linux/arch/x86/tools/relocs.c
H.J. Lu b21ebf2fb4 x86: Treat R_X86_64_PLT32 as R_X86_64_PC32
On i386, there are 2 types of PLTs, PIC and non-PIC.  PIE and shared
objects must use PIC PLT.  To use PIC PLT, you need to load
_GLOBAL_OFFSET_TABLE_ into EBX first.  There is no need for that on
x86-64 since x86-64 uses PC-relative PLT.

On x86-64, for 32-bit PC-relative branches, we can generate PLT32
relocation, instead of PC32 relocation, which can also be used as
a marker for 32-bit PC-relative branches.  Linker can always reduce
PLT32 relocation to PC32 if function is defined locally.   Local
functions should use PC32 relocation.  As far as Linux kernel is
concerned, R_X86_64_PLT32 can be treated the same as R_X86_64_PC32
since Linux kernel doesn't use PLT.

R_X86_64_PLT32 for 32-bit PC-relative branches has been enabled in
binutils master branch which will become binutils 2.31.

[ hjl is working on having better documentation on this all, but a few
  more notes from him:

   "PLT32 relocation is used as marker for PC-relative branches. Because
    of EBX, it looks odd to generate PLT32 relocation on i386 when EBX
    doesn't have GOT.

    As for symbol resolution, PLT32 and PC32 relocations are almost
    interchangeable. But when linker sees PLT32 relocation against a
    protected symbol, it can resolved locally at link-time since it is
    used on a branch instruction. Linker can't do that for PC32
    relocation"

  but for the kernel use, the two are basically the same, and this
  commit gets things building and working with the current binutils
  master   - Linus ]

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-22 09:01:10 -08:00

1106 lines
26 KiB
C

// SPDX-License-Identifier: GPL-2.0
/* This is included from relocs_32/64.c */
#define ElfW(type) _ElfW(ELF_BITS, type)
#define _ElfW(bits, type) __ElfW(bits, type)
#define __ElfW(bits, type) Elf##bits##_##type
#define Elf_Addr ElfW(Addr)
#define Elf_Ehdr ElfW(Ehdr)
#define Elf_Phdr ElfW(Phdr)
#define Elf_Shdr ElfW(Shdr)
#define Elf_Sym ElfW(Sym)
static Elf_Ehdr ehdr;
struct relocs {
uint32_t *offset;
unsigned long count;
unsigned long size;
};
static struct relocs relocs16;
static struct relocs relocs32;
#if ELF_BITS == 64
static struct relocs relocs32neg;
static struct relocs relocs64;
#endif
struct section {
Elf_Shdr shdr;
struct section *link;
Elf_Sym *symtab;
Elf_Rel *reltab;
char *strtab;
};
static struct section *secs;
static const char * const sym_regex_kernel[S_NSYMTYPES] = {
/*
* Following symbols have been audited. There values are constant and do
* not change if bzImage is loaded at a different physical address than
* the address for which it has been compiled. Don't warn user about
* absolute relocations present w.r.t these symbols.
*/
[S_ABS] =
"^(xen_irq_disable_direct_reloc$|"
"xen_save_fl_direct_reloc$|"
"VDSO|"
"__crc_)",
/*
* These symbols are known to be relative, even if the linker marks them
* as absolute (typically defined outside any section in the linker script.)
*/
[S_REL] =
"^(__init_(begin|end)|"
"__x86_cpu_dev_(start|end)|"
"(__parainstructions|__alt_instructions)(|_end)|"
"(__iommu_table|__apicdrivers|__smp_locks)(|_end)|"
"__(start|end)_pci_.*|"
"__(start|end)_builtin_fw|"
"__(start|stop)___ksymtab(|_gpl|_unused|_unused_gpl|_gpl_future)|"
"__(start|stop)___kcrctab(|_gpl|_unused|_unused_gpl|_gpl_future)|"
"__(start|stop)___param|"
"__(start|stop)___modver|"
"__(start|stop)___bug_table|"
"__tracedata_(start|end)|"
"__(start|stop)_notes|"
"__end_rodata|"
"__initramfs_start|"
"(jiffies|jiffies_64)|"
#if ELF_BITS == 64
"__per_cpu_load|"
"init_per_cpu__.*|"
"__end_rodata_hpage_align|"
#endif
"__vvar_page|"
"_end)$"
};
static const char * const sym_regex_realmode[S_NSYMTYPES] = {
/*
* These symbols are known to be relative, even if the linker marks them
* as absolute (typically defined outside any section in the linker script.)
