Archipelago » qemu

#include <stdlib.h>

#include <stdio.h>

#include <stdarg.h>

#include <inttypes.h>

#include <elf.h>

#include <unistd.h>

#include <fcntl.h>

#include "thunk.h"

/* all dynamically generated functions begin with this code */

#define OP_PREFIX "op"

int elf_must_swap(Elf32_Ehdr *h)

{

  union {

      uint32_t i;

      uint8_t b[4];

  } swaptest;

  swaptest.i = 1;

  return (h->e_ident[EI_DATA] == ELFDATA2MSB) != 

      (swaptest.b[0] == 0);

}

void swab16s(uint16_t *p)

{

    *p = bswap16(*p);

}

void swab32s(uint32_t *p)

{

    *p = bswap32(*p);

}

void swab64s(uint32_t *p)

{

    *p = bswap64(*p);

}

void elf_swap_ehdr(Elf32_Ehdr *h)

{

    swab16s(&h->e_type);                        /* Object file type */

    swab16s(&h->        e_machine);                /* Architecture */

    swab32s(&h->        e_version);                /* Object file version */

    swab32s(&h->        e_entry);                /* Entry point virtual address */

    swab32s(&h->        e_phoff);                /* Program header table file offset */

    swab32s(&h->        e_shoff);                /* Section header table file offset */

    swab32s(&h->        e_flags);                /* Processor-specific flags */

    swab16s(&h->        e_ehsize);                /* ELF header size in bytes */

    swab16s(&h->        e_phentsize);                /* Program header table entry size */

    swab16s(&h->        e_phnum);                /* Program header table entry count */

    swab16s(&h->        e_shentsize);                /* Section header table entry size */

    swab16s(&h->        e_shnum);                /* Section header table entry count */

    swab16s(&h->        e_shstrndx);                /* Section header string table index */

}

void elf_swap_shdr(Elf32_Shdr *h)

{

  swab32s(&h->        sh_name);                /* Section name (string tbl index) */

  swab32s(&h->        sh_type);                /* Section type */

  swab32s(&h->        sh_flags);                /* Section flags */

  swab32s(&h->        sh_addr);                /* Section virtual addr at execution */

  swab32s(&h->        sh_offset);                /* Section file offset */

  swab32s(&h->        sh_size);                /* Section size in bytes */

  swab32s(&h->        sh_link);                /* Link to another section */

  swab32s(&h->        sh_info);                /* Additional section information */

  swab32s(&h->        sh_addralign);                /* Section alignment */

  swab32s(&h->        sh_entsize);                /* Entry size if section holds table */

}

void elf_swap_phdr(Elf32_Phdr *h)

{

    swab32s(&h->p_type);                        /* Segment type */

    swab32s(&h->p_offset);                /* Segment file offset */

    swab32s(&h->p_vaddr);                /* Segment virtual address */

    swab32s(&h->p_paddr);                /* Segment physical address */

    swab32s(&h->p_filesz);                /* Segment size in file */

    swab32s(&h->p_memsz);                /* Segment size in memory */

    swab32s(&h->p_flags);                /* Segment flags */

    swab32s(&h->p_align);                /* Segment alignment */

}

int do_swap;

int e_machine;

uint16_t get16(uint16_t *p)

{

    uint16_t val;

    val = *p;

    if (do_swap)

        val = bswap16(val);

    return val;

}

uint32_t get32(uint32_t *p)

{

    uint32_t val;

    val = *p;

    if (do_swap)

        val = bswap32(val);

    return val;

}

void put16(uint16_t *p, uint16_t val)

{

    if (do_swap)

        val = bswap16(val);

    *p = val;

}

void put32(uint32_t *p, uint32_t val)

{

    if (do_swap)

        val = bswap32(val);

    *p = val;

}

void __attribute__((noreturn)) error(const char *fmt, ...)

