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x86, relocs: Add 64-bit ELF support to relocs tool

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This adds the ability to process relocations from the 64-bit kernel ELF,
if built with ELF_BITS=64 defined. The special case for the percpu area is
handled, along with some other symbols specific to the 64-bit kernel.

Based on work by Neill Clift and Michael Davidson.

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: http://lkml.kernel.org/r/1365797627-20874-4-git-send-email-keescook@chromium.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Kees Cook 2013-04-12 13:13:44 -07:00 committed by H. Peter Anvin
parent 5d442e63d6
commit 946166af95
1 changed files with 261 additions and 6 deletions
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265
arch/x86/tools/relocs.c
View File

@ -17,19 +17,39 @@
#define _ElfW(bits, type) __ElfW(bits, type)
#define __ElfW(bits, type) Elf##bits##_##type
#ifndef ELF_BITS
#define ELF_BITS 32
#endif
#if (ELF_BITS == 64)
#define ELF_MACHINE EM_X86_64
#define ELF_MACHINE_NAME "x86_64"
#define SHT_REL_TYPE SHT_RELA
#define Elf_Rel Elf64_Rela
#else
#define ELF_MACHINE EM_386
#define ELF_MACHINE_NAME "i386"
#define SHT_REL_TYPE SHT_REL
#define Elf_Rel ElfW(Rel)
#endif
#if (ELF_BITS == 64)
#define ELF_CLASS ELFCLASS64
#define ELF_R_SYM(val) ELF64_R_SYM(val)
#define ELF_R_TYPE(val) ELF64_R_TYPE(val)
#define ELF_ST_TYPE(o) ELF64_ST_TYPE(o)
#define ELF_ST_BIND(o) ELF64_ST_BIND(o)
#define ELF_ST_VISIBILITY(o) ELF64_ST_VISIBILITY(o)
#else
#define ELF_CLASS ELFCLASS32
#define ELF_R_SYM(val) ELF32_R_SYM(val)
#define ELF_R_TYPE(val) ELF32_R_TYPE(val)
#define ELF_ST_TYPE(o) ELF32_ST_TYPE(o)
#define ELF_ST_BIND(o) ELF32_ST_BIND(o)
#define ELF_ST_VISIBILITY(o) ELF32_ST_VISIBILITY(o)
#endif
#define Elf_Rel ElfW(Rel)
#define Elf_Addr ElfW(Addr)
#define Elf_Ehdr ElfW(Ehdr)
#define Elf_Phdr ElfW(Phdr)
#define Elf_Shdr ElfW(Shdr)
@ -48,6 +68,7 @@ struct relocs {
static struct relocs relocs16;
static struct relocs relocs32;
static struct relocs relocs64;
struct section {
Elf_Shdr shdr;
@ -77,6 +98,9 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
"^(xen_irq_disable_direct_reloc$|"
"xen_save_fl_direct_reloc$|"
"VDSO|"
#if (ELF_BITS == 64)
"__vvar_page|"
#endif
"__crc_)",
/*
@ -100,6 +124,11 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
"__end_rodata|"
"__initramfs_start|"
"(jiffies|jiffies_64)|"
#if (ELF_BITS == 64)
"__per_cpu_load|"
"init_per_cpu__.*|"
"__end_rodata_hpage_align|"
#endif
"_end)$"
};
@ -226,6 +255,24 @@ static const char *rel_type(unsigned type)
{
static const char *type_name[] = {
#define REL_TYPE(X) [X] = #X
#if (ELF_BITS == 64)
REL_TYPE(R_X86_64_NONE),
REL_TYPE(R_X86_64_64),
REL_TYPE(R_X86_64_PC32),
REL_TYPE(R_X86_64_GOT32),
REL_TYPE(R_X86_64_PLT32),
REL_TYPE(R_X86_64_COPY),
REL_TYPE(R_X86_64_GLOB_DAT),
REL_TYPE(R_X86_64_JUMP_SLOT),
REL_TYPE(R_X86_64_RELATIVE),
REL_TYPE(R_X86_64_GOTPCREL),
REL_TYPE(R_X86_64_32),
REL_TYPE(R_X86_64_32S),
REL_TYPE(R_X86_64_16),
REL_TYPE(R_X86_64_PC16),
REL_TYPE(R_X86_64_8),
REL_TYPE(R_X86_64_PC8),
#else
REL_TYPE(R_386_NONE),
REL_TYPE(R_386_32),
REL_TYPE(R_386_PC32),
@ -241,6 +288,7 @@ static const char *rel_type(unsigned type)
REL_TYPE(R_386_PC8),
REL_TYPE(R_386_16),
REL_TYPE(R_386_PC16),
#endif
#undef REL_TYPE
};
const char *name = "unknown type rel type name";
@ -281,15 +329,42 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym)
