tccelf.c

Tiny C&C++,看看吧,也许用的着

            p = section_ptr_add(plt, 16);
	    put32(p  , 0xe59fc004);
	    put32(p+4, 0xe08fc00c);
	    put32(p+8, 0xe59cf000);
	    put32(p+12, s1->got->data_offset);

            /* the symbol is modified so that it will be relocated to
               the PLT */
            if (s1->output_type == TCC_OUTPUT_EXE)
                offset = plt->data_offset - 16;
        }
#elif defined(TCC_TARGET_C67)
        error("C67 got not implemented");
#else
#error unsupported CPU
#endif
        index = put_elf_sym(s1->dynsym, offset, 
                            size, info, 0, sym->st_shndx, name);
        /* put a got entry */
        put_elf_reloc(s1->dynsym, s1->got, 
                      s1->got->data_offset, 
                      reloc_type, index);
    }
    ptr = section_ptr_add(s1->got, sizeof(int));
    *ptr = 0;
}

/* build GOT and PLT entries */
static void build_got_entries(TCCState *s1)
{
    Section *s, *symtab;
    Elf32_Rel *rel, *rel_end;
    Elf32_Sym *sym;
    int i, type, reloc_type, sym_index;

    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type != SHT_REL)
            continue;
        /* no need to handle got relocations */
        if (s->link != symtab_section)
            continue;
        symtab = s->link;
        rel_end = (Elf32_Rel *)(s->data + s->data_offset);
        for(rel = (Elf32_Rel *)s->data;
            rel < rel_end;
            rel++) {
            type = ELF32_R_TYPE(rel->r_info);
            switch(type) {
#if defined(TCC_TARGET_I386)
            case R_386_GOT32:
            case R_386_GOTOFF:
            case R_386_GOTPC:
            case R_386_PLT32:
                if (!s1->got)
                    build_got(s1);
                if (type == R_386_GOT32 || type == R_386_PLT32) {
                    sym_index = ELF32_R_SYM(rel->r_info);
                    sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
                    /* look at the symbol got offset. If none, then add one */
                    if (type == R_386_GOT32)
                        reloc_type = R_386_GLOB_DAT;
                    else
                        reloc_type = R_386_JMP_SLOT;
                    put_got_entry(s1, reloc_type, sym->st_size, sym->st_info, 
                                  sym_index);
                }
                break;
#elif defined(TCC_TARGET_ARM)
	    case R_ARM_GOT32:
            case R_ARM_GOTOFF:
            case R_ARM_GOTPC:
            case R_ARM_PLT32:
                if (!s1->got)
                    build_got(s1);
                if (type == R_ARM_GOT32 || type == R_ARM_PLT32) {
                    sym_index = ELF32_R_SYM(rel->r_info);
                    sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
                    /* look at the symbol got offset. If none, then add one */
                    if (type == R_ARM_GOT32)
                        reloc_type = R_ARM_GLOB_DAT;
                    else
                        reloc_type = R_ARM_JUMP_SLOT;
                    put_got_entry(s1, reloc_type, sym->st_size, sym->st_info, 
                                  sym_index);
                }
                break;
#elif defined(TCC_TARGET_C67)
	    case R_C60_GOT32:
            case R_C60_GOTOFF:
            case R_C60_GOTPC:
            case R_C60_PLT32:
                if (!s1->got)
                    build_got(s1);
                if (type == R_C60_GOT32 || type == R_C60_PLT32) {
                    sym_index = ELF32_R_SYM(rel->r_info);
                    sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
                    /* look at the symbol got offset. If none, then add one */
                    if (type == R_C60_GOT32)
                        reloc_type = R_C60_GLOB_DAT;
                    else
                        reloc_type = R_C60_JMP_SLOT;
                    put_got_entry(s1, reloc_type, sym->st_size, sym->st_info, 
                                  sym_index);
                }
                break;
#else
#error unsupported CPU
#endif
            default:
                break;
            }
        }
    }
}

static Section *new_symtab(TCCState *s1,
                           const char *symtab_name, int sh_type, int sh_flags,
                           const char *strtab_name, 
                           const char *hash_name, int hash_sh_flags)
{
    Section *symtab, *strtab, *hash;
    int *ptr, nb_buckets;

