From 31094560f786ea29b96e095efbbbbdc955d39407 Mon Sep 17 00:00:00 2001
From: Martin Nowak <code@dawg.eu>
Date: Tue, 22 Apr 2014 15:45:49 +0200
Subject: [PATCH 1/3] use const data segments for Mach-O

- add __DATA,__const section as CDATAREL for
  const data with relocations
---
 src/backend/machobj.c | 3 ++-
 src/backend/out.c     | 8 +-------
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/src/backend/machobj.c b/src/backend/machobj.c
index 02ba7f269b45..7d83a0e27331 100644
--- a/src/backend/machobj.c
+++ b/src/backend/machobj.c
@@ -482,9 +482,10 @@ Obj *Obj::init(Outbuffer *objbuf, const char *filename, const char *csegname)
     seg_count = 0;
     int align = I64 ? 4 : 2;            // align to 16 bytes for floating point
     MachObj::getsegment("__text",  "__TEXT", 2, S_REGULAR | S_ATTR_PURE_INSTRUCTIONS | S_ATTR_SOME_INSTRUCTIONS);
-    MachObj::getsegment("__data",  "__DATA", align, S_REGULAR);         // DATA
+    MachObj::getsegment("__data",  "__DATA", align, S_REGULAR);     // DATA
     MachObj::getsegment("__const", "__TEXT", 2, S_REGULAR);         // CDATA
     MachObj::getsegment("__bss",   "__DATA", 4, S_ZEROFILL);        // UDATA
+    MachObj::getsegment("__const", "__DATA", align, S_REGULAR);     // CDATAREL
 
     if (config.fulltypes)
         dwarf_initfile(filename);
diff --git a/src/backend/out.c b/src/backend/out.c
index 55cc1ee988d4..d23362b1a5c1 100644
--- a/src/backend/out.c
+++ b/src/backend/out.c
@@ -514,7 +514,7 @@ void outcommon(symbol *s,targ_size_t n)
 void out_readonly(symbol *s)
 {
     // The default is DATA
-#if ELFOBJ
+#if ELFOBJ || MACHOBJ
     /* Cannot have pointers in CDATA when compiling PIC code, because
      * they require dynamic relocations of the read-only segment.
      * Instead use the .data.rel.ro section. See Bugzilla 11171.
@@ -524,12 +524,6 @@ void out_readonly(symbol *s)
     else
         s->Sseg = CDATA;
 #endif
-#if MACHOBJ
-    /* Because of PIC and CDATA being in the _TEXT segment;
-     * cannot have pointers in CDATA.
-     * Should check s->Sdt and make it CDATA if it has no pointers.
-     */
-#endif
 #if OMFOBJ
     // Haven't really worked out where immutable read-only data can go.
 #endif

From 46e3d2e01702d7d86f5b4c9712c5f71d0375089d Mon Sep 17 00:00:00 2001
From: Martin Nowak <code@dawg.eu>
Date: Tue, 22 Apr 2014 15:58:23 +0200
Subject: [PATCH 2/3] use CDATA for strings on x86_64

- not sure why it was disabled

- also remove similar old code in elfobj.c
---
 src/backend/elfobj.c  | 22 +++++-----------------
 src/backend/machobj.c | 22 +++++-----------------
 2 files changed, 10 insertions(+), 34 deletions(-)

diff --git a/src/backend/elfobj.c b/src/backend/elfobj.c
index d7fbf7c20e04..edf5ec0869ca 100644
--- a/src/backend/elfobj.c
+++ b/src/backend/elfobj.c
@@ -634,23 +634,11 @@ symbol *Obj::sym_cdata(tym_t ty,char *p,int len)
 
 int Obj::data_readonly(char *p, int len, int *pseg)
 {
-    int oldoff;
-    /*if (OPT_IS_SET(OPTfwritable_strings))
-    {
-        oldoff = Doffset;
-        SegData[DATA]->SDbuf->reserve(len);
-        SegData[DATA]->SDbuf->writen(p,len);
-        Doffset += len;
-        *pseg = DATA;
-    }
-    else*/
-    {
-        oldoff = CDoffset;
-        SegData[CDATA]->SDbuf->reserve(len);
-        SegData[CDATA]->SDbuf->writen(p,len);
-        CDoffset += len;
-        *pseg = CDATA;
-    }
+    int oldoff = CDoffset;
+    SegData[CDATA]->SDbuf->reserve(len);
+    SegData[CDATA]->SDbuf->writen(p,len);
+    CDoffset += len;
+    *pseg = CDATA;
     return oldoff;
 }
 
diff --git a/src/backend/machobj.c b/src/backend/machobj.c
index 7d83a0e27331..39c3e9e90bfb 100644
--- a/src/backend/machobj.c
+++ b/src/backend/machobj.c
@@ -384,23 +384,11 @@ symbol * Obj::sym_cdata(tym_t ty,char *p,int len)
 
 int Obj::data_readonly(char *p, int len, int *pseg)
 {
-    int oldoff;
-    if (I64)
-    {
-        oldoff = Doffset;
-        SegData[DATA]->SDbuf->reserve(len);
-        SegData[DATA]->SDbuf->writen(p,len);
-        Doffset += len;
-        *pseg = DATA;
-    }
-    else
-    {
-        oldoff = CDoffset;
-        SegData[CDATA]->SDbuf->reserve(len);
-        SegData[CDATA]->SDbuf->writen(p,len);
-        CDoffset += len;
-        *pseg = CDATA;
-    }
+    int oldoff = CDoffset;
+    SegData[CDATA]->SDbuf->reserve(len);
+    SegData[CDATA]->SDbuf->writen(p,len);
+    CDoffset += len;
+    *pseg = CDATA;
     return oldoff;
 }
 

From a48547e6060c75de8648f384f7549f8e425a1e25 Mon Sep 17 00:00:00 2001
From: Martin Nowak <code@dawg.eu>
Date: Wed, 23 Apr 2014 00:07:33 +0200
Subject: [PATCH 3/3] fix for code->cdata relocation

- The codegen assumes an indirect access to data,
  but cdata was treated as code segment so a direct
  relocation was emitted.
---
 src/backend/machobj.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/backend/machobj.c b/src/backend/machobj.c
index 39c3e9e90bfb..15018d6e2f43 100644
--- a/src/backend/machobj.c
+++ b/src/backend/machobj.c
@@ -162,6 +162,12 @@ static IDXSTR extdef;
 
 int seg_data::isCode()
 {
+    // The codegen assumes that code->data references are indirect,
+    // but when CDATA is treated as code reftoident will emit a direct
+    // relocation.
+    if (this == SegData[CDATA])
+        return false;
+
     if (I64)
     {
         //printf("SDshtidx = %d, x%x\n", SDshtidx, SecHdrTab64[SDshtidx].flags);