return name;
}
static Elf_Sym *sym_lookup(const char *symname)
{
int i;
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
long nsyms;
char *strtab;
Elf_Sym *symtab;
Elf_Sym *sym;
if (sec->shdr.sh_type != SHT_SYMTAB)
continue;
nsyms = sec->shdr.sh_size/sizeof(Elf_Sym);
symtab = sec->symtab;
strtab = sec->link->strtab;
for (sym = symtab; --nsyms >= 0; sym++) {
if (!sym->st_name)
continue;
if (strcmp(symname, strtab + sym->st_name) == 0)
return sym;
}
}
return 0;
}
#if BYTE_ORDER == LITTLE_ENDIAN
#define le16_to_cpu(val) (val)
#define le32_to_cpu(val) (val)
#define le64_to_cpu(val) (val)
#endif
#if BYTE_ORDER == BIG_ENDIAN
#define le16_to_cpu(val) bswap_16(val)
#define le32_to_cpu(val) bswap_32(val)
#define le64_to_cpu(val) bswap_64(val)
#endif
static uint16_t elf16_to_cpu(uint16_t val)
@ -304,9 +379,20 @@ static uint32_t elf32_to_cpu(uint32_t val)
#define elf_half_to_cpu(x) elf16_to_cpu(x)
#define elf_word_to_cpu(x) elf32_to_cpu(x)
#if (ELF_BITS == 64)
static uint64_t elf64_to_cpu(uint64_t val)
{
return le64_to_cpu(val);
}
#define elf_addr_to_cpu(x) elf64_to_cpu(x)
#define elf_off_to_cpu(x) elf64_to_cpu(x)
#define elf_xword_to_cpu(x) elf64_to_cpu(x)
#else
#define elf_addr_to_cpu(x) elf32_to_cpu(x)
#define elf_off_to_cpu(x) elf32_to_cpu(x)
#define elf_xword_to_cpu(x) elf32_to_cpu(x)
#endif
static void read_ehdr(FILE *fp)
{
@ -483,6 +569,9 @@ static void read_relocs(FILE *fp)
Elf_Rel *rel = &sec->reltab[j];
rel->r_offset = elf_addr_to_cpu(rel->r_offset);
rel->r_info = elf_xword_to_cpu(rel->r_info);
#if (SHT_REL_TYPE == SHT_RELA)
rel->r_addend = elf_xword_to_cpu(rel->r_addend);
#endif
}
}
}
@ -491,6 +580,13 @@ static void read_relocs(FILE *fp)
static void print_absolute_symbols(void)
{
int i;
const char *format;
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
format = "%5d %016"PRIx64" %5"PRId64" %10s %10s %12s %s\n";
else
format = "%5d %08"PRIx32" %5"PRId32" %10s %10s %12s %s\n";
printf("Absolute symbols\n");
printf(" Num: Value Size Type Bind Visibility Name\n");
for (i = 0; i < ehdr.e_shnum; i++) {
@ -510,7 +606,7 @@ static void print_absolute_symbols(void)
if (sym->st_shndx != SHN_ABS) {
continue;
}
printf("%5d %08x %5d %10s %10s %12s %s\n",
printf(format,
j, sym->st_value, sym->st_size,
sym_type(ELF_ST_TYPE(sym->st_info)),
sym_bind(ELF_ST_BIND(sym->st_info)),
@ -524,6 +620,12 @@ static void print_absolute_symbols(void)
static void print_absolute_relocs(void)
{
int i, printed = 0;
const char *format;
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
format = "%016"PRIx64" %016"PRIx64" %10s %016"PRIx64" %s\n";
else
format = "%08"PRIx32" %08"PRIx32" %10s %08"PRIx32" %s\n";
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
@ -576,7 +678,7 @@ static void print_absolute_relocs(void)
printed = 1;
}
printf("%08x %08x %10s %08x %s\n",
printf(format,
rel->r_offset,
rel->r_info,
rel_type(ELF_R_TYPE(rel->r_info)),
@ -636,7 +738,139 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,
}
}
static int do_reloc(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
/*
* The .data..percpu section is a special case for x86_64 SMP kernels.
* It is used to initialize the actual per_cpu areas and to provide
* definitions for the per_cpu variables that correspond to their offsets
* within the percpu area. Since the values of all of the symbols need
* to be offsets from the start of the per_cpu area the virtual address
* (sh_addr) of .data..percpu is 0 in SMP kernels.
