tccelf.c

Tiny C&C++,看看吧,也许用的着

            build_got(s1);

            /* scan for undefined symbols and see if they are in the
               dynamic symbols. If a symbol STT_FUNC is found, then we
               add it in the PLT. If a symbol STT_OBJECT is found, we
               add it in the .bss section with a suitable relocation */
            sym_end = (Elf32_Sym *)(symtab_section->data + 
                                    symtab_section->data_offset);
            if (file_type == TCC_OUTPUT_EXE) {
                for(sym = (Elf32_Sym *)symtab_section->data + 1; 
                    sym < sym_end;
                    sym++) {
                    if (sym->st_shndx == SHN_UNDEF) {
                        name = symtab_section->link->data + sym->st_name;
                        sym_index = find_elf_sym(s1->dynsymtab_section, name);
                        if (sym_index) {
                            esym = &((Elf32_Sym *)s1->dynsymtab_section->data)[sym_index];
                            type = ELF32_ST_TYPE(esym->st_info);
                            if (type == STT_FUNC) {
                                put_got_entry(s1, R_JMP_SLOT, esym->st_size, 
                                              esym->st_info, 
                                              sym - (Elf32_Sym *)symtab_section->data);
                            } else if (type == STT_OBJECT) {
                                unsigned long offset;
                                offset = bss_section->data_offset;
                                /* XXX: which alignment ? */
                                offset = (offset + 16 - 1) & -16;
                                index = put_elf_sym(s1->dynsym, offset, esym->st_size, 
                                                    esym->st_info, 0, 
                                                    bss_section->sh_num, name);
                                put_elf_reloc(s1->dynsym, bss_section, 
                                              offset, R_COPY, index);
                                offset += esym->st_size;
                                bss_section->data_offset = offset;
                            }
                        } else {
                                /* STB_WEAK undefined symbols are accepted */
                                /* XXX: _fp_hw seems to be part of the ABI, so we ignore
                                   it */
                            if (ELF32_ST_BIND(sym->st_info) == STB_WEAK ||
                                !strcmp(name, "_fp_hw")) {
                            } else {
                                error_noabort("undefined symbol '%s'", name);
                            }
                        }
                    } else if (s1->rdynamic && 
                               ELF32_ST_BIND(sym->st_info) != STB_LOCAL) {
                        /* if -rdynamic option, then export all non
                           local symbols */
                        name = symtab_section->link->data + sym->st_name;
                        put_elf_sym(s1->dynsym, sym->st_value, sym->st_size, 
                                    sym->st_info, 0, 
                                    sym->st_shndx, name);
                    }
                }
            
                if (s1->nb_errors)
                    goto fail;

                /* now look at unresolved dynamic symbols and export
                   corresponding symbol */
                sym_end = (Elf32_Sym *)(s1->dynsymtab_section->data + 
                                        s1->dynsymtab_section->data_offset);
                for(esym = (Elf32_Sym *)s1->dynsymtab_section->data + 1; 
                    esym < sym_end;
                    esym++) {
                    if (esym->st_shndx == SHN_UNDEF) {
                        name = s1->dynsymtab_section->link->data + esym->st_name;
                        sym_index = find_elf_sym(symtab_section, name);
                        if (sym_index) {
                            /* XXX: avoid adding a symbol if already
                               present because of -rdynamic ? */
                            sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
                            put_elf_sym(s1->dynsym, sym->st_value, sym->st_size, 
                                        sym->st_info, 0, 
                                        sym->st_shndx, name);
                        } else {
                            if (ELF32_ST_BIND(esym->st_info) == STB_WEAK) {
                                /* weak symbols can stay undefined */
                            } else {
                                warning("undefined dynamic symbol '%s'", name);
                            }
                        }
                    }
                }
            } else {
                int nb_syms;
                /* shared library case : we simply export all the global symbols */
                nb_syms = symtab_section->data_offset / sizeof(Elf32_Sym);
                s1->symtab_to_dynsym = tcc_mallocz(sizeof(int) * nb_syms);
                for(sym = (Elf32_Sym *)symtab_section->data + 1; 
                    sym < sym_end;
                    sym++) {
                    if (ELF32_ST_BIND(sym->st_info) != STB_LOCAL) {
                        name = symtab_section->link->data + sym->st_name;
                        index = put_elf_sym(s1->dynsym, sym->st_value, sym->st_size, 
                                            sym->st_info, 0, 
                                            sym->st_shndx, name);
                        s1->symtab_to_dynsym[sym - 
                                            (Elf32_Sym *)symtab_section->data] = 
                            index;
                    }
                }
            }

            build_got_entries(s1);
        
            /* add a list of needed dlls */
            for(i = 0; i < s1->nb_loaded_dlls; i++) {
                DLLReference *dllref = s1->loaded_dlls[i];
                if (dllref->level == 0)
                    put_dt(dynamic, DT_NEEDED, put_elf_str(dynstr, dllref->name));
            }
            /* XXX: currently, since we do not handle PIC code, we
               must relocate the readonly segments */
            if (file_type == TCC_OUTPUT_DLL)
                put_dt(dynamic, DT_TEXTREL, 0);

