snix/src/resolve-system-dependencies/resolve-system-dependencies.cc

#include "derivations.hh"
#include "globals.hh"
#include "shared.hh"
#include "store-api.hh"
#include <sys/utsname.h>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <mach-o/loader.h>
#include <mach-o/swap.h>

using namespace nix;

static auto cacheDir = Path{};

Path resolveCacheFile(Path lib) {
    std::replace(lib.begin(), lib.end(), '/', '%');
    return cacheDir + "/" + lib;
}

std::set<string> readCacheFile(const Path & file) {
    return tokenizeString<set<string>>(readFile(file), "\n");
}

void writeCacheFile(const Path & file, std::set<string> & deps) {
    std::ofstream fp;
    fp.open(file);
    for (auto & d : deps) {
        fp << d << "\n";
    }
    fp.close();
}

std::string findDylibName(FILE *obj_file, struct load_command cmd) {
    fpos_t pos;
    fgetpos(obj_file, &pos);
    struct dylib_command dylc;
    dylc.cmd = cmd.cmd;
    dylc.cmdsize = cmd.cmdsize;
    fread(&dylc.dylib, sizeof(struct dylib), 1, obj_file);

    char *dylib_name = (char*)calloc(cmd.cmdsize, sizeof(char));
    fseek(obj_file,
            // offset is calculated from the beginning of the load command, which is two
            // uint32_t's backwards
            dylc.dylib.name.offset - (sizeof(uint32_t) * 2) + pos,
            SEEK_SET);
    fread(dylib_name, sizeof(char), cmd.cmdsize, obj_file);
    fseek(obj_file, pos, SEEK_SET);
    return std::string(dylib_name);
}

bool seekMach64Blob(FILE *obj_file, enum NXByteOrder end) {
    struct fat_header head;
    fread(&head, sizeof(struct fat_header), 1, obj_file);
    swap_fat_header(&head, end);
    for(uint32_t narches = 0; narches < head.nfat_arch; narches++) {
        struct fat_arch arch;
        fread(&arch, sizeof(struct fat_arch), 1, obj_file);
        swap_fat_arch(&arch, 1, end);
        if(arch.cputype == CPU_TYPE_X86_64) {
            fseek(obj_file, arch.offset, SEEK_SET);
            return true;
        }
    }
    return false;
}

std::set<std::string> runResolver(const Path & filename) {
    FILE *obj_file = fopen(filename.c_str(), "rb");
    uint32_t magic;
    fread(&magic, sizeof(uint32_t), 1, obj_file);
    fseek(obj_file, 0, SEEK_SET);
    enum NXByteOrder endianness;
    if(magic == 0xBEBAFECA) {
        endianness = NX_BigEndian;
        if(!seekMach64Blob(obj_file, endianness)) {
            std::cerr << "Could not find any mach64 blobs in file " << filename << ", continuing..." << std::endl;
            return std::set<string>();
        }
    }
    struct mach_header_64 header;
    fread(&header, sizeof(struct mach_header_64), 1, obj_file);
    if(!(header.magic == MH_MAGIC_64 || header.magic == MH_CIGAM_64)) {
        std::cerr << "Not a mach-o object file: " << filename << std::endl;
        return std::set<string>();
    }
    std::set<string> libs;
    for(uint32_t i = 0; i < header.ncmds; i++) {
        struct load_command cmd;
        fread(&cmd.cmd, sizeof(cmd.cmd), 1, obj_file);
        fread(&cmd.cmdsize, sizeof(cmd.cmdsize), 1, obj_file);
        switch(cmd.cmd) {
            case LC_LOAD_DYLIB:
            case LC_LOAD_UPWARD_DYLIB:
            case LC_REEXPORT_DYLIB:
                libs.insert(findDylibName(obj_file, cmd));
                break;
        }
        fseek(obj_file, cmd.cmdsize - (sizeof(uint32_t) * 2), SEEK_CUR);
    }
    fclose(obj_file);
    libs.erase(filename);
    return libs;
}

bool isSymlink(const Path & path) {
    struct stat st;
    if(lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path ‘%1%’") % path);

    return S_ISLNK(st.st_mode);
}

Path resolveSymlink(const Path & path) {
    char buf[PATH_MAX];
    ssize_t len = readlink(path.c_str(), buf, sizeof(buf) - 1);
    if(len != -1) {
        buf[len] = 0;
        return Path(buf);
    } else {
        throw SysError(format("readlink('%1%')") % path);
    }
}

std::set<string> resolveTree(const Path & path, PathSet & deps) {
    std::set<string> results;
    if(deps.find(path) != deps.end()) {
        return std::set<string>();
    }
    deps.insert(path);
    for (auto & lib : runResolver(path)) {
        results.insert(lib);
        for (auto & p : resolveTree(lib, deps)) {
            results.insert(p);
        }
    }
    return results;
}

std::set<string> getPath(const Path & path) {
    Path cacheFile = resolveCacheFile(path);
    if(pathExists(cacheFile)) {
        return readCacheFile(cacheFile);
    }

    std::set<string> deps;
    std::set<string> paths;
    paths.insert(path);

    Path next_path = Path(path);
    while(isSymlink(next_path)) {
        next_path = resolveSymlink(next_path);
        paths.insert(next_path);
    }

    for(auto & t : resolveTree(next_path, deps)) {
        paths.insert(t);
    }

    writeCacheFile(cacheFile, paths);

    return paths;
}

int main(int argc, char ** argv) {
    return handleExceptions(argv[0], [&]() {
            initNix();

            struct utsname _uname;

            uname(&_uname);

            cacheDir = (format("%1%/dependency-maps/%2%-%3%-%4%")
                    % settings.nixStateDir
                    % _uname.machine
                    % _uname.sysname
                    % _uname.release).str();

            auto store = openStore();

            auto drv = store->derivationFromPath(Path(argv[1]));
            Strings impurePaths = tokenizeString<Strings>(get(drv.env, "__impureHostDeps"));

            std::set<string> all_paths;

            for (auto & path : impurePaths) {
                for(auto & p : getPath(path)) {
                    all_paths.insert(p);
                }
            }

            std::cout << "extra-chroot-dirs" << std::endl;
            for(auto & path : all_paths) {
                std::cout << path << std::endl;
            }
            std::cout << std::endl;
    });
}