path: root/Replicant_contributors_meeting_27_28_July_2019_Paris_France/modems/Replicant_and_modems_Samsung-ipc.tex

\documentclass{beamer}
\usepackage[english]{babel}
\usepackage{color}
\usepackage{graphicx}
\usepackage{ifthen}
\usepackage[utf8]{inputenc}
\usepackage{listings}
\usepackage{pdfpages}

\lstdefinestyle{terminal}{
  backgroundcolor=\color{black},
  basicstyle=\scriptsize\color{green},
}

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\newcommand{\pictureframe}[1] {
  {
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                {\includegraphics{#1}}
                \hspace*{-\textwidth}
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  }
}

\usetheme{Singapore}

\title{Samsung-ipc compatible modems in Replicant}
\author{Denis 'GNUtoo' Carikli}
\date{\today}

\begin{document}

\maketitle

%% TODO: Using \itemize{} fails to compile
%% TODO: convert \center frames to chapter title

\begin{frame}
  \center{Samsung IPC}
\end{frame}

\begin{frame}
  \center{Samsung IPC: Hardware part}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$RAM$\rightarrow$SOC }
  \begin{itemize}
  \item Galaxy S           (I9100)
  \item Nexus S            (I902x)
  \item Galaxy Tab   (unsupported)
  \end{itemize}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$RAM$\rightarrow$SOC: Isolation }
  \begin{itemize}
    \item Nexus S: The modem kernel driver shows that part of a RAM chip is shared between the modem and the SOC
    \item No hardware guarantees that the modem cannot take control of the SOC
    \item IOMMU:
      \begin{itemize}
      \item Requires a mainline kernel to trust the code
      \item And the SOC documentation on that...
      \item And people having analyzed its security...
      \item And to be setup before the RAM is even initialized...
      \item But the bootloader is not free software...
      \end{itemize}
  \end{itemize}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$MIPI$\rightarrow$SOC }
  \begin{itemize}
  \item Galaxy Nexus       (I9250)
  \item Galaxy Tab II 7.0  (P3100)
  \item Galaxy Tab II 10.1 (P5100)
  \end{itemize}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$MIPI$\rightarrow$SOC: Isolation }
  \begin{itemize}
    \item Not analyzed in depth but probably ok
    \item Same interface than camera and screens
  \end{itemize}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$HSIC$\rightarrow$SOC }
  \begin{itemize}
  \item Galaxy S2          (I9100)
  \item Galaxy SIII        (I9300)
  \item Galaxy Note        (N7000)
  \item Galaxy Note II     (N7100)
  \item Galaxy Note 8.0    (N5100)
  \end{itemize}
\end{frame}

\begin{frame}
  \center{XMM626 $\leftarrow$HSIC$\rightarrow$SOC: Isolation }
  \begin{itemize}
  \item No DMA to the SOC RAM
  \item USB-like bus: USB without the PHY
  \item The host need to reset the bus to get the devices re-enumerated
  \item $\rightarrow$ More complicated for the modem to become a keyboard
  \item Ideally (not looked into yet):
  \begin{itemize}
  \item usbguard
  \item USB peripherals whitelist
  \item $\rightarrow$ re-usable for USB modems (GTA04, PinePhone, Librem5, etc).
  \end{itemize}
  \end{itemize}
\end{frame}

\begin{frame}
  \center{Samsung IPC}
  \begin{itemize}
  \item We will look more specifically at the case with the XMM626 connected through HSIC.
  \item Other transports are similar: transports are abstracted by the kernel driver and libsamsung-ipc transport drivers.
  \end{itemize}
\end{frame}

\pictureframe{output/xmm626_hsic.png}

\begin{frame}
  \center{The samsung-ipc protocol}
  \begin{itemize}
  \item Asyncronous
  \item $\rightarrow$ You get asyncronous responses from the modem
  \item $\rightarrow$ You match with the request (sequence numbers)
  \item $\rightarrow$ libsamsung-ril needs receive asyncronous responses too
  \item $\rightarrow$ More complex design with callbacks
  \end{itemize}
\end{frame}

\begin{frame}
  \center{libsamsung-ril}
\end{frame}

\begin{frame}
  \center{The initialization not very different from the reference-ril}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  RIL_RadioFunctions ril_radio_functions = {
    RIL_VERSION,
    ril_on_request,
    ril_on_state_request,
    ril_supports,
    ril_on_cancel,
    ril_get_version
  };
  ...