*
* This means that:
*
* Relocations that reference symbols in the per_cpu area do not
* need further relocation (since the value is an offset relative
* to the start of the per_cpu area that does not change).
*
* Relocations that apply to the per_cpu area need to have their
* offset adjusted by by the value of __per_cpu_load to make them
* point to the correct place in the loaded image (because the
* virtual address of .data..percpu is 0).
*
* For non SMP kernels .data..percpu is linked as part of the normal
* kernel data and does not require special treatment.
*
*/
static int per_cpu_shndx = -1;
Elf_Addr per_cpu_load_addr;
static void percpu_init(void)
{
int i;
for (i = 0; i < ehdr.e_shnum; i++) {
ElfW(Sym) *sym;
if (strcmp(sec_name(i), ".data..percpu"))
continue;
if (secs[i].shdr.sh_addr != 0) /* non SMP kernel */
return;
sym = sym_lookup("__per_cpu_load");
if (!sym)
die("can't find __per_cpu_load\n");
per_cpu_shndx = i;
per_cpu_load_addr = sym->st_value;
return;
}
}
/*
* Check to see if a symbol lies in the .data..percpu section.
* For some as yet not understood reason the "__init_begin"
* symbol which immediately preceeds the .data..percpu section
* also shows up as it it were part of it so we do an explict
* check for that symbol name and ignore it.
*/
static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
{
return (sym->st_shndx == per_cpu_shndx) &&
strcmp(symname, "__init_begin");
}
static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
const char *symname)
{
unsigned r_type = ELF64_R_TYPE(rel->r_info);
ElfW(Addr) offset = rel->r_offset;
int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
if (sym->st_shndx == SHN_UNDEF)
return 0;
/*
* Adjust the offset if this reloc applies to the percpu section.
*/
if (sec->shdr.sh_info == per_cpu_shndx)
offset += per_cpu_load_addr;
switch (r_type) {
case R_X86_64_NONE:
case R_X86_64_PC32:
/*
* NONE can be ignored and PC relative relocations don't
* need to be adjusted.
*/
break;
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64:
/*
* References to the percpu area don't need to be adjusted.
*/
if (is_percpu_sym(sym, symname))
break;
if (shn_abs) {
/*
* Whitelisted absolute symbols do not require
* relocation.
*/
if (is_reloc(S_ABS, symname))
break;
die("Invalid absolute %s relocation: %s\n",
rel_type(r_type), symname);
break;
}
/*
* Relocation offsets for 64 bit kernels are output
* as 32 bits and sign extended back to 64 bits when
* the relocations are processed.
* Make sure that the offset will fit.
*/
if ((int32_t)offset != (int64_t)offset)
die("Relocation offset doesn't fit in 32 bits\n");
if (r_type == R_X86_64_64)
add_reloc(&relocs64, offset);
else
add_reloc(&relocs32, offset);
break;
default:
die("Unsupported relocation type: %s (%d)\n",
rel_type(r_type), r_type);
break;
}
return 0;
}
static int do_reloc32(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
const char *symname)
{
unsigned r_type = ELF32_R_TYPE(rel->r_info);
@ -779,9 +1013,18 @@ static void emit_relocs(int as_text, int use_real_mode)
{
int i;
int (*write_reloc)(uint32_t, FILE *) = write32;
int (*do_reloc)(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
const char *symname);
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
do_reloc = do_reloc64;
else if (!use_real_mode)
do_reloc = do_reloc32;
else
do_reloc = do_reloc_real;
/* Collect up the relocations */
walk_relocs(use_real_mode ? do_reloc_real : do_reloc);
walk_relocs(do_reloc);
if (relocs16.count && !use_real_mode)
die("Segment relocations found but --realmode not specified\n");
@ -789,6 +1032,7 @@ static void emit_relocs(int as_text, int use_real_mode)
/* Order the relocations for more efficient processing */
sort_relocs(&relocs16);
sort_relocs(&relocs32);
sort_relocs(&relocs64);
/* Print the relocations */
if (as_text) {
@ -809,6 +1053,15 @@ static void emit_relocs(int as_text, int use_real_mode)
for (i = 0; i < relocs32.count; i++)
write_reloc(relocs32.offset[i], stdout);
} else {
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
/* Print a stop */
write_reloc(0, stdout);
/* Now print each relocation */
for (i = 0; i < relocs64.count; i++)
write_reloc(relocs64.offset[i], stdout);
}
/* Print a stop */
write_reloc(0, stdout);
@ -876,6 +1129,8 @@ int main(int argc, char **argv)
read_strtabs(fp);
read_symtabs(fp);
read_relocs(fp);
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
percpu_init();
if (show_absolute_syms) {
print_absolute_symbols();
goto out;