relocs.c

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#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <elf.h>
#include <byteswap.h>
#define USE_BSD
#include <endian.h>
#include <regex.h>
#include <tools/le_byteshift.h>

static void die(char *fmt, ...);

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
static Elf32_Ehdr ehdr;
static unsigned long reloc_count, reloc_idx;
static unsigned long *relocs;
static unsigned long reloc16_count, reloc16_idx;
static unsigned long *relocs16;

struct section {
    Elf32_Shdr     shdr;
    struct section *link;
    Elf32_Sym      *symtab;
    Elf32_Rel      *reltab;
    char           *strtab;
};
static struct section *secs;

enum symtype {
    S_ABS,
    S_REL,
    S_SEG,
    S_LIN,
    S_NSYMTYPES
};

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)|"
    "_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 void die(char *fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    exit(1);
}

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
        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),
#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, Elf32_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;
}



#if BYTE_ORDER == LITTLE_ENDIAN
#define le16_to_cpu(val) (val)
#define le32_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)
#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);
}

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] != ELFCLASS32) {
        die("Not a 32 bit executable\n");
    }
    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      = elf16_to_cpu(ehdr.e_type);
    ehdr.e_machine   = elf16_to_cpu(ehdr.e_machine);
    ehdr.e_version   = elf32_to_cpu(ehdr.e_version);
    ehdr.e_entry     = elf32_to_cpu(ehdr.e_entry);
    ehdr.e_phoff     = elf32_to_cpu(ehdr.e_phoff);
    ehdr.e_shoff     = elf32_to_cpu(ehdr.e_shoff);
    ehdr.e_flags     = elf32_to_cpu(ehdr.e_flags);
    ehdr.e_ehsize    = elf16_to_cpu(ehdr.e_ehsize);
    ehdr.e_phentsize = elf16_to_cpu(ehdr.e_phentsize);
    ehdr.e_phnum     = elf16_to_cpu(ehdr.e_phnum);
    ehdr.e_shentsize = elf16_to_cpu(ehdr.e_shentsize);
    ehdr.e_shnum     = elf16_to_cpu(ehdr.e_shnum);
    ehdr.e_shstrndx  = elf16_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 != EM_386) {
        die("Not for x86\n");
    }
    if (ehdr.e_version != EV_CURRENT) {
        die("Unknown ELF version\n");
    }
    if (ehdr.e_ehsize != sizeof(Elf32_Ehdr)) {
        die("Bad Elf header size\n");
    }
    if (ehdr.e_phentsize != sizeof(Elf32_Phdr)) {
        die("Bad program header entry\n");
    }
    if (ehdr.e_shentsize != sizeof(Elf32_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;
    Elf32_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      = elf32_to_cpu(shdr.sh_name);
        sec->shdr.sh_type      = elf32_to_cpu(shdr.sh_type);
        sec->shdr.sh_flags     = elf32_to_cpu(shdr.sh_flags);
        sec->shdr.sh_addr      = elf32_to_cpu(shdr.sh_addr);
        sec->shdr.sh_offset    = elf32_to_cpu(shdr.sh_offset);
        sec->shdr.sh_size      = elf32_to_cpu(shdr.sh_size);
        sec->shdr.sh_link      = elf32_to_cpu(shdr.sh_link);
        sec->shdr.sh_info      = elf32_to_cpu(shdr.sh_info);
        sec->shdr.sh_addralign = elf32_to_cpu(shdr.sh_addralign);
        sec->shdr.sh_entsize   = elf32_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(Elf32_Sym); j++) {
            Elf32_Sym *sym = &sec->symtab[j];
            sym->st_name  = elf32_to_cpu(sym->st_name);
            sym->st_value = elf32_to_cpu(sym->st_value);
            sym->st_size  = elf32_to_cpu(sym->st_size);
            sym->st_shndx = elf16_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) {
            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(Elf32_Rel); j++) {
            Elf32_Rel *rel = &sec->reltab[j];
            rel->r_offset = elf32_to_cpu(rel->r_offset);
            rel->r_info   = elf32_to_cpu(rel->r_info);
        }
    }
}


