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linuxdebug/arch/x86/tools/relocs.c

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null pointer error
2024-07-16 15:50:57 +02:00
// 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;
static unsigned long shnum;
static unsigned int shstrndx;
static unsigned int shsymtabndx;
static unsigned int shxsymtabndx;
static int sym_index(Elf_Sym *sym);
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;
#define FMT PRIu64
#else
#define FMT PRIu32
#endif
struct section {
Elf_Shdr shdr;
struct section *link;
Elf_Sym *symtab;
Elf32_Word *xsymtab;
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|"
"__kcfi_typeid_|"
"__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_.*|"
#if CONFIG_FW_LOADER
"__(start|end)_builtin_fw|"
#endif
"__(start|stop)___ksymtab(_gpl)?|"
"__(start|stop)___kcrctab(_gpl)?|"
"__(start|stop)___param|"
"__(start|stop)___modver|"
"__(start|stop)___bug_table|"
"__tracedata_(start|end)|"
"__(start|stop)_notes|"
"__end_rodata|"
"__end_rodata_aligned|"
"__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_PC64),
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[shstrndx].strtab;
name = "<noname>";
if (shndx < 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_index(sym));
}
return name;
}
static Elf_Sym *sym_lookup(const char *symname)
{
int i;
for (i = 0; i < 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 int sym_index(Elf_Sym *sym)
{
Elf_Sym *symtab = secs[shsymtabndx].symtab;
Elf32_Word *xsymtab = secs[shxsymtabndx].xsymtab;
unsigned long offset;
int index;
if (sym->st_shndx != SHN_XINDEX)
return sym->st_shndx;
/* calculate offset of sym from head of table. */
offset = (unsigned long)sym - (unsigned long)symtab;
index = offset / sizeof(*sym);
return elf32_to_cpu(xsymtab[index]);
}
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);
shnum = ehdr.e_shnum;
shstrndx = 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 (shnum == SHN_UNDEF || shstrndx == SHN_XINDEX) {
Elf_Shdr shdr;
if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0)
die("Seek to %" FMT " failed: %s\n", ehdr.e_shoff, strerror(errno));
if (fread(&shdr, sizeof(shdr), 1, fp) != 1)
die("Cannot read initial ELF section header: %s\n", strerror(errno));
if (shnum == SHN_UNDEF)
shnum = elf_xword_to_cpu(shdr.sh_size);
if (shstrndx == SHN_XINDEX)
shstrndx = elf_word_to_cpu(shdr.sh_link);
}
if (shstrndx >= shnum)
die("String table index out of bounds\n");
}
static void read_shdrs(FILE *fp)
{
int i;
Elf_Shdr shdr;
secs = calloc(shnum, sizeof(struct section));
if (!secs) {
die("Unable to allocate %ld section headers\n",
shnum);
}
if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0) {
die("Seek to %" FMT " failed: %s\n",
ehdr.e_shoff, strerror(errno));
}
for (i = 0; i < shnum; i++) {
struct section *sec = &secs[i];
if (fread(&shdr, sizeof(shdr), 1, fp) != 1)
die("Cannot read ELF section headers %d/%ld: %s\n",
i, 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 < shnum)
sec->link = &secs[sec->shdr.sh_link];
}
}
static void read_strtabs(FILE *fp)
{
int i;
for (i = 0; i < 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 %" FMT " bytes for strtab failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %" FMT " 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 < shnum; i++) {
struct section *sec = &secs[i];
int num_syms;
switch (sec->shdr.sh_type) {
case SHT_SYMTAB_SHNDX:
sec->xsymtab = malloc(sec->shdr.sh_size);
if (!sec->xsymtab) {
die("malloc of %" FMT " bytes for xsymtab failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %" FMT " failed: %s\n",
sec->shdr.sh_offset, strerror(errno));
}
if (fread(sec->xsymtab, 1, sec->shdr.sh_size, fp)
!= sec->shdr.sh_size) {
die("Cannot read extended symbol table: %s\n",
strerror(errno));
}
shxsymtabndx = i;
continue;
case SHT_SYMTAB:
num_syms = sec->shdr.sh_size / sizeof(Elf_Sym);
sec->symtab = malloc(sec->shdr.sh_size);
if (!sec->symtab) {
die("malloc of %" FMT " bytes for symtab failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %" FMT " 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 < num_syms; 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);
}
shsymtabndx = i;
continue;
default:
continue;
}
}
}
static void read_relocs(FILE *fp)
{
int i,j;
for (i = 0; i < 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 %" FMT " bytes for relocs failed\n",
sec->shdr.sh_size);
}
if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) {
die("Seek to %" FMT " 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 < 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 < 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 < 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 < 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__fixed_percpu_data
* init_per_cpu__gdt_page
*/
static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
{
int shndx = sym_index(sym);
return (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_PC64:
/*
* Only used by jump labels
*/
if (is_percpu_sym(sym, symname))
die("Invalid R_X86_64_PC64 relocation against per-CPU symbol %s\n",
symname);
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:
case R_386_PLT32:
/*
* NONE can be ignored and PC relative relocations don't need
* to be adjusted. Because sym must be defined, R_386_PLT32 can
* be treated the same way as R_386_PC32.
*/
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:
case R_386_PLT32:
/*
* NONE can be ignored and PC relative relocations don't need
* to be adjusted. Because sym must be defined, R_386_PLT32 can
* be treated the same way as R_386_PC32.
*/
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_index(sym)));
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);
}