  const RIL_RadioFunctions *RIL_Init(
            const struct RIL_Env *env, int argc,
            char **argv) {
        ...
        return radio_functions;
  }
\end{lstlisting}

\begin{frame}
  \center{The interface with rild is not that different either}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  void ril_on_request(int request, void *data,
                   size_t size, RIL_Token token) {
  ...
  ril_request_register(request, data, size, token);
  ...
}
\end{lstlisting}

\begin{frame}
\center{ril\_request\_register}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ril_request_register(int request, void *data,
                   size_t size, RIL_Token token) {
  ...
  list_end = ril_data->requests;
  ...
  list = list_head_alloc(list_end, NULL,
                        (void *) ril_request);
  ...
  ril_data->requests = list;
}
\end{lstlisting}

\begin{frame}
  \center{Global ril\_Data variable}
\end{frame}

\lstset{language=bash}
\begin{lstlisting}[style=terminal]
$ git grep "extern.*ril_data;"
samsung-ril.h:extern struct ril_data *ril_data;
\end{lstlisting}

\begin{frame}
  \center{Why?}
  \begin{itemize}
  \item Asyncronous design $\rightarrow$ Faster
  \item Enqueue the request and continue serving new requests.
  \item We will see how getting the response works in a second time
  \end{itemize}
\end{frame}

\begin{frame}
  \begin{itemize}
  \item We got a request to power on the phone from the RIL
  \item We got rid of it by adding it to a list
  \item Now what happens to it?
  \end{itemize}
\end{frame}

\begin{frame}
  \center{RIL\_Init}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  const RIL_RadioFunctions *RIL_Init(
           const struct RIL_Env *env, int argc,
           char **argv) {
  ...
  rc = pthread_create(&ril_data->request_thread,
                 &attr, ril_request_loop, NULL);
  ...
}
\end{lstlisting}

\begin{frame}
  \center{ril\_request\_loop}
\end{frame}
\lstset{language=C}
\begin{lstlisting}

void *ril_request_loop(void *data) { ...
  while (1) {
    do {
      request = ril_request_find_status(
                           RIL_REQUEST_UNHANDLED);
      ...
      request->status = RIL_REQUEST_PENDING;
    } while (request != NULL);
    do {
      ...
      request = ril_request_find_status(
                             RIL_REQUEST_PENDING);
      ...
      rc = ril_request_dispatch(request);
    } while (request != NULL);
  }
\end{lstlisting}

\begin{frame}
  \center{ril\_request\_dispatch}
\end{frame}

\lstset{language=C}
\begin{lstlisting}
  int ril_request_dispatch(
  struct ril_request *request) {
    ...
    for (i = 0; i < ril_request_handlers_count;
    i++) {
      ...
      if (ril_request_handlers[i].request ==
                              request->request) {
        status = ril_request_handlers[i].handler(
                      quest->data, request->size,
                      request->token);
        ...
        request->status = status; ...
      } ...
    } ...
    return 0;
  }
\end{lstlisting}

\begin{frame}
  \center{ril\_request\_handler}
\end{frame}

\lstset{language=C}
\begin{lstlisting}
  struct ril_request_handler
                        ril_request_handlers[] = {
    /* Power */
    {
      .request = RIL_REQUEST_RADIO_POWER,
      .handler = ril_request_radio_power,
    }, ...
  }
\end{lstlisting}

\begin{frame}
  \center{ril\_request\_radio\_power}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ril_request_radio_power(void *data,
  size_t size, RIL_Token token) {
    ...
    power_state = *((int *)data);
    ...
    if (power_state > 0) {
      request_data.state =
           IPC_PWR_PHONE_STATE_REQUEST_NORMAL; ...
    } else {
      request_data.state =
              IPC_PWR_PHONE_STATE_REQUEST_LPM; ...
    } ...
    rc = ipc_fmt_send(ipc_fmt_request_seq(token),
              IPC_PWR_PHONE_STATE, IPC_TYPE_EXEC,
              (void *) &request_data,
              sizeof(request_data)); ...
  }
\end{lstlisting}

\begin{frame}
  \center{ipc\_fmt\_send}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ipc_fmt_send(unsigned char mseq,
  unsigned short command, unsigned char type,
  const void *data, size_t size) {
    ...
    ipc_fmt_data = (struct ipc_fmt_data *)
                                     client->data;
    ...
    rc = ipc_client_send(ipc_fmt_data->ipc_client,
                 mseq, command, type, data, size);
    ...
}

