[ELF] - Implemented -N (-omagic) command line option.

-N (-omagic)
  Set the text and data sections to be readable and writable. 
  Also, do not page-align the data segment.

Differential revision: https://reviews.llvm.org/D26888

llvm-svn: 288123

lld/ELF/Config.h

@@ -114,6 +114,7 @@ struct Configuration {
   bool NoUndefinedVersion;
   bool Nostdlib;
   bool OFormatBinary;
+  bool OMagic;
   bool Pic;
   bool Pie;
   bool PrintGcSections;

lld/ELF/Driver.cpp

@@ -526,6 +526,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
   Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
   Config->Nostdlib = Args.hasArg(OPT_nostdlib);
+  Config->OMagic = Args.hasArg(OPT_omagic);
   Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
   Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
   Config->Relocatable = Args.hasArg(OPT_relocatable);

lld/ELF/Options.td

@@ -161,6 +161,9 @@ def o: JoinedOrSeparate<["-"], "o">, MetaVarName<"<path>">,
 def oformat: Separate<["--"], "oformat">, MetaVarName<"<format>">,
   HelpText<"Specify the binary format for the output object file">;
 
+def omagic: F<"omagic">, MetaVarName<"<magic>">,
+  HelpText<"Set the text and data sections to be readable and writable">;
+
 def pie: F<"pie">, HelpText<"Create a position independent executable">;
 
 def print_gc_sections: F<"print-gc-sections">,
@@ -261,6 +264,7 @@ def alias_format_b: S<"b">, Alias<format>;
 def alias_hash_style_hash_style: J<"hash-style=">, Alias<hash_style>;
 def alias_init_init: J<"init=">, Alias<init>;
 def alias_l__library: J<"library=">, Alias<l>;
+def alias_omagic: Flag<["-"], "N">, Alias<omagic>;
 def alias_o_output: Joined<["--"], "output=">, Alias<o>;
 def alias_o_output2 : Separate<["--"], "output">, Alias<o>;
 def alias_pie_pic_executable: F<"pic-executable">, Alias<pie>;

lld/ELF/Writer.cpp

@@ -1096,6 +1096,8 @@ template <class ELFT> static bool needsPtLoad(OutputSectionBase *Sec) {
 // cannot create a PT_LOAD there.
 template <class ELFT>
 static typename ELFT::uint computeFlags(typename ELFT::uint F) {
+  if (Config->OMagic)
+    return PF_R | PF_W | PF_X;
   if (Config->SingleRoRx && !(F & PF_W))
     return F | PF_X;
   return F;

lld/test/ELF/segments.s

@@ -74,6 +74,26 @@
 # NOROSEGMENT-NEXT: ProgramHeader {
 # NOROSEGMENT-NEXT:   Type: PT_GNU_STACK
 
+# RUN: ld.lld -N %t -o %t3
+# RUN: llvm-readobj --program-headers %t3 | FileCheck --check-prefix=OMAGIC %s
+
+# OMAGIC:     ProgramHeader {
+# OMAGIC:      Type: PT_LOAD
+# OMAGIC-NEXT:   Offset: 0x0
+# OMAGIC-NEXT:   VirtualAddress:
+# OMAGIC-NEXT:   PhysicalAddress:
+# OMAGIC-NEXT:   FileSize:
+# OMAGIC-NEXT:   MemSize:
+# OMAGIC-NEXT:   Flags [
+# OMAGIC-NEXT:     PF_R
+# OMAGIC-NEXT:     PF_W
+# OMAGIC-NEXT:     PF_X
+# OMAGIC-NEXT:   ]
+# OMAGIC-NEXT:   Alignment: 4096
+# OMAGIC-NEXT: }
+# OMAGIC-NEXT: ProgramHeader {
+# OMAGIC-NEXT:   Type: PT_GNU_STACK
+
 .global _start
 _start:
  nop