kbuild: check for section mismatch during modpost stage

Section mismatch is identified as references to .init*
sections from non .init sections. And likewise references
to .exit.* sections outside .exit sections.

.init.* sections are discarded after a module is initialized
and references to .init.* sections are oops candidates.
.exit.* sections are discarded when a module is built-in and
thus references to .exit are also oops candidates.

The checks were possible to do using 'make buildcheck' which
called the two perl scripts: reference_discarded.pl and
reference_init.pl. This patch just moves the same functionality
inside modpost and the scripts are then obsoleted.
They will though be kept for a while so users can do double
checks - but note that some .o files are skipped by the perl scripts
so result is not 1:1.
All credit for the concept goes to Keith Owens who implemented
the original perl scrips - this patch just moves it to modpost.

Compared to the perl script the implmentation in modpost will be run
for each kernel build - thus catching the error much sooner, but
the downside is that the individual .o file are not always identified.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/mod/modpost.h

@@ -16,17 +16,27 @@
 #define Elf_Ehdr    Elf32_Ehdr 
 #define Elf_Shdr    Elf32_Shdr 
 #define Elf_Sym     Elf32_Sym
+#define Elf_Addr    Elf32_Addr
+#define Elf_Section Elf32_Section
 #define ELF_ST_BIND ELF32_ST_BIND
 #define ELF_ST_TYPE ELF32_ST_TYPE
 
+#define Elf_Rela    Elf32_Rela
+#define ELF_R_SYM   ELF32_R_SYM
+#define ELF_R_TYPE  ELF32_R_TYPE
 #else
 
 #define Elf_Ehdr    Elf64_Ehdr 
 #define Elf_Shdr    Elf64_Shdr 
 #define Elf_Sym     Elf64_Sym
+#define Elf_Addr    Elf64_Addr
+#define Elf_Section Elf64_Section
 #define ELF_ST_BIND ELF64_ST_BIND
 #define ELF_ST_TYPE ELF64_ST_TYPE
 
+#define Elf_Rela    Elf64_Rela
+#define ELF_R_SYM   ELF64_R_SYM
+#define ELF_R_TYPE  ELF64_R_TYPE
 #endif
 
 #if KERNEL_ELFDATA != HOST_ELFDATA