*/
[S_REL] =
"^pa_",
/*
* These are 16-bit segment symbols when compiling 16-bit code.
*/
[S_SEG] =
"^real_mode_seg$",
/*
* These are offsets belonging to segments, as opposed to linear addresses,
* when compiling 16-bit code.
*/
[S_LIN] =
"^pa_",
};
static const char * const *sym_regex;
static regex_t sym_regex_c[S_NSYMTYPES];
static int is_reloc(enum symtype type, const char *sym_name)
{
return sym_regex[type] &&
!regexec(&sym_regex_c[type], sym_name, 0, NULL, 0);
}
static void regex_init(int use_real_mode)
{
char errbuf[128];
int err;
int i;
if (use_real_mode)
sym_regex = sym_regex_realmode;
else
sym_regex = sym_regex_kernel;
for (i = 0; i < S_NSYMTYPES; i++) {
if (!sym_regex[i])
continue;
err = regcomp(&sym_regex_c[i], sym_regex[i],
REG_EXTENDED|REG_NOSUB);
if (err) {
regerror(err, &sym_regex_c[i], errbuf, sizeof errbuf);
die("%s", errbuf);
}
}
}
static const char *sym_type(unsigned type)
{
static const char *type_name[] = {
#define SYM_TYPE(X) [X] = #X
SYM_TYPE(STT_NOTYPE),
SYM_TYPE(STT_OBJECT),
SYM_TYPE(STT_FUNC),
SYM_TYPE(STT_SECTION),
SYM_TYPE(STT_FILE),
SYM_TYPE(STT_COMMON),
SYM_TYPE(STT_TLS),
#undef SYM_TYPE
};
const char *name = "unknown sym type name";
if (type < ARRAY_SIZE(type_name)) {
name = type_name[type];
}
return name;
}
static const char *sym_bind(unsigned bind)
{
static const char *bind_name[] = {
#define SYM_BIND(X) [X] = #X
SYM_BIND(STB_LOCAL),
SYM_BIND(STB_GLOBAL),
SYM_BIND(STB_WEAK),
#undef SYM_BIND
};
const char *name = "unknown sym bind name";
if (bind < ARRAY_SIZE(bind_name)) {
name = bind_name[bind];
}
return name;
}
static const char *sym_visibility(unsigned visibility)
{
static const char *visibility_name[] = {
#define SYM_VISIBILITY(X) [X] = #X
SYM_VISIBILITY(STV_DEFAULT),
SYM_VISIBILITY(STV_INTERNAL),
SYM_VISIBILITY(STV_HIDDEN),
SYM_VISIBILITY(STV_PROTECTED),
#undef SYM_VISIBILITY
};
const char *name = "unknown sym visibility name";
if (visibility < ARRAY_SIZE(visibility_name)) {
name = visibility_name[visibility];
}
return name;
}
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),
REL_TYPE(R_386_GOT32),
REL_TYPE(R_386_PLT32),
REL_TYPE(R_386_COPY),
REL_TYPE(R_386_GLOB_DAT),
REL_TYPE(R_386_JMP_SLOT),
REL_TYPE(R_386_RELATIVE),
REL_TYPE(R_386_GOTOFF),
REL_TYPE(R_386_GOTPC),
REL_TYPE(R_386_8),
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";
if (type < ARRAY_SIZE(type_name) && type_name[type]) {
name = type_name[type];
}
return name;
}
static const char *sec_name(unsigned shndx)
{
const char *sec_strtab;
const char *name;
sec_strtab = secs[ehdr.e_shstrndx].strtab;
name = "<noname>";
if (shndx < ehdr.e_shnum) {
name = sec_strtab + secs[shndx].shdr.sh_name;
}
else if (shndx == SHN_ABS) {
name = "ABSOLUTE";
}
else if (shndx == SHN_COMMON) {
name = "COMMON";
}
return name;
}
static const char *sym_name(const char *sym_strtab, Elf_Sym *sym)
{
const char *name;
name = "<noname>";
if (sym->st_name) {
name = sym_strtab + sym->st_name;
}
else {
name = sec_name(sym->st_shndx);
}
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)
{
return le16_to_cpu(val);
}
static uint32_t elf32_to_cpu(uint32_t val)
{
return le32_to_cpu(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)
{
if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) {