\end{lstlisting}

\begin{frame}
  \center{The rest happens in libsamsung-ipc}
\end{frame}

\lstset{language=bash}
\begin{lstlisting}[style=terminal]
$ git grep IPC_PWR_PHONE_STATE_REQUEST_NORMAL
  include/pwr.h:
  #define IPC_PWR_PHONE_STATE_REQUEST_NORMAL 0x0202
$ git grep ipc_client_send
  include/samsung-ipc.h:
  int ipc_client_send(struct ipc_client *client, ...
  samsung-ipc/ipc.c:
  int ipc_client_send(struct ipc_client *client, ...
\end{lstlisting}


\begin{frame}
  \center{Now what happens with notifications from the modem?}
\end{frame}

\begin{frame}
  \center{Again RIL\_Init}
\end{frame}

\lstset{language=C}
\begin{lstlisting}
  const RIL_RadioFunctions *RIL_Init(
  const struct RIL_Env *env,
  __attribute__((unused)) int argc,
  __attribute__((unused)) char **argv) {
    ...
    rc = ril_client_loop(ril_clients[i]);
    ...
  }
\end{lstlisting}

\begin{frame}
  \center{ril\_clients[i]?}
\end{frame}

\begin{frame}
  \center{ril\_clients}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ril_client *ril_clients[] = {
        &ipc_fmt_client,
        &ipc_rfs_client,
        &srs_client,
};
\end{lstlisting}

\begin{frame}
  \center{IPC and RFS}
  \begin{itemize}
  \item RFS: Modem's remote filesystem (EFS)
  \item SRS: For the audio part
  \item IPC: The rest of the protocol
  \end{itemize}
\end{frame}

\lstset{language=bash}
\begin{lstlisting}[style=terminal]
$ git grep XMM626_SEC_MODEM_IPC0_DEVICE
  modems/xmm626/xmm626_sec_modem.c:
  fd = open(XMM626_SEC_MODEM_IPC0_DEVICE,
                  O_RDWR | O_NOCTTY | O_NONBLOCK);
  modems/xmm626/xmm626_sec_modem.h:
  #define XMM626_SEC_MODEM_IPC0_DEVICE
                                  "/dev/umts_ipc0"
  $ git grep XMM626_SEC_MODEM_RFS0_DEVICE
  modems/xmm626/xmm626_sec_modem.c:
  fd = open(XMM626_SEC_MODEM_RFS0_DEVICE,
                  O_RDWR | O_NOCTTY | O_NONBLOCK);
  modems/xmm626/xmm626_sec_modem.h:
  #define XMM626_SEC_MODEM_RFS0_DEVICE
                                  "/dev/umts_rfs0"
\end{lstlisting}

\begin{frame}
  \center{ril\_client\_loop}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ril_client_loop(struct ril_client *client) {
    ...
    rc = pthread_create(&client->thread, &attr,
               ril_client_thread, (void *) client);
    ...
  }

\end{lstlisting}

\begin{frame}
  \center{ril\_client\_thread}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  void *ril_client_thread(void *data) {
    ...
    client = (struct ril_client *) data;
    ...
    rc = client->handlers->loop(client);
    ...
  }
\end{lstlisting}

\begin{frame}
  \center{ril\_client}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ril_client ipc_fmt_client = {
        .id = RIL_CLIENT_IPC_FMT,
        .name = "IPC FMT",
        .handlers = &ipc_fmt_handlers,
        .callbacks = &ipc_fmt_callbacks,
};
\end{lstlisting}

