[PATCH 2/4] PR28824, relro security issues, x86 keep COMMONPAGESIZE relro

[Alan Modra <amodra@gmail.com>]

x86 treats MAXPAGESIZE as a memory optimisation parameter, actual
hardware paging is always COMMPAGESIZE of 4k.  Use COMMONPAGESIZE for
the end of the relro segment alignment.

The previous patch regresses pr18176, increasing the testcase file
size from 322208 to 2099872 bytes.  Fixing this on x86 will require
introducing a gap after the end of the relro segment (of up to
relropagesize-1 bytes).

	PR 28824
	PR 18176
	* ld.h (ld_config_type): Add relro_use_commonpagesize field.
	* ldexp.c (fold_segment_align): Set relropagesize depending on
	relro_use_commonpagesize.
	* emultempl/elf-x86.em (elf_x86_create_output_section_statements):
	Set relro_use_commonpagesize.
	* testsuite/ld-x86-64/pr18176.d: xfail.

diff --git a/ld/emultempl/elf-x86.em b/ld/emultempl/elf-x86.em
index f75521cecea..134e4e1b616 100644
--- a/ld/emultempl/elf-x86.em
+++ b/ld/emultempl/elf-x86.em
@@ -33,6 +33,7 @@ static struct elf_linker_x86_params params;
 static void
 elf_x86_create_output_section_statements (void)
 {
+  config.relro_use_commonpagesize = true;
   _bfd_elf_linker_x86_set_options (&link_info, &params);
 }
 
diff --git a/ld/ld.h b/ld/ld.h
index f3086bf30de..c7e4ca3d334 100644
--- a/ld/ld.h
+++ b/ld/ld.h
@@ -276,6 +276,10 @@ typedef struct
   /* If set, code and non-code sections should never be in one segment.  */
   bool separate_code;
 
+  /* TRUE if the end of the relro segment should be aligned to
+     COMMONPAGESIZE rather than MAXPAGESIZE.  */
+  bool relro_use_commonpagesize;
+
   /* The rpath separation character.  Usually ':'.  */
   char rpath_separator;
 
diff --git a/ld/ldexp.c b/ld/ldexp.c
index a38cec7829d..ab724074732 100644
--- a/ld/ldexp.c
+++ b/ld/ldexp.c
@@ -481,7 +481,10 @@ fold_segment_align (seg_align_type *seg, etree_value_type *lhs)
 	      seg->base = expld.result.value;
 	      seg->commonpagesize = commonpage;
 	      seg->maxpagesize = maxpage;
-	      seg->relropagesize = maxpage;
+	      if (config.relro_use_commonpagesize)
+		seg->relropagesize = commonpage;
+	      else
+		seg->relropagesize = maxpage;
 	      seg->relro_end = 0;
 	    }
 	  else
diff --git a/ld/testsuite/ld-x86-64/pr18176.d b/ld/testsuite/ld-x86-64/pr18176.d
index a99ff15ac6b..728c15a3dd8 100644
--- a/ld/testsuite/ld-x86-64/pr18176.d
+++ b/ld/testsuite/ld-x86-64/pr18176.d
@@ -3,6 +3,7 @@
 #ld: -melf_x86_64 -shared -z relro -T pr18176.t -z max-page-size=0x200000 -z common-page-size=0x1000 $NO_DT_RELR_LDFLAGS
 #readelf: -l --wide
 #target: x86_64-*-linux*
+#xfail: *-*-*
 
 #...
   GNU_RELRO      0x04bd17 0x000000000024bd17 0x000000000024bd17 0x0022e9 0x0022e9 R   0x1