zircon/system/core/devmgr/fshost/pkgfs-launcher.cpp

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <fbl/unique_fd.h>
#include <fs-management/mount.h>
#include <lib/fdio/directory.h>
#include <lib/fdio/fd.h>
#include <lib/fdio/fdio.h>
#include <lib/zx/channel.h>
#include <lib/zx/process.h>
#include <loader-service/loader-service.h>
#include <zircon/processargs.h>
#include <zircon/status.h>
#include <zircon/syscalls.h>

#include <utility>

#include "pkgfs-launcher.h"

namespace devmgr {
namespace {

void pkgfs_finish(FilesystemMounter* filesystems, zx::process proc, zx::channel pkgfs_root) {
    auto deadline = zx::deadline_after(zx::sec(5));
    zx_signals_t observed;
    zx_status_t status =
        proc.wait_one(ZX_USER_SIGNAL_0 | ZX_PROCESS_TERMINATED, deadline, &observed);
    if (status != ZX_OK) {
        printf("fshost: pkgfs did not signal completion: %d (%s)\n", status,
               zx_status_get_string(status));
        return;
    }
    if (!(observed & ZX_USER_SIGNAL_0)) {
        printf("fshost: pkgfs terminated prematurely\n");
        return;
    }
    // re-export /pkgfs/system as /system
    zx::channel system_channel, system_req;
    if (zx::channel::create(0, &system_channel, &system_req) != ZX_OK) {
        return;
    }
    if (fdio_open_at(pkgfs_root.get(), "system", FS_READONLY_DIR_FLAGS,
                     system_req.release()) != ZX_OK) {
        return;
    }
    // re-export /pkgfs/packages/shell-commands/0/bin as /bin
    zx::channel bin_chan, bin_req;
    if (zx::channel::create(0, &bin_chan, &bin_req) != ZX_OK) {
        return;
    }
    if (fdio_open_at(pkgfs_root.get(), "packages/shell-commands/0/bin", FS_READONLY_DIR_FLAGS,
                     bin_req.release()) != ZX_OK) {
        // non-fatal.
        printf("fshost: failed to install /bin (could not open shell-commands)\n");
    }
    if (filesystems->InstallFs("/pkgfs", std::move(pkgfs_root)) != ZX_OK) {
        printf("fshost: failed to install /pkgfs\n");
        return;
    }
    if (filesystems->InstallFs("/system", std::move(system_channel)) != ZX_OK) {
        printf("fshost: failed to install /system\n");
        return;
    }
    // as above, failure of /bin export is non-fatal.
    if (filesystems->InstallFs("/bin", std::move(bin_chan)) != ZX_OK) {
        printf("fshost: failed to install /bin\n");
    }
    // start the appmgr
    filesystems->FuchsiaStart();
}

// Launching pkgfs uses its own loader service and command lookup to run out of
// the blobfs without any real filesystem.  Files are found by
// getenv("zircon.system.pkgfs.file.PATH") returning a blob content ID.
// That is, a manifest of name->blob is embedded in /boot/config/devmgr.
zx_status_t pkgfs_ldsvc_load_blob(void* ctx, const char* prefix, const char* name,
                                  zx_handle_t* vmo) {
    const int fs_blob_fd = static_cast<int>(reinterpret_cast<intptr_t>(ctx));
    char key[256];
    if (snprintf(key, sizeof(key), "zircon.system.pkgfs.file.%s%s", prefix, name) >=
        (int)sizeof(key)) {
        return ZX_ERR_BAD_PATH;
    }
    const char* blob = getenv(key);
    if (blob == nullptr) {
        return ZX_ERR_NOT_FOUND;
    }
    int fd = openat(fs_blob_fd, blob, O_RDONLY);
    if (fd < 0) {
        return ZX_ERR_NOT_FOUND;
    }

    zx::vmo nonexec_vmo;
    zx::vmo exec_vmo;
    zx_status_t status = fdio_get_vmo_clone(fd, nonexec_vmo.reset_and_get_address());
    close(fd);
    if (status != ZX_OK) {
        return status;
    }
    status = nonexec_vmo.replace_as_executable(zx::handle(), &exec_vmo);
    if (status != ZX_OK) {
        return status;
    }
    status = zx_object_set_property(exec_vmo.get(), ZX_PROP_NAME, key, strlen(key));
    if (status != ZX_OK) {
        return status;
    }

