[xen stable-4.12] x86/build32: Discard all orphaned sections

[patchbot@xxxxxxx]

commit a022f3679aae642d702f9ef3137c8d3db46018a7
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Jun 24 16:58:51 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jun 24 16:58:51 2020 +0200

    x86/build32: Discard all orphaned sections
    
    Linkers may put orphaned sections ahead of .text, which breaks the calling
    requirements.  A concrete example is Ubuntu's GCC-9 default of enabling
    -fcf-protection which causes us to try and execute .note.gnu.properties 
during
    Xen's boot.
    
    Put .got.plt in its own section as it specifically needs preserving from the
    linkers point of view, and discard everything else.  This will hopefully be
    more robust to other unexpected toolchain properties.
    
    Fixes boot from an Ubuntu build of Xen.
    
    Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Tested-by: Jason Andryuk <jandryuk@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/boot/build32.lds | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/boot/build32.lds b/xen/arch/x86/boot/build32.lds
index da35aee910..97454b40ff 100644
--- a/xen/arch/x86/boot/build32.lds
+++ b/xen/arch/x86/boot/build32.lds
@@ -31,7 +31,7 @@ SECTIONS
         *(.bss.*)
   }
 
-  /DISCARD/ : {
+  .got.plt : {
         /*
          * PIC/PIE executable contains .got.plt section even if it is not 
linked
          * with dynamic libraries. In such case it is just placeholder for
@@ -47,6 +47,14 @@ SECTIONS
          *
          * Please check build32.mk for more details.
          */
-        /* *(.got.plt) */
+        *(.got.plt)
+  }
+
+  /DISCARD/ : {
+        /*
+         * Discard everything else, to prevent linkers from putting
+         * orphaned sections ahead of .text, which needs to be first.
+         */
+        *(*)
   }
 }
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12