die("Cannot read ELF header: %s\n",
strerror(errno));
}
if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0) {
die("No ELF magic\n");
}
if (ehdr.e_ident[EI_CLASS] != ELF_CLASS) {
die("Not a %d bit executable\n", ELF_BITS);
}
if (ehdr.e_ident[EI_DATA] != ELFDATA2LSB) {
die("Not a LSB ELF executable\n");
}
if (ehdr.e_ident[EI_VERSION] != EV_CURRENT) {
die("Unknown ELF version\n");
}
/* Convert the fields to native endian */
ehdr.e_type = elf_half_to_cpu(ehdr.e_type);
ehdr.e_machine = elf_half_to_cpu(ehdr.e_machine);
ehdr.e_version = elf_word_to_cpu(ehdr.e_version);
ehdr.e_entry = elf_addr_to_cpu(ehdr.e_entry);
ehdr.e_phoff = elf_off_to_cpu(ehdr.e_phoff);
ehdr.e_shoff = elf_off_to_cpu(ehdr.e_shoff);
ehdr.e_flags = elf_word_to_cpu(ehdr.e_flags);
ehdr.e_ehsize = elf_half_to_cpu(ehdr.e_ehsize);
ehdr.e_phentsize = elf_half_to_cpu(ehdr.e_phentsize);
ehdr.e_phnum = elf_half_to_cpu(ehdr.e_phnum);
ehdr.e_shentsize = elf_half_to_cpu(ehdr.e_shentsize);
ehdr.e_shnum = elf_half_to_cpu(ehdr.e_shnum);
ehdr.e_shstrndx = elf_half_to_cpu(ehdr.e_shstrndx);
if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN)) {
die("Unsupported ELF header type\n");
}
if (ehdr.e_machine != ELF_MACHINE) {
die("Not for %s\n", ELF_MACHINE_NAME);
}
if (ehdr.e_version != EV_CURRENT) {
die("Unknown ELF version\n");
}
if (ehdr.e_ehsize != sizeof(Elf_Ehdr)) {
die("Bad Elf header size\n");
}
if (ehdr.e_phentsize != sizeof(Elf_Phdr)) {
die("Bad program header entry\n");
}
if (ehdr.e_shentsize != sizeof(Elf_Shdr)) {
die("Bad section header entry\n");
}
if (ehdr.e_shstrndx >= ehdr.e_shnum) {
die("String table index out of bounds\n");
}
}
static void read_shdrs(FILE *fp)
{
int i;
Elf_Shdr shdr;
secs = calloc(ehdr.e_shnum, sizeof(struct section));
if (!secs) {
die("Unable to allocate %d section headers\n",
ehdr.e_shnum);
}
if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
die("Seek to %d failed: %s\n",
ehdr.e_shoff, strerror(errno));
}
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
if (fread(&shdr, sizeof shdr, 1, fp) != 1)
die("Cannot read ELF section headers %d/%d: %s\n",
i, ehdr.e_shnum, strerror(errno));
sec->shdr.sh_name = elf_word_to_cpu(shdr.sh_name);
sec->shdr.sh_type = elf_word_to_cpu(shdr.sh_type);
sec->shdr.sh_flags = elf_xword_to_cpu(shdr.sh_flags);
sec->shdr.sh_addr = elf_addr_to_cpu(shdr.sh_addr);
sec->shdr.sh_offset = elf_off_to_cpu(shdr.sh_offset);
sec->shdr.sh_size = elf_xword_to_cpu(shdr.sh_size);
sec->shdr.sh_link = elf_word_to_cpu(shdr.sh_link);
sec->shdr.sh_info = elf_word_to_cpu(shdr.sh_info);
sec->shdr.sh_addralign = elf_xword_to_cpu(shdr.sh_addralign);
sec->shdr.sh_entsize = elf_xword_to_cpu(shdr.sh_entsize);
if (sec->shdr.sh_link < ehdr.e_shnum)
sec->link = &secs[sec->shdr.sh_link];
}
}
static void read_strtabs(FILE *fp)
{
int i;
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
if (sec->shdr.sh_type != SHT_STRTAB) {
continue;
}
sec->strtab = malloc(sec->shdr.sh_size);
if (!sec->strtab) {
die("malloc of %d bytes for strtab failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %d failed: %s\n",
sec->shdr.sh_offset, strerror(errno));
}
if (fread(sec->strtab, 1, sec->shdr.sh_size, fp)
!= sec->shdr.sh_size) {
die("Cannot read symbol table: %s\n",
strerror(errno));
}
}
}
