[PATCH] [gold] Implement -z stack-size option

[Roland McGrath]

This implementation doesn't seem particularly elegant, but the separation
of duties between Output_segment::set_offset and (its sole caller)
Layout::set_segment_offsets seems fairly arbitrary to me as it is and this
doesn't seem to make that any worse.

Ok for trunk and 2.27?


Thanks,
Roland


gold/
2016-08-15  Roland McGrath  <roland@hack.frob.com>

	* options.h (General_options): Grok -z stack-size.
	* layout.cc (Layout::create_executable_stack_info): Always create
	the segment if -z stack-size was used.
	* output.cc (Output_segment::set_offset): If output_lists_[0] is
	empty and type_ is PT_GNU_STACK, set memsz_ to -z stack-size value
	and min_p_align_ to a constant 16.

diff --git a/gold/layout.cc b/gold/layout.cc
index 376051d..518b802 100644
--- a/gold/layout.cc
+++ b/gold/layout.cc
@@ -2985,10 +2985,12 @@ Layout::create_gold_note()
 // executable.  Otherwise, if at least one input file a
 // .note.GNU-stack section, and some input file has no .note.GNU-stack
 // section, we use the target default for whether the stack should be
-// executable.  Otherwise, we don't generate a stack note.  When
-// generating a object file, we create a .note.GNU-stack section with
-// the appropriate marking.  When generating an executable or shared
-// library, we create a PT_GNU_STACK segment.
+// executable.  If -z stack-size was used to set a p_memsz value for
+// PT_GNU_STACK, we generate the segment regardless.  Otherwise, we
+// don't generate a stack note.  When generating a object file, we
+// create a .note.GNU-stack section with the appropriate marking.
+// When generating an executable or shared library, we create a
+// PT_GNU_STACK segment.

 void
 Layout::create_executable_stack_info()
@@ -3003,7 +3005,9 @@ Layout::create_executable_stack_info()
 	gold_warning(_("one or more inputs require executable stack, "
 		       "but -z noexecstack was given"));
     }
-  else if (!this->input_with_gnu_stack_note_)
+  else if (!this->input_with_gnu_stack_note_
+	   && (!parameters->options().user_set_stack_size()
+	       || parameters->options().relocatable()))
     return;
   else
     {
diff --git a/gold/options.h b/gold/options.h
index 23c9658..4c5b2ae 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -1339,6 +1339,8 @@ class General_options
   DEFINE_bool(relro, options::DASH_Z, '\0', DEFAULT_LD_Z_RELRO,
 	      N_("Where possible mark variables read-only after relocation"),
 	      N_("Don't mark variables read-only after relocation"));
+  DEFINE_uint64(stack_size, options::DASH_Z, '\0', 0,
+		N_("Set PT_GNU_STACK segment p_memsz to SIZE"), N_("SIZE"));
   DEFINE_bool(text, options::DASH_Z, '\0', false,
 	      N_("Do not permit relocations in read-only segments"),
 	      N_("Permit relocations in read-only segments (default)"));
diff --git a/gold/output.cc b/gold/output.cc
index 0a9e58f..433a09a 100644
--- a/gold/output.cc
+++ b/gold/output.cc
@@ -4660,6 +4660,13 @@ Output_segment::set_offset(unsigned int increase)
       this->min_p_align_ = 0;
       this->offset_ = 0;
       this->filesz_ = 0;
+      if (this->type_ == elfcpp::PT_GNU_STACK)
+	{
+	  this->memsz_ = parameters->options().stack_size();
+	  // BFD lets targets override this default alignment, but the only
+	  // targets that do so are ones that Gold does not support so far.
+	  this->min_p_align_ = 16;
+	}
       return;
     }