[ELF] - More direct implementation of edata/etext

[grimar]

Summary

As was suggested in mails, this patch implements edata/etext
symbols in a more direct way.
It iterates through PT_LOADs.

Result seems to be the same and equal to gold output.

[• rafael]

LGTM

[ruiu]

LGTM

lld/trunk/ELF/Writer.cpp

if (Out<ELFT>::RelaPlt) {
     ElfSym<ELFT>::RelaIpltStart.st_value = Start;
     ElfSym<ELFT>::RelaIpltEnd.st_value = Start + Out<ELFT>::RelaPlt->getSize();
   }
 
   // Update MIPS _gp absolute symbol so that it points to the static data.
   if (Config->EMachine == EM_MIPS)
     ElfSym<ELFT>::MipsGp.st_value = getMipsGpAddr<ELFT>();
 
-  // _etext points to location after the last read-only loadable segment.
-  // _edata points to the end of the last non SHT_NOBITS section.
-  for (OutputSectionBase<ELFT> *Sec : OutputSections) {
-    if (!(Sec->getFlags() & SHF_ALLOC))
+  // _etext is the first location after the last read-only loadable segment.
+  // _edata is the first location after the last read-write loadable segment.
+  for (Phdr &PHdr : Phdrs) {
+    if (PHdr.H.p_type != PT_LOAD)
       continue;
-    if (!(Sec->getFlags() & SHF_WRITE))
-      ElfSym<ELFT>::Etext.st_value = Sec->getVA() + Sec->getSize();
-    if (Sec->getType() != SHT_NOBITS)
-      ElfSym<ELFT>::Edata.st_value = Sec->getVA() + Sec->getSize();
+    uintX_t Val = PHdr.H.p_vaddr + PHdr.H.p_filesz;
+    if (PHdr.H.p_flags & PF_W)
+      ElfSym<ELFT>::Edata.st_value = Val;
+    else
+      ElfSym<ELFT>::Etext.st_value = Val;
   }
 }
 
 template <class ELFT> void Writer<ELFT>::writeHeader() {
   uint8_t *Buf = Buffer->getBufferStart();
   memcpy(Buf, "\177ELF", 4);
 
   auto &FirstObj = cast<ELFFileBase<ELFT>>(*Config->FirstElf);