static void read_symtabs(FILE *fp)
{
int i,j;
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
if (sec->shdr.sh_type != SHT_SYMTAB) {
continue;
}
sec->symtab = malloc(sec->shdr.sh_size);
if (!sec->symtab) {
die("malloc of %d bytes for symtab failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %d failed: %s\n",
sec->shdr.sh_offset, strerror(errno));
}
if (fread(sec->symtab, 1, sec->shdr.sh_size, fp)
!= sec->shdr.sh_size) {
die("Cannot read symbol table: %s\n",
strerror(errno));
}
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Sym); j++) {
Elf_Sym *sym = &sec->symtab[j];
sym->st_name = elf_word_to_cpu(sym->st_name);
sym->st_value = elf_addr_to_cpu(sym->st_value);
sym->st_size = elf_xword_to_cpu(sym->st_size);
sym->st_shndx = elf_half_to_cpu(sym->st_shndx);
}
}
}
static void read_relocs(FILE *fp)
{
int i,j;
for (i = 0; i < ehdr.e_shnum; i++) {
struct section *sec = &secs[i];
if (sec->shdr.sh_type != SHT_REL_TYPE) {
continue;
}
sec->reltab = malloc(sec->shdr.sh_size);
if (!sec->reltab) {
die("malloc of %d bytes for relocs failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %d failed: %s\n",
sec->shdr.sh_offset, strerror(errno));
}
if (fread(sec->reltab, 1, sec->shdr.sh_size, fp)
!= sec->shdr.sh_size) {
die("Cannot read symbol table: %s\n",
strerror(errno));
}
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {
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
}
}
}
static void print_absolute_symbols(void)
{
int i;
const char *format;
if (ELF_BITS == 64)
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++) {
struct section *sec = &secs[i];
char *sym_strtab;
int j;
if (sec->shdr.sh_type != SHT_SYMTAB) {
continue;
}
sym_strtab = sec->link->strtab;
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Sym); j++) {
Elf_Sym *sym;
const char *name;
sym = &sec->symtab[j];
name = sym_name(sym_strtab, sym);
if (sym->st_shndx != SHN_ABS) {
continue;
}
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)),
sym_visibility(ELF_ST_VISIBILITY(sym->st_other)),
name);
}
}
printf("\n");
}
static void print_absolute_relocs(void)
{
int i, printed = 0;
const char *format;
if (ELF_BITS == 64)
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];
struct section *sec_applies, *sec_symtab;
char *sym_strtab;
Elf_Sym *sh_symtab;
int j;
if (sec->shdr.sh_type != SHT_REL_TYPE) {
continue;
}
sec_symtab = sec->link;
sec_applies = &secs[sec->shdr.sh_info];
if (!(sec_applies->shdr.sh_flags & SHF_ALLOC)) {
continue;
}
sh_symtab = sec_symtab->symtab;
sym_strtab = sec_symtab->link->strtab;
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {
Elf_Rel *rel;
Elf_Sym *sym;
const char *name;
rel = &sec->reltab[j];
sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
name = sym_name(sym_strtab, sym);
if (sym->st_shndx != SHN_ABS) {
continue;
}
/* Absolute symbols are not relocated if bzImage is
* loaded at a non-compiled address. Display a warning
* to user at compile time about the absolute
* relocations present.
*
* User need to audit the code to make sure
* some symbols which should have been section
* relative have not become absolute because of some
* linker optimization or wrong programming usage.
*
* Before warning check if this absolute symbol
* relocation is harmless.
