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SubjectRe: [RFC] Crash on modpost, addend_386_rel()
On Mon, 21 May 2007 21:52:59 -0700 (PDT), Linus Torvalds <torvalds@linux-foundation.org> wrote:
> Would you mind also just making this whole logic (that is generic and
> shared with all the different arch versions) be an inline function of its
> own?
>
> > + Elf_Shdr *sechdrs = elf->sechdrs;
> > + unsigned int *location;
> > + int section = sechdrs[rsection].sh_info;
> > +
> > + location = (void *)elf->hdr + sechdrs[section].sh_offset +
> > + (r->r_offset - sechdrs[section].sh_addr);
>
> so that all the functions could just use some generic
>
> location = reloc_location(elf, rsection, r);
>
> or similar, instead of having that complex thing duplicated three times
> (arm, mips and i386)?

Sure, updated.

> Especially since other architectures will likely end up doing the same
> thing too...

Archs using RELA instead of REL section are not affected by this
patch. But I'm not sure how many are using RELA.


Subject: [PATCH] kbuild: make better section mismatch reports on i386, arm and mips (take 3)

On i386, ARM 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>
---
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 8e5610d..44c3960 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -384,6 +384,8 @@ 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 +755,8 @@ 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 +899,69 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
}
}

+static inline 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 void 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;
+ break;
+ }
+}
+
+static void addend_arm_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_ARM_ABS32:
+ r->r_addend = TO_NATIVE(*location);
+ break;
+ case R_ARM_PC24:
+ r->r_addend = ((TO_NATIVE(*location) & 0x00ffffff) << 2) + 8;
+ break;
+ }
+}
+
+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 +1005,11 @@ 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 +1042,11 @@ 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 +1056,14 @@ static void check_sec_ref(struct module *mod, const char *modname,
r_sym = ELF_R_SYM(r.r_info);
#endif
r.r_addend = 0;
+ if (hdr->e_machine == EM_386)
+ addend_386_rel(elf, i, &r);
+ else if (hdr->e_machine == EM_ARM)
+ addend_arm_rel(elf, i, &r);
+ else if (hdr->e_machine == EM_MIPS) {
+ if (addend_mips_rel(elf, i, &r))
+ continue;
+ }
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 0858caa..4156dd3 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)
-
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