{

    va_list ap;

    va_start(ap, fmt);

    fprintf(stderr, "dyngen: ");

    vfprintf(stderr, fmt, ap);

    fprintf(stderr, "\n");

    va_end(ap);

    exit(1);

}

Elf32_Shdr *find_elf_section(Elf32_Shdr *shdr, int shnum, const char *shstr, 

                             const char *name)

{

    int i;

    const char *shname;

    Elf32_Shdr *sec;

    for(i = 0; i < shnum; i++) {

        sec = &shdr[i];

        if (!sec->sh_name)

            continue;

        shname = shstr + sec->sh_name;

        if (!strcmp(shname, name))

            return sec;

    }

    return NULL;

}

void *load_data(int fd, long offset, unsigned int size)

{

    char *data;

    data = malloc(size);

    if (!data)

        return NULL;

    lseek(fd, offset, SEEK_SET);

    if (read(fd, data, size) != size) {

        free(data);

        return NULL;

    }

    return data;

}

int strstart(const char *str, const char *val, const char **ptr)

{

    const char *p, *q;

    p = str;

    q = val;

    while (*q != '\0') {

        if (*p != *q)

            return 0;

        p++;

        q++;

    }

    if (ptr)

        *ptr = p;

    return 1;

}

#define MAX_ARGS 3

/* generate op code */

void gen_code(const char *name, unsigned long offset, unsigned long size, 

              FILE *outfile, uint8_t *text, void *relocs, int nb_relocs, int reloc_sh_type,

              Elf32_Sym *symtab, char *strtab)

{

    int copy_size = 0;

    uint8_t *p_start, *p_end;

    int nb_args, i;

    uint8_t args_present[MAX_ARGS];

    const char *sym_name, *p;

    /* compute exact size excluding return instruction */

    p_start = text + offset;

    p_end = p_start + size;

    switch(e_machine) {

    case EM_386:

        {

            uint8_t *p;

            p = p_end - 1;

            /* find ret */

            while (p > p_start && *p != 0xc3)

                p--;

            /* skip double ret */

            if (p > p_start && p[-1] == 0xc3)

                p--;

            if (p == p_start)

                error("empty code for %s", name);

            copy_size = p - p_start;

        }

        break;

    case EM_PPC:

        {

            uint8_t *p;

            p = (void *)(p_end - 4);

            /* find ret */

            while (p > p_start && get32((uint32_t *)p) != 0x4e800020)

                p -= 4;

            /* skip double ret */

            if (p > p_start && get32((uint32_t *)(p - 4)) == 0x4e800020)

                p -= 4;

            if (p == p_start)

                error("empty code for %s", name);

            copy_size = p - p_start;

        }

        break;

    default:

        error("unsupported CPU (%d)", e_machine);

    }

    /* compute the number of arguments by looking at the relocations */

    for(i = 0;i < MAX_ARGS; i++)

        args_present[i] = 0;

    if (reloc_sh_type == SHT_REL) {

        Elf32_Rel *rel;

        int n;

        for(i = 0, rel = relocs;i < nb_relocs; i++, rel++) {

            if (rel->r_offset >= offset && rel->r_offset < offset + copy_size) {

                sym_name = strtab + symtab[ELF32_R_SYM(rel->r_info)].st_name;

                if (strstart(sym_name, "__op_param", &p)) {

                    n = strtoul(p, NULL, 10);

                    if (n >= MAX_ARGS)

                        error("too many arguments in %s", name);

                    args_present[n - 1] = 1;

                }

            }

        }

    } else {

        Elf32_Rela *rel;

        int n;

        for(i = 0, rel = relocs;i < nb_relocs; i++, rel++) {

            if (rel->r_offset >= offset && rel->r_offset < offset + copy_size) {

                sym_name = strtab + symtab[ELF32_R_SYM(rel->r_info)].st_name;

                if (strstart(sym_name, "__op_param", &p)) {

                    n = strtoul(p, NULL, 10);

                    if (n >= MAX_ARGS)

                        error("too many arguments in %s", name);

                    args_present[n - 1] = 1;

                }

            }

        }

    }

    nb_args = 0;

    while (nb_args < MAX_ARGS && args_present[nb_args])

        nb_args++;

    for(i = nb_args; i < MAX_ARGS; i++) {

        if (args_present[i])

            error("inconsistent argument numbering in %s", name);

    }

    /* output C code */

    fprintf(outfile, "extern void %s();\n", name);

    fprintf(outfile, "static inline void gen_%s(", name);

    if (nb_args == 0) {

        fprintf(outfile, "void");

