ELF2: LinkerScript: lookup absolute paths under sysroot

[atanasyan]

Summary

In case a sysroot prefix is configured, and the filename starts with the '/' character, and the script being processed was located inside the sysroot prefix, the file's name will be looked for in the sysroot prefix. Otherwise, the linker falls to the common lookup scheme.

https://www.sourceware.org/binutils/docs-2.24/ld/File-Commands.html

[ruiu]

ELF/Driver.h

59 ↗

(On Diff #40909)

Can you use MemoryBufferRef::getBufferIdentifier() instead of Path?

ELF/LinkerScript.cpp

31 ↗

(On Diff #40909)

"bool B" for consistency.

167 ↗

(On Diff #40909)

Can you separate this into two lines?

SmallString<128> Path;
(Config->Sysroot + S).toStringRef(Path);
if (sys::fs::exists(Path))
  S = Path;

306–307 ↗

(On Diff #40909)

LinkerScript(A, MB.getBuffer(), true).run();
return;

309 ↗

(On Diff #40909)

LinkerScript(A, MB.getBuffer(), false).run();

[atanasyan]

• Use MemoryBufferRef::getBufferIdentifier() to get a path to the linker script
• Fix code formatting issues mentioned on the review

[ruiu]

LGTM

lld/trunk/ELF/LinkerScript.cpp

 
 using namespace llvm;
 using namespace lld;
 using namespace lld::elf2;
 
 namespace {
 class LinkerScript {
 public:
-  LinkerScript(BumpPtrAllocator *A, StringRef S)
-      : Saver(*A), Tokens(tokenize(S)) {}
+  LinkerScript(BumpPtrAllocator *A, StringRef S, bool B)
+      : Saver(*A), Tokens(tokenize(S)), IsUnderSysroot(B) {}
   void run();
 
 private:
   static std::vector<StringRef> tokenize(StringRef S);
   static StringRef skipSpace(StringRef S);
   StringRef next();
   bool skip(StringRef Tok);
   bool atEOF() { return Tokens.size() == Pos; }
private:
   void readSearchDir();
   void readSections();
 
   void readOutputSectionDescription();
 
   StringSaver Saver;
   std::vector<StringRef> Tokens;
   size_t Pos = 0;
+  bool IsUnderSysroot;
 };
 }
 
 void LinkerScript::run() {
   while (!atEOF()) {
     StringRef Tok = next();
     if (Tok == ";")
       continue;

 void LinkerScript::expect(StringRef Expect) {
   StringRef Tok = next();
   if (Tok != Expect)
     error(Expect + " expected, but got " + Tok);
 }
 
 void LinkerScript::addFile(StringRef S) {
   if (sys::path::is_absolute(S)) {
+    if (IsUnderSysroot) {
+      SmallString<128> Path;
+      (Config->Sysroot + S).toStringRef(Path);
+      if (sys::fs::exists(Path))
+        S = Saver.save(Path.str());
+    }
     Driver->addFile(S);
   } else if (S.startswith("=")) {
     if (Config->Sysroot.empty())
       Driver->addFile(S.substr(1));
     else
       Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)));
   } else if (S.startswith("-l")) {
     Driver->addFile(searchLibrary(S.substr(2)));
while (!skip("}")) {
     expect("(");
     while (!skip(")"))
       InputSections.push_back(next());
   }
 }
 
 // Entry point. The other functions or classes are private to this file.
 void lld::elf2::readLinkerScript(BumpPtrAllocator *A, MemoryBufferRef MB) {
-  LinkerScript(A, MB.getBuffer()).run();
+  StringRef Path = MB.getBufferIdentifier();
+  if (!Config->Sysroot.empty())
+    for (; !Path.empty(); Path = sys::path::parent_path(Path))
+      if (sys::fs::equivalent(Config->Sysroot, Path)) {
+        LinkerScript(A, MB.getBuffer(), true).run();
+        return;
+      }
+  LinkerScript(A, MB.getBuffer(), false).run();
 }

lld/trunk/test/ELF/linkerscript.s

 # RUN: ld.lld -o %t2 %t.script -L%t.dir
 # RUN: llvm-readobj %t2 > /dev/null
 
 # RUN: echo "GROUP(" %t libxyz.a ")" > %t.script
 # RUN: not ld.lld -o %t2 %t.script
 # RUN: ld.lld -o %t2 %t.script -L%t.dir
 # RUN: llvm-readobj %t2 > /dev/null
 
+# RUN: echo "GROUP(" %t /libxyz.a ")" > %t.script
+# RUN: echo "GROUP(" %t /libxyz.a ")" > %t.dir/xyz.script
+# RUN: not ld.lld -o %t2 %t.script
+# RUN: not ld.lld -o %t2 %t.script --sysroot=%t.dir
+# RUN: ld.lld -o %t2 %t.dir/xyz.script --sysroot=%t.dir
+# RUN: llvm-readobj %t2 > /dev/null
+
 # RUN: echo "GROUP(" %t.script2 ")" > %t.script1
 # RUN: echo "GROUP(" %t ")" > %t.script2
 # RUN: ld.lld -o %t2 %t.script1
 # RUN: llvm-readobj %t2 > /dev/null
 
 # RUN: echo "ENTRY(_label)" > %t.script
 # RUN: ld.lld -o %t2 %t.script %t
 # RUN: llvm-readobj %t2 > /dev/null