kbuild: make better section mismatch reports on i386 and mips

On i386 and MIPS, warn_sec_mismatch() sometimes fails to show
usefull symbol name.  This is because empty 'refsym' due to 0 r_addend
value.  This patch is to adjust r_addend value, consulting with
apply_relocate() routine in kernel code.

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

2 files changed, 76 insertions, 0 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3645e980da71..b83cddb8dca9 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -374,6 +374,7 @@ static int parse_elf(struct elf_info *info, const char *filename)
         hdr->e_shstrndx = TO_NATIVE(hdr->e_shstrndx);
         hdr->e_shnum    = TO_NATIVE(hdr->e_shnum);
         hdr->e_machine  = TO_NATIVE(hdr->e_machine);
+        hdr->e_type     = TO_NATIVE(hdr->e_type);
         sechdrs = (void *)hdr + hdr->e_shoff;
         info->sechdrs = sechdrs;
 
@@ -384,6 +385,8 @@ static int parse_elf(struct elf_info *info, const char *filename)
                 sechdrs[i].sh_size   = TO_NATIVE(sechdrs[i].sh_size);
                 sechdrs[i].sh_link   = TO_NATIVE(sechdrs[i].sh_link);
                 sechdrs[i].sh_name   = TO_NATIVE(sechdrs[i].sh_name);
+                sechdrs[i].sh_info   = TO_NATIVE(sechdrs[i].sh_info);
+                sechdrs[i].sh_addr   = TO_NATIVE(sechdrs[i].sh_addr);
         }
         /* Find symbol table. */
         for (i = 1; i < hdr->e_shnum; i++) {
@@ -753,6 +756,8 @@ static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf_Addr addr,
         for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
                 if (sym->st_shndx != relsym->st_shndx)
                         continue;
+                if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
+                        continue;
                 if (sym->st_value == addr)
                         return sym;
         }
@@ -895,6 +900,58 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
         }
 }
 
+static unsigned int *reloc_location(struct elf_info *elf,
+                                           int rsection, Elf_Rela *r)
+{
+        Elf_Shdr *sechdrs = elf->sechdrs;
+        int section = sechdrs[rsection].sh_info;
+
+        return (void *)elf->hdr + sechdrs[section].sh_offset +
+                (r->r_offset - sechdrs[section].sh_addr);
+}
+
+static int addend_386_rel(struct elf_info *elf, int rsection, Elf_Rela *r)
+{
+        unsigned int r_typ = ELF_R_TYPE(r->r_info);
+        unsigned int *location = reloc_location(elf, rsection, r);
+
+        switch (r_typ) {
+        case R_386_32:
+                r->r_addend = TO_NATIVE(*location);
+                break;
+        case R_386_PC32:
+                r->r_addend = TO_NATIVE(*location) + 4;
+                /* For CONFIG_RELOCATABLE=y */
+                if (elf->hdr->e_type == ET_EXEC)
+                        r->r_addend += r->r_offset;
+                break;
+        }
+        return 0;
+}
+
+static int addend_mips_rel(struct elf_info *elf, int rsection, Elf_Rela *r)
+{
+        unsigned int r_typ = ELF_R_TYPE(r->r_info);
+        unsigned int *location = reloc_location(elf, rsection, r);
+        unsigned int inst;
+
+        if (r_typ == R_MIPS_HI16)
+                return 1;       /* skip this */
+        inst = TO_NATIVE(*location);
+        switch (r_typ) {
+        case R_MIPS_LO16:
+                r->r_addend = inst & 0xffff;
+                break;
+        case R_MIPS_26:
+                r->r_addend = (inst & 0x03ffffff) << 2;
+                break;
+        case R_MIPS_32:
+                r->r_addend = inst;
+                break;
+        }
+        return 0;
+}
+
 /**
  * A module includes a number of sections that are discarded
  * either when loaded or when used as built-in.
@@ -938,8 +995,11 @@ static void check_sec_ref(struct module *mod, const char *modname,
                                 r.r_offset = TO_NATIVE(rela->r_offset);
 #if KERNEL_ELFCLASS == ELFCLASS64
                                 if (hdr->e_machine == EM_MIPS) {
+                                        unsigned int r_typ;
                                         r_sym = ELF64_MIPS_R_SYM(rela->r_info);
                                         r_sym = TO_NATIVE(r_sym);
+                                        r_typ = ELF64_MIPS_R_TYPE(rela->r_info);
+                                        r.r_info = ELF64_R_INFO(r_sym, r_typ);
                                 } else {
                                         r.r_info = TO_NATIVE(rela->r_info);
                                         r_sym = ELF_R_SYM(r.r_info);
@@ -972,8 +1032,11 @@ static void check_sec_ref(struct module *mod, const char *modname,
                                 r.r_offset = TO_NATIVE(rel->r_offset);
 #if KERNEL_ELFCLASS == ELFCLASS64
                                 if (hdr->e_machine == EM_MIPS) {
+                                        unsigned int r_typ;
                                         r_sym = ELF64_MIPS_R_SYM(rel->r_info);
                                         r_sym = TO_NATIVE(r_sym);
+                                        r_typ = ELF64_MIPS_R_TYPE(rel->r_info);
+                                        r.r_info = ELF64_R_INFO(r_sym, r_typ);
                                 } else {
                                         r.r_info = TO_NATIVE(rel->r_info);
                                         r_sym = ELF_R_SYM(r.r_info);
@@ -983,6 +1046,16 @@ static void check_sec_ref(struct module *mod, const char *modname,
                                 r_sym = ELF_R_SYM(r.r_info);
 #endif
                                 r.r_addend = 0;
+                                switch (hdr->e_machine) {
+                                case EM_386:
+                                        if (addend_386_rel(elf, i, &r))
+                                                continue;
+                                        break;
+                                case EM_MIPS:
+                                        if (addend_mips_rel(elf, i, &r))
+                                                continue;
+                                        break;
+                                }
                                 sym = elf->symtab_start + r_sym;
                                 /* Skip special sections */
                                 if (sym->st_shndx >= SHN_LORESERVE)
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 0858caa9c03f..4156dd34c5de 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -60,6 +60,9 @@ typedef union
 #define ELF64_MIPS_R_SYM(i) \
   ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_sym)
 
+#define ELF64_MIPS_R_TYPE(i) \
+  ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_type1)
+
 #if KERNEL_ELFDATA != HOST_ELFDATA
 
 static inline void __endian(const void *src, void *dest, unsigned int size)