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 <[email protected]> Signed-off-by: Andrew Cooper <[email protected]> Tested-by: Jason Andryuk <[email protected]> Acked-by: Jan Beulich <[email protected]>
nephele-vm · May 13, 2020 · 24f94fc · 24f94fc
1 parent 9f74a7b
commit 24f94fc
Showing 1 changed file with 10 additions and 2 deletions.
diff --git 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.
+         */
+        *(*)
   }
 }