\begin{frame}
  \center{ipc\_fmt\_handers}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ril_client_handlers ipc_fmt_handlers = {
        .create = ipc_fmt_create,
        .destroy = ipc_fmt_destroy,
        .open = ipc_fmt_open,
        .close = ipc_fmt_close,
        .loop = ipc_fmt_loop,
};
\end{lstlisting}

\begin{frame}
  \center{ipc\_fmt\_loop}
\end{frame}

\lstset{language=C}
\begin{lstlisting}
  int ipc_fmt_loop(struct ril_client *client) {
    ...
    rc = ipc_client_recv(data->ipc_client,
                                        &message);
    ...
    rc = ipc_fmt_dispatch(client, &message);
    ...
  }
\end{lstlisting}

\begin{frame}
  \center{ipc\_fmt\_dispatch}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ipc_fmt_dispatch(struct ril_client *client,
                   struct ipc_message *message) {
    ...
    for (i = 0;
      i < ipc_fmt_dispatch_handlers_count; i++) {
    ...
    if (ipc_fmt_dispatch_handlers[i].command ==
                              message->command) {
    ...
    rc = ipc_fmt_dispatch_handlers[i].handler(
                                        message);
    ...
    }
  }
  ...
}
\end{lstlisting}

\begin{frame}
  \center{ipc\_fmt\_dispatch\_handlers}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  struct ipc_dispatch_handler
                  ipc_fmt_dispatch_handlers[] = {
    /* Power */
    {
      .command = IPC_PWR_PHONE_PWR_UP,
      .handler = ipc_pwr_phone_pwr_up,
    },
\end{lstlisting}

\begin{frame}
  \center{ipc\_pwr\_phone\_pwr\_up}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ipc_pwr_phone_pwr_up(__attribute__((unused))
                    struct ipc_message *message) {
    ril_radio_state_update(RADIO_STATE_OFF);

    return 0;
  }
\end{lstlisting}

\begin{frame}
  \center{libsamsung-ipc}
\end{frame}

\begin{frame}
  \center{ipc\_client\_send}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ipc_client_send(struct ipc_client *client,
  unsigned char mseq, unsigned short command,
  unsigned char type, const void *data,
                                 size_t size) {
    ...
    memset(&message, 0, sizeof(message));
    message.mseq = mseq;
    message.aseq = 0xff;
    message.command = command;
    message.type = type;
    message.data = (void *) data;
    message.size = size;

    return client->ops->send(client, &message);
}
\end{lstlisting}

\begin{frame}
  \center{client$\rightarrow$ops$\rightarrow$send}
\end{frame}


\begin{frame}
  \center{ipc\_client\_create}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ipc_client *ipc_client_create(int type) {
  ...
  rc = ipc_device_detect();
  ...
  switch (type) {
    ...
    case IPC_CLIENT_TYPE_FMT:
      client->ops =
               ipc_devices[device_index].fmt_ops;
      break;
      ...
  }
  ...
}
\end{lstlisting}

\begin{frame}
  \center{ipc\_device\_detect}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int ipc_device_detect(void) {
    ...
    fd = open("/proc/cpuinfo", O_RDONLY);
    ...
    if (strncmp(line, "Hardware", 8) == 8) {
    ...
    if (...  && strcmp(kernel_version,
              ipc_devices[i].kernel_version) != 0)
    ...
}

\end{lstlisting}

\begin{frame}
  \center{ipc\_devices}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ipc_device_desc ipc_devices[] = {
  ...
  {
        .name = "i9300",
        .board_name = "smdk4x12",
        .kernel_version = NULL,
        .fmt_ops = &i9300_fmt_ops,
        .rfs_ops = &i9300_rfs_ops,
        .handlers = &i9300_handlers,
        .gprs_specs = &i9300_gprs_specs,
        .nv_data_specs = &i9300_nv_data_specs,
    },
\end{lstlisting}

\begin{frame}
  \center{ipc\_client\_ops}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
struct ipc_client_ops i9300_fmt_ops = {
    .boot = i9300_boot,
    .send = xmm626_sec_modem_fmt_send,
    .recv = xmm626_sec_modem_fmt_recv,
};
\end{lstlisting}

\begin{frame}
  \center{xmm626\_sec\_modem\_fmt\_send}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int xmm626_sec_modem_fmt_send(
                    struct ipc_client *client,
                  struct ipc_message *message) {
    ...
    rc = client->handlers->write(
                client->handlers->transport_data,
                              p, length - count);
  }
\end{lstlisting}


