t S = LC->OutSec->Addr + LC->getOffset(LC->getSize());
-  uint64_t P = this->getVA();
+  uint64_t S = 0;
+  uint64_t P = getVA();
+  InputSection *Highest = nullptr;
+  std::vector<std::vector<InputSection *> *> Ranges =
+      Script->inputSectionRanges(OutSec);
+  // The Sections are sorted in order of ascending PREL31 address with the
+  // sentinel last. We need to find the InputSection that precedes the
+  // sentinel, this may not be in the same Range.
+  for (auto Range = Ranges.rbegin(); Range != Ranges.rend(); ++Range) {
+    auto NonSentinel = std::find_if(
+        (*Range)->rbegin(), (*Range)->rend(),
+        [](InputSection *IS) { return !isa<SyntheticSection>(IS); });
+    if (NonSentinel != (*Range)->rend()) {
+      Highest = *NonSentinel;
+      break;
+    }
+  }
+  assert(Highest != nullptr);
+  InputSection *LS = cast<InputSection>(Highest->getLinkOrderDep());
+  S = std::max(S, LS->OutSec->Addr + LS->getOffset(LS->getSize()));
   Target->relocateOne(Buf, R_ARM_PREL31, S - P);
   write32le(Buf + 4, 0x1);
 }
Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -258,6 +258,8 @@
 
   std::vector<OutputSection *> *OutputSections;
   void fabricateDefaultCommands();
+  std::vector<std::vector<InputSection *> *>
+  inputSectionRanges(OutputSection* OS);
   void addOrphanSections(OutputSectionFactory &Factory);
   void removeEmptyCommands();
   void adjustSectionsBeforeSorting();
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -480,6 +480,22 @@
   Opt.Commands = std::move(Commands);
 }
 
+// For an OutputSection S, return the InputSectionDescriptions that are
+// associated with S. The intention is that callers can iterate over
+// InputSectionDescription::Sections and insert sections such as Thunks.
+std::vector<std::vector<InputSection *> *>
+LinkerScript::inputSectionRanges(OutputSection *OS) {
+  std::vector<std::vector<InputSection *> *> Ranges;
+  OutputSectionCommand *OutCmd = getCmd(OS);
+  if (!OutCmd)
+    return Ranges;
+  for (auto *BaseCmd : OutCmd->Commands) {
+    if (auto *ISD = dyn_cast<InputSectionDescription>(BaseCmd))
+      Ranges.push_back(&ISD->Sections);
+  }
+  return Ranges;
+}
+
 // Add sections that didn't match any sections command.
 void LinkerScript::addOrphanSections(OutputSectionFactory &Factory) {
   for (InputSectionBase *S : InputSections) {


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