    symtab = new_section(s1, symtab_name, sh_type, sh_flags);
    symtab->sh_entsize = sizeof(Elf32_Sym);
    strtab = new_section(s1, strtab_name, SHT_STRTAB, sh_flags);
    put_elf_str(strtab, "");
    symtab->link = strtab;
    put_elf_sym(symtab, 0, 0, 0, 0, 0, NULL);
    
    nb_buckets = 1;

    hash = new_section(s1, hash_name, SHT_HASH, hash_sh_flags);
    hash->sh_entsize = sizeof(int);
    symtab->hash = hash;
    hash->link = symtab;

    ptr = section_ptr_add(hash, (2 + nb_buckets + 1) * sizeof(int));
    ptr[0] = nb_buckets;
    ptr[1] = 1;
    memset(ptr + 2, 0, (nb_buckets + 1) * sizeof(int));
    return symtab;
}

/* put dynamic tag */
static void put_dt(Section *dynamic, int dt, unsigned long val)
{
    Elf32_Dyn *dyn;
    dyn = section_ptr_add(dynamic, sizeof(Elf32_Dyn));
    dyn->d_tag = dt;
    dyn->d_un.d_val = val;
}

static void add_init_array_defines(TCCState *s1, const char *section_name)
{
    Section *s;
    long end_offset;
    char sym_start[1024];
    char sym_end[1024];
    
    snprintf(sym_start, sizeof(sym_start), "__%s_start", section_name + 1);
    snprintf(sym_end, sizeof(sym_end), "__%s_end", section_name + 1);

    s = find_section(s1, section_name);
    if (!s) {
        end_offset = 0;
        s = data_section;
    } else {
        end_offset = s->data_offset;
    }

    add_elf_sym(symtab_section, 
                0, 0,
                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                s->sh_num, sym_start);
    add_elf_sym(symtab_section, 
                end_offset, 0,
                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                s->sh_num, sym_end);
}

/* add tcc runtime libraries */
static void tcc_add_runtime(TCCState *s1)
{
    char buf[1024];

#ifdef CONFIG_TCC_BCHECK
    if (do_bounds_check) {
        unsigned long *ptr;
        Section *init_section;
        unsigned char *pinit;
        int sym_index;

        /* XXX: add an object file to do that */
        ptr = section_ptr_add(bounds_section, sizeof(unsigned long));
        *ptr = 0;
        add_elf_sym(symtab_section, 0, 0, 
                    ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                    bounds_section->sh_num, "__bounds_start");
        /* add bound check code */
        snprintf(buf, sizeof(buf), "%s/%s", tcc_lib_path, "bcheck.o");
        tcc_add_file(s1, buf);
#ifdef TCC_TARGET_I386
        if (s1->output_type != TCC_OUTPUT_MEMORY) {
            /* add 'call __bound_init()' in .init section */
            init_section = find_section(s1, ".init");
            pinit = section_ptr_add(init_section, 5);
            pinit[0] = 0xe8;
            put32(pinit + 1, -4);
            sym_index = find_elf_sym(symtab_section, "__bound_init");
            put_elf_reloc(symtab_section, init_section, 
                          init_section->data_offset - 4, R_386_PC32, sym_index);
        }
#endif
    }
#endif
    /* add libc */
    if (!s1->nostdlib) {
        tcc_add_library(s1, "c");

        snprintf(buf, sizeof(buf), "%s/%s", tcc_lib_path, "libtcc1.a");
        tcc_add_file(s1, buf);
    }
    /* add crt end if not memory output */
    if (s1->output_type != TCC_OUTPUT_MEMORY && !s1->nostdlib) {
        tcc_add_file(s1, CONFIG_TCC_CRT_PREFIX "/crtn.o");
    }
}

/* add various standard linker symbols (must be done after the
   sections are filled (for example after allocating common
   symbols)) */
static void tcc_add_linker_symbols(TCCState *s1)
{
    char buf[1024];
    int i;
    Section *s;

    add_elf_sym(symtab_section, 
                text_section->data_offset, 0,
                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                text_section->sh_num, "_etext");
    add_elf_sym(symtab_section, 
                data_section->data_offset, 0,
                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                data_section->sh_num, "_edata");
    add_elf_sym(symtab_section, 
                bss_section->data_offset, 0,
                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                bss_section->sh_num, "_end");
    /* horrible new standard ldscript defines */
    add_init_array_defines(s1, ".preinit_array");
    add_init_array_defines(s1, ".init_array");
    add_init_array_defines(s1, ".fini_array");
    
