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Date: Tue, 22 May 2007 17:48:09 +0300
From: Mika Penttilä <mika.penttila@...umbus.fi>
To: Atsushi Nemoto <anemo@....ocn.ne.jp>
CC: torvalds@...ux-foundation.org, ben.collins@...ntu.com,
linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
sam@...nborg.org, dwmw2@...radead.org, adobriyan@...il.com
Subject: Re: [RFC] Crash on modpost, addend_386_rel()
Atsushi Nemoto kirjoitti:
> On Tue, 22 May 2007 14:29:29 +0900 (JST), Atsushi Nemoto <nemoto@...hiba-tops.co.jp> wrote:
>
>> Subject: [PATCH] kbuild: make better section mismatch reports on i386, arm and mips (take 3)
>>
>
> Updated again to get a little bit better report on i386 relocatable
> vmlinux.
>
>
> Subject: [PATCH] kbuild: make better section mismatch reports on i386, arm and mips (take 4)
>
> 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@....ocn.ne.jp>
> ---
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 8e5610d..760b2b3 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 +900,72 @@ 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;
> + /* For CONFIG_RELOCATABLE=y */
> + if (elf->hdr->e_type == ET_EXEC)
> + r->r_addend += r->r_offset;
> + 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 +1009,11 @@ 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 +1046,11 @@ 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 +1060,14 @@ 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)
> -
>
>
I can't see how this use of r_attend is going to work. find_elf_symbol
compares relsym->st_value to Elf_Rela->r_attend. I think it doesn't work
for RELA archs and even with this patch for REL.
--Mika
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