            /* add necessary space for other entries */
            saved_dynamic_data_offset = dynamic->data_offset;
            dynamic->data_offset += 8 * 9;
        } else {
            /* still need to build got entries in case of static link */
            build_got_entries(s1);
        }
    }

    memset(&ehdr, 0, sizeof(ehdr));

    /* we add a section for symbols */
    strsec = new_section(s1, ".shstrtab", SHT_STRTAB, 0);
    put_elf_str(strsec, "");
    
    /* compute number of sections */
    shnum = s1->nb_sections;

    /* this array is used to reorder sections in the output file */
    section_order = tcc_malloc(sizeof(int) * shnum);
    section_order[0] = 0;
    sh_order_index = 1;
    
    /* compute number of program headers */
    switch(file_type) {
    default:
    case TCC_OUTPUT_OBJ:
        phnum = 0;
        break;
    case TCC_OUTPUT_EXE:
        if (!s1->static_link)
            phnum = 4;
        else
            phnum = 2;
        break;
    case TCC_OUTPUT_DLL:
        phnum = 3;
        break;
    }

    /* allocate strings for section names and decide if an unallocated
       section should be output */
    /* NOTE: the strsec section comes last, so its size is also
       correct ! */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        s->sh_name = put_elf_str(strsec, s->name);
        /* when generating a DLL, we include relocations but we may
           patch them */
        if (file_type == TCC_OUTPUT_DLL && 
            s->sh_type == SHT_REL && 
            !(s->sh_flags & SHF_ALLOC)) {
            prepare_dynamic_rel(s1, s);
        } else if (do_debug || 
            file_type == TCC_OUTPUT_OBJ || 
            (s->sh_flags & SHF_ALLOC) ||
            i == (s1->nb_sections - 1)) {
            /* we output all sections if debug or object file */
            s->sh_size = s->data_offset;
        }
    }

    /* allocate program segment headers */
    phdr = tcc_mallocz(phnum * sizeof(Elf32_Phdr));
        
    if (s1->output_format == TCC_OUTPUT_FORMAT_ELF) {
        file_offset = sizeof(Elf32_Ehdr) + phnum * sizeof(Elf32_Phdr);
    } else {
        file_offset = 0;
    }
    if (phnum > 0) {
        /* compute section to program header mapping */
        if (s1->has_text_addr) { 
            int a_offset, p_offset;
            addr = s1->text_addr;
            /* we ensure that (addr % ELF_PAGE_SIZE) == file_offset %
               ELF_PAGE_SIZE */
            a_offset = addr & (ELF_PAGE_SIZE - 1);
            p_offset = file_offset & (ELF_PAGE_SIZE - 1);
            if (a_offset < p_offset) 
                a_offset += ELF_PAGE_SIZE;
            file_offset += (a_offset - p_offset);
        } else {
            if (file_type == TCC_OUTPUT_DLL)
                addr = 0;
            else
                addr = ELF_START_ADDR;
            /* compute address after headers */
            addr += (file_offset & (ELF_PAGE_SIZE - 1));
        }
        
        /* dynamic relocation table information, for .dynamic section */
        rel_size = 0;
        rel_addr = 0;

        /* leave one program header for the program interpreter */
        ph = &phdr[0];
        if (interp)
            ph++;

        for(j = 0; j < 2; j++) {
            ph->p_type = PT_LOAD;
            if (j == 0)
                ph->p_flags = PF_R | PF_X;
            else
                ph->p_flags = PF_R | PF_W;
            ph->p_align = ELF_PAGE_SIZE;
            
            /* we do the following ordering: interp, symbol tables,
               relocations, progbits, nobits */
            /* XXX: do faster and simpler sorting */
            for(k = 0; k < 5; k++) {
                for(i = 1; i < s1->nb_sections; i++) {
                    s = s1->sections[i];
                    /* compute if section should be included */
                    if (j == 0) {
                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) != 
                            SHF_ALLOC)
                            continue;
                    } else {
                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) != 
                            (SHF_ALLOC | SHF_WRITE))
                            continue;
                    }
                    if (s == interp) {
                        if (k != 0)
                            continue;
                    } else if (s->sh_type == SHT_DYNSYM ||
                               s->sh_type == SHT_STRTAB ||
                               s->sh_type == SHT_HASH) {
                        if (k != 1)
                            continue;
                    } else if (s->sh_type == SHT_REL) {
                        if (k != 2)
                            continue;
                    } else if (s->sh_type == SHT_NOBITS) {
                        if (k != 4)
                            continue;
                    } else {
                        if (k != 3)
                            continue;
                    }
                    section_order[sh_order_index++] = i;