    /* add start and stop symbols for sections whose name can be
       expressed in C */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type == SHT_PROGBITS &&
            (s->sh_flags & SHF_ALLOC)) {
            const char *p;
            int ch;

            /* check if section name can be expressed in C */
            p = s->name;
            for(;;) {
                ch = *p;
                if (!ch)
                    break;
                if (!isid(ch) && !isnum(ch))
                    goto next_sec;
                p++;
            }
            snprintf(buf, sizeof(buf), "__start_%s", s->name);
            add_elf_sym(symtab_section, 
                        0, 0,
                        ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                        s->sh_num, buf);
            snprintf(buf, sizeof(buf), "__stop_%s", s->name);
            add_elf_sym(symtab_section,
                        s->data_offset, 0,
                        ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
                        s->sh_num, buf);
        }
    next_sec: ;
    }
}

/* name of ELF interpreter */
#ifdef __FreeBSD__
static char elf_interp[] = "/usr/libexec/ld-elf.so.1";
#else
static char elf_interp[] = "/lib/ld-linux.so.2";
#endif

static void tcc_output_binary(TCCState *s1, FILE *f,
                              const int *section_order)
{
    Section *s;
    int i, offset, size;

    offset = 0;
    for(i=1;i<s1->nb_sections;i++) {
        s = s1->sections[section_order[i]];
        if (s->sh_type != SHT_NOBITS &&
            (s->sh_flags & SHF_ALLOC)) {
            while (offset < s->sh_offset) {
                fputc(0, f);
                offset++;
            }
            size = s->sh_size;
            fwrite(s->data, 1, size, f);
            offset += size;
        }
    }
}

/* output an ELF file */
/* XXX: suppress unneeded sections */
int tcc_output_file(TCCState *s1, const char *filename)
{
    Elf32_Ehdr ehdr;
    FILE *f;
    int fd, mode, ret;
    int *section_order;
    int shnum, i, phnum, file_offset, offset, size, j, tmp, sh_order_index, k;
    unsigned long addr;
    Section *strsec, *s;
    Elf32_Shdr shdr, *sh;
    Elf32_Phdr *phdr, *ph;
    Section *interp, *dynamic, *dynstr;
    unsigned long saved_dynamic_data_offset;
    Elf32_Sym *sym;
    int type, file_type;
    unsigned long rel_addr, rel_size;
    
    file_type = s1->output_type;
    s1->nb_errors = 0;

    if (file_type != TCC_OUTPUT_OBJ) {
        tcc_add_runtime(s1);
    }

    phdr = NULL;
    section_order = NULL;
    interp = NULL;
    dynamic = NULL;
    dynstr = NULL; /* avoid warning */
    saved_dynamic_data_offset = 0; /* avoid warning */
    
    if (file_type != TCC_OUTPUT_OBJ) {
        relocate_common_syms();

        tcc_add_linker_symbols(s1);

        if (!s1->static_link) {
            const char *name;
            int sym_index, index;
            Elf32_Sym *esym, *sym_end;
            
            if (file_type == TCC_OUTPUT_EXE) {
                char *ptr;
                /* add interpreter section only if executable */
                interp = new_section(s1, ".interp", SHT_PROGBITS, SHF_ALLOC);
                interp->sh_addralign = 1;
                ptr = section_ptr_add(interp, sizeof(elf_interp));
                strcpy(ptr, elf_interp);
            }
        
            /* add dynamic symbol table */
            s1->dynsym = new_symtab(s1, ".dynsym", SHT_DYNSYM, SHF_ALLOC,
                                    ".dynstr", 
                                    ".hash", SHF_ALLOC);
            dynstr = s1->dynsym->link;
            
            /* add dynamic section */
            dynamic = new_section(s1, ".dynamic", SHT_DYNAMIC, 
                                  SHF_ALLOC | SHF_WRITE);
            dynamic->link = dynstr;
            dynamic->sh_entsize = sizeof(Elf32_Dyn);
        
            /* add PLT */
            s1->plt = new_section(s1, ".plt", SHT_PROGBITS, 
                                  SHF_ALLOC | SHF_EXECINSTR);
            s1->plt->sh_entsize = 4;