Dwarf-EH: add -fPIC support

src/backend/cc.h

@@ -1273,6 +1273,8 @@ struct Symbol
     int Sweight;                // usage count, the higher the number,
                                 // the more worthwhile it is to put in
                                 // a register
+    int Sdw_ref_idx;            // !=0 means index of DW.ref.name symbol (Dwarf EH)
+
     union
     {
         unsigned Sxtrnnum_;     // SCcomdef,SCextern,SCcomdat: external symbol # (starting from 1)

src/backend/cod3.c

@@ -551,6 +551,7 @@ regm_t regmask(tym_t tym, tym_t tyf)
     {
         case TYvoid:
         case TYstruct:
+        case TYarray:
             return 0;
         case TYbool:
         case TYwchar_t:

src/backend/dwarf.c

@@ -60,6 +60,12 @@
 
 extern int seg_count;
 
+#if ELFOBJ
+IDXSYM elf_addsym(IDXSTR nam, targ_size_t val, unsigned sz,
+        unsigned typ, unsigned bind, IDXSEC sec,
+        unsigned char visibility = STV_DEFAULT);
+#endif
+
 static char __file__[] = __FILE__;      // for tassert.h
 #include        "tassert.h"
 
@@ -626,10 +632,16 @@ static void writeEhFrameHeader(IDXSEC dfseg, Outbuffer *buf, Symbol *personality
     buf->writeByten(I64 ? 16 : 8);      // return address register
     if (config.ehmethod == EH_DWARF)
     {
+        const unsigned char personality_pointer_encoding = config.flags3 & CFG3pic
+                ? DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4
+                : DW_EH_PE_absptr | DW_EH_PE_udata4;
+        const unsigned char LSDA_pointer_encoding = config.flags3 & CFG3pic
+                ? DW_EH_PE_pcrel | DW_EH_PE_sdata4
+                : DW_EH_PE_absptr | DW_EH_PE_udata4;
         buf->writeByten(7);                                  // Augmentation Length
-        buf->writeByten(DW_EH_PE_absptr | DW_EH_PE_udata4);  // P: personality routing address encoding
-        ElfObj::reftoident(dfseg, buf->size(), personality, 0, CFoff); // PC_begin
-        buf->writeByten(DW_EH_PE_absptr | DW_EH_PE_udata4);  // L: address encoding for LSDA in FDE
+        buf->writeByten(personality_pointer_encoding);       // P: personality routine address encoding
+        dwarf_reftoident(dfseg, buf->size(), personality, 0);
+        buf->writeByten(LSDA_pointer_encoding);              // L: address encoding for LSDA in FDE
         buf->writeByten(DW_EH_PE_pcrel  | DW_EH_PE_sdata4);  // R: encoding of addresses in FDE
     }
     else
@@ -785,8 +797,18 @@ void writeEhFrameFDE(IDXSEC dfseg, Symbol *sfunc)
     {
         buf->writeByten(4);                             // Augmentation Data Length
         int etseg = dwarf_getsegment_alloc(except_table_name, 1);
+        // if CFG3pic, fixup should be R_X86_64_PC32
         buf->write32(0);                                // address of LSDA (".gcc_except_table")
-        dwarf_addrel(dfseg, buf->size() - 4, etseg, sfunc->Sfunc->LSDAoffset);      // and the fixup
+        if (config.flags3 & CFG3pic)
+        {
+#if ELFOBJ
+            ElfObj::addrel(dfseg, buf->size() - 4, R_X86_64_PC32, MAP_SEG2SYMIDX(etseg), sfunc->Sfunc->LSDAoffset);
+#else
+            assert(0);                                  // not supported yet
+#endif
+        }
+        else
+            dwarf_addrel(dfseg, buf->size() - 4, etseg, sfunc->Sfunc->LSDAoffset);      // and the fixup
     }
     else
         buf->writeByten(0);                             // Augmentation Data Length

src/backend/dwarf.h

@@ -18,6 +18,7 @@ unsigned dwarf_abbrev_code(unsigned char *data, size_t nbytes);
 int dwarf_regno(int reg);
 
 void dwarf_addrel(int seg, targ_size_t offset, int targseg, targ_size_t val = 0);
+int dwarf_reftoident(int seg, targ_size_t offset, Symbol *s, targ_size_t val);
 void dwarf_except_gentables(Funcsym *sfunc, unsigned startoffset, unsigned retoffset);
 void genDwarfEh(Funcsym *sfunc, int seg, Outbuffer *et, bool scancode, unsigned startoffset, unsigned retoffset);
 

src/backend/dwarfeh.c

@@ -293,7 +293,9 @@ void genDwarfEh(Funcsym *sfunc, int seg, Outbuffer *et, bool scancode, unsigned
     if (LPstart != DW_EH_PE_omit)
         et->writeuLEB128(LPbase);
 