                    /* section matches: we align it and add its size */
                    tmp = addr;
                    addr = (addr + s->sh_addralign - 1) & 
                        ~(s->sh_addralign - 1);
                    file_offset += addr - tmp;
                    s->sh_offset = file_offset;
                    s->sh_addr = addr;
                    
                    /* update program header infos */
                    if (ph->p_offset == 0) {
                        ph->p_offset = file_offset;
                        ph->p_vaddr = addr;
                        ph->p_paddr = ph->p_vaddr;
                    }
                    /* update dynamic relocation infos */
                    if (s->sh_type == SHT_REL) {
                        if (rel_size == 0)
                            rel_addr = addr;
                        rel_size += s->sh_size;
                    }
                    addr += s->sh_size;
                    if (s->sh_type != SHT_NOBITS)
                        file_offset += s->sh_size;
                }
            }
            ph->p_filesz = file_offset - ph->p_offset;
            ph->p_memsz = addr - ph->p_vaddr;
            ph++;
            if (j == 0) {
                if (s1->output_format == TCC_OUTPUT_FORMAT_ELF) {
                    /* if in the middle of a page, we duplicate the page in
                       memory so that one copy is RX and the other is RW */
                    if ((addr & (ELF_PAGE_SIZE - 1)) != 0)
                        addr += ELF_PAGE_SIZE;
                } else {
                    addr = (addr + ELF_PAGE_SIZE - 1) & ~(ELF_PAGE_SIZE - 1);
                    file_offset = (file_offset + ELF_PAGE_SIZE - 1) & 
                        ~(ELF_PAGE_SIZE - 1);
                }
            }
        }

        /* if interpreter, then add corresponing program header */
        if (interp) {
            ph = &phdr[0];
            
            ph->p_type = PT_INTERP;
            ph->p_offset = interp->sh_offset;
            ph->p_vaddr = interp->sh_addr;
            ph->p_paddr = ph->p_vaddr;
            ph->p_filesz = interp->sh_size;
            ph->p_memsz = interp->sh_size;
            ph->p_flags = PF_R;
            ph->p_align = interp->sh_addralign;
        }
        
        /* if dynamic section, then add corresponing program header */
        if (dynamic) {
            Elf32_Sym *sym_end;

            ph = &phdr[phnum - 1];
            
            ph->p_type = PT_DYNAMIC;
            ph->p_offset = dynamic->sh_offset;
            ph->p_vaddr = dynamic->sh_addr;
            ph->p_paddr = ph->p_vaddr;
            ph->p_filesz = dynamic->sh_size;
            ph->p_memsz = dynamic->sh_size;
            ph->p_flags = PF_R | PF_W;
            ph->p_align = dynamic->sh_addralign;

            /* put GOT dynamic section address */
            put32(s1->got->data, dynamic->sh_addr);

            /* relocate the PLT */
            if (file_type == TCC_OUTPUT_EXE) {
                uint8_t *p, *p_end;

                p = s1->plt->data;
                p_end = p + s1->plt->data_offset;
                if (p < p_end) {
#if defined(TCC_TARGET_I386)
                    put32(p + 2, get32(p + 2) + s1->got->sh_addr);
                    put32(p + 8, get32(p + 8) + s1->got->sh_addr);
                    p += 16;
                    while (p < p_end) {
                        put32(p + 2, get32(p + 2) + s1->got->sh_addr);
                        p += 16;
                    }
#elif defined(TCC_TARGET_ARM)
		    int x;
		    x=s1->got->sh_addr - s1->plt->sh_addr - 12;
		    p +=16;
		    while (p < p_end) {
		        put32(p + 12, x + get32(p + 12) + s1->plt->data - p);
			p += 16;
		    }
#elif defined(TCC_TARGET_C67)
                    /* XXX: TODO */
#else
#error unsupported CPU
#endif
                }
            }

            /* relocate symbols in .dynsym */
            sym_end = (Elf32_Sym *)(s1->dynsym->data + s1->dynsym->data_offset);
            for(sym = (Elf32_Sym *)s1->dynsym->data + 1; 
                sym < sym_end;
                sym++) {
                if (sym->st_shndx == SHN_UNDEF) {
                    /* relocate to the PLT if the symbol corresponds
                       to a PLT entry */
                    if (sym->st_value)
                        sym->st_value += s1->plt->sh_addr;
                } else if (sym->st_shndx < SHN_LORESERVE) {
                    /* do symbol relocation */
                    sym->st_value += s1->sections[sym->st_shndx]->sh_addr;
                }
            }

            /* put dynamic section entries */
            dynamic->data_offset = saved_dynamic_data_offset;
            put_dt(dynamic, DT_HASH, s1->dynsym->hash->sh_addr);
            put_dt(dynamic, DT_STRTAB, dynstr->sh_addr);
            put_dt(dynamic, DT_SYMTAB, s1->dynsym->sh_addr);