#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>

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;

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

/*
 * 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.
 */
static const char abs_sym_regex[] =
        "^(xen_irq_disable_direct_reloc$|"
        "xen_save_fl_direct_reloc$|"
        "VDSO|"
        "__crc_)";
static regex_t abs_sym_regex_c;
static int is_abs_reloc(const char *sym_name)
{
        return !regexec(&abs_sym_regex_c, sym_name, 0, NULL, 0);
}

/*
 * These symbols are known to be relative, even if the linker marks them
 * as absolute (typically defined outside any section in the linker script.)
 */
static const char rel_sym_regex[] =
        "^_end$";
static regex_t rel_sym_regex_c;
static int is_rel_reloc(const char *sym_name)
{
        return !regexec(&rel_sym_regex_c, sym_name, 0, NULL, 0);
}

static void regex_init(void)
{
        char errbuf[128];
        int err;
        
        err = regcomp(&abs_sym_regex_c, abs_sym_regex,
                      REG_EXTENDED|REG_NOSUB);
        if (err) {
                regerror(err, &abs_sym_regex_c, errbuf, sizeof errbuf);
                die("%s", errbuf);
        }

        err = regcomp(&rel_sym_regex_c, rel_sym_regex,
                      REG_EXTENDED|REG_NOSUB);
        if (err) {
                regerror(err, &rel_sym_regex_c, 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),
#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(secs[sym->st_shndx].shdr.sh_name);
        }
        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;
                Elf32_Sym *sh_symtab;
                int j;

                if (sec->shdr.sh_type != SHT_SYMTAB) {
                        continue;
                }
                sh_symtab = sec->symtab;
                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_abs_reloc(name) || is_rel_reloc(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 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;
                        rel = &sec->reltab[j];
                        sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
                        r_type = ELF32_R_TYPE(rel->r_info);
                        /* Don't visit relocations to absolute symbols */
                        if (sym->st_shndx == SHN_ABS &&
                            !is_rel_reloc(sym_name(sym_strtab, sym))) {
                                continue;
                        }
                        switch (r_type) {
                        case R_386_NONE:
                        case R_386_PC32:
                                /*
                                 * NONE can be ignored and and PC relative
                                 * relocations don't need to be adjusted.
                                 */
                                break;
                        case R_386_32:
                                /* Visit relocations that need to be adjusted */
                                visit(rel, sym);
                                break;
                        default:
                                die("Unsupported relocation type: %s (%d)\n",
                                    rel_type(r_type), r_type);
                                break;
                        }
                }
        }
}

static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
{
        reloc_count += 1;
}

static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
{
        /* Remember the address that needs to be adjusted. */
        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 void emit_relocs(int as_text)
{
        int i;
        /* Count how many relocations I have and allocate space for them. */
        reloc_count = 0;
        walk_relocs(count_reloc);
        relocs = malloc(reloc_count * sizeof(relocs[0]));
        if (!relocs) {
                die("malloc of %d entries for relocs failed\n",
                        reloc_count);
        }
        /* Collect up the relocations */
        reloc_idx = 0;
        walk_relocs(collect_reloc);

        /* Order the relocations for more efficient processing */
        qsort(relocs, reloc_count, sizeof(relocs[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");
                for (i = 0; i < reloc_count; i++) {
                        printf("\t .long 0x%08lx\n", relocs[i]);
                }
                printf("\n");
        }
        else {
                unsigned char buf[4];
                /* Print a stop */
                fwrite("\0\0\0\0", 4, 1, stdout);
                /* Now print each relocation */
                for (i = 0; i < reloc_count; i++) {
                        buf[0] = (relocs[i] >>  0) & 0xff;
                        buf[1] = (relocs[i] >>  8) & 0xff;
                        buf[2] = (relocs[i] >> 16) & 0xff;
                        buf[3] = (relocs[i] >> 24) & 0xff;
                        fwrite(buf, 4, 1, stdout);
                }
        }
}

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

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

        regex_init();

        show_absolute_syms = 0;
        show_absolute_relocs = 0;
        as_text = 0;
        fname = NULL;
        for (i = 1; i < argc; i++) {
                char *arg = argv[i];
                if (*arg == '-') {
                        if (strcmp(argv[1], "--abs-syms") == 0) {
                                show_absolute_syms = 1;
                                continue;
                        }

                        if (strcmp(argv[1], "--abs-relocs") == 0) {
                                show_absolute_relocs = 1;
                                continue;
                        }
                        else if (strcmp(argv[1], "--text") == 0) {
                                as_text = 1;
                                continue;
                        }
                }
                else if (!fname) {
                        fname = arg;
                        continue;
                }
                usage();
        }
        if (!fname) {
                usage();
        }
        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);
        return 0;
}