UBUNTU: Ubuntu-5.15.0-39.42

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / tools / relocs.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;
static unsigned long    shnum;
static unsigned int     shstrndx;

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;
        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)?|"
        "__(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->st_shndx);
        }
        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 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];
                if (sec->shdr.sh_type != SHT_SYMTAB) {
                        continue;
                }
                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 < 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 < 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)
{
        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_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->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);
}