*/
if (is_reloc(S_ABS, name) || is_reloc(S_REL, name))
continue;
if (!printed) {
printf("WARNING: Absolute relocations"
" present\n");
printf("Offset Info Type Sym.Value "
"Sym.Name\n");
printed = 1;
}
printf(format,
rel->r_offset,
rel->r_info,
rel_type(ELF_R_TYPE(rel->r_info)),
sym->st_value,
name);
}
}
if (printed)
printf("\n");
}
static void add_reloc(struct relocs *r, uint32_t offset)
{
if (r->count == r->size) {
unsigned long newsize = r->size + 50000;
void *mem = realloc(r->offset, newsize * sizeof(r->offset[0]));
if (!mem)
die("realloc of %ld entries for relocs failed\n",
newsize);
r->offset = mem;
r->size = newsize;
}
r->offset[r->count++] = offset;
}
static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,
Elf_Sym *sym, const char *symname))
{
int i;
/* Walk through the relocations */
for (i = 0; i < ehdr.e_shnum; i++) {
char *sym_strtab;
Elf_Sym *sh_symtab;
struct section *sec_applies, *sec_symtab;
int j;
struct section *sec = &secs[i];
if (sec->shdr.sh_type != SHT_REL_TYPE) {
continue;
}
sec_symtab = sec->link;
sec_applies = &secs[sec->shdr.sh_info];
if (!(sec_applies->shdr.sh_flags & SHF_ALLOC)) {
continue;
}
sh_symtab = sec_symtab->symtab;
sym_strtab = sec_symtab->link->strtab;
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {
Elf_Rel *rel = &sec->reltab[j];
Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
const char *symname = sym_name(sym_strtab, sym);
process(sec, rel, sym, symname);
}
}
}
/*
* 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;
static 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;
}
}
#if ELF_BITS == 64
/*
* Check to see if a symbol lies in the .data..percpu section.
*
* The linker incorrectly associates some symbols with the
* .data..percpu section so we also need to check the symbol
* name to make sure that we classify the symbol correctly.
*
* The GNU linker incorrectly associates:
* __init_begin
* __per_cpu_load
*
* The "gold" linker incorrectly associates:
* init_per_cpu__irq_stack_union
* init_per_cpu__gdt_page
*/
static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
{
return (sym->st_shndx == per_cpu_shndx) &&
strcmp(symname, "__init_begin") &&
strcmp(symname, "__per_cpu_load") &&
strncmp(symname, "init_per_cpu_", 13);
}
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:
/* NONE can be ignored. */
break;
case R_X86_64_PC32:
case R_X86_64_PLT32:
/*
* PC relative relocations don't need to be adjusted unless
* referencing a percpu symbol.
*
* NB: R_X86_64_PLT32 can be treated as R_X86_64_PC32.
*/
if (is_percpu_sym(sym, symname))
add_reloc(&relocs32neg, offset);
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;
}
#else
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);
int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
switch (r_type) {
case R_386_NONE:
case R_386_PC32:
case R_386_PC16:
case R_386_PC8:
/*
* NONE can be ignored and PC relative relocations don't
* need to be adjusted.
*/
break;
case R_386_32:
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;
}
add_reloc(&relocs32, rel->r_offset);
break;
default:
die("Unsupported relocation type: %s (%d)\n",
rel_type(r_type), r_type);
break;
}
return 0;
}
static int do_reloc_real(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
const char *symname)
{
unsigned r_type = ELF32_R_TYPE(rel->r_info);
int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
switch (r_type) {
case R_386_NONE:
case R_386_PC32:
case R_386_PC16:
case R_386_PC8:
/*
* NONE can be ignored and PC relative relocations don't
* need to be adjusted.
*/
break;
case R_386_16:
if (shn_abs) {
/*
* Whitelisted absolute symbols do not require
* relocation.
*/
if (is_reloc(S_ABS, symname))
break;
if (is_reloc(S_SEG, symname)) {
add_reloc(&relocs16, rel->r_offset);
break;
}
} else {
if (!is_reloc(S_LIN, symname))
break;
}
die("Invalid %s %s relocation: %s\n",
shn_abs ? "absolute" : "relative",
rel_type(r_type), symname);
break;
case R_386_32:
if (shn_abs) {
/*
* Whitelisted absolute symbols do not require
* relocation.
