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Message-Id: <20070522.134015.65004318.nemoto@toshiba-tops.co.jp>
Date: Tue, 22 May 2007 13:40:15 +0900 (JST)
From: Atsushi Nemoto <anemo@....ocn.ne.jp>
To: ben.collins@...ntu.com
Cc: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
sam@...nborg.org, torvalds@...ux-foundation.org,
dwmw2@...radead.org, adobriyan@...il.com
Subject: Re: [RFC] Crash on modpost, addend_386_rel()
On Mon, 21 May 2007 22:01:27 -0400, Ben Collins <ben.collins@...ntu.com> wrote:
> Got this crash in modpost. Bisect blames this commit:
>
> commit f892b7d480eec809a5dfbd6e65742b3f3155e50e
> Author: Atsushi Nemoto <anemo@....ocn.ne.jp>
> Date: Thu May 17 01:14:38 2007 +0900
> kbuild: make better section mismatch reports on i386, arm and mips
Sorry, the patch breaks CONFIG_RELOCATABLE=y build. Actually I had
not tested with that configuration.
Linus already have reverted the commmit on git tree due to this breakage.
Unfortunately, fixing whole things in the _right_ way is somewhat out
of my ELF understanding. Some help from ELF gurus are welcome!
Anyway, here is a updated patch tested on i386 (RELOCATABLE=y/n), arm,
and mips. On calculation of 'location', sh_addr should be subtracted
(thank you for debugging, Linus). And this patch contains an another
fix and an improvement of added_mips_rel
(kbuild-fix-and-improve-mips-rel-handling.patch in mm tree).
Subject: [PATCH] kbuild: make better section mismatch reports on i386, arm and mips (take 2)
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..e0bd1cd 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 +899,74 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
}
}
+static void addend_386_rel(struct elf_info *elf, int rsection, Elf_Rela *r)
+{
+ Elf_Shdr *sechdrs = elf->sechdrs;
+ unsigned int r_typ;
+ unsigned int *location;
+ int section = sechdrs[rsection].sh_info;
+
+ r_typ = ELF_R_TYPE(r->r_info);
+ location = (void *)elf->hdr + sechdrs[section].sh_offset +
+ (r->r_offset - sechdrs[section].sh_addr);
+ 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)
+{
+ Elf_Shdr *sechdrs = elf->sechdrs;
+ unsigned int r_typ;
+ unsigned int *location;
+ int section = sechdrs[rsection].sh_info;
+
+ r_typ = ELF_R_TYPE(r->r_info);
+ location = (void *)elf->hdr + sechdrs[section].sh_offset +
+ (r->r_offset - sechdrs[section].sh_addr);
+ 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)
+{
+ Elf_Shdr *sechdrs = elf->sechdrs;
+ unsigned int r_typ;
+ unsigned int *location;
+ int section = sechdrs[rsection].sh_info;
+ unsigned int inst;
+
+ r_typ = ELF_R_TYPE(r->r_info);
+ if (r_typ == R_MIPS_HI16)
+ return 1; /* skip this */
+ location = (void *)elf->hdr + sechdrs[section].sh_offset +
+ (r->r_offset - sechdrs[section].sh_addr);
+ 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 +1010,11 @@ 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 +1047,11 @@ 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 +1061,14 @@ 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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