static void print_absolute_symbols(void)
{
    int i;
    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(Elf32_Sym); j++) {
            Elf32_Sym *sym;
            const char *name;
            sym = &sec->symtab[j];
            name = sym_name(sym_strtab, sym);
            if (sym->st_shndx != SHN_ABS) {
                continue;
            }
            printf("%5d %08x %5d %10s %10s %12s %s\n",
                j, sym->st_value, sym->st_size,
                sym_type(ELF32_ST_TYPE(sym->st_info)),
                sym_bind(ELF32_ST_BIND(sym->st_info)),
                sym_visibility(ELF32_ST_VISIBILITY(sym->st_other)),
                name);
        }
    }
    printf("\n");
}

static void print_absolute_relocs(void)
{
    int i, printed = 0;

    for (i = 0; i < ehdr.e_shnum; i++) {
        struct section *sec = &secs[i];
        struct section *sec_applies, *sec_symtab;
        char *sym_strtab;
        Elf32_Sym *sh_symtab;
        int j;
        if (sec->shdr.sh_type != SHT_REL) {
            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(Elf32_Rel); j++) {
            Elf32_Rel *rel;
            Elf32_Sym *sym;
            const char *name;
            rel = &sec->reltab[j];
            sym = &sh_symtab[ELF32_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("%08x %08x %10s %08x  %s\n",
                rel->r_offset,
                rel->r_info,
                rel_type(ELF32_R_TYPE(rel->r_info)),
                sym->st_value,
                name);
        }
    }

    if (printed)
        printf("\n");
}

static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym),
            int use_real_mode)
{
    int i;
    /* Walk through the relocations */
    for (i = 0; i < ehdr.e_shnum; i++) {
        char *sym_strtab;
        Elf32_Sym *sh_symtab;
        struct section *sec_applies, *sec_symtab;
        int j;
        struct section *sec = &secs[i];

        if (sec->shdr.sh_type != SHT_REL) {
            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(Elf32_Rel); j++) {
            Elf32_Rel *rel;
            Elf32_Sym *sym;
            unsigned r_type;
            const char *symname;
            int shn_abs;

            rel = &sec->reltab[j];
            sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
            r_type = ELF32_R_TYPE(rel->r_info);

            shn_abs = sym->st_shndx == SHN_ABS;

            switch (r_type) {
            case R_386_NONE:
            case R_386_PC32:
            case R_386_PC16:
            case R_386_PC8:
                /*
                 * NONE can be ignored and and PC relative
                 * relocations don't need to be adjusted.
                 */
                break;

            case R_386_16:
                symname = sym_name(sym_strtab, sym);
                if (!use_real_mode)
                    goto bad;
                if (shn_abs) {
                    if (is_reloc(S_ABS, symname))
                        break;
                    else if (!is_reloc(S_SEG, symname))
                        goto bad;
                } else {
                    if (is_reloc(S_LIN, symname))
                        goto bad;
                    else
                        break;
                }
                visit(rel, sym);
                break;

            case R_386_32:
                symname = sym_name(sym_strtab, sym);
                if (shn_abs) {
                    if (is_reloc(S_ABS, symname))
                        break;
                    else if (!is_reloc(S_REL, symname))
                        goto bad;
                } else {
                    if (use_real_mode &&
                        !is_reloc(S_LIN, symname))
                        break;
                }
                visit(rel, sym);
                break;
            default:
                die("Unsupported relocation type: %s (%d)\n",
                    rel_type(r_type), r_type);
                break;
            bad:
                symname = sym_name(sym_strtab, sym);
                die("Invalid %s %s relocation: %s\n",
                    shn_abs ? "absolute" : "relative",
                    rel_type(r_type), symname);
            }
        }
    }
}

static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
{
    if (ELF32_R_TYPE(rel->r_info) == R_386_16)
        reloc16_count++;
    else
        reloc_count++;
}

static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
{
    /* Remember the address that needs to be adjusted. */
    if (ELF32_R_TYPE(rel->r_info) == R_386_16)
        relocs16[reloc16_idx++] = rel->r_offset;
    else
        relocs[reloc_idx++] = rel->r_offset;
}