    *vmo = exec_vmo.release();
    return ZX_OK;
}

zx_status_t pkgfs_ldsvc_load_object(void* ctx, const char* name, zx_handle_t* vmo) {
    return pkgfs_ldsvc_load_blob(ctx, "lib/", name, vmo);
}

zx_status_t pkgfs_ldsvc_load_abspath(void* ctx, const char* name, zx_handle_t* vmo) {
    return pkgfs_ldsvc_load_blob(ctx, "", name + 1, vmo);
}

zx_status_t pkgfs_ldsvc_publish_data_sink(void* ctx, const char* name, zx_handle_t vmo) {
    zx_handle_close(vmo);
    return ZX_ERR_NOT_SUPPORTED;
}

void pkgfs_ldsvc_finalizer(void* ctx) {
    close(static_cast<int>(reinterpret_cast<intptr_t>(ctx)));
}

const loader_service_ops_t pkgfs_ldsvc_ops = {
    .load_object = pkgfs_ldsvc_load_object,
    .load_abspath = pkgfs_ldsvc_load_abspath,
    .publish_data_sink = pkgfs_ldsvc_publish_data_sink,
    .finalizer = pkgfs_ldsvc_finalizer,
};

// Create a local loader service with a fixed mapping of names to blobs.
zx_status_t pkgfs_ldsvc_start(fbl::unique_fd fs_blob_fd, zx::channel* ldsvc) {
    loader_service_t* service;
    zx_status_t status =
        loader_service_create(nullptr, &pkgfs_ldsvc_ops,
                              reinterpret_cast<void*>(static_cast<intptr_t>(fs_blob_fd.get())),
                              &service);
    if (status != ZX_OK) {
        printf("fshost: cannot create pkgfs loader service: %d (%s)\n", status,
               zx_status_get_string(status));
        return status;
    }
    // The loader service now owns this FD
    __UNUSED auto fd = fs_blob_fd.release();

    status = loader_service_connect(service, ldsvc->reset_and_get_address());
    loader_service_release(service);
    if (status != ZX_OK) {
        printf("fshost: cannot connect pkgfs loader service: %d (%s)\n", status,
               zx_status_get_string(status));
    }
    return status;
}

bool pkgfs_launch(FilesystemMounter* filesystems) {
    const char* cmd = getenv("zircon.system.pkgfs.cmd");
    if (cmd == nullptr) {
        return false;
    }

    fbl::unique_fd fs_blob_fd(open("/fs/blob", O_RDONLY | O_DIRECTORY));
    if (!fs_blob_fd) {
        printf("fshost: open(/fs/blob): %m\n");
        return false;
    }

    zx::channel h0, h1;
    zx_status_t status = zx::channel::create(0, &h0, &h1);
    if (status != ZX_OK) {
        printf("fshost: cannot create pkgfs root channel: %d (%s)\n", status,
               zx_status_get_string(status));
        return false;
    }

    auto args = ArgumentVector::FromCmdline(cmd);
    auto argv = args.argv();
    // Remove leading slashes before asking pkgfs_ldsvc_load_blob to load the
    // file.
    const char* file = argv[0];
    while (file[0] == '/') {
        ++file;
    }
    zx::vmo executable;
    status = pkgfs_ldsvc_load_blob(reinterpret_cast<void*>(static_cast<intptr_t>(fs_blob_fd.get())),
                                   "", argv[0], executable.reset_and_get_address());
    if (status != ZX_OK) {
        printf("fshost: cannot load pkgfs executable: %d (%s)\n", status,
               zx_status_get_string(status));
        return false;
    }

    zx::channel loader;
    status = pkgfs_ldsvc_start(std::move(fs_blob_fd), &loader);
    if (status != ZX_OK) {
        printf("fshost: cannot pkgfs loader: %d (%s)\n", status, zx_status_get_string(status));
        return false;
    }

    const zx_handle_t raw_h1 = h1.release();
    zx::process proc;
    args.Print("fshost");
    status = devmgr_launch_with_loader(*zx::job::default_job(), "pkgfs",
                                       std::move(executable), std::move(loader),
                                       argv, nullptr, -1, &raw_h1,
                                       (const uint32_t[]){PA_HND(PA_USER0, 0)}, 1, &proc,
                                       FS_DATA | FS_BLOB | FS_SVC);
    if (status != ZX_OK) {
        printf("fshost: failed to launch %s: %d (%s)\n", cmd, status, zx_status_get_string(status));
        return false;
    }

    pkgfs_finish(filesystems, std::move(proc), std::move(h0));
    return true;
}

} // namespace

void LaunchBlobInit(FilesystemMounter* filesystems) {
    pkgfs_launch(filesystems);
}

} // namespace devmgr