    } else {

        for(i = 0; i < nb_args; i++) {

            if (i != 0)

                fprintf(outfile, ", ");

            fprintf(outfile, "long param%d", i + 1);

        }

    }

    fprintf(outfile, ")\n");

    fprintf(outfile, "{\n");

    fprintf(outfile, "    memcpy(gen_code_ptr, &%s, %d);\n", name, copy_size);

    /* patch relocations */

    switch(e_machine) {

    case EM_386:

        {

            Elf32_Rel *rel;

            char name[256];

            int type;

            long addend;

            for(i = 0, rel = relocs;i < nb_relocs; i++, rel++) {

                if (rel->r_offset >= offset && rel->r_offset < offset + copy_size) {

                    sym_name = strtab + symtab[ELF32_R_SYM(rel->r_info)].st_name;

                    if (strstart(sym_name, "__op_param", &p)) {

                        snprintf(name, sizeof(name), "param%s", p);

                    } else {

                        snprintf(name, sizeof(name), "(long)(&%s)", sym_name);

                    }

                    type = ELF32_R_TYPE(rel->r_info);

                    addend = get32((uint32_t *)(text + rel->r_offset));

                    switch(type) {

                    case R_386_32:

                        fprintf(outfile, "    *(uint32_t *)(gen_code_ptr + %ld) = %s + %ld;\n", 

                                rel->r_offset - offset, name, addend);

                        break;

                    case R_386_PC32:

                        fprintf(outfile, "    *(uint32_t *)(gen_code_ptr + %ld) = %s - (long)(gen_code_ptr + %ld) + %ld;\n", 

                                rel->r_offset - offset, name, rel->r_offset - offset, addend);

                        break;

                    default:

                        error("unsupported i386 relocation (%d)", type);

                    }

                }

            }

        }

        break;

    default:

        error("unsupported CPU for relocations (%d)", e_machine);

    }

    fprintf(outfile, "    gen_code_ptr += %d;\n", copy_size);

    fprintf(outfile, "}\n\n");

}

/* load an elf object file */

int load_elf(const char *filename, FILE *outfile)

{

    int fd;

    Elf32_Ehdr ehdr;

    Elf32_Shdr *sec, *shdr, *symtab_sec, *strtab_sec, *text_sec;

    int i, j, nb_syms;

    Elf32_Sym *symtab, *sym;

    const char *cpu_name;

    char *shstr, *strtab;

    uint8_t *text;

    void *relocs;

    int nb_relocs, reloc_sh_type;

    fd = open(filename, O_RDONLY);

    if (fd < 0) 

        error("can't open file '%s'", filename);

    /* Read ELF header.  */

    if (read(fd, &ehdr, sizeof (ehdr)) != sizeof (ehdr))

        error("unable to read file header");

    /* Check ELF identification.  */

    if (ehdr.e_ident[EI_MAG0] != ELFMAG0

     || ehdr.e_ident[EI_MAG1] != ELFMAG1

     || ehdr.e_ident[EI_MAG2] != ELFMAG2

     || ehdr.e_ident[EI_MAG3] != ELFMAG3

     || ehdr.e_ident[EI_CLASS] != ELFCLASS32

     || ehdr.e_ident[EI_VERSION] != EV_CURRENT) {

        error("bad ELF header");

    }

    do_swap = elf_must_swap(&ehdr);

    if (do_swap)

        elf_swap_ehdr(&ehdr);

    if (ehdr.e_type != ET_REL)

        error("ELF object file expected");

    if (ehdr.e_version != EV_CURRENT)

        error("Invalid ELF version");

    e_machine = ehdr.e_machine;

    /* read section headers */

    shdr = load_data(fd, ehdr.e_shoff, ehdr.e_shnum * sizeof(Elf32_Shdr));

    if (do_swap) {

        for(i = 0; i < ehdr.e_shnum; i++) {

            elf_swap_shdr(&shdr[i]);

        }

    }

    sec = &shdr[ehdr.e_shstrndx];

    shstr = load_data(fd, sec->sh_offset, sec->sh_size);

    /* text section */

    text_sec = find_elf_section(shdr, ehdr.e_shnum, shstr, ".text");

    if (!text_sec)

        error("could not find .text section");

    text = load_data(fd, text_sec->sh_offset, text_sec->sh_size);

