plcrash_error_t plcrash_async_macho_symtab_reader_init()

in Source/PLCrashAsyncMachOImage.c [629:720]

• 65 lines of code
• 10 McCabe index (conditional complexity)

plcrash_error_t plcrash_async_macho_symtab_reader_init (plcrash_async_macho_symtab_reader_t *reader, plcrash_async_macho_t *image) {
    plcrash_error_t retval;

    /* Fetch the symtab commands, if available. */
    struct symtab_command *symtab_cmd = plcrash_async_macho_find_command(image, LC_SYMTAB);
    struct dysymtab_command *dysymtab_cmd = plcrash_async_macho_find_command(image, LC_DYSYMTAB);

    /* The symtab command is required */
    if (symtab_cmd == NULL) {
        PLCF_DEBUG("could not find LC_SYMTAB load command");
        return PLCRASH_ENOTFOUND;
    }
    
    /* Map in the __LINKEDIT segment, which includes the symbol and string tables */
    plcrash_error_t err = plcrash_async_macho_map_segment(image, "__LINKEDIT", &reader->linkedit);
    if (err != PLCRASH_ESUCCESS) {
        PLCF_DEBUG("plcrash_async_mobject_init() failure: %d in %s", err, PLCF_DEBUG_IMAGE_NAME(image));
        return PLCRASH_EINTERNAL;
    }
    
    /* Determine the string and symbol table sizes. */
    uint32_t nsyms = image->byteorder->swap32(symtab_cmd->nsyms);
    size_t nlist_struct_size = image->m64 ? sizeof(struct nlist_64) : sizeof(struct nlist);
    size_t nlist_table_size = nsyms * nlist_struct_size;
    
    size_t string_size = image->byteorder->swap32(symtab_cmd->strsize);
    
    /* Fetch pointers to the symbol and string tables, and verify their size values */
    void *nlist_table;
    char *string_table;
    
    nlist_table = plcrash_async_mobject_remap_address(&reader->linkedit.mobj, reader->linkedit.mobj.task_address, (pl_vm_off_t)(image->byteorder->swap32(symtab_cmd->symoff) - reader->linkedit.fileoff), nlist_table_size);
    if (nlist_table == NULL) {
        PLCF_DEBUG("plcrash_async_mobject_remap_address(mobj, %" PRIx64 ", %" PRIx64") returned NULL mapping __LINKEDIT.symoff in %s",
                   (uint64_t) reader->linkedit.mobj.address + image->byteorder->swap32(symtab_cmd->symoff), (uint64_t) nlist_table_size, PLCF_DEBUG_IMAGE_NAME(image));
        retval = PLCRASH_EINTERNAL;
        goto cleanup;
    }
    
    string_table = plcrash_async_mobject_remap_address(&reader->linkedit.mobj, reader->linkedit.mobj.task_address, (pl_vm_off_t)(image->byteorder->swap32(symtab_cmd->stroff) - reader->linkedit.fileoff), string_size);
    if (string_table == NULL) {
        PLCF_DEBUG("plcrash_async_mobject_remap_address(mobj, %" PRIx64 ", %" PRIx64") returned NULL mapping __LINKEDIT.stroff in %s",
                   (uint64_t) reader->linkedit.mobj.address + image->byteorder->swap32(symtab_cmd->stroff), (uint64_t) string_size, PLCF_DEBUG_IMAGE_NAME(image));
        retval = PLCRASH_EINTERNAL;
        goto cleanup;
    }

    /* Initialize common elements. */
    reader->image = image;
    reader->string_table = string_table;
    reader->string_table_size = string_size;
    reader->symtab = nlist_table;
    reader->nsyms = nsyms;

    /* Initialize the local/global table pointers, if available */
    if (dysymtab_cmd != NULL) {
        /* dysymtab is available; use it to constrain our symbol search to the global and local sections of the symbol table. */
        
        uint32_t idx_syms_global = image->byteorder->swap32(dysymtab_cmd->iextdefsym);
        uint32_t idx_syms_local = image->byteorder->swap32(dysymtab_cmd->ilocalsym);
        
        uint32_t nsyms_global = image->byteorder->swap32(dysymtab_cmd->nextdefsym);
        uint32_t nsyms_local = image->byteorder->swap32(dysymtab_cmd->nlocalsym);
        
        /* Sanity check the symbol offsets to ensure they're within our known-valid ranges */
        if (idx_syms_global + nsyms_global > nsyms || idx_syms_local + nsyms_local > nsyms) {
            PLCF_DEBUG("iextdefsym=%" PRIx32 ", ilocalsym=%" PRIx32 " out of range nsym=%" PRIx32, idx_syms_global+nsyms_global, idx_syms_local+nsyms_local, nsyms);
            retval = PLCRASH_EINVAL;
            goto cleanup;
        }

        /* Initialize reader state */
        reader->nsyms_global = nsyms_global;
        reader->nsyms_local = nsyms_local;

        if (image->m64) {
            struct nlist_64 *n64 = nlist_table;
            reader->symtab_global = (pl_nlist_common *) (n64 + idx_syms_global);
            reader->symtab_local = (pl_nlist_common *) (n64 + idx_syms_local);
        } else {
            struct nlist *n32 = nlist_table;
            reader->symtab_global = (pl_nlist_common *) (n32 + idx_syms_global);
            reader->symtab_local = (pl_nlist_common *) (n32 + idx_syms_local);
        }        
    }

    return PLCRASH_ESUCCESS;
    
cleanup:
    plcrash_async_macho_mapped_segment_free(&reader->linkedit);
    return retval;
}