-    const unsigned char TType = DW_EH_PE_absptr | DW_EH_PE_udata4;
+    const unsigned char TType = (config.flags3 & CFG3pic)
+                                ? DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4
+                                : DW_EH_PE_absptr | DW_EH_PE_udata4;
     et->writeByte(TType);
 
     /* Compute TTbase, which is the sum of:
@@ -345,8 +347,7 @@ void genDwarfEh(Funcsym *sfunc, int seg, Outbuffer *et, bool scancode, unsigned
     for (int i = sfunc->Sfunc->typesTableDim; i--; )
     {
         Symbol *s = typesTable[i];
-        ElfObj::reftoident(seg, et->size(), s, 0, CFoff); //dwarf_addrel(seg, et->size(), s->Sseg, s->Soffset);
-        //et->write32(s->Soffset);
+        dwarf_reftoident(seg, et->size(), s, 0);
     }
     assert(TToffset == et->size() - startsize);
 }

src/backend/elfobj.c

@@ -3496,4 +3496,54 @@ void Obj::gotref(symbol *s)
 }
 
 #endif
+
+/******************************************
+ * Generate fixup specific to .eh_frame and .gcc_except_table sections.
+ * Params:
+ *      seg = segment of where to write fixup
+ *      offset = offset of where to write fixup
+ *      s = fixup is a reference to this Symbol
+ *      val = displacement from s
+ * Returns:
+ *      number of bytes written at seg:offset
+ */
+int dwarf_reftoident(int seg, targ_size_t offset, Symbol *s, targ_size_t val)
+{
+    assert(I64);                // I32 not implemented yet
+
+    if (config.flags3 & CFG3pic)
+    {
+        /* fixup: R_X86_64_PC32 sym="DW.ref.name"
+         * symtab: .weak DW.ref.name,@OBJECT,VALUE=.data.DW.ref.name+0x00,SIZE=8
+         * Section 13  .data.DW.ref.name  PROGBITS,ALLOC,WRITE,SIZE=0x0008(8),OFFSET=0x0138,ALIGN=8
+         *  0138:   0  0  0  0  0  0  0  0                           ........
+         * Section 14  .rela.data.DW.ref.name  RELA,ENTRIES=1,OFFSET=0x0E18,ALIGN=8,LINK=22,INFO=13
+         *   0 offset=00000000 addend=0000000000000000 type=R_X86_64_64 sym="name"
+         */
+        if (!s->Sdw_ref_idx)
+        {
+            int dataDWref_seg = ElfObj::getsegment(".data.DW.ref.", s->Sident, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE, 8);
+            Outbuffer *buf = SegData[dataDWref_seg]->SDbuf;
+            assert(buf->size() == 0);
+            ElfObj::reftoident(dataDWref_seg, 0, s, 0, CFoffset64);
+
+            // Add "DW.ref." ~ name to the symtab_strings table
+            IDXSTR namidx = symtab_strings->size();
+            symtab_strings->writeString("DW.ref.");
+            symtab_strings->setsize(symtab_strings->size() - 1);  // back up over terminating 0
+            symtab_strings->writeString(s->Sident);
+
+            s->Sdw_ref_idx = elf_addsym(namidx, val, 8, STT_OBJECT, STB_WEAK, MAP_SEG2SECIDX(dataDWref_seg), STV_HIDDEN);
+        }
+        ElfObj::writerel(seg, offset, R_X86_64_PC32, s->Sdw_ref_idx, 0);
+    }
+    else
+    {
+        ElfObj::reftoident(seg, offset, s, val, CFoff);
+        //dwarf_addrel(seg, offset, s->Sseg, s->Soffset);
+        //et->write32(s->Soffset);
+    }
+    return 4;
+}
+
 #endif

src/backend/machobj.c

@@ -2309,9 +2309,6 @@ void MachObj::addrel(int seg, targ_size_t offset, symbol *targsym,
         unsigned targseg, int rtype, int val)
 {
     Relocation rel;
-#ifdef DEBUG
-    memset(&rel, 0, sizeof(rel));
-#endif
     rel.offset = offset;
     rel.targsym = targsym;
     rel.targseg = targseg;
@@ -2704,5 +2701,21 @@ void Obj::gotref(symbol *s)
     }
 }
 
+/******************************************
+ * Generate fixup specific to .eh_frame and .gcc_except_table sections.
+ * Params:
+ *      seg = segment of where to write fixup
+ *      offset = offset of where to write fixup
+ *      s = fixup is a reference to this Symbol
+ *      val = displacement from s
+ * Returns:
+ *      number of bytes written at seg:offset
+ */
+int dwarf_reftoident(int seg, targ_size_t offset, Symbol *s, targ_size_t val)
+{
+    assert(0);          // not implemented yet
+    return 4;
+}
+
 #endif
 #endif