static int cmp_relocs(const void *va, const void *vb)
{
    const unsigned long *a, *b;
    a = va; b = vb;
    return (*a == *b)? 0 : (*a > *b)? 1 : -1;
}

static int write32(unsigned int v, FILE *f)
{
    unsigned char buf[4];

    put_unaligned_le32(v, buf);
    return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;
}

static void emit_relocs(int as_text, int use_real_mode)
{
    int i;
    /* Count how many relocations I have and allocate space for them. */
    reloc_count = 0;
    walk_relocs(count_reloc, use_real_mode);
    relocs = malloc(reloc_count * sizeof(relocs[0]));
    if (!relocs) {
        die("malloc of %d entries for relocs failed\n",
            reloc_count);
    }

    relocs16 = malloc(reloc16_count * sizeof(relocs[0]));
    if (!relocs16) {
        die("malloc of %d entries for relocs16 failed\n",
            reloc16_count);
    }
    /* Collect up the relocations */
    reloc_idx = 0;
    walk_relocs(collect_reloc, use_real_mode);

    if (reloc16_count && !use_real_mode)
        die("Segment relocations found but --realmode not specified\n");

    /* Order the relocations for more efficient processing */
    qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
    qsort(relocs16, reloc16_count, sizeof(relocs16[0]), cmp_relocs);

    /* 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");
        if (use_real_mode) {
            printf("\t.long %lu\n", reloc16_count);
            for (i = 0; i < reloc16_count; i++)
                printf("\t.long 0x%08lx\n", relocs16[i]);
            printf("\t.long %lu\n", reloc_count);
            for (i = 0; i < reloc_count; i++) {
                printf("\t.long 0x%08lx\n", relocs[i]);
            }
        } else {
            /* Print a stop */
            printf("\t.long 0x%08lx\n", (unsigned long)0);
            for (i = 0; i < reloc_count; i++) {
                printf("\t.long 0x%08lx\n", relocs[i]);
            }
        }

        printf("\n");
    }
    else {
        if (use_real_mode) {
            write32(reloc16_count, stdout);
            for (i = 0; i < reloc16_count; i++)
                write32(relocs16[i], stdout);
            write32(reloc_count, stdout);

            /* Now print each relocation */
            for (i = 0; i < reloc_count; i++)
                write32(relocs[i], stdout);
        } else {
            /* Print a stop */
            write32(0, stdout);

            /* Now print each relocation */
            for (i = 0; i < reloc_count; i++) {
                write32(relocs[i], stdout);
            }
        }
    }
}

static void usage(void)
{
    die("relocs [--abs-syms|--abs-relocs|--text|--realmode] vmlinux\n");
}

int main(int argc, char **argv)
{
    int show_absolute_syms, show_absolute_relocs;
    int as_text, use_real_mode;
    const char *fname;
    FILE *fp;
    int i;

    show_absolute_syms = 0;
    show_absolute_relocs = 0;
    as_text = 0;
    use_real_mode = 0;
    fname = NULL;
    for (i = 1; i < argc; i++) {
        char *arg = argv[i];
        if (*arg == '-') {
            if (strcmp(arg, "--abs-syms") == 0) {
                show_absolute_syms = 1;
                continue;
            }
            if (strcmp(arg, "--abs-relocs") == 0) {
                show_absolute_relocs = 1;
                continue;
            }
            if (strcmp(arg, "--text") == 0) {
                as_text = 1;
                continue;
            }
            if (strcmp(arg, "--realmode") == 0) {
                use_real_mode = 1;
                continue;
            }
        }
        else if (!fname) {
            fname = arg;
            continue;
        }
        usage();
    }
    if (!fname) {
        usage();
    }
    regex_init(use_real_mode);
    fp = fopen(fname, "r");
    if (!fp) {
        die("Cannot open %s: %s\n",
            fname, strerror(errno));
    }
    read_ehdr(fp);
    read_shdrs(fp);
    read_strtabs(fp);
    read_symtabs(fp);
    read_relocs(fp);
    if (show_absolute_syms) {
        print_absolute_symbols();
        return 0;
    }
    if (show_absolute_relocs) {
        print_absolute_relocs();
        return 0;
    }
    emit_relocs(as_text, use_real_mode);
    return 0;
}