[ELF] - Implemented -no-rosegment.

--no-rosegment: Do not put read-only non-executable sections in their own segment

Differential revision: https://reviews.llvm.org/D26889

llvm-svn: 288020

lld/ELF/Config.h

@@ -120,6 +120,7 @@ struct Configuration {
   bool Rela;
   bool Relocatable;
   bool SaveTemps;
+  bool SingleRoRx;
   bool Shared;
   bool Static = false;
   bool SysvHash = true;

lld/ELF/Driver.cpp

@@ -696,6 +696,12 @@ void LinkerDriver::createFiles(opt::InputArgList &Args) {
     }
   }
 
+  // -no-rosegment is used to avoid placing read only non-executable sections in
+  // their own segment. We do the same if SECTIONS command is present in linker
+  // script. See comment for computeFlags().
+  Config->SingleRoRx =
+      Args.hasArg(OPT_no_rosegment) || ScriptConfig->HasSections;
+
   if (Files.empty() && ErrorCount == 0)
     error("no input files");
 }

lld/ELF/Options.td

@@ -147,6 +147,8 @@ def noinhibit_exec: F<"noinhibit-exec">,
 
 def nopie: F<"nopie">, HelpText<"Do not create a position independent executable">;
 
+def no_rosegment: F<"no-rosegment">, HelpText<"Do not put read-only non-executable sections in their own segment">;
+
 def no_undefined: F<"no-undefined">,
   HelpText<"Report unresolved symbols even if the linker is creating a shared library">;
 

lld/ELF/Writer.cpp

@@ -1096,7 +1096,7 @@ 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 (ScriptConfig->HasSections && !(F & PF_W))
+  if (Config->SingleRoRx && !(F & PF_W))
     return F | PF_X;
   return F;
 }

lld/test/ELF/segments.s

@@ -0,0 +1,88 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld %t -o %t1
+# RUN: llvm-readobj --program-headers %t1 | FileCheck --check-prefix=ROSEGMENT %s
+
+# ROSEGMENT:      ProgramHeader {
+# ROSEGMENT:        Type: PT_LOAD
+# ROSEGMENT-NEXT:    Offset: 0x0
+# ROSEGMENT-NEXT:    VirtualAddress:
+# ROSEGMENT-NEXT:    PhysicalAddress:
+# ROSEGMENT-NEXT:    FileSize:
+# ROSEGMENT-NEXT:    MemSize:
+# ROSEGMENT-NEXT:    Flags [
+# ROSEGMENT-NEXT:      PF_R
+# ROSEGMENT-NEXT:    ]
+# ROSEGMENT-NEXT:    Alignment: 4096
+# ROSEGMENT-NEXT:  }
+# ROSEGMENT-NEXT:  ProgramHeader {
+# ROSEGMENT-NEXT:    Type: PT_LOAD
+# ROSEGMENT-NEXT:    Offset: 0x1000
+# ROSEGMENT-NEXT:    VirtualAddress:
+# ROSEGMENT-NEXT:    PhysicalAddress:
+# ROSEGMENT-NEXT:    FileSize:
+# ROSEGMENT-NEXT:    MemSize:
+# ROSEGMENT-NEXT:    Flags [
+# ROSEGMENT-NEXT:      PF_R
+# ROSEGMENT-NEXT:      PF_X
+# ROSEGMENT-NEXT:    ]
+# ROSEGMENT-NEXT:    Alignment: 4096
+# ROSEGMENT-NEXT:  }
+# ROSEGMENT-NEXT:  ProgramHeader {
+# ROSEGMENT-NEXT:    Type: PT_LOAD
+# ROSEGMENT-NEXT:    Offset: 0x2000
+# ROSEGMENT-NEXT:    VirtualAddress:
+# ROSEGMENT-NEXT:    PhysicalAddress:
+# ROSEGMENT-NEXT:    FileSize: 1
+# ROSEGMENT-NEXT:    MemSize: 1
+# ROSEGMENT-NEXT:    Flags [
+# ROSEGMENT-NEXT:      PF_R
+# ROSEGMENT-NEXT:      PF_W
+# ROSEGMENT-NEXT:    ]
+# ROSEGMENT-NEXT:    Alignment: 4096
+# ROSEGMENT-NEXT:  }
+
+# RUN: ld.lld -no-rosegment %t -o %t2
+# RUN: llvm-readobj --program-headers %t2 | FileCheck --check-prefix=NOROSEGMENT %s
+
+# NOROSEGMENT:     ProgramHeader {
+# NOROSEGMENT:       Type: PT_LOAD
+# NOROSEGMENT-NEXT:   Offset: 0x0
+# NOROSEGMENT-NEXT:   VirtualAddress:
+# NOROSEGMENT-NEXT:   PhysicalAddress:
+# NOROSEGMENT-NEXT:   FileSize:
+# NOROSEGMENT-NEXT:   MemSize:
+# NOROSEGMENT-NEXT:   Flags [
+# NOROSEGMENT-NEXT:     PF_R
+# NOROSEGMENT-NEXT:     PF_X
+# NOROSEGMENT-NEXT:   ]
+# NOROSEGMENT-NEXT:   Alignment: 4096
+# NOROSEGMENT-NEXT: }
+# NOROSEGMENT-NEXT: ProgramHeader {
+# NOROSEGMENT-NEXT:   Type: PT_LOAD
+# NOROSEGMENT-NEXT:   Offset: 0x1000
+# NOROSEGMENT-NEXT:   VirtualAddress:
+# NOROSEGMENT-NEXT:   PhysicalAddress:
+# NOROSEGMENT-NEXT:   FileSize:
+# NOROSEGMENT-NEXT:   MemSize:
+# NOROSEGMENT-NEXT:   Flags [
+# NOROSEGMENT-NEXT:     PF_R
+# NOROSEGMENT-NEXT:     PF_W
+# NOROSEGMENT-NEXT:   ]
+# NOROSEGMENT-NEXT:   Alignment: 4096
+# NOROSEGMENT-NEXT: }
+# NOROSEGMENT-NEXT: ProgramHeader {
+# NOROSEGMENT-NEXT:   Type: PT_GNU_STACK
+
+.global _start
+_start:
+ nop
+
+.section .ro,"a"
+nop
+
+.section .rw,"aw"
+nop
+
+.section .rx,"ax"
+nop