[PATCH] D14450: [ELF2] Add mandatory .dynamic section entries on MIPS.

[Simon Atanasyan via llvm-commits]

atanasyan added inline comments.

================
Comment at: ELF/OutputSections.cpp:491
@@ -480,3 +490,3 @@
     ++NumEntries; // DT_PLTRELSZ
-    ++NumEntries; // DT_PLTGOT
+    ++NumEntries; // DT_PLTGOT or DT_MIPS_PLTGOT
     ++NumEntries; // DT_PLTREL
----------------
ikudrin wrote:
> atanasyan wrote:
> > Do you read MIPS ABI? DT_MIPS_PLTGOT is used in the non-PIC MIPS code only. PIC MIPS code uses DT_PLTGOT entry but this entry points to the .got section.
> The logic of this line: if we have .plt.got section, then store its address to DT_MIPS_PLTGOT entry. Is something wrong here?
> Please note, the DT_PLTGOT entry for MIPS target is mentioned a bit later in this function.
If MIPS dynamic binary has a .got section, DT_PLTGOT entry should point to it. The DT_MIPS_PLTGOT entry should point to the .got.plt entry if MIPS dynamic binary is non-PIC.

https://sourceware.org/ml/binutils/2008-07/txt00000.txt

================
Comment at: ELF/OutputSections.cpp:659
@@ +658,3 @@
+    WriteVal(DT_MIPS_SYMTABNO, Out<ELFT>::DynSymTab->getNumSymbols());
+    if (const SymbolBody *B = Out<ELFT>::Got->getFirstEntry()) {
+      WriteVal(DT_MIPS_LOCAL_GOTNO, B->GotIndex);
----------------
ikudrin wrote:
> atanasyan wrote:
> > What is the case covered by this `if` statement?
> We can have global entries in the GOT or it may consist of reserved and local entries only. In the later case, we'll have to change the expression "Target->getGotHeaderEntriesNum()" to something more reasonable when local GOT entries are added.
Maybe it is better at first to complete GOT implementation and add local entries support and then add dynamic entries support.

================
Comment at: ELF/OutputSections.h:121
@@ -120,2 +120,3 @@
   uintX_t getEntryAddr(const SymbolBody &B) const;
+  const SymbolBody *getFirstEntry() const;
 
----------------
ikudrin wrote:
> atanasyan wrote:
> > What is the meaning of the "First" here: Lazy resolver, first local entry of first global entry?
> For MIPS, it's the first global entry, because we don't have SymbolBody for anything else.
> For all other targets it's just the first entry of the GOT, although nobody is interested in it.
In that case "First" might confuse. Because you have to read code to realize that the "First" means first global but sometimes just first entry. If you ask somebody familiar with MIPS what is the first GOT entry he or she answers that it is either "Lazy resolver" entry or "first local entry"


http://reviews.llvm.org/D14450