\begin{frame}
  \center{i9300\_handlers}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  struct ipc_client_handlers i9300_handlers = {
    .read = i9300_read,
    .write = i9300_write,
    .open = i9300_open,
    .close = i9300_close,
    .poll = i9300_poll,
    .transport_data = NULL,
    .power_on = i9300_power_on,
    .power_off = i9300_power_off,
    .power_data = NULL,
    .gprs_activate = i9300_gprs_activate,
    .gprs_deactivate = i9300_gprs_deactivate,
    .gprs_data = NULL,
    .data_create = i9300_data_create,
    .data_destroy = i9300_data_destroy,
  };
\end{lstlisting}

\begin{frame}
  \center{i9300\_open}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
int i9300_open(void *data, int type)
{
  ...
  transport_data->fd =
                     xmm626_sec_modem_open(type);
  ...
  return 0;
}
\end{lstlisting}

\begin{frame}
  \center{xmm626\_sec\_modem\_open}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
int xmm626_sec_modem_open(int type) {
    switch (type) {
      case IPC_CLIENT_TYPE_FMT:
        fd = open(XMM626_SEC_MODEM_IPC0_DEVICE,
                 O_RDWR | O_NOCTTY | O_NONBLOCK);
          break;
      case IPC_CLIENT_TYPE_RFS:
        fd = open(XMM626_SEC_MODEM_RFS0_DEVICE,
                 O_RDWR | O_NOCTTY | O_NONBLOCK);
          break;
      default:
          return -1;
    }
    ...
}
\end{lstlisting}

\begin{frame}
  \center{xmm626\_sec\_modem\_fmt\_send}
\end{frame}
\lstset{language=bash}
\begin{lstlisting}[style=terminal]
  $ git grep XMM626_SEC_MODEM_IPC0_DEVICE
  devices/xmm626/xmm626_sec_modem.h:
  #define XMM626_SEC_MODEM_IPC0_DEVICE "/dev/umts_ipc0"
  $ git grep XMM626_SEC_MODEM_RFS0_DEVICE
  devices/xmm626/xmm626_sec_modem.h:
  #define XMM626_SEC_MODEM_RFS0_DEVICE "/dev/umts_rfs0"
\end{lstlisting}

\begin{frame}
  \center{i9300\_write}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int i9300_write(void *data,
       const void *buffer, size_t length) {
  ...
  rc = xmm626_sec_modem_write(
       transport_data->fd, buffer, length);

  return rc;
}
\end{lstlisting}

\begin{frame}
  \center{xmm626\_modem\_write}
\end{frame}
\lstset{language=C}
\begin{lstlisting}
  int xmm626_sec_modem_write(int fd,
            const void *buffer, size_t length) {
    ...
    status = ioctl(fd, IOCTL_MODEM_STATUS, 0);
    if (status != STATE_ONLINE &&
                        status != STATE_BOOTING)
       return -1;

    rc = write(fd, buffer, length);

    return rc;
}
\end{lstlisting}

\begin{frame}
  \center{Sharing the work with other Android distributions}
  \begin{itemize}
  \item Not complete enough to be merged in LineageOS
  \end{itemize}
\end{frame}

\begin{frame}
  \center{Sharing the work with GNU/Linux distributions}
  \begin{itemize}
  \item Freesmartphone.org
  \item Ofono + rild + libamsung-ril + libsamsung-ipc
  \item Ofono + libsamsung-ipc
  \item PostmarketOS?
  \item PureOS, Parabola?
  \end{itemize}
\end{frame}

\begin{frame}
  \center{Discussions:}
  \begin{itemize}
  \item Sharing code with other distributions?
  \item USB Guard?
  \item Device requirements: Require modem to be isolated ?
  \item Other modems and GNU/Linux stack (PinePhone, GTA04)?
  \item Using GNU/Linux modem stack as much as possible?
  \item Automatic testing infrastructure and ofono?
  \item GNU/Linux and testing?
  \end{itemize}
\end{frame}

\begin{thebibliography}{99}
\end{thebibliography}

\end{document}