kbuild: fix modpost segfault for 64bit mipsel kernel

64bit mips has different r_info layout.  This patch fixes modpost
segfault for 64bit little endian mips kernel.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

2 files changed, 28 insertions, 2 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index cd00e9f07589..fcd4306fa002 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -709,10 +709,17 @@ static void check_sec_ref(struct module *mod, const char *modname,
                 for (rela = start; rela < stop; rela++) {
                         Elf_Rela r;
                         const char *secname;
+                        unsigned int r_sym;
                         r.r_offset = TO_NATIVE(rela->r_offset);
-                        r.r_info   = TO_NATIVE(rela->r_info);
+                        if (hdr->e_ident[EI_CLASS] == ELFCLASS64 &&
+                            hdr->e_machine == EM_MIPS) {
+                                r_sym = ELF64_MIPS_R_SYM(rela->r_info);
+                                r_sym = TO_NATIVE(r_sym);
+                        } else {
+                                r_sym = ELF_R_SYM(TO_NATIVE(rela->r_info));
+                        }
                         r.r_addend = TO_NATIVE(rela->r_addend);
-                        sym = elf->symtab_start + ELF_R_SYM(r.r_info);
+                        sym = elf->symtab_start + r_sym;
                         /* Skip special sections */
                         if (sym->st_shndx >= SHN_LORESERVE)
                                 continue;
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index b14255c72a37..89b96c6d8ef5 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -39,6 +39,25 @@
 #define ELF_R_TYPE  ELF64_R_TYPE
 #endif
 
+/* The 64-bit MIPS ELF ABI uses an unusual reloc format. */
+typedef struct
+{
+  Elf32_Word    r_sym;          /* Symbol index */
+  unsigned char r_ssym;         /* Special symbol for 2nd relocation */
+  unsigned char r_type3;        /* 3rd relocation type */
+  unsigned char r_type2;        /* 2nd relocation type */
+  unsigned char r_type1;        /* 1st relocation type */
+} _Elf64_Mips_R_Info;
+
+typedef union
+{
+  Elf64_Xword   r_info_number;
+  _Elf64_Mips_R_Info r_info_fields;
+} _Elf64_Mips_R_Info_union;
+
+#define ELF64_MIPS_R_SYM(i) \
+  ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_sym)
+
 #if KERNEL_ELFDATA != HOST_ELFDATA
 
 static inline void __endian(const void *src, void *dest, unsigned int size)