*/
if (is_reloc(S_ABS, symname))
break;
if (is_reloc(S_REL, symname)) {
add_reloc(&relocs32, rel->r_offset);
break;
}
} else {
if (is_reloc(S_LIN, symname))
add_reloc(&relocs32, rel->r_offset);
break;
}
die("Invalid %s %s relocation: %s\n",
shn_abs ? "absolute" : "relative",
rel_type(r_type), symname);
break;
default:
die("Unsupported relocation type: %s (%d)\n",
rel_type(r_type), r_type);
break;
}
return 0;
}
#endif
static int cmp_relocs(const void *va, const void *vb)
{
const uint32_t *a, *b;
a = va; b = vb;
return (*a == *b)? 0 : (*a > *b)? 1 : -1;
}
static void sort_relocs(struct relocs *r)
{
qsort(r->offset, r->count, sizeof(r->offset[0]), cmp_relocs);
}
static int write32(uint32_t v, FILE *f)
{
unsigned char buf[4];
put_unaligned_le32(v, buf);
return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;
}
static int write32_as_text(uint32_t v, FILE *f)
{
return fprintf(f, "\t.long 0x%08"PRIx32"\n", v) > 0 ? 0 : -1;
}
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 ELF_BITS == 64
if (!use_real_mode)
do_reloc = do_reloc64;
else
die("--realmode not valid for a 64-bit ELF file");
#else
if (!use_real_mode)
do_reloc = do_reloc32;
else
do_reloc = do_reloc_real;
#endif
/* Collect up the relocations */
walk_relocs(do_reloc);
if (relocs16.count && !use_real_mode)
die("Segment relocations found but --realmode not specified\n");
/* Order the relocations for more efficient processing */
sort_relocs(&relocs32);
#if ELF_BITS == 64
sort_relocs(&relocs32neg);
sort_relocs(&relocs64);
#else
sort_relocs(&relocs16);
#endif
/* Print the relocations */
if (as_text) {
/* Print the relocations in a form suitable that
* gas will like.
*/
printf(".section \".data.reloc\",\"a\"\n");
printf(".balign 4\n");
write_reloc = write32_as_text;
}
if (use_real_mode) {
write_reloc(relocs16.count, stdout);
for (i = 0; i < relocs16.count; i++)
write_reloc(relocs16.offset[i], stdout);
write_reloc(relocs32.count, stdout);
for (i = 0; i < relocs32.count; i++)
write_reloc(relocs32.offset[i], stdout);
} else {
#if ELF_BITS == 64
/* 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);
/* Now print each inverse 32-bit relocation */
for (i = 0; i < relocs32neg.count; i++)
write_reloc(relocs32neg.offset[i], stdout);
#endif
/* Print a stop */
write_reloc(0, stdout);
/* Now print each relocation */
for (i = 0; i < relocs32.count; i++)
write_reloc(relocs32.offset[i], stdout);
}
}
/*
* As an aid to debugging problems with different linkers
* print summary information about the relocs.
* Since different linkers tend to emit the sections in
* different orders we use the section names in the output.
*/
static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
const char *symname)
{
printf("%s\t%s\t%s\t%s\n",
sec_name(sec->shdr.sh_info),
rel_type(ELF_R_TYPE(rel->r_info)),
symname,
sec_name(sym->st_shndx));
return 0;
}
static void print_reloc_info(void)
{
printf("reloc section\treloc type\tsymbol\tsymbol section\n");
walk_relocs(do_reloc_info);
}
#if ELF_BITS == 64
# define process process_64
#else
# define process process_32
#endif
void process(FILE *fp, int use_real_mode, int as_text,
int show_absolute_syms, int show_absolute_relocs,
int show_reloc_info)
{
regex_init(use_real_mode);
read_ehdr(fp);
read_shdrs(fp);
read_strtabs(fp);
read_symtabs(fp);
read_relocs(fp);
if (ELF_BITS == 64)
percpu_init();
if (show_absolute_syms) {
print_absolute_symbols();
return;
}
if (show_absolute_relocs) {
print_absolute_relocs();
return;
}
if (show_reloc_info) {
print_reloc_info();
return;
}
emit_relocs(as_text, use_real_mode);
}