complete e390f9a port for v4.9.106

objtool ports introduced in v4.9.106 were not totally complete. Therefore
they resulted in issues like:

  module: overflow in relocation type 10 val XXXXXXXXXXX
  ‘usbcore’ likely not compiled with -mcmodel=kernel
  module: overflow in relocation type 10 val XXXXXXXXXXX
  ‘scsi_mod’ likely not compiled with -mcmodel=kernel

Missing part was the complete backport of commit e390f9a.

Original notes by Josh Poimboeuf:

The '__unreachable' and '__func_stack_frame_non_standard' sections are
only used at compile time.  They're discarded for vmlinux but they
should also be discarded for modules.

Since this is a recurring pattern, prefix the section names with
".discard.".  It's a nice convention and vmlinux.lds.h already discards
such sections.

Also remove the 'a' (allocatable) flag from the __unreachable section
since it doesn't make sense for a discarded section.

Signed-off-by: Philip Müller <philm@manjaro.org>
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: https://gitlab.manjaro.org/packages/core/linux49/issues/2
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kernel/vmlinux.lds.S

@@ -352,8 +352,6 @@ SECTIONS
 	DISCARDS
 	/DISCARD/ : {
 		*(.eh_frame)
-		*(__func_stack_frame_non_standard)
-		*(__unreachable)
 	}
 }
 

include/linux/compiler-gcc.h

@@ -206,7 +206,7 @@
 #ifdef CONFIG_STACK_VALIDATION
 #define annotate_unreachable() ({					\
 	asm("1:\t\n"							\
-	    ".pushsection __unreachable, \"a\"\t\n"			\
+	    ".pushsection .discard.unreachable\t\n"			\
 	    ".long 1b\t\n"						\
 	    ".popsection\t\n");						\
 })