    /* find text relocations, if any */

    nb_relocs = 0;

    relocs = NULL;

    reloc_sh_type = 0;

    for(i = 0; i < ehdr.e_shnum; i++) {

        sec = &shdr[i];

        if ((sec->sh_type == SHT_REL || sec->sh_type == SHT_RELA) &&

            sec->sh_info == (text_sec - shdr)) {

            reloc_sh_type = sec->sh_type;

            relocs = load_data(fd, sec->sh_offset, sec->sh_size);

            nb_relocs = sec->sh_size / sec->sh_entsize;

            if (do_swap) {

                if (sec->sh_type == SHT_REL) {

                    Elf32_Rel *rel = relocs;

                    for(j = 0, rel = relocs; j < nb_relocs; j++, rel++) {

                        swab32s(&rel->r_offset);

                        swab32s(&rel->r_info);

                    }

                } else {

                    Elf32_Rela *rel = relocs;

                    for(j = 0, rel = relocs; j < nb_relocs; j++, rel++) {

                        swab32s(&rel->r_offset);

                        swab32s(&rel->r_info);

                        swab32s(&rel->r_addend);

                    }

                }

            }

            break;

        }

    }

    symtab_sec = find_elf_section(shdr, ehdr.e_shnum, shstr, ".symtab");

    if (!symtab_sec)

        error("could not find .symtab section");

    strtab_sec = &shdr[symtab_sec->sh_link];

    symtab = load_data(fd, symtab_sec->sh_offset, symtab_sec->sh_size);

    strtab = load_data(fd, strtab_sec->sh_offset, strtab_sec->sh_size);

    nb_syms = symtab_sec->sh_size / sizeof(Elf32_Sym);

    if (do_swap) {

        for(i = 0, sym = symtab; i < nb_syms; i++, sym++) {

            swab32s(&sym->st_name);

            swab32s(&sym->st_value);

            swab32s(&sym->st_size);

            swab16s(&sym->st_shndx);

        }

    }

    switch(e_machine) {

    case EM_386:

        cpu_name = "i386";

        break;

    case EM_PPC:

        cpu_name = "ppc";

        break;

    case EM_MIPS:

        cpu_name = "mips";

        break;

    case EM_ARM:

        cpu_name = "arm";

        break;

    case EM_SPARC:

        cpu_name = "sparc";

        break;

    default:

        error("unsupported CPU (e_machine=%d)", e_machine);

    }

    fprintf(outfile, "#include \"gen-%s.h\"\n\n", cpu_name);

    for(i = 0, sym = symtab; i < nb_syms; i++, sym++) {

        const char *name;

        name = strtab + sym->st_name;

        if (strstart(name, "op_", NULL) ||

            strstart(name, "op1_", NULL) ||

            strstart(name, "op2_", NULL) ||

            strstart(name, "op3_", NULL)) {

#if 0

            printf("%4d: %s pos=0x%08x len=%d\n", 

                   i, name, sym->st_value, sym->st_size);

#endif

            if (sym->st_shndx != (text_sec - shdr))

                error("invalid section for opcode (0x%x)", sym->st_shndx);

            gen_code(name, sym->st_value, sym->st_size, outfile, 

                     text, relocs, nb_relocs, reloc_sh_type, symtab, strtab);

        }

    }

    close(fd);

    return 0;

}

void usage(void)

{

    printf("dyngen (c) 2003 Fabrice Bellard\n"

           "usage: dyngen [-o outfile] objfile\n"

           "Generate a dynamic code generator from an object file\n");

    exit(1);

}

int main(int argc, char **argv)

{

    int c;

    const char *filename, *outfilename;

    FILE *outfile;

    outfilename = "out.c";

    for(;;) {

        c = getopt(argc, argv, "ho:");

        if (c == -1)

            break;

        switch(c) {

        case 'h':

            usage();

            break;

        case 'o':

            outfilename = optarg;

            break;

        }

    }

    if (optind >= argc)

        usage();

    filename = argv[optind];

    outfile = fopen(outfilename, "w");

    if (!outfile)

        error("could not open '%s'", outfilename);

    load_elf(filename, outfile);

    fclose(outfile);

    return 0;

}